Pinewood Derby Times Volume 6, Issue 15

– Feature Article – Top Fuel Cars: Propeller Car

– Pinewood Derby Car Showcase

– Memory – Sad Day for the True Cub Scout Boys

– Q&A


Top Fuel Cars: Propeller Car

(The third in a series of articles on cars that ‘stretch the rules’ – this is an updated version of an article that first appeared in Volume 3, Issue 5, November 26, 2003)

Many organizations give parents and siblings an opportunity to race by sponsoring an open competition race. Typically the rules for these races are somewhat relaxed, allowing more innovation and creativity in car design.

In today’s article I would like to first share some typical ways to ‘open-up’ the rules for this type of race. Then I would like to explore a more radical way to add excitement to your derby event.

Rules For Open Competition Races

Here are some common ways to allow more flexibility in open competitions:

  1. Wheelbase – If the organization event mandates the use of a standard wheelbase (distance between the front and back axles) then allow the wheelbase to be modified as desired, as long as the overall length specification is maintained.
  2. Alternate axles – Instead of requiring the use of the organization standard axles, allow the use of after-market ‘speed axles’.
  3. Wheel shape – Typically, standard rules allow minimal wheel modification (e.g., only a light sanding). Try removing this restriction, allowing any plastic wheel, as well as any wheel treatment including narrowed, grooved tread surface, and/or overall weight reduction.
  4. Length – Try changing the maximum length from the typical seven inches to twelve inches (or one inch less than the distance from the starting pin to the back edge of the track).
  5. Weight – Consider changing the maximum weight to one or more pounds (with standard wheels and axles, I don’t recommend exceeding 1 pound).

A More Radical Approach

Wouldn’t it be fun to add a whole new dimension to your open competition? I’m thinking power!

Okay, I know what you’re thinking. Someone will strap a rocket engine on the car, and the car will damage the track, a person, or the building! But of course, restrictions would be necessary to minimize any risk. So, I suggest the following rules.

Rules for a Radical Open Competition
Dimensions – (Adjust to fit your track, and leave an open lane between cars)

  • 11 inches maximum length
  • 5 inches maximum width
  • No limit on height (remove the electronic finish line)
  • 3 inches maximum inside wheel base
  • 3/8 inch minimum track clearance
  • 16 ounces maximum weight

Power Sources
In addition to gravity power, other power sources may be used as long as they do not pose a risk to the spectators or to the track.

  1. Allowed power sources include, but are not limited to electrical, mechanical, and pneumatic.
  2. Power sources which use combustion of any type are explicitly disallowed. This includes combustion engines, rocket engines, and explosives.

Wheels, Axles and Body
A pinewood derby kit may be used, but it is not required. Any material can be used for the car as long as the finished product meets the specifications. However, the wheels must be made of a material that will not damage the track. Metal, ceramic, glass, or other hard substances may not be used for wheels. Allowable materials include plastic, rubber, and wood.

Race Procedure
The owner of each car will stage the car on the starting line, and pick the car up at the end of the run. Cars may be adjusted between races as long as the adjustment does not delay the race. However, cars may not be lubricated during the race.

Possible Designs
I have heard of all sorts of ideas for adding power to pinewood derby cars. Listed below are a few that have merit.

Powered Rear Axle

  • Spring wind-up mechanism
  • Rubber-band powered
  • Mouse-trap powered
  • Electric motor powered (R/C type)
  • Weight powered (suspended weight drops and turns rear axle)

All of these ideas can be made to work. But two problems must be worked out:

  1. How to apply power when the starting pin drops, or
  2. If power is applied before the pin drops, how to apply the maximum torque without the wheels spinning-out.

Non-powered Rear Axle

The design ideas below eliminate problem number two above, but problem number one must still be resolved.

  1. Compressed CO2 or Air (acts like a ‘jet’ engine)
  2. Propeller powered (push or pull)

Propeller Power

I have had some experience with propeller power, so I would like to share the design of three cars that I have built. The first one was built in 2002, the second in 2005, and the third in 2007. I have also included photos of a few propeller cars submitted by readers.

First, here are some principles that I have learned through experience.

  1. Maximize thrust through higher RPM motors, steeper blade pitch, and larger props.
  2. Maximize acceleration by minimizing weight. This mainly means lighter weight batteries.
  3. The longer the track, the greater the speed (and the larger the advantage over conventional cars).

My First Propeller Car
Please don’t laugh too hard; I severely over-engineered this car. But I can say the car has never had to be repaired! This car smoked the competition when it raced in 2002, and it easily beats any standard pinewood derby car (2.7 seconds on a track measuring 33 feet, 3 inches from the starting pin to the finish line – measured with a stop watch as it doesn’t fit under the finish line bridge).


First Car: Front View

First Car – Rear View

Here is a parts list and some notes on implementation.

  • Motor: 12 VDC motor, RF-370CA by Mabuchi Motors. This is a VCR motor, but other motors would work as well. I drove the motor at 18V for more power. This would eventually burn out the motor, but the on-time is so short that the motor doesn’t get a chance to overheat.

    Motor Diagram
  • Motor Mounting: The two screw holes on the front of the motor are for mounting. The required ISO screws can be purchased at a hardware store. I used a piece of thin stainless steel (hardware store item), drilled holes for the mounting screws, shaft, and assembly bolts (see front view picture).
  • Propeller: I used a plastic prop intended for rubber band powered airplanes. The hobby store I visited sold them in packs of three. The prop is about 5 inches long, and I had to trim the tips a bit for clearance. The shaft hole was too small, so I drilled it out to fit snuggly on the motor shaft. I then used epoxy to glue it in place. I believe this type of propeller works better than an R/C airplane propeller. R/C propellers are heavier, and the blade angle is smaller, providing less thrust.
  • Infrastructure: I had access to an old erector set, but you can use any light metal strapping. It does need to be securely mounted as some torque is generated. Make sure there is clearance for the propeller. I had to remove some metal from the erector material. If you look carefully at the front view, you can see where it was removed.
  • Motor Shroud: Quaker Oats oatmeal container. I put this on for two reasons: (1) To keep hands from touching the blades (it hurts, but doesn’t cut if you touch the spinning blades), and (2) To keep the blade from breaking if the car rolled over – if the blade comes off, the race if over.
  • Motor Alignment: The motor does need to be pointing as straight forward as possible. Add/remove small washers where the stainless steel strap fastens to the infrastructure to adjust alignment.
  • Starting Pin Switch: I used a contact switch (part #275-016 at Radio Shack). It is normally on. When the car rests against the starting pin, the weight of the car closes the switch turning the motor off. Thus, when the pin drops, away it goes.
  • Kill Switch: If you look carefully at the front view you will see a small toggle switch (part #275-624 at Radio Shack) that is used to turn the motor off when not in use. Just make sure to turn it on at the starting gate!
  • Batteries and Holders: Two standard 9V batteries. The battery holders are Radio Shack part #275-326.
  • Wiring: Light gauge electronics wire. Positive side of the battery goes to the Kill Switch, then to the Starting Pin Switch, then to the motor. The negative wire goes to the motor. Batteries are wired in series.
  • Wood: Pine, 1-3/4 inches wide. The car is 10 inches long, but it could be shortened.
  • Wheels/axles: Standard BSA issue. Axle holes are drilled with a drill press. All four wheels touch the ground.

My Second Car
After seeing the propeller cars built by others, I decided to build another car. This one would be less bulky, but would use the same basic components. The main differences are the use of Outlaw Wheels, the full 5 inch long propeller (did not need to be shortened), and significant weight reduction.


Second Car: Front View


Second Car – Rear View

With the reduced weight the performance improved significantly, completing the same distance as prop car 1 in 2.2 seconds, 1/2 second faster than my first car (again measured with a stopwatch). But remember the reason for the oatmeal container on the first car? Sure enough, on the second run, the car tipped over on the braking section, and the propeller flew off. So the lesson is that if you run this type of car, keep the finish line area clear of people (to avoid an eye injury), and have someone stationed at the end to catch the car and turn off the motor.

My Third Car
I decided I needed to build a car that fit within the standard dimensions, so that it would go under the finish line bridge. After a reader posted some information on a derby forum, I decided to do this with a ducted fan from an R/C ‘Jet’ plane (purchased from Hobby Lobby). To get a high enough RPM, I used a 7.2 V Speed 300 compatible motor that was intended for an R/C boat. The motor is powered at 9 volts. The two batteries are wired in parallel to provide enough current for the motor.


Third Car: Front View

Third Car – Rear View
This car is loud and fast, but not quite as fast as the second car. It runs the same course in 2.3 seconds. I believe the speed could be improved with a smooth ring around the intake (like on a real jet engine). According to the documentation that came with the duct fan, this can improve thrust by as much as 25 percent.

Reader Submitted Cars

Here are a few propeller cars sent to me by readers.


Keith Gosselin
Like my car, this one has a starting pin contact switch and a kill switch. Hanging the propeller (tri-blade in this case) off the back of the car permits the use of a longer propeller.


Mark Pugsley
A similar design using a rubber band airplane propeller (and liberal use of rubber bands in the infrastructure).


Unknown
A dual prop model that uses an R/C type battery and control. It appears to be quite heavy, so I am not sure how will it performed. (This photo was sent to me by another participant in the race. If this is your car, please let me know so that I can give you credit).


Unknown
(If this is your car, please let me know so that I can give you credit).

Conclusion

Maybe this all seems a bit ridiculous to you. But I guarantee that if you have a group with a lot of handy parents, an open competition race with power assist is a blast and a certain crowd pleaser!


Pinewood Derby Car Showcase

Low-Rider: Paul & Jordan Messineo

Jordan is 9 years old, and for two years he entered the Derby only to come in last each year. He went to his dad and said enough is enough; he wanted to at least be competitive. Dad enlisted grand pap and stated the problem. Papap went online and found Maximum Velocity, who helped with a lot of the details. Guess what? Jordan came in 1st out of 50 cars. That was last year, now everyone in the district was waiting for the latest entry of Jordan’s. Jordan showed up with a great running Wedge car that looked like a winner. However, the rules were modified and Jordan’s father did not receive the changes due to his out of town travels. The Wedge car had three wheels touching, and the rules clearly stated that all four wheels had to touch. When Jordan showed up with his father, one hour before the race they were told of the rule changes and the car was declared ineligible. Jordan was devastated and heartbroken. Papap and Dad went back home and decided to look at the other cars that Jordan had built to see if anything could be done. Jordan’s brothers, Paul III and Brandon, worked on this previously built Low-Rider (with Papap and Dad) to lower the fourth wheel. With only 22 minutes remaining they completed the revision and started back to the race. They arrived with only 6 minutes remaining and checked in with the revised Low-Rider. The car was carefully checked by the officials and passed.

The race started, and low and behold Jordan finished second. This was quite an accomplishment considering the work that had to be done in order to compete. Well compete they did, what a lesson in life this taught Jordan, NEVER GIVE UP!

But the story does not end here. The following week Jordan entered the Pittsburgh Council regional event with the same car and took 1st in Webelos and 2nd overall. What a great time Jordan had in telling this story – three trophies in two weeks!

Wii: Jim, Josh & Jake Heidecker </b

Josh (1st year Webelo) and Jake (Bear) had selected your Wing design for their car this year but were not sure how they were going to paint it. Both really wanted a Nintendo Wii game console for Christmas – when I mentioned that the controller for the game was about the same size as their pinewood derby cars, they got the inspiration for this design. With the help of the speed tips we learned from your site, Josh came in 1st and Jake came in 2nd out of 66 cars! The attached picture is Josh’s car; Jake’s was similar except it was white.

Dale Earnhardt’s 1998 Daytona 500 Winner: James Gravely

Last year was my son’s last year of scouting, so my last hold on pinewood derby racing is gone! I love pinewood derby racing, and am now thinking if I want to ask my wife to have more kids. My only problem is I would have to wait five years before they could join Cub Scouts and, oh my, suppose they were girls!? Well let’s just forget that idea (for now).

Anyway, while my son was in Cub Scouts, every year we came up with the most exciting concept that we could (actually I hoped my son would let me decide on the design because his were more intricate than mine, and I knew I would have great difficulty fabricating his desires).

This car is a replica of the late Dale Earnhardt’s 1998 Daytona 500 winner, complete with all the correct details. The car would have been our 2007 entry if my som was still active in Cub Scouts. I built the entire car myself with no help from my son since it was not intended to be raced. The car is built to specification and is completely legal for derby racing: correct wheels, axles, weight, and size dimensions. The car is bathed in ‘Racer Black’ lacquer, and the decals and paint are protected by five coats of clear gloss top coat.


Pinewood Derby Memory

Sad Day for the True Cub Scout Boys

Every year my brother would get help on his car from the “winning family”, but for some reason his car never placed. This year we decided to try someone different – help from a friend that has helped build winning cars for his nephews and grand-kids.

It was a great race. My son, who is a Wolf, and my brother, who is a Webelo II, had two of the fastest cars there. My son took first in his den, while my brother took first in his. The final race was with the first place cars from each den.

It ended up being my son’s car racing my brother’s car. The people putting the cars on the track sent my brother’s car down crooked. My son’s car won that race and got the trophy, but I asked the Cubmaster to re-race the cars because my son needed to know that he won fair and square.

In the second race my brother’s car won. They raced the cars two more times in different lanes, but my brother’s car won every time.

Then the sad event occurred. The “winning family”, whose cars did not win this year, were angry because their cars would not being going to the district race. They confronted the Cubmaster who told them that nothing could be done. The parent then replied, “I don’t know how I am going to keep my boy in Cub Scouts anymore.” But that was not the end of it. They tried to talk other people out of taking their car to districts, so that their son’s car could go. But the Cubmaster put an end to that.

It is sad to think that the biggest event in Cub Scouts had become the only event for this family. The pinewood derby is supposed to teach sportsmanship and be fun, but now it seems to have become a competition that teaches “win or whine”.

Cora Brandon

Editor’s Note: Please do yourself and your children a favor; remember that the pinewood derby is intended to be a friendly competition that is fun for the kids. An improper attitude will only serve to sour the experience for yourself, your children, and other participants.


Q&A

Do you sell – or know where to get – the old style BSA wheels? I’ve got an old car from about 1972 that has a cracked wheel. The wheels are like the ones on the Don Murphy and Craig Breedlove signature cars in Volume 6, Issue 14.

Beta Crafts is still making the kit, but they appear to only sell then in quantity lots. See: www.betacrafts.com

What is the best way to clean graphite overspray off the car?

There is no sure way to remove graphite, but here are several methods that people have had success with:

  1. Rubber pencil eraser
  2. Vegetable oil on a soft rag
  3. Liquid dish soap on a soft rag
  4. Auto cleaner wax on a soft rag (e.g., Meguiar’s No. 6 Cleaner Wax)
  5. WD-40 on Q-tip, then use a good paste wax
  6. Pledge wipes

I’ve got a car that I’m trying to align. I have a left front wheel that’s just barely raised (makes contact occasionally). The car tracks 1 inch to the right over a test of 6 feet. It’s my opinion that I’d gain more from a car that’s perfectly straight running, than I would from only 3 wheels making contact with the track. Putting a premium on alignment instead of the reduced friction of 3 wheel contact, do you share this opinion?

I would continue with 3 wheels, but then make an adjustment to the steering wheel to get the car to drift towards the raised wheel. First, make sure that the raised wheel doesn’t touch. The main advantage of the raised wheel is that it doesn’t rob energy by spinning up. If it touches at all, there is no benefit.  The drift towards the raised wheel is to make sure it doesn’t contact the center guide rail.

Next, make sure that the test ramp is dead level left-right, and slightly pitched downhill. Use a bubble level, or a ‘steely’ marble (roll it down the track to see if it deviates).

Final adjust the steering.  You will need a slight bent axle for the front steering wheel.  I recommend a drift of 5 inches over 8 feet.

 

Pinewood Derby Times Volume 6, Issue 14

– Feature Article – Car Collection on the Move

– Pinewood Derby Car Showcase

– Memory – I’ll Take the Checkered Flag

– Q&A


Car Collection on the Move
By Todd Paxson

Hello, my name is Todd and I’m a pinehead. I’ve been collecting derby cars for over 10 years. My addiction began innocently enough with some boxes of my stuff that my parents had packed up when they moved. It was mostly junk. Then I found my three derby cars and a couple of trophies I had won. Thank goodness I hadn’t blown them up like most of my other toys!

I started reminiscing about the fun times I had in scouts, and how much fun we had during derby season. My mom and dad got a little crazy, and I had to wrestle the cars away from them from time to time. Anyway, after remembering the good times, the cars and trophies went up on the shelf for a couple of years. One day, my mom and I were at an auction and there was a nice old derby car there. I bought it and put it on the shelf next to the others. One day when I was looking at the cars it popped into my head that these things would be fun to collect!

I was hooked. After my first year of garage sales, I had about 35 cars. After the second year, I had 75. Then I got on the Internet and the hook went in a little deeper. Before I knew it, I was up to 175. My wife told me I had to slow down, so I had my mom buy some for me on the side. My wife wasn’t happy when she found that out – I think she knew I had a problem.

Lately, I have let more more cars go than I have bought. I haven’t gone cold turkey, but I have gotten a little picky. I’m still a pinehead.

As if the collecting wasn’t bad enough, I started buying kits at the local dime store and building them just for the enjoyment of it. One fun car I built was an Elmo car for my daughter, Hanna. I even built cars out of scraps of wood that I found. As if that wasn’t bad enough, I needed power tools. I now have a scroll saw, band saw, belt sander, disk sander, drill press and a full set of carving tools. My wife put her foot down, so I didn’t get a wood lathe.

My son, Chris, and I built our first car together when he was four. He loved to work the drill press. He is twelve now and out of scouting, but he had fun while in scouts. I still keep up with my scout friends as I have made my collection portable by making folding cases to hold the cars (Figures 1 and 2). I take the collection to local pack and council events. Most of the cars I get now are from donations from packs where I show the cars. I have over 700 cars and derby memorabilia on display. I also have about 200 cars that were used in the movie “Down and Derby”. My cars have also been featured on a pinewood derby web site, but my friend and fellow pinehead has since passed on to ‘Derby Heaven’.

Figure 1
Car Collection on Display

Figure 2
Close-up of Left Display Cases

I don’t really have any one car that is my favorite car, but I do have some special cars. Two are cars made for a vintage race in California, signed by Don “The Creator” Murphy and Craig Breedlove (Figures 3 and 4). I also have a car that belonged to the brother of the Olson Twins (Figure 5).

Figure 3
Signature Cars

Figure 4
Signature Cars, Bottom View

Figure 5
Olson Twins’ Brother’s Car

That’s enough for now. If anyone has questions or would like to see pictures, I can be contacted at ‘toddpaxson (at) yahoo (dot) com’. Also, if you are close to southern Wisconsin and are interested in having me display my collection at your event, you can contact me at the above email address.


Pinewood Derby Car Showcase

Police Cruiser: Jeff & Jack Jouett

Once again Maximum Velocity came through for Jack’s derby car, and we didn’t really hold to speed specs. Jack had never lost a head to head race in the past two years, collecting 1st Place in speed in his category at the pack meetings, and winning 1st Place in district. After last year’s race he told me that he wanted to go for style this year. This is what he came up with. He got 1st Place in style and will be entered in district in the style category. He also got 2nd Place in speed. He was very close to collecting top honors in speed and style, but he is mostly proud of his 1st Place style finish. I really like this car because he designed it and put it all together – I didn’t have to do much this year.

What, me win?: Chris & Greyson Skafidas

My son and I set out to make our 2006 cars stand out from the crowd. My son wanted to have a car that was barely there. We worked on the design on an ‘as it goes’ basis. Originally we were going to put the weight in the back upper portion of the car, but thanks to a Dremel incident we had to chop out the space. The car was only 3.5 ounces. It ran sharp, but did not win anything. Regarding my car, I love Mad Magazine, ever since a fateful day in 1977. Alfred was fast but not a winner.

Flintstones: Susan Hanna

When I sent you the info on my son’s great experiences at the pinewood derby using the fantastic info you have provided, I was so excited that he had taken first in every race, set a track record and was on to Districts that I forgot to include the 2 cars that I had built for the adult/sibling race.

The idea for these cars came from our local Halloween parade. Our pack had entered a float (the Flintstones’ mobile), as the theme this year was cartoon characters. We took Grand Prize with the float. I decided at that point I would make a Flintstones’ car and a Rubble mobile to enter in the race.

The cars were a big hit with all the men and the kids alike. Wilma and Betty didn’t win – heck Wilma barely made it to the finish line – but we laughed so hard and had such a good time. The Flintstones’ mobile used all scrap wood from the workshop, and the Rubble mobile was a limb I cut from my brother’s burn pile. The only thing ‘official’ on either car was the BSA wheels and axles.


Pinewood Derby Memory

I’ll Take the Checkered Flag

My seven year old grandson was in his first pinewood derby race this year. He was very proud of his car, as he and his dad had worked long hard hours getting it just right (his dad builds and races real race cars at different race tracks in our state). My grandson wanted it to be perfect.

The race started, and with all of the excitement of a seven year old and an avid race fan of NASCAR he watched as his car went down the ramp. He came in first place 2 times and second place two times. Each race he would look over at me and give me a thumbs up sign.

At the time, we did not know they would select the fastest car by time. At the end, as the leaders were calling out winners, his name was not called. I saw the sadness and the tears, and then he ran to a table and put his head down sobbing. We all tried to comfort him. His dad told him, “Son, I’ve lost a lot of races, but I always went back on the track. Next year you will get another chance.” At this he looked his dad in the eyes and said, “Yea dad, next year I won’t be black flagged; I’ll take the checkered.”

Nan Phillips


Q&A

Do you have any experience with trying to suspend graphite in a liquid for easier application to the wheel shaft?

I have tried to use graphite in suspension (isopropyl alcohol), but with no success. Graphite needs to be in a powdered form to work best, and it will self-regulate to the amount needed. If you get too much graphite in the bore, the wheel will spin slowly until the excess graphite is shed. So the key is to keep adding and spinning until the wheel spins at peak performance. Generally, we add graphite 5 times, spinning at least 10 times by hand after each application. Graphite suspension puts too much graphite in the bore, and since it is essentially caked into the bore, it takes quite a while to shed the excess.

Many of the current BSA axles (nails) have an off-center head. Do you think this would cause problems with performance?

Since the axles don’t rotate, the out of round head generally causes no problems. The only issue would be if the head was so off-center that the edge of the head contacted the faux-spokes on the face of the wheel. In this case, the head would need to be trimmed down, or the axle replaced.

Does angling the axles (head higher than the tip) help performance?

Theoretically, if the wheel/axle system is running perfectly (minimized friction, dead straight mounting, perfect alignment), then straight and flat is best. But in practice, perfect is impossible to achieve. So, implementing an alignment technique known as “rail-riding” will generally give best performance.  This technique involves angling the axles and then adjusting them for alignment.

Pinewood Derby Times Volume 6, Issue 13

– Feature Article – DVD Review: An American Race

– Pinewood Derby Car Showcase

– Memory – Bittersweet Day

– Q&A


DVD Review: An American Race

While going through the bonus features on the ‘Down and Derby’ DVD, I ran across a trailer for “An American Race”. I was not entirely sure what was being advertised, but since I pursue anything relating to pinewood derby racing, I dutifully surfed to their web site to investigate. As stated on the web site, “An American Race” is a one-hour, multiple award winning, real-life documentary film (included as a finalist in the International Family Film Festival in LA), which follows three boy’s (Brady, Nick, and Matt) quest to make the fastest Pinewood Derby race car.

Okay, I was hooked. I purchased the DVD on-line ($14.99 + shipping, I paid $18.94 total), and waited for the DVD to arrive.

While waiting I found a little more information. The documentary was directed and produced by the father-son filmmaker team of Marc and Jake Wortman. Marc is a Northwestern University Graduate in Television and Film, while Jake (his son) is a former Pinewood Derby participant. Apparently, the documentary received commendations from several film festivals (quite a parent-child project!).

When the DVD arrived, I stuck it in the DVD player on my laptop and sat back to watch. Much to my confusion, there was no menu, so I couldn’t figure out how to get it playing! Finally, my teenage son figured out that all I had to do was press the enter button (duh).

The DVD is truly a documentary, with (apparently) no script. After the usual introductory whiz-bang cinematography, the three boys were introduced and the car building began.

Although the web site states, “The DVD is also a great ‘How To’ build your own Derby car, by actually watching real-life families building their cars, with lots of ‘Tips and Tricks’!!”, this is really just marketing hype. There are only a few tips mentioned, and they are the same ones you can find on any of 100,000 web sites. So, if you are looking to purchase a video to help you build a faster car, this is not the one.

Instead, the documentary is really a human-interest story with a pinewood derby race as the venue. In my opinion, the human interest story is quite well done. The boys are shown as they apparently really are, a little spoiled, a little quirky, and certainly competitive. I appreciate that the character flaws were left in, as it allowed the documentary to really reflect life.

Would this DVD be of interest to you? Well, if you are a “pinehead” (like me), then you would certainly enjoy the video. The track is a double-hump monster (over 4 seconds for a heat), and clearly demonstrates the need for a less abrupt braking section! The “speed tip” of wetting the axle sanding paper with spit, was certainly unique, and watching Nick attach wheels with gluey hands was to me like fingernails on the chalkboard (the car ended up doing quite well, so I have to believe that the “pinewood derby fairy” did quite a bit of work on the car while Nick was asleep – although the parents swore he did all the work himself). I also felt “justified” when Matt’s car did poorly (he kept the basic block shape in an attempt to prove that the shape of the car didn’t matter).

If you are not a pinehead, but do like documentaries, then you will likely enjoy the DVD. At the beginning I thought it would be somewhat boring, but by the end I was starting to empathize with the characters. When the story ended, I was actually hoping for the story to continue.

Although there are no bonus features (and no menu), the DVD is well done. For an independent (likely low-budget) project, the sound, lighting, and editing are quite good.

So, if you are like me – liking all things pinewood derby – or if you like documentaries, then you will likely enjoy “An American Race”.


Car Showcase

Canyon Dragon: John & Jake Harig

This is the second year for Jake, and he won 1st place again. This year the ‘Canyon Dragon’ car was fastest overall. The name comes from the base coat of ‘Canyon Orange’ and, of course, dragon decals.

We used your wheels and axles, and the block was yours with drilled holes, extended wheel base and raised wheel. COG was 0.9 inch forward of rear axle, much too aggressive for what I now realize is a rough wood track. I used a 1/2 inch diameter steel tube cut 2.5 inches long that protruded 1/2 inch out the back end to look like a jet engine nozzle. It also served as a weight chamber for your tungsten cylinders and beads. The part I liked best was using an ear plug to hold the weights in place – the approach worked sweet at the weigh-in.

Mach 5: John & Billie White

My daughter Billie and I raced our Mach 5 in the Awana Grand Prix this past fall. She was placed in the adult/leader group. The competition was TOUGH, but she placed third for speed and third for design. We raced this year on a new aluminum track. Many of my old secrets didn’t seem to want to work, but it was still a fun race.

Arrow of Light: Millisa & Cody Kramer

This is my son Cody’s car for his last Pinewood Derby. As a Webelo II, he has been working on his Arrow of Light achievements for the last year; so this year’s car design was based on that. After cutting out so much of the block and inserting a dowel for the arrow shaft, the car barely weighed anything at all. So there are weights across the entire bottom of the car, in a hole drilled out of the back. The fin on the top is even a weight! It weighed exactly 5.0 ounces. The axle holes were not quite straight, slowing down the car a little. It came in a very close 3rd out of 5 cars in his den, but it won Best of Show for the Pack.>


Pinewood Derby Memory

Bittersweet Day

Our pack was involved in a combined three pack pinewood derby this year. Not only did the boys race against their own dens, they also raced against the winners of the other packs. Our pack had purchased a brand new aluminum track with digital sensors. It was cool! Not one car jumped the track this year. No more jarring bumps as the cars raced down the track. The cars seems to go faster than in years past as well. The track was carefully roped off so anxious cub scouts couldn’t bump it or step on it. The cubs placed their cars on the track and had to walk around the audience to the finish line to receive their cars from the cub master at the end.

The derby this year took almost two hours to run. As the winners from each den were announced, their cars were put aside for the final race of the day – the three pack champion race. By this time, some of the boys not advancing to the district were leaving with their families or playing with the cars on the gym floor. Nine cars competed in the tournament of champions. There were multiple races and scoring to determine the overall winner. My son’s car had won against his Weblos den. He was the three pack champion last year, so he was one of the nine again this year. Tension was high – would he take first place again?

There were 9 heats to determine the overall winner. For each heat, four cars raced and five sat out. The cars were rotated so they were constantly racing other cars. About halfway through these heats my son’s name was called to get his car. It should have been on the judges table with the others – it wasn’t. We started looking around – did someone steal his car? My poor excited son (and his anxious dad!) couldn’t find the car. Everyone started looking. It took just a few seconds to see that some little girls were imitating the other cub scouts by playing with HIS car on the gym floor – pushing it back and forth. My daughter raced over and picked up the car from the girls playing with it. Now the problem wasn’t finding the car – it was to get it back in the race. No time to look at it to clean off the wheels or check alignment.

My son didn’t win the tournament of champions. We weren’t even allowed to handle the car after the final race, as the district wanted the cars quarantined until the district race next month. We requested time to examine and repair the car since it was mishandled. No such luck. Everyone agreed that we should be able to examine it – but whoever has the cars in quarantine isn’t letting us know where they are being stored. So next month my son will race his car against the district, and we won’t know until after that race if any damage was done – it’s sad that we know already his chances to win are slim. This will be his last pinewood derby before he bridges to boys scouts. What a bittersweet day.

Michael Law
Live Oak, CA


Q&A

We want to run our race outside, but can’t find a timer that works outside. What do you suggest?

As you have found, virtually all timers are designed for indoor use. However, ‘The Judge’ from New Directions can be optionally equipped to work in sunlight. See: www.newdirections.ws

Alternately, you can shield the finish line from all IR by building a shelter around the finish line. Unfortunately, this generally blocks the view of spectators.

Is it possible that a car using lathed wheels may not clear the center section of the track properly since the lathed wheels are smaller and therefore the car runs closer to the track?

This isn’t typically a problem. All speed wheels are turned on a lathe to make them round. This reduces the diameter (on our wheels the resulting diameter is 1.170 inches) from the original 1.190. So the radius reduction is only .010, or less than 1/64 of an inch.

The issue that people do have with light-weight speed wheels is the need to load the car with extra weight to make up for the loss of wheel weight. When using the lightest (1 gram) wheels over stock wheels, you need to add a little over 1/3 ounce of extra weight.

We want to have a semi truck race and are looking for information as to rules and truck kits. Can you help?

I don’t know of any specific web site for rules and information, but you can search Google for either:

pinewood 18 wheeler
Pinewood semi-truck

Pinewood Derby Times Volume 6, Issue 12

– Feature Article – Scaling Up: Design a Pinewood Derby Car from a Toy Car

– Pinewood Derby Car Showcase

– Memory – Second Place in Speed Goes to …

– Q&A


Scaling Up: Design a Pinewood Derby Car from a Toy Car
I generally build pinewood derby cars that don’t look like real cars. Oftentimes it is awkward to coerce a real car design into the pinewood derby car form factor. However, many people like to use a real car as the basis for a design, and in fact, I have done so a few times. So in this article I will explain how this conversion is accomplished, and the design decisions that will need to be made. Although I will focus on scaling up from a toy car, the same principles apply when scaling down from a full-size car.

What Is The ‘Scale’ Of A Pinewood Derby Car?

When building models, the ‘scale’ refers to the size of the model relative to the original. For example, many people have heard of “HO Scale”, a popular scale for model railroading. The HO scale is 1:87. That is, for every 1 inch in length (also width and height) of the model, the real train is 87 inches. Thus a train car that measures 44 feet long would be a little over 6 inches long in HO scale (44 feet, times 12 inches per foot, divided by 87).

Pinewood Derby Cars do not have a specific scale factor, as they are forced to be 7 inches long by 1-3/4 inches wide (instead of varying in size based on the size of the original). For many standard automobile sizes, 1:24 is pretty close, and in fact 1:24 scale decals generally work pretty well. However, the scale would be reduced when modeling a compact car, while the scale would be increased when modeling a large vehicle. So, instead of using a specific scale the designer must calculate a scale factor for the given original.

Calculating The Scale

To determine the scale, measure the length of the original vehicle, and then divide that number into 7 (inches). For example, let’s consider modeling a toy car that measures 3 inches long, 3/4 of an inch wide (excluding wheel wells), and 11/16 of an inch tall (see Figure 1). With these measurements, dividing the length (3) into 7 gives 2.33.1 Thus, for every 1 inch dimension of the toy car, the pinewood derby car will be 2.33 inches. Therefore, the pinewood derby car will be 7 inches long (2.33 times 3), 1-3/4 inches wide (2.33 times 3/4), and 1.6 inches tall (2.33 times 11/16). All other dimensions, such as the placement of the cockpit and engine, the location of the body curves, etc. are calculated using the same scale factor.


Figure 1
Hot Wheels Sweet 16 II
At this point, a tradeoff may need to be made. In this case, the width is fine, however, 1.6 inches is quite tall for a pinewood derby car. If realism is the primary goal, then maintaining the 1.6 inches is okay. However, if speed is the primary goal, then it is best to reduce the height of the car as much as possible.

If the width is too narrow, then it would need to be arbitrarily increased to 1-3/4 inches. If the width is too wide, then two options exist:

  • Arbitrarily reduce the width to 1-3/4 inches, slightly skewing the final car.
  • Recalculate the scale factor based on the width instead of the length. This will result in a pinewood derby car that is shorter than 7 inches; however, the proportions of the toy car would be maintained.

Wheelbase Considerations

The next design issue that must be resolved is the wheelbase. When the wheelbase of the toy car is scaled up, almost certainly it will not match the wheelbase required by your local rules. For example, on the toy car in Figure 1, using the 2.33 scale factor, the front wheels would be 0.73 inch from the front of the car, and 1.16 inches from the rear of the car. Obviously this does not match the BSA wheelbase (nor any other for that matter). At this point, the following options could be implemented (based on the rules for your race).

  1. If your race rules require a wheelbase distance AND a wheelbase position, then adjust the wheelbase to meet the regulations. This will certainly skew the resulting car, but there isn’t really a choice in this case.
  2. If your race rules require a wheelbase distance, but does not require a relative location then adjust the wheelbase to meet the required distance, but position the resulting wheelbase as close as possible to the position calculated with the scale factor. The resulting car will be skewed, but less so than in option 1.
  3. If your race rules do not specify a wheelbase, then use the wheelbase calculated with the scale factor.

Wheel Wells

Another design issue is that of wheel wells. Many toy cars have wheel wells, so to accurately model the car the wheel wells must be included. This will require the addition of material to the sides of the car, followed by shaping the wheel wells to accommodate the pinewood derby wheels.

But wait; now we may have another issue. Measure the diameter of the wheels on the toy car, and then multiply the diameter by the scaling factor. Does the result closely match the diameter of a pinewood derby wheel? If not, the wheel wells will need to be adjusted to fit the pinewood derby wheels, which could skew the car.


Figure 2
Hot Wheels Silver Bullet
As an example, for the car in Figure 2 (which also has a 2.33 scale factor), the rear wheels scale up to 1.16, but the front wheels scale up to 1.02. Since the standard BSA Speed is about 1.18, the wheel wells (mainly the front wheel wells) would need to be increased in size to accommodate the pinewood derby wheels.

Selecting A Car To Model

When choosing a car to scale, you will need to consider the following factors before doing any wood working:

  1. Given the rules for the local race, when the toy car is made to fit within the required dimensions, will it maintain the look of the original toy? With strict wheelbase rules, try to find a toy car that will fit well within the local wheel base restrictions.
  2. If you don’t want to deal with wheel wells, choose a car without them.
  3. Make sure to consider car weighting. You will likely need to add 2 to 3 ounces of weight, so space must be available on the car to accommodate the weight.
  4. Some toy cars are quite complex. Consider whether the car can be built with your tools, or whether the design can be simplified without sacrificing the original look.
  5. Actually, if you have a young boy like mine, the most difficult problem will be finding a toy car that is still intact!

Examples

Here are three examples of modeled cars:

Humvee
The Humvee in Figure 3 was modeled from a drawing on the internet. To model the wheelbase as accurately as possible, and to meet the BSA wheelbase specification, the car was shortened to 6.2 inches (see Figure 4 – blue lines show original body location, red lines show shortened location). The result is a wheelbase that matches the BSA wheelbase length, but is moved slightly forward from the standard location.

The body is made from three parts (you can see the glue lines running front to back). Before the parts were glued together, much of the middle part was cut away to eliminate weight. Even so, the final car required little to no added weight.


Figure 3
Humvee Body

Figure 4
Humvee Drawing Showing Shortened Body
 

Hot Wheels Car
This race car was modeled by a customer (see Figure 5). As you can see, the wheelbase was lengthened, the wheel wells were enlarged, but the general look was maintained.


Figure 5
Hotwheels Car
Stock Car
This (unfinished) Stock Car body is for sale on our web site. The wheel base is lengthened to match the BSA wheelbase, but is offset to maintain the NASCAR look. The height of the car is slightly lowered (looks slightly mashed, but not overly so). 1:24 scale decals are used, but they had to be trimmed slightly as the actual scale factor is slightly larger than 1:24.


Figure 6
Stock Car
Conclusion

If you need inspiration for a pinewood derby car design, your child’s toy box (or the local toy store) can provide a lot of great ideas. Then, by calculating a scale factor, creating a pinewood derby car from the toy car is not as hard as it may first appear. Just make sure to consider the overall dimensions, the wheelbase, wheel wells, and the overall complexity of the design before making any sawdust.

1Most ‘Hot Wheels’ brand cars are 3 inches long, resulting in a 2.33 scale factor.


Pinewood Derby Car Showcase

Bear-ly Finished: John & Heidi Row

This is my wife’s car (Heidi). Named appropriately “Bear-ly Finished”. She was up until 2 AM the morning of the race! The car is hand-chiseled with Exacto blades and Dremel bits. I lubed the wheels and aligned them (Max V Official BSA Matched Speed Wheels & Axles). Because we were running late I only spent about 3 to 4 minutes on the wheels. Despite the lack of time they ran straight as an arrow, and the car was the second fastest of all cars participating. This car goes totally against all reasoning of physics! The COG is 21/4 inches(!!!) in front of the rear axle and only weighed in at 4.90 ounces!

Champ Car: Chuck Baum

This car was never raced, it was just made for show. It was constructed from a standard BSA kit. The wings are made from tongue depressors and popsicle sticks, and the side pods from 3/8 inch thick pine. My son and I are open-wheel (Champ Car) race fans and I believe that this car was modeled after a car that Michael Andretti was racing circa early 90’s. We continue to get together for Champ Car races.

Rollin’ Rattler: Lisa & Ryan Ford

Attached is a picture of my son’s Pinewood Derby car from this year. He has won two first place overall trophies with a Wedge and the Formula 1 from your car plans. This year he wanted the Most Creative trophy, so we purchased the Extreme Car Plans booklet and attempted the Rollin’ Rattler. This is his version; I helped with the Dremel work and wheel polishing and he mixed the paint to get the right colors. He did take home the most creative trophy and came in 6th overall.


Pinewood Derby Memory

Second Place in Speed Goes to …

My son Connor is now a Bear Cub. When he was a Tiger Cub he won for most unique. I also thought he had a fast car. Since then he has been bitten by this bug and has gone for unique designs instead of speed. Last year he made a ‘Tank’ which was pretty cool. It didn’t win anything, but he still enjoyed building and racing the car. This year I decided that no matter which car he built, it would also be fast!

He again came up with a unique design: a tombstone. He carved it and painted it to look really nice with a stone paint finish. I had some leftover tungsten weights from building a car for the adult race, so we used them in Connor’s car.

I think these tungsten weights made a difference because of their density and small size. I was able to create a small hole to put them in (over the rear wheels). Then I was able to carve out some wood underneath to make the 5.0 ounce limit.

During the time trials the night before the derby we got excited. His car beat most that he went against. His time was also competitive with the adult cars. We had done something right! On the day of the big race he was very excited. We had a fast car and a unique car. Most of the other scouts liked Connor’s design. Everyone wanted to touch it and feel the stone finish.

When the race started everyone, except me, was surprised that this ‘rock’ was so fast ! It was not aerodynamic at all. It did not look fast, but it was. In his heats he had two first place finishes and two second place finishes. Connor was so thrilled just to win two heats that he would have been happy just with that.

When they called the third place winner in speed, it was not Connor. I felt like he would at least get third. “What went wrong,” I thought.

Next … “Second place in speed goes to … CONNOR.” Yes, he won second place in speed! WE ARE GOING ON TO THE DISTRICTS RACE IN MARCH!

I think the speed of the car has a lot to do with the tungsten weights we got from you and where we placed them. I recommended these weights highly!

Kyle & Connor Wilson


Q&A

Another question for you. My son is interested in lightening his BSA wheels in order to maximize weight placement back. We can get them down to about 1.5 grams. With the mass loss, does the 20 to 30 second spin rule still apply? The reason I ask is that we have lost a couple of seconds off the wheel spin time.

As the weight of the wheel is reduced, the spin time of the wheel will be reduced accordingly. The momentum of the wheel is what keeps the wheel spinning, and momentum is based on the weight of the wheel and the velocity of the spin.

If my son’s car wins and goes on to the next level, before the next race we want to re-lubricate the wheels. We put two drops of white glue in each axle slot to hold the axles in place. How can we pull the wheels and axles out of the slots without damaging anything?

With white glue, you should be able to grasp the axle head with a pair of pliers, then gently twist and pull the axle out. The glue bond should release when you give the axle a slight twist. After removing the axles, clean out most of the glue from the slot, then re-glue after you re-install.

We have a car body with drilled axle holes, and one front wheel is drilled higher. What is the best way to make all four wheels touch the ground?

First, verify that the rules for your race do require four wheels touching. If you don’t need four wheels touching, then I would leave the car as is (better performance).

To get four wheels touching, there are two options.

  1. Plug both front axles holes with round toothpicks, then re-drill the front two holes with a drill press, or with the Pro-Body Tool. A #44 or #43 bit is required. Don’t try to just plug one hole and re-drill. It is extremely difficult to drill a new hole that matches the others.
  2. Plug both front axle holes with round toothpicks. Then use a saw to cut a slot at the front axle position. A radial arm, or table saw work best. Just make sure that the width of the blade is the correct size (test this on a scrap piece of wood). In a pinch, you can use a band saw or hand saw, but these tools are not as accurate.

Pinewood Derby Times Volume 6, Issue 11

– Feature Article – Points or Times: Which Method Should I Use?

– Pinewood Derby Car Showcase

– Memory – Never Too Late to Start

– Q&A


Points or Times: Which Method Should I Use?

Life used to be simple. Only a few TV channels to choose from, no Starbucks to give us multiple coffee options, and pinewood derby winners were decided by elimination. But since humans thrive on innovation, we now have lots of channels and coffee choices, and we have other options for running pinewood races.

I for one am pleased that other options exist for deciding pinewood derby winners. For years we used a double-elimination method. I tried very hard to make the race fair, but I realized that issues existed. Although reasonably simple to implement, elimination methods are fraught with problems, and – unless very carefully implemented – are not very fair (see Volume 3, Issue 7 – “Elimination Methods – Let’s Make Some Improvements”).

So, when I discovered Points racing, our organization quickly shifted over to that method. At the time, we had a finish line judge, but it was not a timer, so there was no debate as to whether to use Points or Times; Points was the only choice.

Then we replaced the finish line judge with a timer, and integrated the timer with the Grand Prix Race Manager software. By the magic of software, we could now use Points or Times, and – after the race – dynamically switch back and forth to compare the two methods.

I first did this comparison for our 2004 race. We were using Points and each car ran once in each lane. The top finishers then advanced to a finals round (we advanced 10 car). In the finals my son’s car ended up taking fourth place. This seemed strange to me, for as I watched the heats I expected him to take third place.

So after the race, I did a little investigation and discovered that, by average heat time, his car was actually the third-fastest car. How did he end up in fourth place? This happened because of the race mix in the finals.

If each car had raced against every car the same number of times, then the heat mix would not matter. But my son’s car ended up racing against the two fastest cars more than the third place car. So, he accumulated fewer points than the third place car, thus taking fourth place.

When I made this discovery, my first thought was, “Next year we are going to use Times!” But later, I decided that making a rash decision wasn’t the wisest move. So, I did some investigation regarding the two methods, the result of which I will now share with you.

Defining Points Vs. Times
Just to make sure we are all thinking the same thing, let’s define Points and Times.

The Points method uses a preset race schedule (we use Perfect-N), wherein each car races the same number of times in each lane, and races against as many other cars as possible. The results of each heat are recorded, with points assigned based on the finish order. Points can be assigned as 4, 3, 2, 1 for 1st, 2nd, 3rd, and 4th places (high points wins), or 1, 2, 3, and 4 points for 1st, 2nd, 3rd, and 4th places (low points wins). The points are then totaled and the winners decided.

The Times method uses a preset race schedule, wherein each car races the same number of times in each lane. Generally, the cars race against as many other cars as possible, but the heat mix does not affect the outcome. The heat times are accumulated, and then trophies are awarded based on the lowest cumulative time, or lowest average time.

Points – Advantages/Disadvantages
Let’s first look at the advantages and disadvantages of the Points method.

Advantages

  • Does not require a timer.
  • The audience can “validate” the heat results by seeing that the finish order on the scoreboard matches what they witnessed. This leads to higher audience confidence.
  • The eventual winner of the race is not obvious, and cannot be decided until the heats are completed (with Times, the audience can oftentimes pick out the fastest car by watching the timer results). This leads to more excitement and anticipation at the race.
  • Heat placement is meaningful. A car must place well in the heats in order to place well overall (with Times, heat placement is largely irrelevant).
  • A poor heat only slightly penalizes a car (with Times, a slow heat oftentimes eliminates the car from any chance of winning).
  • If the operator running the start gate causes a slow heat (which can happen with the older style gates), the results are still valid as the heat time is irrelevant. With Times, the heat would need to be rerun (if the problem was detected).

Disadvantages

  • More heats are required. With Times, only 1 heat per lane is required to determine the trophy winners. With Points, depending on the number of cars, an additional round (or more) will likely be needed to accurately give out the trophies.
  • Heat mix affects the results. As described earlier, if scheduled to race against predominantly faster cars, a given car will be penalized.

Times – Advantages/Disadvantages
Now, let’s look at the advantages and disadvantages of the Times method.

Advantages

  • Fewer heats are required – only 1 heat per lane.
  • Heat mix does not affect the results.

Disadvantages

  • Requires a timer.
  • The audience cannot ‘validate’ the heat results. The timer must be trusted to accurately capture each heat.
  • The final winner can sometimes be determined by the audience by simply watching the timer results.
  • The finish order within a given heat (or set of heats) is largely irrelevant. For example, if a car is scheduled to race against slower cars, that car can win every heat, and still not win a trophy. (How do you explain to a child that although their car never lost, they didn’t win?)
  • A poor heat significantly penalizes a car. To rectify this, the slowest heat can be eliminated before accumulating or averaging the heats.
  • On some tracks operator error can significantly affect times. A fool-proof starting gate is a must for this method of scoring.

Conclusion
After this analysis, I decided to stick with the Points method for our local race. I believe this method has fewer problems and is more easily understood and accepted by the participants and their parents.

However, I concede that the Times method has a place. If your race involves a large number of cars, then the Times method can greatly increase the speed of the event. Large events such as district or regional championship commonly use a Times method for scoring the race. But if you choose to use a Times method, make sure that the method is clearly explained to the participants.


Pinewood Derby Car Showcase

Hot Dog: Ron Bosma

I have 2 boys who have since grown out of Cub Scouts and the pinewood derby. But for several years our family looked foreword to our annual fun. We couldn’t build just 2 cars; we also had to build one each for my wife and I. This helped me get over the urge to help Alex and Greg too much with their creations.

Another leader and I always had a fun race after the boys were through. The pack would challenge each other and us until it was time to leave. Over the years we got better and better thanks to your newsletter, tools, and tips. Throughout the years we have built race cars, space shuttles, a dog car, a porcupine, and even a shark. With this hot dog car I ignored aerodynamics altogether to get a fun design. It wasn’t the fastest car that year, but the kids loved it and it ran respectable times. We have a lot of great pinewood derby memories and still really enjoy reading about other peoples experiences in the Pinewood Derby Times. Thanks Maximum Velocity!

Scooby-Doo: Kyle McInerney

This is my son’s second year Pinewood derby car. He was into Scooby-Doo more than anything. Scooby won best design and 4th out of 10 Tigers. It may not have been the fastest, but to my son it’s the best car ever.

Speeder: Bob Drag

In 2006, Glenn’s (my son’s) car placed 3rd out of 29 Tigers. This year, I asked him what his goal would be – looks or speed. He enthusiastically chose speed – he didn’t really care whether it looked good! So after researching car designs he fell in love with the look of ‘The Speeder’. After numerous hours of prep work, sanding the body, axle polishing, wheel prep, and weight placement to find the optimum center of gravity – that required all of Dad’s patience – we got the car put together. At the Pack race Glenn’s car placed 1st out of 21 Wolves, and the icing on the cake was that he also won 1st Place for the Best Car Design. Now, we’re off to the Council races!


Pinewood Derby Memory

Never too Late to Start

This was my first pinewood derby as a Dad. Due to lots of time constraints (Christmas break, where we went out of town, a science fair project for school that had concurrent preparatory time as the as pinewood derby, life in general, etc.) we started way too late, like the Thursday before the race. About the only thing that saved the day was that I had the forethought to subscribe to the Maximum Velocity newsletter in November!

Anyway, when installing the weights I accidentally splintered the wood severely, enough that it was beyond repair. Luckily, my son had selected a wedge-shaped car and still had enough wood to make another car out of the other half of the wood block. Obviously, the axle slots were not cut, but we went ahead anyway. My son sanded, painted, and put the pin stripes on the car. Then he helped polish the axles and wheels. We didn’t wet sand as my wife had already thought that I had gone “Down and Derby”, and I didn’t need to give her any more fuel for that fire! I hand drilled the axle holes, which I know is blasphemous, but it was my only choice. We lubricated with McLube Sailkote, since I had some for my sailboat. The wheels spun for a long time. After a rough alignment check we were ready.

At the weigh-in we started heavy, but got it down to 5.0 ounces. Since we had started so late I really had no hope, especially since there were no local rules published, and I saw lots of kit cars and speed wheels (no outlaw wheels, however) among the entrants.

After the first heat, my son and I got hopeful. As the heats wore on, and his friends slowly got eliminated, he got more excited. We made it to the 5th heat, where there were only 6 cars competing, before we were eliminated. So, out of 31 entrants, my son was tied for 5th. He was a little disappointed, but still very happy to have finished where he did.

Next year, we’re starting earlier; and we are buying the Pro-Body Tool!!

Christopher Brown


Q&A

Do you have any information related to Royal Ranger pinewood derby cars?

Yes, we have a couple of resources.

What would BSA wheels do if they were run inside-out? Would the outside side wall be smoother when hitting the guide rail, or would the car jump off the track?

I haven’t tried running them inside out, however, I think the performance would be much worse:

  1. The sidewall of the wheel would rub on the car body, which would be worse than the inside hub rubbing on the body.
  2. The raised lettering would cause more drag on the guide rail and car body than would the inside edge of the wheel.
  3. As you indicate, there might also be a tendency for the car to climb the rail.

If you try it, let know how it goes.

Would you be able to direct me to a design for an alligator car? We’re going all out this year, but are having trouble finding anything alligator oriented (at least something without an extended tail).

Here is an Alligator Car that looks good and would be relatively easy to build (car designed by Greg Walters).

Also, we do offer a Gator Body Skin (part 5324), and a Gator Decal Sheet (part 5354).

I think the car in the photo with the Gator Body Skin would be a good compromise between design and performance.

Pinewood Derby Times Volume 6, Issue 10

– Feature Article – Utilizing Video Systems in Your Race

– Pinewood Derby Car Showcase

– Memory – You Never Know

– Q&A


Utilizing Video Systems in Your Race
By Randy Lisano

More and more race coordinators these days are using projection systems or large TVs in their races for the benefit and enjoyment of their audiences. Not only are these systems great for displaying the race results, they can also be useful before and during the race for displaying a variety of material.

First of all, you need a computer, projector, projection screen, and a cable to connect the computer to the projector. If you don’t have a portable projection screen, you can simply use a blank section of wall. However, you may need to hang up a white sheet to make the projected image easier to see.

To connect the computer to the projector, most laptops have an external monitor port and/or an S-Video port. If connecting to a TV, you can use the S-Video connection; otherwise, use a regular computer video cable to connect to a projector. Once connected, you need to output the computer’s video signal to the projector/TV. Generally, this means holding down the Function (Fn) key and then pressing one of the F keys at the top of the keyboard. If the keyboard labeling does not make it obvious, check your owner’s manual for the appropriate F key to use. You may have to push the F key several times in order to send the video signal to both your laptop screen and the projector/TV. Once you have the video connection working, everything you see on the computer screen will be displayed on the projector/TV. Now you can start utilizing the system for your audience.

Before the race you can display a photo slideshow of last year’s race (cars, racers, candid shots, etc.), show a promotional video, or information on the race. Windows gives you an easy way to do a photo slideshow. Just drop the photos into a folder on your hard drive and then use the Windows Picture and Fax Viewer program to control the slideshow. If you have video from your last race, you can show that before your race as a primer. I have also heard of someone using a video with real race footage and spectacular crashes. You can also run a PowerPoint slideshow to display race rules, list of your racers and other information.

During the race there is a lot that you can display. If you have race management software that can interface to your timer, the audience really enjoys seeing the race results as each heat is run. You can also display the final race standings and list of awards during your awards ceremony. If you have a video camera hooked up to the computer, you can even display some live action video, instant video replays1 or photo finishes2. This may also help those that cannot get a good view of the finish line to be able to see the action. Also, during the race, sometimes problems occur which cause a delay. You can use the projection system to help stall for time by distracting the audience with a funny video, or slides with derby song lyrics that they can sing along with.

The use of a projection systems or large TV can greatly enhance the enjoyment of the race for your audience, by keeping them informed of race results, entertaining them, and even by giving them an alternative view of the race action. If you have access to such a system, it is highly worth the time to setup and use.

On a final note, don’t forget to save your photos and video footage for use at your next race!

1Lisano Enterprises, developer of GrandPrix Race Manager software, also offers RaceReplay, a software package that records race video, and displays instant video replays.

2eTekGadget, makers of the SmartLine timers, offer a photo finish device and software combo.

Randy Lisano is the owner of Lisano Enterprise, makers of GrandPrix Race Manager, RaceFX and RaceReplay software, and other race products. He also maintains these race related websites:

GrandPrix Software Central
GrandPrix Race Central
Derby Talk


Pinewood Derby Car Showcase

SpongBob: Don Jones

This is the car I made for the adult race. He is made with a real sponge. Although he wasn’t a winner he was a kid favorite!

Twins: Dutch Weathers

In my son Jack’s first year in the pinewood derby I cut out two cars so we could build them together (his car is the red one). I showed him what to do on mine, and he did the same to his. His attention span was quite short at times, so I helped him complete some tasks. I think there are three different layers of paint because he kept changing his mind about the color. When race day came, he was ecstatic; his car came in first out of all the Tigers. Here in Bergen County, New Jersey, the Tigers have their own race in the Regionals. We had a bit of a problem here because the Regionals require that all four wheels touch the ground. So we had to fill in the axle hole and drill a new one. We made the change, and his car went on to win the Regionals. Something that surprised me was how much faster my car was than his. We used my car as the prototype, and used the best wheels and axles on his car. The wheels on my car were a lot sloppier on the axles than his, they wobbled a lot when spun. We didn’t have a test track, so we didn’t find out my car was faster until I raced his after the derby was over.

Tank: Jon Joslin

My son Tommy and I have been working on our first Awana car since our Christmas break. I ordered your booklet of suggestions for making a derby car in early December, then I ordered several of your speed products. Tommy wanted to paint the car ‘camo’ colors, so we decided on the tank design. Being our first project, we have spent many hours already, and still have a ways to go. Melting and pouring lead into holes in the back of the car has been the most challenging part, but we were successful in obtaining 5.03 oz on an electronic balance with the COG about 1.75″ in front of the back axle. Our derby is in February, so we still have time to polish and lubricate the axles, and go through the alignment process. We are looking forward to the final event in February, and have already started making plans for next year’s design.

Editor’s Note: We strongly recommend not melting lead, as it is a potentially dangerous practice.


Pinewood Derby Memory

You Never Know

My Son, Zachary is now a Webelo 1. We have been racing Pinewood Derby in our Pack since he was a Tiger. His first race was a heart breaker to say the least. His car came in third out of three cars! But, he got to go on to the District race because the top three from each Den gets to go.

The car was a disaster from the beginning. We used a standard Cub Scout block, and I just about cut off a finger trying to work on it! We had the wrong kind of paint, and had to put it on the stove to get the paint to dry, since we didn’t get it finished till the night before the race.

Before the District race, we had some more time to work on it. Well, the extra work didn’t do anything but make it run slower. It barely made it to the finish line! We were both heart broken, and he looked at me as if to say, “What happened former Cub Scout, Eagle Scout, now Den Leader?” I just told him that we learned from our mistakes, and we would work harder next year.

The next year he was a Wolf. This year we bought a kit instead of using the Cub Scout block, but we used the official BSA wheels from the official kit. We put the weight inside the car, which was a rail type. The night before the race while we where helping set up the track it ran fantastic! But the day of the race, we found out it was way too light. So, we added weight to the back. Well again, he came in last. I believe that adding the extra weight at the last minute threw off the balance of the car. I had put it towards the back.

So last year, we went with the rail type kit again. But instead of putting the weight inside, we got the weights that go across the full bottom of the car. I took a few off just in case it was over weight, but could add on at the last minute if need be. It came in at 5 oz. exactly.

Needless to say, he came in first in his Den, and third in the Pack. Then third in the District race a few weeks later. We where both very happy campers after that.

Funny thing is, the Cub who came in first in the Pack had hardly done any work on his car. He stood at the weigh-in putting washer’s on his car until it got to 5 ounces. Then he taped them on with masking tape!!! He didn’t place at District, but still! Like I told my son, it just goes to show you, you just never know how your car is going to run.

Our Pack race is going to be at the end of January this year. We are again going with the rail-type. I’ll let you know how we do!

Don Hoard
Cubmaster, Pack 202 in Greenbelt, Maryland


Q&A

Has anyone ever done a study on lifting a rear wheel instead of a front wheel?

Generally, cars perform better with the weight shifted to the rear of the car. If you raise a rear wheel, the car will rock towards the raised wheel, resulting in the car running with the nose angled upward. Thus, the front wheel is always raised (on a rear-weighted car).

We are looking to build a chamber inside a pinewood derby car. The chamber would be larger in the back, smaller in the front, and long enough for the powder to flow back and forth. Tungsten powder would fill the back of the chamber, and as the car tilts to the downward position the powder would flow towards the front of the car, giving it an extra push. Would this work?

The tungsten powder would flow as you suggest. However, I don’t recommend doing this for two reasons:

  1. Most rules require all parts to be firmly secured. Moveable weight is typically disallowed.
  2. More importantly, having the weight shift to the front of the car on the incline will slow the car down. Best speed is achieved with the weight towards the rear of the car. The goal is to have the balance point of the car located at about 3/4 and 1 inch in front of the rear axle.

Some advantage might be gained if the weight was located at the rear while the car negotiated the slope and transition, and then the weight moved to the middle while the car was on the flat. This would equalize the load on the wheels (this assumes a four-wheel-on-the-ground car), allowing the car to maintain speed for a longer period time. But of course, a setup that would move the weight in this manner would still violate the moveable weight rule.

I am using a 3000 grit paper to polish axles. The axles are always leaving a black mark on the sandpaper, which seems odd. No matter how much I polish them, they always leave marks on the paper. Is this normal?

Polishing involves removing increasingly smaller particles of material from the axles, resulting in a smoother finish. What you are seeing on the polishing paper is the axle material (zinc, nickel, or steel) that is being removed. As long as you keep polishing, material will continue to be removed, leaving black marks on the paper.

Pinewood Derby Times Volume 6, Issue 9

– Feature Article – Effect of Track Configuration on Car Performance

– Pinewood Derby Car Showcase

– Memory – Yes, Sir, That’s my Derby

– Q&A


Effect of Track Configuration on Car Performance

I have often been asked about the specifications of the ‘official’ pinewood derby track. A standard length, a standard height, a standard radius for the transition: if it were only so.

As you likely know, there is not one standard for pinewood derby tracks, so manufacturers are free to offer their own design. And of course, “do-it-yourselfers” build tracks based on existing plans, or their own conception. All of this leads to tracks of varying lengths, heights, transitions (some with no transition), and surface materials.

With this wide variety of racing conditions, the question for car builders is, “For a given track configuration, what car design elements will produce the best results?” This is actually quite a broad question, and thus cannot be fully answered in this brief article. However, I will provide some basic design considerations when confronting various track configurations. To simplify matters I will assume a center-guide track with an initial slope, a curved transition, followed by a flat section.1

Center of Gravity
Before discussing track configurations, a brief review of the Center of Gravity (COG) is appropriate. The COG is the point at which the completed car balances front-to-back. A COG further back on the car will produce more speed, but will sacrifice some stability. A COG of 1 to 1-1/4 inches in front of the rear axle is appropriate for most tracks. A more aggressive COG (closer to the rear axle) can achieve better results under optimum track conditions, while a more conservative COG (further from the rear axle) is more appropriate for adverse conditions. With this in mind, let’s discuss tracks.

Height Of Starting Gate
The height of the starting gate from the floor dictates the amount of potential energy that is available to the car. Thus, a higher starting gate will produce higher speeds, which in turn require more stable cars. The starting gate of most tracks is approximately 4 feet. At this height, no special consideration is required. However, if you will be running on a track with a higher starting gate, then a less aggressive COG may be required if warranted by other track factors.

Transition Radius
A large transition radius (see Figure 1) is slightly more ‘gentle’ on cars, thus allowing a more aggressive configuration. On the other hand the front end of cars equipped with a very aggressive COG will tend to lift slightly when negotiating a small transition radius. Most of the manufacturers offer a large transition radius, while one manufacturer offers a slightly smaller transition radius.2


Figure 1
Transition Radius Comparison
Track Length
Longer tracks have a longer horizontal run-out, thus providing more opportunity for cars to slow down before reaching the finish line. To maintain momentum on longer tracks, cars must be at maximum weight, have good aerodynamics, and must be as frictionless as possible. In addition, a less aggressive COG will generally provide better results, as the frictional forces will be more evenly divided among the wheels.

Track Surface
Smooth track surfaces produce faster results and allow for more aggressive car configurations. Thus, on smooth tracks, the COG can be moved further to the rear of the car. Rougher tracks require a more stable configuration with a COG closer to the center of the car.

Track Tilt
Tracks should be virtually level side-to-side. However, it is of course impossible to achieve a perfectly level state, so all tracks will exhibit some amount of side-to-side tilt. This results in cars moving towards the lower side until the guide rail is encountered.

The fastest times will be achieved when the amount of guide rail contact is minimized. However, recognizing that some guide rail contact will occur, and that the side-to-side tilt of the track cannot be predicted, is there any advantage to purposely ‘steering’ the car left or right? Some anecdotal evidence indicates that if the car is equipped with a raised front wheel (the car runs on three wheels), then it is best to minimize contact with the raised wheel.3 To accomplish this, the car can be aligned to purposely ‘steer’ towards the side of the car on which the raised wheel is mounted. This eliminates any contact between the guide rail and the raised wheel, possibly increasing performance.

Practical Considerations

  1. Each track has its own performance characteristics. This article discusses general design considerations based on track configuration, however, to accurately ascertain the performance characteristics of a given track, tests must be run on that specific track.
  2. Sometimes the track configuration at a local event and the subsequent district event are quite different. In this case, consider designing the car with adjustable weight so that the COG can be changed between events.
  3. Regardless of the track, smooth and round wheels, polished axles, good lubrication, and good alignment will overcome many obstacles.

1All of the commercial track manufacturers produce a track with these design features, except for one (SuperTimer) which has side guides.

2The original BestTrack transition was quite small, however, that was replaced several years ago with a larger radius.

3One advantage to a raised wheel is that it does not have to spin while the car is accelerating. However, if the raised wheel contacts the guide rail, it will be spun-up, thus robbing some energy from the car.


Pinewood Derby Car Showcase

Show Cars: Joe Burns

I was at my in-law’s house over the holidays, and their neighbor came over and asked if I wanted to see his son’s pinewood derby cars. This neighbor works in a body shop and it shows. The cars have an unbelievable amount of detail – the pictures don’t do the cars justice. They built all these from scratch without kits like they have today.

Model T: Duane Rubink

This car was built by my dad and me about 34 years ago; it’s my pride and joy. My dad is such a talented woodworker. I remember this car ran just like an old model T, shaky and slow, but what a looker! It’s pretty old and beat up now, but it is of great value to me.

It’s Fast!: John Phillips

I made this car for last year’s races. The side rails are 1/32 inch aircraft plywood, with a wire starting bar. I don’t really have a name for the car but it is fast!


Pinewood Derby Memory

Yes, Sir, That’s my Derby

Whenever I hear about a childhood competition, it brings back memories of the contests I took part in as a youth – memories of everything from slightly embarrassing mishaps, like going back for a catch in centerfield and tumbling head-over-heels like Clouseau going over a couch, to those really earth-shattering failures I’d rather not elaborate on here.

The reason I bring this up is because several scout troops on the North Shore held their annual Pinewood Derbies this past weekend. This is not to be confused with the Soap Box Derby, in which small children are placed into wooden boxes and sent hurtling down a hill toward a pile of none-too-comforting bales of hay. (I recall asking my mother if I could participate in one of these, and she was diplomatic, answering, “Not while I have breath left in my lungs.”)

No, the Pinewood Derby is the event in which you are issued a block of wood and four plastic wheels and asked to turn it into something aerodynamically suitable for racing – the “you” in most cases being, of course, your father. My particular father has a long history of “helping” us with various projects and assignments, and if I’m not mistaken is still smarting over the C+ my “sister” received on a 10th grade English essay.

Anyway, in this instance – my first year as a Cub Scout – we divided up the car-building chores, my father handling carving the wood and attaching the plastic wheels, while I, working painstakingly well into the night, picked the color. (Red.)

As far as the specifics of our model, my father and I decided to concentrate on function over form – specifically, on weight. Back then there were no limits to how much your car could weigh, so we dug out a good portion of the front of the car and filled it with lead fishing weights, and covered the consequent hole with a large, metal plate. The result was an 8-by-2-inch car whose nose weighed more than my brother.

And soon it was time to put it to the test. The big race was held in conjunction with our summer barbecue at our local county park, which was one of those parks you find in New York with a murky lake and a man-made beach; if you dug down far enough through the sand with your little shovel you would actually hit the plastic lining.

The race was supposed to take place after swim time, but as I approached the race area, eating a hot dog and picking seaweed (lakeweed?) off myself, I noticed the medals had already been awarded – and next to my car was a big, fat empty space. Of course, next to Billy Enderlee’s car was a gold medal.

My initial thought was that they’d run the races without us present, sparing me the indignity of watching myself lose to Billy, who’d had it in for me ever since I accidentally thwocked him in the head with a ball during baseball practice. But as they gathered us together, it became clear that those initial medals were just for presentation – which made sense, as Billy’s car had been meticulously carved into the shape of an alligator more sophisticated than any 8-year-old could even visualize, much less execute. It was the envy of every father there.

So my heart pounded in my chest as the true test of our wooden creations began. I watched as the scoutmaster put my car on the starting line and flicked the switch letting the cars loose. It hung in the air for a second, as if hesitating momentarily – and then whipped down the track like a bobsled slathered in baby oil.

The other fathers’ cars never knew what hit them.

My car progressed through the heats, beating the James Bond car, the Starsky & Hutch car, the car made to look like a stegosaurus (a notoriously slow dinosaur, incidentally), until only mine and Billy Enderlee’s alligator special remained. My father tried to remain calm, but he had that same look on his face he used to get on those rare occasions in the fourth quarter when it looked like the Giants might actually win a game. (I should mention that the Giants and I had about the same winning percentage at everything we tried during most of the 1970s.)

I remember that last heat distinctly; the alligator took off like a shot, my square red model tailing it ever-so-slightly. The whole course was negotiable in about 12 seconds, but time stood still as they shot down the track. The crowd stood silent. A bead of sweat appeared on my father’s forehead. My stomach rumbled, and I realized I hadn’t finished my hot dog.

And then, as my dragster inched its lead-weighted nose past the alligator to cross the finish line, the crowd exploded. Well, maybe it didn’t explode, but it seemed pleased.

My father stood beside me proudly as I was issued my medal, although both of us wondered later why the pack couldn’t have just sprung for a trophy. Regardless, we savored the moment, not realizing at the time it would be the first in a very short line of competitive accolades I would earn, capped off five years later with my “Most Improved Bowler” trophy.

I felt a little bad for Billy Enderlee, though, and even unofficially raced him a few times afterward until he finally beat me – by turning the alligator around and sending it down the track backwards. Too much weight in the tail; how many of us have been found ourselves undone by the same predicament?

Anyway, I hope the local scouts enjoyed their respective derbies last weekend, and realized, like I did, that it’s not about winning, but about doing your best. Or about your father doing his best. One of those two things.

Although, as I think my dad would attest, winning is not bad either.

Copyright ©2003 Peter Chianca
www.chianca-at-large.com
Reprinted by permission


Q&A

Our pack has switched from the BSA kits to the PineCar kits with solid axles this year. The explanation was that the nail axles were too difficult for most boys. My son worked hard to prepare his, and has won the pack 2 out 3 years, so we’re disappointed with the decision. Anyway, do you have any ideas on how best to prepare the solid axles? I don’t think we are allowed to cut them. We actually have 2 kits, and on every axle the heads are crooked.

Well, I don’t think your pack made things any easier, as the solid rod axles are not particularly easy to use.

If you can cut the axles in half (check with your race leader), then that would really help, as you can then properly set a wheel to car body gap, and you can mount them in a drill for polishing. If not, then make sure that the block is not too wide. You will likely need to narrow the block so that the wheel to car body gap is correct. When you do this, make sure to account for paint.

I’m not sure what to do about the bent tips. If the hub cap stays on, then they may be fine. But if not, I would try to replace them. You will need to polish the axles. Hopefully you can find a drill with a deep enough chuck so that you can insert the axle and clamp somewhere in the middle. Then polish both ends as you would with nail axle. Just avoid the end – if you reduce the end, then the hub cap may not stay on. You will also want to remove the mold flaw from the hub cap.

For next year, you might let your pack know about our MV Car kits. They use the BSA block, the PineCar wheels, and our speed axles. This is the best of all worlds (and they are less expensive than the PineCar kits). You can find them Here.

Would it help to cover the back of the wheels from the tread to the outer rim of the axle hub with a lightweight yet rigid plastic (adhering the plastic to the wheel of course)? I am thinking that this might reduce drag from the air the open areas catch as the car goes down the track. Do you know if this is in violation of any rules that you have heard?

Interesting idea. First, I don’t know how much aerodynamic loss there is in that area. Second, wheel weight is critical, so you may lose more by the added weight than you would gain by aerodynamics. Then, of course, the race inspectors may think you are hiding something, and want them removed. So, I would get it cleared with the officials before trying it.

When checking for the Center of Gravity, is that done with the wheels on or off?

The center of gravity is checked with the wheels on, and with all added accessories and weight.

Pinewood Derby Times Volume 6, Issue 8

– Feature Article – Top Fuel Cars: Rocket, Rubber Band, and More

– Q&A


Top Fuel Cars: Rocket, Rubber Band, and More
By Dave Noble

(The second in a series of articles on cars that ‘stretch the rules’)

My hobby is pinewood derby cars, especially cars that ‘stretch the rules’ just a bit. Even though my son is way beyond Cub Scout years, I still go to the pinewood derby each year to demonstrate my latest invention, and to put on a show for the kids and their parents. But before I tell you about my cars, let me share a little history so that you can see how I got the pinewood derby bug.

Background
During his first year as a cub scout my son Bret’s best friend was 3 years ahead of him. So when the pinewood derby came around he quickly found that his friend had all kinds of tips and tricks on how to make a pinewood car go fast. Little did he know that when he started to win, a curse would follow!

During his first pinewood derby race, Bret’s car was nearly as fast as the first place car. Everyone loves an underdog, and they were chanting, “Go Bret!”

The second year – when he built a car that was fast enough to win the derby and also District – no one was chanting, “Go Bret!” anymore (remember, they always chant for the underdog). During this second year at the district race there was an unlimited division. In that division were several rocket-powered cars. The cars were self-starting, with a switch on the front that fired the rocket motor automatically when the starting pin dropped. Sometimes a rocket motor would not fire. This was the ‘kiss of death’, since the winner was picked by average time. Bret and I took all of this in and wondered how the automatic firing device worked.

For his third year of racing Bret decided to build a ‘pretty’ car, even if it did not win. Winning was no longer important – he just wanted to be accepted. But to his dismay even the ‘pretty’ car won by a hair. The electronic finish line was really needed as the race was so close that even stop action video could not call the race.

The last year in Cub Scouts, Bret felt that he was an outsider, and no one wanted him to win. So he built a car that was faster than any car before, even beating his newest best friend. This car was fast enough that for the next seven years, when the car was entered into races against the winner of the derby, it was undefeated. Finally, someone built a three-wheeled car that beat Bret’s car by half a length. Since that time we have made changes to the car. Now outlaw wheels are mounted inside of the regulation wheels. The regulation wheels do not touch the track.


Bret’s Car with Outlaw Wheels Mounted Inside
Bret moved on to Boy Scouts, and the first year the Eagle Scouts decided to sponsor a pinewood derby just for the Scouts in the troop. Every one knew about Bret’s reputation. Bret announced that he would not compete so that others would have a chance. When the winner was presented with a cash prize of fifty dollars, Bret exclaimed, “Dad I think I messed up on that one!”

A Rocket Car
Later that year we attended the movie “October Sky”. The movie is about a boy and his friends that built model rockets during the Sputnik era. After the movie I asked Bret this question: “How would you like to build a rocket powered pinewood derby car?” The answer was a resounding, “YES!”

So, we got out the video we had shot years before at the district race to try to figure out how the switches worked. We decided that we would need 3 switches. The first switch would turn the power on and off. The second switch, located in the front of the car, would trigger the firing mechanism when the starting pin dropped. The last switch on the top of the car was to arm the front switch (so that the rocket didn’t fire if switch one was turned on when the car was not against the starting pin). When Bret, his older scout friend, and I tried to figure out how to make this work, we were stumped. Suddenly Bret – who was only ten years-old at the time – announced, “I’ve got it!” Reluctantly, I gave the wires to him. About a minute later he correctly assembled the wires and switches so they worked.

The next step was to build the car and put all the wires and switches in place using the wiring pattern previously developed. I thought it would be neat to build a car that was only 5.0 ounces, but the final car weighed 6.5 ounces. We had no idea of how to test the car, but we wanted it to run on a normal pinewood track with no strings.

I remembered from my younger days building rocket boats that the rocket motor had to be mounted very straight in the back of the boat. We did not have a drill press, so instead we carefully used a variable speed drill to get the motor hole close to square.


First Rocket Car
We built a test track that was only 15 feet long (that was all the wood I had). The test track ended in the grass on the front lawn. When we fired the car, it was so much faster than we expected that when it hit the grass it tumbled like an airliner during a crash. The good news was that it stayed on the short track until it hit the grass.

The next year we took the rocket car to the pinewood derby. We test fired it the day before, just to show the other leaders that it would really stay on the track. When we fired the car the first time in front of a crowd, they screamed at the sheer speed. The car covered the 32 foot track in 0.8 seconds.

Over the years we have improved the speed of the rocket car. Wheel-work, removing weight from the car, overcharging the battery, and last year we went to a nickel-metal-hydride battery (much lighter than an alkaline battery). The original 6.5 ounces is now down to 5.1 ounces. We plan to go with outlaw wheels this next year to get the weight to 4.9 ounces. One other note, the little man ‘driving’ the rocket car gets ejected out of the car when the parachute charge goes off. We wanted to put a chute on him but there was not enough room in the car to hold it.

Rubber Band Car
The first year, the rocket car ran solo. The second year, we decided to give the rocket car some competition, so we built a rubber band car to run against it.


Rubber Band Car
(The rubber band is stored around the wheels)
The rubber band car started as a retired CO2 car built by my daughter, Andrea. We painted it florescent red, and mounted two cup hooks on the front of the car. Then I went to the hobby store to find a long rubber band. I found one 7 feet long that I could stretch to over 50 feet. I did some calculations and found that when it was stretched to 35 feet it would pull the 1.2 pound car 32 feet in about 1 second. I wanted a close race but I wanted the rocket car to win.


Rocket Car vs. Rubber Band Car
A Hobby
Time rolled on, and Bret graduated from high school. He was a very good student in school and announced that he was going to major in Electrical Engineering. I have never told my son anything to hold him back, but I will admit that when he said those words, I had the same proud feeling as when he stated he had figured out how the rocket car should be wired. Now that he is a 3-year engineering student, I can say, “Look what the pinewood derby did for my kid!”

With Bret in college I declared pinewood derby cars as a hobby, and decided it was time to build a rocket car that would be even faster than the original one. This one needed headlights and taillights. It also needed a better starting method, because rocket cars take about 0.25 seconds to fire the rocket motor. The car also needed to weigh less than 5.0 ounces, and it needed very fast wheels.

The new car needed a new wiring setup to power the two headlights and two taillights. I went back to the original wiring that Bret designed when he was ten years old, and copied it for the new car. When assembling the car I added a magnet onto the front of the car. The stake at our track is made of steel, so when it drops it gives the car a boost. I wired the car three times, tearing it apart again and again, because the car ended up too heavy. I had to get lighter wire. Finally after two weeks of working I had a finished car.


New Rocket Car
I have been invited back to the pack race each year, not to race in the derby, but to put on a show. The rocket car is of course part of the show. It is saved for last in order to keep everyone there till the end of the race (you know, some parents are always in a hurry and want to leave before the end of the race). This year we ran the new rocket car against the rubber band car. If you compared the earlier race with this one you will see a huge difference.

Here is a short video of the rocket car. In the video you will see a flash, and then see the rocket car hit the pillow at the end of the track. The headlights are so bright that the camera was blinded!

 MPEG of New Rocket Car versus Rubber Band Car
Video & Spinner Corvettes
During intermission, I demonstrate other special cars to keep the scouts interested. One car that is popular is the Video Car. This is a 1/25 scale Corvette plastic body that mounts over a pinewood body. Inside of the wood I hollowed out a place for a nine-volt battery. I mounted a tiny color video camera in place of the driver.

So that the Video Corvette would have something to shoot while running, I built a White Corvette with spinner wheels. The spinner wheel Corvette has outlaw wheels mounted inside of smaller wheels with the rubber removed to make sure that they do not touch the ground. I applied black magic marker on the outer wheel surface to make it look like a black tire. The outlaw wheels support the car, and if mounted loosely the outer wheels will spin. I made sure that the spinner wheel Corvette was faster than the video car, so that the video car will always have something to take a picture of when the cars run together.

Both cars weigh exactly five ounces and both have magnets mounted in the front for quick starts – we wouldn’t want the Corvettes to lose to a normal pinewood derby car! I use the magnets to help the scouts know what magnets can do, and that the method is not legal in normal pinewood derby racing.


Video Car

Spinner Wheel Car
The Video car has a built in transmitter so that it can broadcast the view a pinewood driver would have of the track. This is shown on close circuit television while the video car runs down the track. I usually ask the scouts to imagine what it would be like to ride in a pinewood derby car. Once the scouts have the image in their minds we have them watch the car on TV. Then we run it again, because once is never enough!

MPEG of Video Car Run
Other Cars

Another car that is popular is the ‘No Passing Zone Car’. This is based on the car that my son won district with in 1994, but with some not so legal modifications. The main one is that I used coat hangers to build wire wings that stick into the competitions lanes. These are just high enough to clear the track and just long enough to stop anything from passing it. Just to assure a win the coat hanger also sticks out on front of the car about 3 inches. This actually gives the car a 3 inch head start at the starting line.


No Passing Zone Car
The scouts always want to have this car run against the rocket car. I do not attempt this because the rocket car can also go straight up. We discovered this in 2002 when my son’s hand came off the starting lever, and being spring loaded the starting pin came up under the rocket car just as it passed over the stake. Quite a spectacle!

Another car that is well-liked is the ‘Eveready Battery Car’. It features a large six volt lantern battery and has an LED that flashes on the back. A small nine volt battery powers the LED because the larger battery does not have enough voltage. The main feature of this car is the weight – 2.5 pounds. It is fast, and has a lot of momentum. We use a pillow to stop all the cars. The Rocket Car pops the pillow up; the Battery Car just pushes it out of the way. The scouts love to see the power of the heavy car.


Eveready Battery Car
Conclusion
I have so much fun going back to the pinewood derby each year that I will keep doing it as long as the pack will invite me back. I try to develop something new for each year, using the new and sometimes crazy cars to illustrate the principles of inertia, friction, etc.

One reason I wrote this article is to encourage Dads everywhere to take more interest in the pinewood derby. More than anything else, this will help to develop your relationship with your son. It can also result in your son doing something great, because you made it your hobby too.


Q&A

What do you think of using very smooth plastic decals in the wheel well area to reduce friction?

Certainly you want the wheel hub to car body friction to be minimized. A plastic decal may help, as long as it creates a hard surface. If the decal flexes, then it actually could increase friction as the flexing would increase the surface area of contact (the hub essentially ‘sinks’ into the decal a little bit).

I don’t like the idea of running against bare wood (not smooth enough). Instead, I prefer to paint the side of the car, and then overcoat with a hard clear-coat. This leaves a hard, smooth finish for the hub to rub against. Add a bit of graphite, and you are ready to roll.

I noticed a series of three small, raised lines on the axles parallel to the head. Is it better to keep these lines on the axles (as a way to have less contact with the wheel bore if positioned correctly), or to remove them as would probably happen if one were to polish the axles? Also, do you know if these bumps will cause any concerns with the Pro-Axle Press I purchased?

I suggest not running on the ridges. So there are two choices:

  1. Remove the ridges. If you plan to use the Pro-Axle Press, you must remove the ridges before using the press. Otherwise, the ridges will eventually be imprinted into the press.
  2. Orient the axles such that the ridges are facing upwards. When mounted on the car, the bottom side of the axle contacts the wheel bore.

Where do you place feelers (whiskers) on the car?

For extended wheelbase cars, place the feelers between the axles. For standard wheelbase cars, place feelers in front of both axles. For more information on feelers, see “Feelers: Do they Work?” in Volume 6, Issue 7 – December 27, 2006.

Pinewood Derby Times Volume 6, Issue 7

– Feature Article – Feelers: Do they Work?

– Pinewood Derby Car Showcase

– Memory – Boy-Built Car

– Q&A


Feelers: Do they Work?

Feelers?1 What are you talking about? Well, do you know what automobile curb feelers are? These (largely obsolete) devices are spring-steel wires that protrude from underneath the car. They are positioned so that they extend just past the tires. When parking along a curb, the feelers contact the curb before the tires touch the curb. The feelers make a loud scratching noise which helps the driver park the vehicle without rubbing the tires on the curb (or parking too far away).

Clearly, we don’t park pinewood derby cars. But we do like to avoid contact with the center guide rail. So, what if feelers were installed which prevented the wheels from touching the guide rail. Would the frictional loss due to the feeler contact with the rail be less than, or greater than the frictional loss of the wheels touching the guide rail? Well let’s run an experiment and find out.

How To Construct Feelers
First, we must construct a car with feelers. I did this by first gluing a piece of wood onto both sides of the car. This extra wood is drilled to accept feelers. Next, I fashioned two types of feelers: (1) rolling bushings, and (2) thick nylon line.

Figures 1 and 2 below show the rolling bushings. These consist of Awana axles (0.092 OD smooth axles) and #4 Flanged Nylon Bushings (hardware store item). I lubricated the bushings with a drop of thin film oil.


Figure 1
Rolling Bushings Mounted on Car

Figure 2
Close-up of Rolling Bushing
The nylon line feelers are shown in Figure 3. I used 0.068 nylon line from a lawn edger. For both feeler types, holes were drilled in the wood extensions such that both feelers contact the guide rail just before the wheels, and prevent the wheels from contacting the guide rail.


Figure 3
Nylon Line Feelers
Test 1
As shown in the photos, I used an extended wheelbase car with outlaw-style wheels. The outlaw wheels were chosen as they tend to produce the most consistent results.

I aligned the car, and then made five runs without any feelers. Next, five runs were made with the Rolling Bushings, followed by five runs with the nylon feelers. This three step sequence was then repeated, except that due to the poor results, the nylon feeler runs were not repeated.

The tests were run on a 32 foot Piantedosi anodized aluminum track. The results are shown in Figure 4 below.

Trial No Feelers Bushings Nylon Line
1 2.527 2.542 2.702
2 2.527 2.549 2.614
3 2.526 2.535 2.665
4 2.523 2.542 2.635
5 2.526 2.546 2.616
Ave 2.526 2.543 2.646
6 2.526 2.544  
7 2.526 2.533  
8 2.526 2.547  
9 2.519 2.536  
10 2.527 2.538  
Ave 2.525 2.540  

Figure 4
Test Results for Outlaw Wheels

As shown in the data, both versions of feelers actually slowed down the car.

Test 2
After running these tests, it dawned on me that one of the big advantages of outlaw-style wheels is the minimal contact with the guide rail.(2) Therefore it is quite possible that the test results would have been different if standard BSA wheels were used. So, I prepared a set of BSA wheels, and repeated the tests with no feelers, and with the bushings. The results are shown in Figure 5.

Trial No Feelers Bushings
1 2.588 2.559
2 2.594 2.545
3 2.597 2.546
4 2.599 2.550
5 2.593 2.554
Ave 2.594 2.551
6 2.618 2.550
7 2.602 2.554
8 2.596 2.557
9 2.569 2.554
10 2.594 2.553
Ave 2.596 2.554

Figure 5
Test Results for BSA Wheels

Apparently, the BSA wheels generate significant losses when they contact the guide rail, so much so that the bushings provide a big advantage.

Conclusion
The testing indicates that when used with BSA wheels (and I assume any other type of standard profile wheel, such as PineCar or Awana), bushing-type feelers provide a significant advantage. But when using narrow profile wheels, the bushing are generally counterproductive.

Are feelers legal? I have never seen a rule set that prohibited feelers. However, I strongly suggest that you either get a ruling from your officials before using them, or be prepared to remove them at the check-in. You never know when a pinewood derby official may decide to ‘legislate from the bench’!

1Sometimes, these devices are called ‘whiskers’.

2Outlaw wheels contact the guide rail at the upper edge of the rail, resulting in less frictional losses than a standard pinewood derby wheel.


Pinewood Derby Car Showcase

Since we are out of submitted photos for the showcase, I thought I would share our cars from earlier this year.

Modified Wing: Elisa Davis

I built this car for my wife to run in the parent-sibling race. The body is an extended wing, which I modified with the side curves. I also had to enlarge the weight pocket to account for the wood reduction and the light weight wheels. Using a drop of Krytox 100 in each wheel hub, the car took 1st Place for speed.

Patriotic Stealth: Janel Davis

My daughter, Janel, built the Stealth, and did all the decorating. The stars came form a craft store, and the pinstriping is a hobby shop item. The car took 1st Place for speed, and 2nd Place for design.

Wing: Stephen Davis

My son, Stephen, built the Wing. The car took 2nd Place for speed. I’m afraid he will grow up with a complex, as he has never been able to best his sister in the derby! (just kidding).


Pinewood Derby Memory

Boy-Built Car

Fifth graders do not usually join Cub Scouts, but this kid did. He was a friend of a scout in my den; he joined in for a half year or so of fun before moving on to Boy Scouts. Having never seen a pinewood derby much less made a car, this was all new to him. He made a sleek sports car sort of design and painted it shiny silver. Nice job considering our cars are completely boy built in den meetings with nothing more fancy than a coping saw.

Weigh-in night showed the little car exceptionally light, so he used what change I had on hand in my purse: a handful of pennies, nickels, dimes, and quarters that he could add to the car until it reached the magic 5 ounces – or nearly so. Masking tape held them on (kind of ruined the ‘look’ of the car, but what do you do?).

Well this car came in 2nd Place in the den races, even though we had to keep adjusting the coins to hold them on. Time came for the main event where the top cars from each den raced against each other. Some cars were most definitely not boy-built, but engineer dad-built, and the boy’s car did not look to be the favorite. Guess what? It took 2nd Place in the pack. He was happy, and had done it himself!

Keep it simple, make it fun. Isn’t that what it is all about? The smile on the boy says YES!

Janis Tipton-King
Fremont, CA.


Q&A

What is the actual difference between Hob-E-Lube and Tube-O-Lube ? Last year I used Hob-E-Lube, but thinking about switching to Tube-o-Lube.

There are two main differences:

  1. Tube-o-Lube is ground finer, so less break-in is needed.
  2. Hob-E-Lube has molybdenum particles. In our testing, the presence of molybdenum slowed down performance. Moly is apparently an excellent lube for high-temperature, high-pressure, non-conductive applications, none of which apply to pinewood derby racing.

We used to carry Hob-E-Lube, and switched to Tube-O-Lube after testing both products.

I was wondering if you had ever built a car using springs?

A while back I published an article (“Putting Suspense Back into Pinewood Racing”, Volume 4, Issue 2) regarding a car that uses cantilevers as springs. This car, the Flex, uses the wood itself as a spring mechanism. See: Standard Flex and Extended Flex

This may not be the kind of springs you were thinking of, but using coil springs would be a serious technical challenge.

What diameter of wheel is best for speed?

In general you want larger diameter, but lighter weight wheels. This is because larger diameter wheels require fewer revolutions to complete the track, and can spin at a lower RPM.

There is an optimum diameter based on the geometry and weight of the wheel (provides the greatest mechanical advantage over friction). For “outlaw style” wheels, the optimum diameter is about 1.2 inches. For stock width wheels, the optimum diameter is slightly less.

Pinewood Derby Times Volume 6, Issue 6

– Feature Article – Why Do You Have a Pinewood Derby?

– Pinewood Derby Car Showcase

– Q&A


Why Do You Have a Pinewood Derby?

Have you ever considered the question, “Why Do You Have a Pinewood Derby”? I know I hadn’t until I ran across a posting in the DerbyTalk Forum that posed that question.

My immediate response was, “To have fun building and racing cars”. I suppose this purpose is okay, but it is not the only possible reason for holding a race. Other reasons to hold a derby can include education, competition, parent involvement, and others.

Why do you need to have a purpose for the event? Because effective events have a purpose, and all of the promotion, activities, and awards are focused on reinforcing that purpose. Seriously, if you have no purpose, then why have the event?

Can the event have more than one purpose? I believe so, but I recommend limiting the number of goals you are trying to achieve. Trying to meet one or two goals can be accomplished; trying to reach more goals is a recipe for failure.

In this article I will suggest several possible reasons for holding a pinewood derby race, and provide some ideas as to how these purposes can be reinforced through the event promotion, activities, and awards. My goal is to convince each of you to determine your purpose(s) for holding a pinewood derby race, and to make sure the race actually achieves the desired outcome.

Reason 1 – Education
Holding a pinewood derby race for the purpose of teaching the children in the organization is certainly a reasonable goal. But you must first decide what exactly you want to teach and whether the children are old enough for the topic.

Some teaching possibilities include: woodworking, physics, and machine tool use. Generally, this race purpose is best for older children.

 

Education
Woodworking Physics Principles
Promo Focus on craftsmanship and modeling

Offer ‘Show Division’ (cars not raced) and ‘Race Division’ (optional)

Prizes downplayed

Focus on how cars perform

Actual event can be time trials to test theories

Prizes optional or downplayed

Activities Wood tool training

Workshop for car body building

Field trip to professional wood shop

Demonstration of basic physics principles

Car configuration experiments

Field trip to science museum

Awards Best shape

Best car model

Best non-car model

Fastest car

Best use of weight

Most consistent times

Reason 2 – Competition
If the purpose of your event is simply a competition, then you can choose between holding a serious race, or a less serious race with a focus on sportsmanship. I believe serious racing should only be held for adults (corporate races, WIRL, etc.), whereas with children the focus should be on sportsmanship.

Competition
Serious Competition Sportsmanship
Promo Focus on making the fastest car

Win ‘Bragging rights’

Identify prizes (make them worthwhile)

Focus on building a fast car

“Do your best”

Help a friend

Build as a team

Downplay awards

Activities None required, but a workshop could be made available Sportsmanship lesson

General building workshop

Awards Fastest car

Best Design

Fastest team car

Best design, selected through participant voting (be careful that this isn’t a popularity contest)

Sportsmanship awards for helping, encouraging, etc.

Reason 3 – Parental Involvement
In some groups, getting the parents involved is an important goal. Since pinewood derby racing appeals to most Dads (and some Moms) it can be a way to get more parental participation.

Parental Involvement
Promotion “We need you” theme

Consider using pre-cut cars to minimize the need for tools

Consider offering a parent car and a child car, and let them race against each other

Pass out simple ‘how-to’ information

Downplay awards

Activities Offer several workshops, parents required at workshop
Awards Fastest car

‘Child beats parent’ awards

Best Design, selected through parent voting

Reason 4 – Fundraising
A pinewood derby can be a good fundraiser, but I don’t recommend the event as the primary pinewood derby race. Instead, hold a regular pinewood derby race with a different purpose, and then hold a second race as a fundraiser. Get companies to sponsor the event by providing food, prizes, etc. Then charge a somewhat large entry fee (this is where your funds come from) and give out donation receipts. You can also ask companies to sponsor one or more entries, which can be built by members of your club (make sure to put the company name on the car).

Fundraising
Promotion Allow entries from both inside and outside the organization

Hold the event at a shopping center or a large store

Activities Hold planning meetings to make sure the event runs smoothly
Awards Provided by sponsors

Fastest car

Best design

Reason 5 – Recruiting
Since pinewood derby events are very exciting, if done properly your main race can also serve as a recruiting tool.

Recruiting
Promotion Promote the event in the community (bulletin boards, local papers, libraries, schools, etc.)

Hold the event in a public place (store, shopping mall, park, etc.)

Have enrollment table with literature at a prominent place at the event

Provide cars for guests to race in a fun race. Give a prize to everyone entered.

Activities Hold planning meetings to make sure the event runs smoothly

Hold a workshop to build extra cars for guests

Awards Fastest car

Best design

Prize for all guests

Reason 6 – Just for Fun
One of the best reasons to have a pinewood derby race, especially the first race for your group, is “just for fun”. Basically, the event is organized to be exciting and enjoyable for all. The competitive aspect is downplayed (or non-existent).

Just for Fun
Promotion Promote the event as a fun time for all

Decorate the venue in a festive manner

Downplay awards, or promote silly/fun awards

Activities Hold workshops

Consider simpler kits that require less preparation

Awards Fastest car and slowest car (optional)

Best design, selected by participant voting

Series of additional certificates such as ‘Fastest Looking’, ‘Coolest’, ‘Silliest’, ‘Best non-Car’, etc. Try to have a certificate for everyone.

Conclusion
So, what is your reason for holding a pinewood derby race? I know that this next year I am going to carefully select our purpose, and then focus the event on that purpose. I hope that you will do the same.

Feedback
If you have a purpose for your race, please send me an email with your race purpose, and how you reinforce that purpose in the promotion, activities, and awards. I will plan to include some of your feedback in future editions of the newsletter.


Pinewood Derby Car Showcase

Pantera: Sean McLaughlin

This is my cool Pantera that I ran in last year’s Awana Grand Prix. My Dad carved it but I sanded it and painted most of it. The wing is balsa and the sides are pine that I glued to the Awana block. I didn’t win in the design contest but did come in third in the speed contest.

Kranston Wedges: Gary Kranston

In my daughter’s Adventure Guide race, the electronic finish line once again did not work, so two spotters were used on our six lane track. There were, understandably, some incorrect decisions on the close races, so one of the dads used his digital camcorder on each race so the results could be reviewed. After beating the same car easily in three heat races, we finished 2nd in the final heat when our car raced in lane 6, the slowest lane all day (it was so close we reviewed the video three times to confirm the winner – we’ll have to investigate what is wrong with that lane for next year).

My son’s green car participated in the local district Cub Scout pinewood derby. Out of eight cars entered for the Bear rank, his car finished 2nd, losing only to the eventual overall winner. Out of 56 total cars entered, we finished 4th, missing 3rd place by only 1/1000th of a second

Father/Son Cars: Jamie Hill
This is the first year my son was in Awana. It came time for the grand prix, so I wanted to design a car in a late model style with the wheels under the body. As you can see I achieved my goal (left car). My son (age 4) wanted a race car painted blue and with sharks on it (right car). Sad to say neither of us won a race (and I didn’t place for speed or design), but to my delight my son’s car took 3rd in speed and 1st in design. We left the race with our heads held high, as we were proud of our father/son effort.


Q&A

Can you tell me the ‘regulation’ axle positions for BSA pinewood cars?

  • From rear of block to center of rear slot: 15/16 inch
  • From center of rear slot to center of front slot: 4-3/8 inch
    Note that blocks do vary from kit to kit, so some tolerance needs to be allowed for kit variance.

So what is your opinion on rail riders? Some folks are reporting better results when they deliberately guide the car to the rail, versus trying to keep it as straight running as possible. This is counter-intuitive, so what do you, the experts, think?

The theory is that if you can’t guarantee that the car will go straight on a given track, then it is preferable to avoid having the raised wheel hit the guide rail. So the car is purposely aligned such that the front wheel on the ground steers towards the rail. In addition, the body width is narrowed in the front so that the front wheel contacts the rail before the rear wheel. Thus, only one wheel contacts the rail.

Clearly, having the car avoid contacting the rail is better. But, while you can adjust a car to go straight, you cannot control the track; i.e., a perfectly aligned car on an angled track will not go straight. So, given this condition, having one front wheel contact the guide rail is better than multiple wheels contacting the rail, and better than having the raised wheel contact the guide rail.

The amount of intentional deviation must be enough to cause the car to drift in the desired way regardless of the track condition or slope of the track. Typically, this is about 5 inches over 8 feet.

Has there ever been a study performed on grooved axles? It seems like the grooved axles should not outperform standard axles because the friction force has not decreased (since the mass and coefficient of friction are the same), but is now distributed across smaller surfaces of the grooved axle and wheel bore.

The only study of grooved axles, that I am aware of, shows that the grooves improve performance when using liquid lubes, and decrease performance when using dry lubes. The supposition is that the grooves help with the liquid lube by minimizing the amount of fluid in contact with the wheel (as the viscosity of the fluid slows down the system); while the grooves prevent the powdered lubes from being properly crushed and the excess eliminated.