Credibility of the Race

(Updated from the original article published in Volume 1, Issue 9, January 23, 2002)

As a derby leader, I am very much concerned with race credibility. Every participant in a derby wants to know that the race is completely fair, so the derby leader must take every precaution to ensure that there is no bias in the race. To the race participants, the race procedures must be above reproach.

Race bias can come in three ways:

– Intentional: A car or group of cars is unfairly treated by a race official (hopefully this never happens)

– Unintentional: A car or group of cars is unfairly treated due to poor race procedures

– Perceived: Even if all cars are in fact treated the same, a race participant or audience member can still believe that an entry is being treated unfairly.

To run a race with integrity, the derby leader must make every effort to eliminate all of these forms of bias.

The purpose of this article is to provide you with guidelines and practical steps you can follow to keep your race above reproach. Remember that the goal is not just to eliminate race bias, but to also eliminate any perception of bias by the audience and participants.

RACE RULES

The first and very important area to consider are the race rules. Most organizations provide very simplistic rules that are incomplete, and that can be interpreted in many ways. Therefore the rules must be:

– Complete: Thus, the rules should specify all car dimensions (maximum height, maximum overall width, minimum distance between the left and right wheels, maximum length, bottom clearance, wheel base); and allowed/disallowed wheel treatments, axle treatments, accessories, and weighting methods.

– Specific: If the intent of your rules is to ban specific design techniques, then the rules must specifically do so. If the rules do not specifically ban a particular technique, then entries using that technique should be allowed to participate. For example, consider the following rules:

1. A light sanding to remove flaws is allowed as long as the wheel retains the original width, diameter, and shape. The diameter of the wheel must be at least 1.170 inches.

2. The wheels may be lightly sanded.

Rule 1 is very specific as to what can be done with the wheels. A car with narrow wheels, H-Tread wheels, etc. would clearly be disqualified from a race using this rule.

On the other hand, rule 2 is ambiguous and could lead to problems. A car with narrow wheels or H-Tread wheels should be allowed to participate, since the rule does not disallow narrow wheels.

As an example of the need for complete and specific rules, one person wrote to me stating that they wanted to remove material from the wheels. This particular technique was not mentioned in their rules, so they asked a race official (not the head official) if the technique was allowed. The race official gave them permission. But at the weigh-in, the head official disallowed the technique, and the car was banned from the race. This was clearly a case of unintentional bias (hopefully it was not intentional), and could have easily been eliminated with clearly written rules.

CHECK-IN

The next area to consider is the check-in. The purpose of the check-in is to register, inspect, and impound the cars. This procedure must be done in a fair and consistent manner. Here are some specific ways to eliminate bias in this phase of the race:

– Dual Officials: Since race officials typically are the parents of one of the entrants, always have two officials perform the car inspection, including weighing the cars. These two officials must not be related to each other.

– Official Weighing Method: Regardless of the type of scale you use, make sure that all cars are weighed on the same scale (never use two or more scales as the official scale, as there will always be subtle differences between scales), and that the method of weighing is consistent for all cars. With our postal scale, instances have occurred where the scale display alternated between 5.0 and 5.1 ounces. So, our policy is that the scale must consistently show 5.0 ounces or under for 5 seconds before the car’s weight is consider official.

– Scale Location: Locate the official scale on a solid surface, away from any air ducts. Both airflow and a shaky surface can affect the readings on sensitive scales.

As an example of this problem, during one check-in our scale was located under an air-conditioning duct. Whenever airflow was present, the scale would read a slightly greater weight! Once we realized the problem, we covered the duct. But we had to reweigh all of the cars to make sure that everything was fair.

CAR STORAGE

If your check-in occurs immediately prior to your race, then storage is not an issue. But in some races the race evening is shortened by holding the check-in on a prior night. The cars are then stored until the race.

To ensure that our race is above reproach, two non-related officials store the cars, and then put a “seal” on the storage area. On the night of the race, the same two officials check to make sure the seal is not broken. The seal can be as simple as an adhesive label placed across the opening of the storage cabinet. The two race officials then initial the seal.

This process may seem excessive to you, but if a parent ever asks how we ensure that no tampering occurs while the cars are stored, we are ready with a good answer.

RACE FORMAT

Race formats can also introduce bias. We have covered race formats in much greater detail in other articles, however here are some basics.

– Elimination Method: Elimination methods are not as accurate at determining the fastest cars as other methods. However, they can be improved by, among other things, taking into account the number of lanes. With a two-lane track, a double elimination method can only determine the top two cars, not the top three (the third fastest car could get eliminated early by racing the fastest car and then the second fastest car). So with a two-lane track, third place must be determined by rerunning all eliminated cars. With a three or four-lane track, third place can be determined as long as the top two cars in each heat “win”, and the third and fourth place cars (on a four-lane track) “lose”.

– Points and Times Methods: A more fair way to run a race is for each car to race an equal number of times on each lane. If times are recorded, then the trophy winners can be determined by cumulative elapsed time or average time. Alternately, points can be awarded and then accumulated. However, since (except in a few cases) every car will not race an equal number of times against every other car, a finals round must be run to accurately determine the trophy winners.

– Lane Bias: Generally, one or more lanes on a given track are “fast”, while one or more lanes are “slow”. Thus, with any race method, it is important to randomize/equalize lane use. With Points or Times methods lane assignments are randomized or rotated. But with Elimination methods, care must be taken to randomize lane assignments. One way to do this is to have the entrants draw lots for the lane assignment prior to each heat. Alternately, lane assignments can be computer generated. In no case should the race officials select the lane assignment.

CAR HANDLING

One of the worse things that can happen in a race is for a child to drop their car. But even worse is for one of the race officials to drop (or even mishandle) a car! Thus, use a race procedure whereby the officials rarely if ever touch one of the cars. This means that each car owner picks up their car from the staging area, places the car on the track, and then returns the car to the staging area at the end of the race. In the case of very young or disabled car owners, parents or a sibling can take on the car handling responsibility.

FINISH LINE

– Manual Judging: Clearly, if an electronic finish line is not available, then two non-related judges must judge the races. The judges must agree on each finish, or the race must be re-run. If one of the officials misses the finish or cannot distinguish the winner, then rerun the heat. Don’t allow one judge to defer to the other.

– Electronic Judging: For finish lines that display the results to the audience (either on the finish line or via software on a projection screen), no special precaution is required. However, some finish lines display the results on a remote module. In any case where the results are not instantly displayed to the audience, two non-related judges must monitor the results.

CONCLUSION

I realize that to implement all of the above mentioned precautions will take extra work on the part of the race official. However, you must ask yourself one question. If a parent came to me and said, “My child’s car is being treated unfairly,” what would you say? If you have implemented all of the precautions above, you can ask the person to clarify, and then explain how the precautions you have taken ensure that each entry is treated fairly. But if you have not taken the necessary steps to eliminate race bias, you will find yourself in a tough situation.

From Pinewood Derby Times Volume 7, Issue 4

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Maximum Velocity Pinewood Derby Car Plans and Supplies

Pinewood Derby Car Showcase – January 28, 2014

Just one car this time, but it is a doozy!

Dan’s Model T Street Rod – Andy Holzer

During the summer of 2010 I attended a car club event at a drag race
track. The car owners could run the 1/8th or the 1/4 mile with their
cars (depending on how their cars teched out). I saw a friend’s car
there staged for another opportunity to run down the track. While
looking at Dan’s Model T Street Rod I thought to myself, this would
make an excellent extended wheelbase pinewood derby car.

I figured this would be a fairly straightforward build, not having to
make full fenders would make things easier. I started out and drew up
some plans based on the pictures I took at the track. The grille ended
up getting cut down, as it is quite difficult to use a drop axle on a
pinewood derby car and have it race down a standard pinewood derby
track. The body was s-t-r-e-t-c-h-e-d to use up the whole 7 inch
block, so the width looks fairly narrow (compared to the picture).

Now what to use for the motor? Dan’s car had a Chevrolet 396 engine
in it. I was thinking of looking for a model with a 396 to use in the
car. My son, Noah offered me a couple of small block Chevy motors to
use (from some models he has purchased for parts). I didn’t like the
way the Chevy small block looks in a street rod with the “siamesed”
exhaust ports, so I needed a big block. After some thought, I decided
to build the motor from wood (a pine – pinewood derby motor). So I did
some searching on the Internet to see what Chevy 396 parts looked like
(I should have taken better pictures of the motor). It may have been a
better idea to go and find a 1/25th scale motor for my car as I have
about 12 hours in the motor build. There were a lot of parts that were
made and then re-made after the learning had taken place making the
first round of parts.

At this point the motor was adding a lot of weight to the front end.
I had made some headers from 12 gauge copper wire (I was planning to
paint the copper wire silver). I removed most of the wood from the
radiator assembly and the front tank to make them as light as they
could be, but there was still a lot of weight on the front. The
headers weighed .15 ounce each.

I looked at a farm supply store for some aluminum 12 gauge wire and
found some, but it was electric fence wire and I needed to buy a
quarter mile of it (really didn’t know what I would use the other 1318
feet of wire for). I went to the Internet and looked up aluminum 12
gauge wire and found they use aluminum wire in jewelry (not that I
ever needed to know that). I went to a craft store and purchased 3
feet of it for about $3. The aluminum wire was much lighter. I bent up
another header quickly and was wondering what I should use for a
collector on the headers. I found some aluminum tubing I used for
diesel exhausts for a PWD 18 wheel truck. It seemed to be the right
size to fit over the 4 header tubes. I used a flat screwdriver to
crimp the collectors around the aluminum wire and epoxied the assembly
together after polishing each component.

After the motor was painted I was thinking of adding some spark plug
wires to the distributor and run them down to where the spark plugs
would be. I was thinking this would be a big pain to do and I probably
should pass. But I decided to try it. The spark plug wires on Dan’s
car are red, but only had 26 gauge, black copper wire. So I decided
to use the black wire even though it would not be easily seen.

So I went back to the Internet to find the firing order of a Chevy 396
and the direction of rotation of the distributor (if you are going to
do it you might as well do it right). I epoxied all of the wires to
the distributor and then split them into sides and drilled small holes
and epoxied the other end to the block near each header output. I
won’t say this was easy, but it wasn’t that bad. I also used a piece
of wire to create a belt on the exposed pulleys.


The Model T was fast but there were a lot of fast cars in the open
race, it took 5th place.

From Pinewood Derby Times Volume 13, Issue 9

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Maximum Velocity Pinewood Derby Car Plans and Supplies

Height of Weight Vs Performance

by Randy Davis

While looking through the index of Pinewood Derby Times articles, I
realized that I had never performed a test on the performance effect
of the height of the ballast weight. What an oversight. This topic
tends to bring out the extremes. A few people have told me that they
made a wing at the maximum allowable height and put the weight right
at the top of the wing. On the other hand, a larger group of folks
say that the weight must be at the bottom of the car, maybe even
hanging down a bit. These folks won’t even consider using a tungsten
canopy, as “that would make the weight too high”.

I have always believed that the height of the weight has only a
trivial impact on performance. From a physics viewpoint, given two
cars with the center of gravity at the same lengthwise location, but
with one having the center of gravity low on the car (LCG), while the
other has the center of gravity high on the car (HCG), the LCG car
will fall a greater distance. Referring to Figure 1, note that because
of the starting ramp angle, the fall distance for the HCG car is
actually less than the fall distance of the LCG car. The actual
difference is based on the slope angle. But on this hypothetical
track, the HCG car falls only 96.6% of the LCG car’s fall distance.


Figure 1 – Effect of Vertical Weight Position on Fall Distance

Although the LCG car will attain a higher speed, due to a pendulum
effect the HCG car will traverse the curved portion of the track
slightly faster than the LCG car. But unless the flat section of the
track is very short, the LCG car will overtake the HCG car on the flat
section.

But note that the example above is an extreme case, with the
difference in vertical CG of well over one inch. In most cases, the
difference between a high and low CG car is much less than one inch.

Well, enough of this speculation. Let’s do an experiment to see what
really happens.

EXPERIMENTAL SETUP
First, we need to create a car on which the vertical COG can be
changed without affecting any other factor.


Figure 2 – Vertical COG Test Car


Figure 3 – Bottom of Car with Weight and Spacers Inset

The car in Figure 2 has a 1-3/8 inch hole drilled completely through
the car, and a medicine bottle cap with a 1-3/8 inch internal diameter
is glued over the hole. The resulting cavity can hold a 3.25 ounce
tungsten round (9/32 inch thick) and two hollow plastic spacers (same
OD and thickness), and a thin plastic shim to prevent rattling. On
the bottom of the car, the hole is covered with a removable plate
(Figure 3).

The experiment starts with the tungsten round at the bottom and the
two spacers on the top. Three heats are run with this configuration.
Then the plate is removed, the round placed between the spacers, and
the plate replaced. After three heats with this configuration, the
round is placed above the two spacers, and six heats are run. Then
the configuration is changed back to the round in the middle for three
heats, followed by the round at the bottom for the final three heats.
Thus, six heats are run for each configuration.

To minimize variance in heats, Outlaw wheels, nickel speed axles, and
Krytox 100 lube were used. Also, additional ballast weight was added
to bring the car up to five ounces.

EXPERIMENTAL RESULTS
As I stated above, I expected the difference in COG height would have
a relatively trivial affect on performance. But I was surprised to
find that the height of the COG made absolutely no difference in
performance.

2.490 Sec – Low COG Average
2.491 Sec – Middle COG Average
2.490 Sec – High COG Average
.0016 Sec – Standard Deviation

The 1 millisecond variation between the averages is within the
standard deviation, so the difference of 1 millisecond is
statistically insignificant.

CONCLUSION
What does this all mean? Well, within reason(1) don’t worry about the
height of the COG. Certainly get the COG towards the back, keep your
car aerodynamically sleek, and have fun designing your dream car.

(1) In this test, the height of the COG varied by 9/16 inch without
any effect on performance. However, there could be a difference in
performance for more extreme swings in COG height.

From Pinewood Derby Times Volume 13, Issue 9

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Maximum Velocity Pinewood Derby Car Plans and Supplies

Pinewood Derby Memory – Mrs. Bubba’s Do’s and Don’ts

Do – put a towel down to catch paint / sawdust / graphite when using theĀ  Dining Room table as a base of operations.
Don’t – make it a “good” towel (you know the ones).

Do – use any smelly products (Paint, certain adhesives) outside so as not to “funk up” the house.
Don’t – bring wet cars back into the kitchen to dry. Especially don’t suspend them from the kitchen cabinet handles with a piece of wire.

Do – find a spot in the basement / garage for your workshop equipment.
Don’t – hide out there for hours on end with the door closed so that you aren’t able to hear her when she calls for you.

Do – build your wife a sweet Open Class car to her specifications.
Don’t – beat her car yearly in the Open Class.

Do – clean up and put everything away when you are done.
Don’t – clutter up the living room with derby kits, priority mail shipping boxes from Maximum Velocity, printouts of DerbyTalk posts, etc. Especially don’t clutter up the fireplace mantle with “in process” cars that you’re leaving there for inspiration.

Do – share with her stories about heartwarming derby triumphs (e.g., she appreciated “MOM Derby’s” success this year and thinks all you guys are sweet for helping her and her boy out).
Don’t – share with her stories about technical derby triumphs (e.g., new tools – she is not warm towards arcane derby details and/or subtle sales pitches).

Do – allow your younger ones to watch “Down and Derby” – mine think it’s hilarious.
Don’t – allow them to badger their mother about watching it again and again.

Do – clean up any used strips of sandpaper after polishing axles in the drill press.
Don’t – use her pizza scissors (or any other good scissors for that matter) to cut the aforementioned strips of sandpaper.

By Rick Sanner (Go-Bubba-Go on the DerbyTalk Forum)
Originally published on the DerbyTalk Forum
Used by Permission

From Pinewood Derby Times Volume 7, Issue 3

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Maximum Velocity Pinewood Derby Car Plans and Supplies

Pinewood Derby Car Showcase – January 17, 2014

PINEWOOD DERBY CAR SHOWCASE

Cub Scout Theme Cars – Bill & Zachary Williams

Attached is a picture of our recent pinewood derby cars that I thought you may want to share with the other subscribers. I included the car from this year, and the cars from the past two years to show our series of Cub Scout theme cars. When my son was a Tiger Cub, we made the “Flying Tiger”, and when he was a Wolf Cub, we made the “Speedy Wolf”. This year as a Bear Cub, we made the “Smokin’ Bear”. His bear car won first in den and first in pack for speed. He also won the appearance award for Best Scout Theme.

By the way, for the first time this year we used the new Tungsten Plates(1). This is a GREAT product!!! We used 6 of them (3 oz. total) under the rear section of the car. Three of them were recessed into the bottom of the car as to make them flush with the bottom of the car. The other three were mounted on top of these and hung below the bottom of the car. We still have plenty of clearance under the car. Our body was very light, about one ounce, and very light in the front of the car. These tungsten plates added an ENORMOUS amount of stability to the car. We only had to add about 2 tungsten cubes more weight to get to five ounces. This is one of the best new products I have seen come on the market.

Formula One – Chris & Jacob Holan


My son Jacob and I worked on this car for last year’s pinewood derby. He took one of his matchbox cars and asked me to put the design on the wood. We used a Dremel Tool to help with the fine details. He painted and put on the decals himself. The car took first place in design and would have done better during the race, but dad forgot the graphite for the wheels.

Mack Truck – Roger & Cole VandePoel

Attached is the Mack truck that my son Cole and I built and raced in this year’s annual Pack 48 Cub Scout pinewood derby. The truck has six wheels, the center two are raised slightly, such as not to touch the track and slow the truck down. We constructed the top of the cab from material that we removed from the rear. On the rear of the truck is it’s name “Easy Mack” named after Cole’s favorite lunch snack.

(1) Tungsten Plates are available at Here.

From Pinewood Derby Times Volume 7, Issue 3

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Maximum Velocity Pinewood Derby Car Plans and Supplies

Pinewood Derby Car Showcase – January 14, 2014

Cyc’s Factory Special – Bruce Edney


This car is built from a Stock Car kit and was raced with
PWDerbyracing.com. It came in second in the April race. (My other
Stock Car took first place in the same race, but it is not as good
looking! Looks don’t mean it will be fast!)

Awana Cars – Terry Walker

Here are our three cars from our Awana race this year. “1 Cross, 3
Nails, 4 Ever” used balsa to create the top design. “Two Face” used a
Hot Wheels car for part of the weight. The middle car, “Hydro” was my
first attempt at using PVC to create the cover to hide the weights.
Hydro was the fastest car, but all three designs were fun and
functional. My boys had a blast and are already talking about next
year.

Hammer Head – Charles Mott

We made this little shark so small and streamlined that even after
hollowing out the body and filling it with lead, it weighed only 3.5
ounces. So, we made the dorsal fin entirely out of lead. A hole was
drilled and tapped on the bottom of the fin. A threaded rod was
screwed into the fin, then ran through the body and secured with a nut
under the car.

In my son’s first heat the sensor at the end of the track
malfunctioned – TWICE! His car beat the other three easily on the
first two runs, and then came in a close 2nd on the third when they
finally got the sensor working. So, his overall average would have
been even lower than 2.42 if his first two runs had counted. Since he
still placed first after all heats were done, I didn’t complain much!

From Pinewood Derby Times Volume 13, Issue 8

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Maximum Velocity Pinewood Derby Car Plans and Supplies

Let’s Light it Up

By Randy Davis

Driving down the road, every vehicle you see has white headlights and
red taillights. Not only are these lights mandated by law, but they
greatly increase the visibility of the car for improved safety; and at
night, headlights are needed to help you see where you are going.

Of course, none of this is necessary for pinewood derby cars. But if
you did have lights on your car, you would certainly increase the
car’s visibility!

In today’s article, we will be reviewing four products that are
available for adding lights to your car. We will be looking at cost,
quality, ease of implementation, and ease of use.

SOME CAVEATS

First, there is no perfect solution for pinewood derby lighting. All
methods require some careful planning and woodworking.

Second, if your race will not be held immediately after the check-in
(in which case you would turn on the lights before turning in the
car), make sure that you will be allowed to turn on your lights prior
to the race (or make sure an official will do that for you). It would
be a real disappointment to implement lighting, and then find that you
were not able to turn on the lights after the car was checked in.

Finally, implementing lighting does add some weight to the car in
undesirable locations. However, the products are light-weight, so
likely the effect is quite small.

PRODUCT 1 – Fishing Bobber Light Refills(1)

Although the manufacture certainly never thought of pinewood derby
racing when developing this product, bobber light refills are one of
the easier ways to add lights to your car. These refills consist of a
metal tube holding a battery and an LED. The LED is pushed inwards to
turn on the LED, and then pulled outwards to turn it off. The tubes
are just over 1-1/4 inch long and fit nicely in an 11/64 inch hole.
They are available in yellow, red, and green.


Figure 1 – Bobber Lights

For my implementation, I purchased two yellow and two red – too bad
there is no white. Two holes were drilled into the front and back of
the block to accept the lights. But in order to turn them off and on,
you must be able to remove them from the car. So I added access holes
in the bottom of the car. After the lights are installed (don’t glue
them in – press fit only), a small screwdriver can be used to push
them back out of the car so the lights can be turned off or on.


Figure 2 – Bobber Lights Installed(2)


Figure 3 – Bottom of Car

Cost – $20.95 for four lights; includes First Class Mail Shipping

Quality – The lights work and are very bright. They are advertised to
last 21+ continuous hours of use.

Ease of Implementation – The easiest of all products to install, just
drill the four light holes, plus access holes.

Ease of Use – Each light must be individually turned on. They cannot
be glued in place, so the light holes must be exactly the right size.

PRODUCT 2 – Pinewood Headlights(3)

Pinewood Headlights consist of a circuit board with two attached,
white LEDs. A coin battery is installed on the circuit board. Also
included are instructions, double stick tape, and a spare battery
(nice touch). There is no switch; the lights are turned on by removing
a plastic tab, and turned off by replacing the tab.


Figure 4 – Pinewood Headlights
Photo Source: derbylights.com

To install the lights, two 1/8 inch holes were drilled into the front
of the block. A pocket was then created on the bottom of the block to
accept the circuit board. The depth of the pocket must be accurately
measured so that the board sits on the bottom of the pocket with the
LEDs inserted into the holes. I put a thin layer of wood filler in
the bottom of the pocket so that the double stick tape (included)
would have a smooth surface on which to stick.


Figure 5 – Pinewood Headlights Installed


Figure 6 – Bottom of Car

Cost – $12.00 for one set of headlights; includes First Class Mail
Shipping

Quality – The lights work and are very bright. The battery life is
estimated to be 10 hours. Note that no taillights are available.

Ease of Implementation – Because the lights are attached to the
circuit board, the pocket for the circuit board must be placed very
close to the end of the block. This can be difficult to do without
damaging the wood.

Ease of Use – Once installed, the lights can be turned on by removing
the tab. But to turn off the lights, or to replace the battery, the
circuit board must be removed. So the board cannot be permanently
glued into place (double sided tape is provided for installation).

PRODUCT 3 – Pinewood Lights(4)

Pinewood Lights consist of two white and two red LEDs, a do-it-
yourself circuit board, a battery, screws for attaching the board to
the car, and instructions. The completed circuit board includes a
power switch.


Figure 7 – Pinewood Lights
Photo Source: pinewoodlights.com

To install the lights, light holes were drilled with a 5/32 inch drill
bit. Next, pockets were created under the car to hold the circuit
board and for access to the lights. Finally, channels were machined
from the light holes to the pocket. The circuit board was then
constructed following the provided instructions.


Figure 8 – Pinewood Lights Installed(5)


Figure 9 – Bottom of Car(6)

Cost – $11.90 for one set of headlights and taillights; includes First
Class Mail Shipping

Quality – The lights work and are bright. The battery life is
estimated to be 20 hours.

Ease of Implementation – The instruction booklet is 16 pages long, and
seems quite complex. But after doing the project, I realize that many
of the pages explain the engineering/science of LEDs and circuit
boards. If you are all thumbs, this product is probably not for you.
But anyone with some handiness should be able to pull it off. But
note that because of the wiring, quite a bit of underbody woodworking
is required.

Ease of Use – Once installed, the lights can be turned on or off with
a switch on the circuit board. But to replace the battery, a piece of
copper tape must be cut, removed, and then replaced. To do this the
board would need to be removed from the bottom of the car (4 screws –
I only used two in Figure 9). Extra copper tape is provided.

PRODUCT 4 – Flashing Light Bar(7)

The Flashing Light Bar consists of a pre-wired light bar, switch,
circuit board, and battery holder. Two batteries (included) are
required. When turned on, the light bar flashes red, blue, and white
in sequence.


Figure 10 – Flashing Light Bar

To install the light bar, a hole (actually a slot works better) was
drilled into the top of the car and continuing into a pocket under the
car. But how do you get the wires fed through the top of the car?
Well, according to the instructions, you cut the wires, feed them
through the hole, and then twist them back together again (applying
electrical tape – not supplied).


Figure 11 – Flashing Light Bar in Action(8)


Figure 12 – Bottom of Car(9)

Cost – $15-20 from various retailers. Includes First Class Mail
Shipping

Quality – The lights work and are bright. No estimate is provided for
the battery life. The quality of the unit itself is iffy. The one I
purchased had a corroded switch, the light cover was detached from the
light bar circuit board, and one of the wires had to be re-soldered to
the light bar circuit board.

Ease of Implementation – The product is straightforward to implement,
although having to cut and splice wires is not the best solution
(a simple plug connector would be a much better solution). Coupling
this with the quality issues, this product is recommended only for
handy people.

Ease of Use – Once installed, the lights can be turned on or off with
a switch. The batteries are easy to replace.

Bringing it All Together
It seemed a shame to have these products and not make a completed car
so I chose two of the products to implement a police car. Obviously
the light bar was used, but I chose the “Pinewood Lights” product as
it had both white headlights and red taillights.

The resulting car is shown in Figure 13 and 14. A video of the lights
is available Here
(5.6 MB, 5 seconds)


Figure 13 – Completed Police Car


Figure 14 – Bottom of Completed Police Car(10)

CONCLUSION
If you want to light up your car, there are several readily available
products to choose from. But make sure to do your homework and select
the product that is best for you.

(1) Can be purchased from several on-line stores. I purchased
mine from gandermoutain.com

(2) Headlights are yellow and the taillights are red. LED light
does not photograph well.

(3) Available from derbylights.com. This company also offers a set
of scanner lights, which look very cool. They install in a similar way
to the headlights.

(4) Available from pinewoodlights.com

(5) Headlights are white and the taillights are red.

(6) I made the rear pocket for weight; it is not required for the
lights as the main pocket could have been used for access (the rear
light holes could have been drilled all the way to the middle pocket
as long as they are drilled high enough to clear the rear axle slot.
The middle pocket is larger than necessary; you will see why later in
the article.

(7) Manufactured by Amenco. Available at many on-line and walk-in
hobby stores.

(8) The photo doesn’t really do the product justice. See the
video later in the article.

(9) I didn’t make the wiring neat, as this was just a temporary
installation for the photos.

(10) The weights are not very neatly placed. Normally, I use epoxy
for weight, which allows time to reposition the weights. But for this
project I used hot glue so that I could remove the weight if there was
a problem with the lights. Hot Glue holds well, but gives virtually
no time for adjusting the weight.

From Pinewood Derby Times Volume 13, Issue 8

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(C)2013, Maximum Velocity, Inc. All rights reserved.

Maximum Velocity Pinewood Derby Car Plans and Supplies

Effect of Wheel Weight on Performance

One of the major changes to pinewood derby racing during the past serveral year was the wide-spread availability of light-weight speed wheels. For BSA, wheels ranging from 2.5 to 1.0 grams were offered by various vendors including Maximum Velocity.

But what is the performance benefit of lighter weight wheels? To help answer this question, I ran an experiment comparing 1.0, 1.9, and 2.9 gram wheels, the results of which are documented in this article.

However, first I want to position these results. This experiment shows the general effect of wheel weight on performance, and can be used to estimate the benefit of weight reduction. On the other hand, the results cannot be used to absolutely state the benefit of using any given 1.0 gram wheel versus any given heavier wheel. Many wheel-related factors affect speed including the quality of the raw wheel, the machining method, the weight-reduction technique, and the skill/accuracy of the lathe and lathe operator. Therefore, wheel weight is only one factor that should be considered when selecting a set of wheels.

EXPERIMENT EQUIPMENT

The experiment used the following equipment:

– Pinewood test body – This body allows the weight to be readily changed without affecting the balance point.

– Pro-Ultralite Speed Wheels from DerbyWorx(1) – These official BSA wheels weigh 1.0 gram, and are machined with a high level of accuracy

– Speed Axles from Maximum Velocity(2)

– Eight, 1-1/8 x 7/8 x 1/8 O-rings – One or two of these rings were inserted into each wheels to increase the weight

Car Body
The Pinewood Wizard body was set up to weigh 5.0 ounces with the wheels and axles (no o-rings). Sufficient tungsten beads to account for eight o-rings were included as part of the weight. The car was centered weighted, and all four wheels were running on the track (see Figure 1).


Figure 1 – Wizard Body Weighted for 1.0 Gram Wheels

Wheels
The O-Rings were cut, so that they could be inserted into the wheel interior without removing the wheels from the car (see Figure 2). This technique eliminated experimental variance that would have been introduced if the wheels were removed and re-installed during the experiment. Wheel weight was as follows:

– No O-Rings – 1.0 gram

– 1 O-Ring – 1.9 grams

– 2 O-Rings – 2.9 grams


Figure 2 – Wheels with 0, 1, and 2 O-Rings Inserted

Axles
The axles were lightly polished and then lubed with Krytox 100. The wheels/axles were installed on the car, and the alignment was checked to verify that the car rolled virtually straight.

Track
A 32 foot aluminum Freedom Track was used with a Judge Timer. For each run the car was staged in the left lane.

EXPERIMENT PROCEDURE
The car was first run twice for lube break-in. Then, to minimize lube variance, the tests were made from low to high wheel weight, and then again from high to low wheel weight. The sequence was as follows:

1. Three heats were run with the 1.0 gram wheel weight. An o-ring was then added to each wheel, and tungsten beads were removed symmetrically to maintain the 5.0 ounce weight and center balance point.
2. Three heats were run with the 1.9 gram wheel weight. A second o-ring was then added to each wheel, and the weight adjusted to 5.0 ounces.
3. Six heats were run with the 2.9 gram wheel weight. One o-ring was removed from each wheel, and the weight was adjusted.
4. Three additional heats were run with the 1.9 gram wheel weight. The last o-ring was removed, and the weight was adjusted.
5. Three heats were run with the 1.0 gram wheel weight.

EXPERIMENT RESULTS
The following chart shows the results of the test. The red plot shows the results of the raw data, and the blue plot shows the results with the high and low run removed for each weight.


Figure 3 – Experimental Results

CONCLUSIONS
When racing on a 32 foot track, wheel weight has a significant negative impact on performance. Running with the lightest possible wheels (while still maintaining structural integrity) will offer the best performance possibilities.

It is possible that the results of this experiment would vary on a longer track, however, it is my belief that lighter weight wheels will provide better performance on all tracks, with the possible exception of extremely long ‘monster’ tracks.

(1) Pro-Ultralite Speed Wheels are available at:
www.maximum-velocity.com/pinewood_derby_wheels_axles.htm

(2) Speed Axles are available at:
www.maximum-velocity.com/pinewood_derby_wheels_axles.htm
(scroll down to part #4095)

From Pinewood Derby Times Volume 7, Issue 3

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Maximum Velocity Pinewood Derby Car Plans and Supplies

Shop Talk: How to Tune a Band Saw

By Randy Davis

Back in my early days of pinewood derby racing I attended a workshop
and offered to help some folks cut out their cars. The saw that was
to be used was a bench top band saw. Unfortunately, the blade was
really too small for cutting blocks. But even worse, the blade was
not properly tensioned and the guides were not set right. So the
blade moved all over the place, making it very difficult to use and
making it quite unsafe. I am still amazed that the blade didn’t jump
off the wheels.

Since then I have learned quite a bit about adjusting band saws (some
from the “school of hard knocks”). Band saws are great for cutting
out cars, albeit a saw that must be used with great care. But if the
saw is not adjusted correctly, then it can really be a dangerous tool.

So, let’s look at the basic steps of adjusting a blade.

BLADE SELECTION

For most pinewood work, I recommend a Skip Tooth, 3/8 or 1/2 inch
blade, with 4 teeth per inch. However, the steps below apply to any
blade. For more discussion on band saws and blades, please see:
Choose the Right Band Saw for Pinewood Derby Cars in Volume 12, Issue 2.

BLADE TRACKING AND TENSION
After selecting the blade, it must be mounted on the wheels, and then
adjusted so that it runs in the center of the wheels (tracking) and
has the correct tension. Each time a blade is changed on the band
saw, this procedure must be followed.

Tracking and tension should be adjusted together. So, you must
incrementally increase the tension of the blade while adjusting the
tracking.


Figure 1 – Tension Knob

First, unplug the band saw, then slide the blade into place. Next,
apply a small amount of tension, and then rotate the upper wheel by
hand. As needed, adjust the tracking knob to move the blade to the
center of the wheel (normally a clockwise rotation moves the blade
outward, counterclockwise moves the blade inward). Keep rotating the
wheel, adding tension, and adjusting the tracking knob until the blade
is under full tension and tracking in the middle of the wheel.

Most band saws have tension marks to show the proper tension for each
blade width. Make sure to set the tension properly. Both over and
under tensioning can result in blade breakage, and under tensioning
makes cutting difficult and dangerous.


Figure 2 – Tension Knob and Marks

After achieving the proper tension, test the tracking under power.
Close the wheel covers and plug in the saw. Turn on the saw for a few
seconds and then turn it off again. Open the top door and check the
position of the blade. Make an adjustment if needed.

THRUST BEARINGS
The thrust bearings are the (normally two bearings, one is above and
the other below the table) wheels that sit behind the blade. These
bearings keep the blade from moving backwards when cutting. On some
saws, the blade contacts the outer diameter of the bearing. On others,
the blade contacts the face of the bearing.


Figure 3 – Thrust Bearings

While idling, the blade should sit just in front of the bearings.
Contact with the bearing only occurs when the blade is cutting.

To adjust the thrust bearings, set the guide assembly about 1/4 inch
above the saw table. Adjust the top and bottom thrust bearings so
that they are just behind the blade. A business card makes a good gap
gauge. Check your work by turning the saw on and off and watching the
thrust bearings. They should not rotate.


Figure 4 – Thrust Bearing Gap

SIDE GUIDES
The side guides keep the blade from moving left or right while
cutting. More expensive saws use guide wheels as side guides, while
less expensive saws use guide blocks.(1)


Figure 5 – Guide Wheels and Blocks

To adjust the guides, first move the guides until the front edge is
just behind the blade’s gullet (curved indent in the blade). This is
very important. If the teeth of the blade contact the guides, the
blade will become dull very quickly.


Figure 6 – Side Guide Front/Back Position

Next, adjust the distance between the guide and blade. As with the
thrust bearing, when idling the blade should not touch the side
guides. Set the gap between the side guides and the blade to the
thickness of a piece of paper. Make sure to set the gap on both of the
upper guides and both of the lower guides. Again, check your work by
turning the saw on and off and watching the thrust bearings. They
should not rotate. With guide blocks, no contact noise should be
heard.


Figure 7 – Side Guide Gap

CONCLUSION
Now that the band saw is properly adjusted, you are ready to cut out
some cars. Remember to keep safety at the forefront by wearing safety
glasses, not wearing loose clothing or jewelry, tying up long hair,
and keeping your fingers away from the blade.

If you would like more information on this topic, there is a great
article on the American Woodworker site posted at:
http://americanwoodworker.com/blogs/tools/archive/2010/03/15/tune-
your-bandsaw.aspx

(1) Guide blocks wear out, so they must be adjusted regularly. They
will eventually wear out and need to be replaced.

From Pinewood Derby Times Volume 13, Issue 7

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Maximum Velocity Pinewood Derby Car Plans and Supplies