Pinewood Derby Times Volume 8, Issue 15

– Feature Article – Derby Kits: Many Choices for Buyers

– Pinewood Derby Car Showcase

– Memory – Peter’s Car

– Q&A


Derby Kits: Many Choices for Buyers

Although the Cub Scout kit and the PineCar kit are likely the most widely distributed kits, there are a large variety of kits on the market today. In many cases, the kits are sold through the sponsoring club, but several of them are available to any group that would like to use them.

In this article, I will identify each kit, and provide details on kit preparation. The source for each of the tools and supplies mentioned can be found at the end of the article. In addition, there is an applicability chart for our specialty tools Here.

Cub Scout Grand Prix Pinewood Derby® Kit

The Cub Scout Grand Prix Pinewood Derby Kit consists of the following:

  • 1 Wood Block: 1-3/4W x 1-1/4H x 7L inches, offset 1/8 inch deep axle slots, with a wheelbase of 4-3/8 inches
  • 4 Nail Axles
  • 4 Wheels: hard plastic, full profile, solid sidewall, raised lettering “BSA Pinewood Derby”

Block Tips

  • Use a square to verify that the axle slots are square to the block. If not, replace the block.
  • Use the axle slot closest to the end of the block as the rear axle.
  • Use the Pro-Body Tool to pilot drill the axle slots (or if allowed by the local rules, use the Pro-Body Tool to drill axle holes on the opposite side of the block).

Axle Tips

  • Remove the burrs under the nail head, and the crimp marks on the shaft with a Mini-File. Place the axle in the chuck of a drill (head outwards), and apply the file to the spinning axle. To minimize contact with the wheel hub, slightly bevel the axle head with the file.
  • Straighten and round the axle shaft with the Pro-Axle Press
  • Polish with an Axle Polishing Kit

Wheel Tips

  • Optionally, use the Pro-Wheel Shaver to true the wheel before polishing. – Using a Pro-Wheel Mandrel, polish the tread surface and inside edge with wet, 600 grit sandpaper.
  • Use the Pro-Hub Tool to bevel the inside wheel.
  • Polish inside the wheel bore with Wheel Bore Polish.
  • Lubricate with graphite or specialty oil.

Awana Grand Prix Car Kit

The Awana Grand Prix Kit consists of the following:

  • 1 Wood Block: 1-3/4W x 1-1/2H x 6-13/16L inches, centered 3/16 inch deep axle slots with a wheelbase of 3-13/16 inches
  • 4 Axles: hinge-pin type
  • 4 Wheels: soft plastic, full profile, see-through sidewall, 3 spokes, raised lettering “Awana Grand Prix”

Block Tips

  • Most Awana blocks are shorter than 7 inches. If so, replace the block. – In many Awana races, the wheelbase can be extended. If an extended wheelbase is allowed in your race, purchase an Extended Wheelbase Block, or use the Pro-Body Tool (Part #5145) to drill axle holes in your existing block.
  • If you are using the slots on an official Awana block, use a square to verify that the axle slots are square to the block. If not, replace the block.

Axle Tips

  • To minimize contact with the wheel hub, slightly bevel the axle head with the file. Place the axle in the chuck of a drill (head outwards), and apply the file to the spinning axle.
  • Polish with an Axle Polishing Kit. Skip the two coarsest papers in the kit.

Wheel Tips

  • If present, use a sharp knife to cut off the molding spike.
  • Using a Pro-Wheel Mandrel, polish the tread surface and inside edge with wet, 600 grit sandpaper.
  • Use Pro-Hub Tool to bevel the inside wheel hub.
  • Polish inside the wheel bore with the Pro-Bore Polisher.
  • Lubricate with graphite or specialty oil.

CSB “Shape N Race” Car Kit

The CSB Shape N Race car kit consists of the following:

  • 1 Wood Block: 2-1/4W x 1-1/8H x 6-15/16L inches, offset 7/32 inch deep axle slots with a wheelbase of 3-11/16 inches. The wheels inset into the block. A weight pocket is pre-milled into the bottom-middle of the block.
  • 5 Axles: hinge-pin type
  • 4 Wheels: hard plastic, full profile with a raised ridge, see-through sidewall, 4 spokes, no raised lettering

Block Tips

  • Use a square to verify that the axle slots are square to the block. If not, replace the block.
  • Use the axle slot closest to the end of the block as the rear axle.

Axle Tips

  • To minimize contact with the wheel hub, slightly bevel the axle head with the file. Place the axle in the chuck of a drill (head outwards), and apply the file to the spinning axle.
  • Polish with an Axle Polishing Kit. Skip the two coarsest papers in the kit.

Wheel Tips

  • You can use a Pro-Wheel Mandrel to lightly polish the tread surface and inside edge with wet, 600 grit sandpaper. However, due to the raised ridge, it is quite easy to remove too much tread surface material. So polish lightly.
  • Use the Pro-Hub Tool to bevel the inside wheel hub.
  • Polish inside the wheel bore with the Wheel Bore Polish.
  • Lubricate with graphite or specialty oil.

Mv Basic Car Kit

The MV Basic Car Kit consists of the following:

  • 1 Wood Block: 1-3/4W x 1-1/4H x 7L inches, offset 1/8 inch deep axle slots with a wheelbase of 4-3/8 inches
  • 5 Axles: hinge-pin type with beveled head
  • 4 Wheels: hard plastic, full profile, solid sidewall, raised lettering “Maximum Velocity”

Block Tips

  • Use a square to verify that the axle slots are square to the block. If not, replace the block.
  • Use the axle slot closest to the end of the block as the rear axle.
  • Use the Pro-Body Tool to pilot drill the axle slots (or if allowed by the local rules, use the Pro-Body Tool to drill axle holes on the opposite side of the block).

Axle Tips

  • Polish with a metal polish such as “Brasso” (hardware store) or “Mother’s Chrome Polish” (auto parts store).

Wheel Tips

  • Optionally, use the Pro-Wheel Shaver XT to true the wheel before polishing.
  • Using a Pro-Wheel Mandrel, polish the tread surface and inside edge with wet, 600 grit sandpaper.
  • Use the Pro-Hub Tool to bevel the inside wheel hub.
  • Polish inside the wheel bore with Wheel Bore Polish.
  • Lubricate with graphite or specialty oil.

Pinecar Basic Kit

The PineCar Basic Car Kit consists of the following:

  • 1 Wood Block: 1-3/4W x 1-5/16H x 7L inches, offset 1/16 inch deep axle slots with a wheelbase of 4-7/16 inches
  • 2 Axles: Solid rods with retention grooves for hubcaps (the newer kits also include four nail axles)
  • 4 Plastic Hubcaps
  • 4 Wheels: hard plastic, full profile, see-through sidewall, 5 spokes, no raised lettering

Block Tips

  • Use a square to verify that the axle slots are square to the block. If not, replace the block.
  • Use the axle slot closest to the end of the block as the rear axle.
  • If you cannot cut the axles (see step 1 under ‘Axles’), then make sure the block is no wider than 1-11/16 inches wide. Sand the block as needed to reach this measurement.

Axle and Hub Cap Tips

  • If allowed by your local rules, use diagonal cutters to remove 1/4 inch from the middle of each of the axles. You will now have four independent axles, which allows the wheel gap to be properly set, and facilitates a raised front wheel.
  • Place the axle in the chuck of a drill and polish the area near the hub cap retention ring with an Axle Polishing Kit.
  • Polish the inside of the hub caps with wet, 600 grit paper.

Wheel Tips

  • Optionally, use the Pro-Wheel Shaver XT to true the wheel before polishing.
  • Using a Pro-Wheel Mandrel, polish the tread surface and inside edge with wet, 600 grit sandpaper.
  • Use the Pro-Hub Tool to bevel the inside wheel hub.
  • Polish inside the wheel bore with the Wheel Bore Polish.
  • Lubricate with graphite or specialty oil.

RA Car Kit

The RA Car Kit consists of the following:

  • 1 Wood Block: 1-5/8W x 1-3/8H x 7L inches, offset 1/8 inch deep axle slots with a wheelbase of 4-3/16 inches
  • 4 Axles: nail-type
  • 4 Wheels: hard plastic, narrow symmetrical profile, solid sidewall, raised lettering “Royal Racer” on some wheels

Block Tips

  • Use a square to verify that the axle slots are square to the block. If not, replace the block.
  • Use the axle slot closest to the end of the block as the rear axle.
  • Use the Pro-Body Tool (part #5145) to pilot drill the axle slots (or if allowed by the local rules, use the Pro-Body Tool to drill axle holes on the opposite side of the block).

Axle Tips

  • Remove the burrs under the nail head, and the crimp marks on the shaft with a Mini-File. Place the axle in the chuck of a drill (head outwards), and apply the file to the spinning axle. To minimize contact with the wheel hub, slightly bevel the axle head with the file.
  • Straighten and round the axle shaft with Pro-Axle Press.
  • Polish with an Axle Polishing Kit.

Wheel Tips

  • Optionally, use the Pro-Wheel Shaver XT to true the wheel before polishing.
  • Using a Pro-Wheel Mandrel polish the tread surface with wet 600 grit sandpaper. Make sure to remove the seam around the middle of the tread.
  • Use the Pro-Hub Tool to bevel the inside wheel hub.
  • Polish inside the wheel bore with the Pro-Bore Polisher.
  • Lubricate with graphite or specialty oil.

Note that the side of the wheel with the raised lettering is mounted away from the car.

Royal Ranger Kit

The Royal Ranger kit (same kit is also supplied by S&W crafts) consists of the following:

  • 1 Wood Block: 1-3/4W x 1-5/16H x 6-15/16L inches, driver cut-out, extended-centered axle channels (3/8 semi-circular) with a wheelbase of 5 inches
  • 2 Dowel rod axle struts with pilot holes
  • 4 Axles: screw-type
  • 4 Wheels: hard plastic, narrow profile. Some wheels have six spokes on one side and a hemisphere on the other (the inside of the wheel), while other wheels have four spokes on both sides.

Block Tips

  • Use a square to verify that the axle channels are square to the block. If not, replace the block.
  • Many races allow the car to be 7-1/2 inches long. Since the block is only 6-15/16 inches long, extend the length by gluing on a 1/2 inch ‘nose’ of wood or another material.
  • Use the axle channel closest to the end of the block as the rear axle.
  • Use the Pro-Body Tool for Royal Rangers (Part #5148) to re-drill the pilot holes in the axle struts.

Axle Tips

  • Remove the burrs under the screw head with a Mini-File. Place the axle in the chuck of a drill (head outwards), and apply the file to the spinning axle. To minimize contact with the wheel hub, slightly bevel the screw head with the file.
  • Polish with an Axle Polishing Kit.

Wheel Tips

  • Optionally, use the Pro-Wheel Shaver XT to true the wheel before polishing. A 1/8 inch bushing is required.
  • Using a Pro-Wheel Mandrel polish the tread surface with wet 600 grit sandpaper. Make sure to remove the seam around the middle of the tread.
  • Polish inside the wheel bore with the Pro-Bore Polisher.
  • Lubricate with graphite or specialty oil.

Pinewood Derby Car Showcase

1962 Cub Cadet: Bill Mathews

This is a model of our 1962 Cub Cadet original by father-son team Bill and Taylor Mathews. Pine and balsa wood were used in the construction. The snowplow is cut from a scout popcorn tin.

Pink Flip-Flop & Spine-O-Mite: Kevin Willhite

This is my daughter’s “pink flip-flop” car and my “Spine-O-Mite” car. She loves pink and flip-flops and I am a chiropractor. Both cars were made with Maximum Velocity parts, except the flip-flop thong which came off of a car air freshener.


Pinewood Derby Memory

Peter’s Car

Back in 2001, I was a Tiger Cub Den Leader. When the day of our Pinewood Derby arrived, all of the boys brought their cars to the inspection. You could tell that parental help was involved, but you could also tell that the boys had a hand in building the cars.

The exception was Peter. You could tell that Peter’s parents probably offered little help. The block was an unsanded, rough cut wedge with a coat of gold spray paint. When we inspected Peter’s car, it was way under weight. Peter went to the pit area, borrowed some duct tape and taped coins on his car until it weighed exactly 5 ounces. What a sight: rough cut, unsanded, with a clump of duct-taped coins on top. But to our great surprise, that car took 2nd Place and earned Peter a spot in the district competition. I don’t think I’ve ever seen a boy more excited at a Pinewood Derby.

Gary Holewinski, Scoutmaster, Troop 38
Erie Shores Council, Toledo, Ohio


Q&A

My grandson competed in a district meet. After the completion of the first four runs he was in second place out 106 cars. But I noticed that each heat was slightly slower than the previous. This same thing happened last year. What might be the problem?

Congratulations on building a fast car, but sorry to hear that the speed didn’t hold. Assuming you used graphite as the lubricant, it sounds like either:

  1. Not enough graphite was applied (so it ran out very quickly), or
  2. Enough graphite was applied but too much break-in was done (so, the car was past the peak of performance when it started).

Make sure to thoroughly lubricate and then simulate a few runs by spinning the wheels. Just don’t over do it.

When our car ran at the district race, the times were inconsistent with a range of about 1/10 of a second. What causes this?

Inconsistent times are generally due to:

  1. Inconsistent staging (common when someone other than the owner is staging the car).
  2. Alignment issues (car hits the guide rail a different number of times on each run). This can largely be eliminated with the rail-riding technique.
  3. Bad track conditions (random as to whether bad spots are hit on a given run).
  4. Varying lane quality. Times between different lanes do vary, so to achieve a fair race cars should always be ran a consistent number of times on each lane.

Pinewood Derby Times Volume 8, Issue 14

– Feature Article – Whoops!

– Pinewood Derby Car Showcase

– Memory – Liam’s Car

– Q&A


Whoops!

(This is an updated version of an article that first appeared in Volume 2, Issue 11 – February 19, 2003)

Building a pinewood derby car is a blend of art and science. Certainly, getting top speed from the vehicle is the science part, while making a good-looking car requires an artistic touch. The pine block is the art media with which you must work, and it is not always the easiest media to work with. While working with this media, many unplanned events can happen, some of which can be classified in the “Whoops!” category.

For example, you may be working away on your pinewood derby car, when suddenly a big chunk of wood breaks off! What do you do? Or maybe the paint has dried, but a big drop of paint has ran down the side of the car! Can it be fixed?

These – and many other – minor catastrophes happen all the time to pinewood derby car builders. Fortunately, most of these things can be fixed with no lasting damage. To help you deal with these situations, today’s feature article will share ideas on how to deal with several “Whoops!” situations.

The Block Splits
Blocks can split when too much force is applied, especially if the block had a hidden flaw to begin with. First, to minimize the chance of splitting:

  1. Pre-insert a spare axle into each axle slot position or each axle hole before working on the car. Then remove the axles with pliers.
  2. Don’t use excessive force to insert weight into a hole or cavity in the wood; either make the hole bigger, or the weight smaller.
  3. When creating a weight cavity with a chisel, use a sharp tool, and work slowly. Don’t try to pry off any more than a thin shaving of wood.
  4. Don’t drive a screw into the wood without first drilling an appropriate sized pilot hole.

But if the wood does split, try one the following actions:

If the block is still in one piece:

  1. Open up the crack by inserting the tip of a small flat blade screwdriver (or another thin metal item) into the crack.
  2. Put white glue or yellow Carpenter’s glue into the crack.
  3. Use a toothpick or something similar to spread the glue in the crack.
  4. Remove the screwdriver and clamp the block. If you don’t have a clamp, wind masking tape tightly around the block.
  5. Wipe off any excess glue, and allow the glue to dry.

If the block is in two pieces that fit well together:

  1. Spread white or yellow glue over the entire broken area.
  2. Put the two pieces back together.
  3. Clamp or tape, wipe off any excess glue, then allow the glue to dry.

If the block does not fit well together, then the best bet is to start again with a new block.

A Chip Breaks Off
This is a common occurrence, especially when creating weight pockets around axle slots. To minimize the problem, leave 1/4 inch or more of wood around axle slots, and work very slowly around axle slots.

Axle supports/struts also tend to break off. To minimize this occurrence, insert a spare axle into the axle slot/hole while working on the strut.

If something does break off, here are some ideas to fix the problem. As a bit of encouragement, a good wood glue is very strong, sometimes even stronger than the original wood.

If the chip fits nicely into place:

  1. Glue the chip in place with white or yellow glue.
  2. Use masking tape to hold the chip in place.
  3. Wipe off excess glue, and then allow the glue to dry.
  4. Sand the repaired area after the glue dries.

If the chip is small and does not fit nicely into place:

  1. Use wood putty to patch the hole.
  2. After drying, sand the patched area.

If the chip is large and does not fit nicely into place:

  1. Find a piece of pine and cut/carve it to fit roughly into place.
  2. Glue the piece of wood in place with white or yellow glue.
  3. Sand the area.
  4. Use wood putty to fill in any gaps.

A Hole Is Drilled In The Wrong Place
This is one of my favorite mistakes. Measure twice and cut (drill) once is the old wood-workers adage, which is an all too easy step to skip. So, to ensure that holes are drilled in the right place, measure and mark the drilling location. Then before drilling, re-check the position of the hole — is the block turned backwards or upside down?

If the hole is 1/8 inch in diameter or larger:

  1. Buy a proper sized dowel rod at the local hardware or craft store.
  2. Cut a piece of the dowel rod about 1/2 inch longer than the depth of the hole.
  3. Place white or yellow Carpenter’s glue into the hole.
  4. Insert the dowel rod piece.
  5. After the glue dries, trim down the dowel rod with a fine toothed saw (a hacksaw works well).
  6. Patch the spot with wood putty and sand.

If the hole is less than 1/8 inch in diameter:

  1. Glue one or two toothpicks into the hole.
  2. After the glue dries, trim off the excess toothpick material.
  3. Patch the spot with wood putty and sand.

A Saw Cut Is Made In The Wrong Place
If the saw cut was barely started before the error is discovered, then the cut can generally be removed by rounding the area with sandpaper, or by patching the cut with wood putty.

If the saw cut is significant, but does not go all the way through the wood, then the choice is between starting again with a new block, or including the saw cut into the design. For example, if the cut is made such that a mirror cut could be made on the opposite side, then the cut could be a design feature. Note how the saw cuts on the rear of this car represent the feathers of the arrow:

If the saw cut goes completely through the car, then the design must be modified or the process must be started again with a new block. When deciding if the design can be modified, please note that:

  1. Cars less than 7 inches long generally run slower than cars of the maximum length.
  2. Additional weight may need to be added to compensate for the removed wood.

The Car Is Dented
Dents happen very easily to pinewood derby cars. Cars get dropped, or banged into the edge of a table. Fortunately, many dents can be corrected.

If an edge or face of an unpainted car is dented deeply, some wood putty can be used to fill the dent. However, if the dent is shallow, it is oftentimes better to remove the dent by swelling the wood fibers with water.

  1. Use a sewing pin to poke several shallow holes in the dented area.
  2. Apply a few drops of water to the dent, and allow the water to dry.
  3. If the wood does not swell enough to correct the dent, repeat the treatment.
  4. Speed up the drying process with a hair dryer.
  5. After the wood is dry, sand the affected area.

The Paint Runs On The Car
Getting a nice paint job takes practice, a good quality paint (mixed very well), a smooth finish, a painting location with no wind or dust, and the correct ambient temperature. Even then, runs can happen if too much paint is applied.

So first, check the directions on the paint and follow them, especially the application temperature range, and the re-coat time. Next, apply several thin coats of paint, instead of one or two thick coats. When spraying, always keep the can moving; don’t hold it still and just spray one spot on the car.

But when the inevitable run does occur don’t panic.

  1. If you plan on applying additional coats of paint, allow the run to dry and then sand off the run. You may have to sand off quite a bit of paint, and then reapply a few coats. Note that when sanding paint, using dampened wet/dry sandpaper works better than dry sandpaper.
  2. If you have finished painting, then cover the run with a nice decal or sticker. Decals are great for hiding paint runs and other flaws in the car finish!

Graphite All Over The Car
Graphite is a great lubricant, but it is also very messy. Here are a few tips to minimize the amount of graphite that gets on the car:

  1. Lubricate the wheels and axles before attaching them to the car. Not only will this keep the car cleaner, it is also easier and results in more thorough lubrication.
  2. Wash your hands after lubricating and before touching the car.
  3. Allow the paint to completely dry before mounting the wheels on the car.

But inevitably some graphite will get onto the paint. So, here are a few ideas for removing graphite. I suggest testing them on the bottom of the car (or a scrap piece of wood). Paints vary considerably in chemical content, so while these tips will work on some paints, they may not work well on all paints.

  1. Erase the graphite with a pencil eraser.
  2. Rub the spot with a dab of vegetable oil on a clean rag.
  3. Use a baby wipe.
  4. Spray some “Simple Green” on a clean rag and wipe.
  5. Spray “WD-40” on a clean rag and wipe.
  6. Apply a paste wax or car polish with a clean rag.

Conclusion
I hope this gives you some ideas for correcting the minor catastrophes that occur when working on your car. But remember, mistakes are part of the process, and is a method by which we learn. So be forgiving of yourself or your child (or parent) and move forward. Mistakes happen to everyone, and in the immortal words of Red Green, “Remember, I’m pulling for you; we’re all in this together.” (Unfortunately, the handyman’s secret weapon (duct tape) is not very useful on pinewood derby cars!)


Pinewood Derby Car Showcase

Viper: Spencer Mortimer

This car was made mostly with a Dremel Tool. It takes a little patience to make sure you’re not cutting through so fast that you actually cut where you don’t intend. After shaping, the car was ready for a good thorough sanding and a paint job. First I applied a deep blue base coat and then a second lighter silver coat, taping off the areas I wanted to remain blue. The really unique thing about this car’s paint job is the scales. I used a woman’s fish net stocking which had to be stretched and fastened using sewing pins. After applying a yellow coat I removed the fish net stocking. I then blended the blue and the scales together with a fine tip hobby paint brush. Once that was done a couple applications of clear coat and the paint was finished.

Toyota 84c Endurance Racer: Ryan Johnson

This car is a replica of the Toms 84c endurance racer. It has not raced, but was built for show and fun. I hope to work on getting it fast for future races. But really, when this car is sitting still it looks like it is going fast!


Pinewood Derby Memory

Liam’s Car

I joined Cub Scouts with my stepson, Liam, last year. He was seven years old and I was the Den Leader. The den shrunk over the winter and there were only 3 boys who attended meetings. I was feeling mighty low. I was not a Cub Scout when I was young but wanted to be more involved with some fun stuff with my stepson.

We received a pinewood derby kit from Santa at the Christmas pack meeting. I did not do any research and knew nothing about pinewood derby racing. I admit that I did not even know the date of the race. There was a Pinewood work day scheduled, but it was canceled due to 30 degree rainy weather.

I went to our den meeting and information was given about the race. It was the following Saturday! I told my son that given the short notice we would not be participating in the derby. Normally, he talks a lot and is very animated, but when I gave him the news he was very sullen. I found out later that he really wanted to enter the race but never had the opportunity.

I felt bad that night. I told my wife, and she said, “You work really hard; don’t worry about it.”

The next morning she said, “Honey don’t worry about the derby; I took care of it.”

I said, “How.”

She said, “eBay.”

I was driven from that moment on. I took off three days from work and every day after school Liam sanded the car and I showed him how to use spray paint.

When the eBay car showed up; it was really slick compared to the one we made.

We went to the weigh-in and had both cars weighed. The eBay car weighed 4.94 ounces, the one we made was exactly 5 ounces. Liam had no idea that his Mom had bought an eBay car.

I said, “Well Liam, which one do you want to race — the car we slaved over or the one the ‘Pinewood Fairy’ brought?”

He picked the car we made. When I asked him why, this very logical boy said, “Because it weighs more.”

Liam’s car ended up taking second place in the pack! The eBay car was not wasted. I entered the Leaders and Cheaters race and blew away every car we ran against. It was the fastest car in the pack and would have won the overall event. But, that doesn’t matter. What’s really important is that we did our best on Liam’s car. In our minds, it was the real winner.

Pete


When using the Pro-Rail Rider tool, do you bend the axle for the raised wheel?

If the raised wheel is accomplished by mounting the axle higher on the car body, then you don’t bend that axle. If you bend it up it may be too high to catch the rail on the braking section. This would allow the car to turn sideways on the braking section, resulting in a collision with other cars.

Does graphite lose its ability to lubricate with age?

As long as it is kept in a dry location, graphite should be good indefinitely.

Pinewood Derby Times Volume 8, Issue 13

– Feature Article – Top Fuel Cars – CO2 Car

– Pinewood Derby Car Showcase

– Memory – Pinewood Derby Song

– Q&A


Top Fuel Cars – CO2 Car

(The sixth in a series of articles on cars that “stretch the rules”)

In previous articles, we have discussed propeller cars (fast, and relatively easy to make – Volume 6, Issue 15), direct drive cars (faster, but more challenging to build – Volume 8, Issue 3), and rocket-powered cars (fastest, but tricky to build – Volume 6, Issue 8). But, today’s topic will be the most challenging of them all, a CO2 cartridge powered car.

One of our readers, Rich Cagle, succeeded in building and racing a CO2 car in 2007. This article will detail his design.


Figure 1 – Rich Cagle’s Car1
Background
CO2 cartridges contain pressurized carbon dioxide. When the end of the cartridge is punctured, the gas is released at high velocity, resulting in considerable thrust. Typically, these cartridges are used on cars that are run along a string in a parking lot. A starting mechanism is used to puncture the cartridge to initiate the run. To adapt this technology for use on a pinewood derby track, a mechanism must be developed which will puncture the cartridge when the starting pin drops.

Rich’s CO2 Car
Rich solved the starting problem with a “trailer” which contains the puncturing mechanism.


Figure 2 – Trailer Attached to Car, and Ready to fire
The trailer contains a spring and a firing pin. The pin is cocked by pulling backward, and then engaging the pin in a large washer (See Figure 2). The washer is moved downwards by a sharp force, which frees the pin to move forward. This force is provided by a mousetrap mechanism. When the mousetrap is released, the trap strikes the plate at the top-rear of the trailer. The plate pushes against the washer, moving it downward and releasing the firing pin. When the cartridge is punctured, the car shoots forward, leaving the trailer to follow at its own pace. The trailer is weighted so that it is not blown backward by the exhaust force.

In Figure 2, the mousetrap is armed and ready to fire. Figure 3 shows the trailer in the un-armed position. Notice the sharp pin at the front of the trailer (for puncturing the cartridge), and the position of the mousetrap lever.


Figure 3 – Trailer in Un-armed position
Starting Pin Mechanism
The mechanism to release the mousetrap is built into the car. A flexible rod (white in the photos) is connected to a spring mechanism on the front of the car (Figure 3). When the spring is relaxed, the rod moves forward on the car. But when the car rests against the starting pin, the rod is pushed backwards. When pushed backward, the rod can latch the mousetrap, and then be lodged under the mousetrap spring (see Figure 2). When the starting pin drops, the rod moves forward, which frees the mousetrap to start the firing sequence.


Figure 4 – Starting pin mechanism
Additional Details
A 12 gram CO2 cartridge is used, which discharges at roughly 900 PSI. The CO2 cartridge is angled in the car to create some down force, keeping the car on the track. When the starting gate drops, the car is tough to see (it finishes the track in about 0.5 seconds) – you hear it more than you see it. To stop the car, a folded blanket was placed at the end of the track.

Rich’s Comments

  • The previous track record was held by a compressed air pop bottle car. That car did not even get out of the gate before this car finished.
  • In its first race the exhaust blew a competitor’s car off the track onto the floor! Oops… (Sorry, no video).
  • Safety was a huge concern. I tested the car to see if it would take flight by firing it in the air off of a ramp; it always spun and flew to the ground. To take no chances I had the entire crowd stand behind the starting gate. I also warned kids and parents how the car was powered and that it was not a toy. Please caution anyone building one of these to think safety first. Don’t take chances, especially with kids around.
  • Building this car with my six year old was a lot of fun, and many lessons were learned. I hope this is something your readers will enjoy.

Editor’s Note
After seeing this car, I decided to build my own version. But I thought it would be great to not have the trailer. So I built a CO2 car with a self- contained mechanism – just this week I got the car working. Next season I’ll include an article about that car, explaining some of the pitfalls, design considerations, and other lessons learned.

1All of the photos in this article were shot by Rich Cagle.


Pinewood Derby Car Showcase</b

Wrench: Michael & Brandon Jones

We came up with the idea for a Wrench car last year and decided to make it a reality. The nut is a 1 1/8″ nut from a towing ball. It is set on top of Tungsten Putty. To reach five ounces, we added Tungsten beads inside the nut. At the race, the Wrench car won 1st in Den, 1st in Pack and Most Original in the design category.

NASCAR COT: James Whitlow, Jr

The NASCAR COT (Car of Tomorrow) pinewood derby cars take a little more prep work than the old style NASCARs, but I think this one turned out really nice.


Pinewood Derby Memory

Pinewood Derby Song

My first derby was in 1975 in the basement of our church and the track seemed larger than life. I had never won anything in all of my 8 years until that day.

This was back in the day when the kits required that you glue a wood axle in place and nail the brads into the wood axle. The wheels were different too, they were harder plastic and shaped differently. Dad had done a lot of the work on the car, but it was the first time he ever let me use the scroll-saw. Thinking back, using that tool was like a right of passage into young manhood. I chose the color (royal blue to match my uniform), and Dad said that it would look cool if we added some silver pinstriping to it. He helped me tape it off, then I got to work with my brush (to this day, I think the three coats of blue forced him to remove some of the weight). When we were all done, he told me that we needed to use this stuff called graphite to lubricate the wheels (it was in an enormous plastic bottle, not like what you buy today).

Back at the church, I remember that there were balloons, decorations and snacks; it seemed like a really big deal. In the first heat, my car finished car-lengths in front of everyone else, but I didn’t watch because I was so nervous. From that moment on, my buddies wouldn’t let me watch because we all thought it would be bad luck if I did. In the end, my car took first place. I still have the car and the trophy, but mostly I remember the song we sang; I still sing it today with our Pack at every derby.

Pinewood Derby Song (To the tune: Camptown Races)

Cub Scouts all join in the song,
Do-da, do-dah!
Pine car track am mighty long,
Oh, do-day-day!

Chorus:
Going to run so fast,
Going to get ahead,
Bet my money on a blue pine car,
Somebody bet on the red.

Black cars, blue cars, green and gray,
Do-da, do-da!
Are running on the track today,
Oh, do-da-day!

Chorus

Pine cars do have lots of class,
Do-da, Do-dah!
Even though they don’t use gas,
Oh, do-da-day!

Chorus

They’re the pride of all the Dens,
Do-da, do-da!
Built by Cub Scouts and their friends,
Oh, do-da-day!

Chorus

Song source:
members . tripod . com / cubbobwhite / songs / pinewood . htm
(remove spaces)

Dave Kish
Pack 54, Lopatcong, New Jersey


Q&A

How important is wheel bore and axle diameter?

Best performance is generally achieved with:

An axle that fits the wheel without excess slop. That is why BSA wheels work best with oversized axles, such as our 4051-Pro-Stainless Steel Axles, or Awana Axles. Both of these are several thousandths larger in diameter than stock BSA axles.

The smallest possible bore. This is something that is not easy to control on kit wheels. But it explains why our Needle Axle Outlaw wheels are faster than our regular Outlaw Wheels. The bore on the Needle Axle Wheels is much smaller than on the regular Outlaw Wheels, thus the Needle Axle Wheels are faster.

I have a question about COG. My kids will be racing on a “ramp only” track. Do you know what COG should be used to achieve the best possible times? Also, when I’m measuring for COG, I measure from the center of the wheel bore. Is this correct?

If the track is truly a ramp only track — no flat section, and the starting angle equals the ending angle — then the COG should be centered between the front and back axle (to equalize the load between the front and back axle).

The COG is measured from the center of the bore (or from the center of the axle).

Pinewood Derby Times Volume 8, Issue 12

– Feature Article – Pinewood Derby Myths

– Pinewood Derby Car Showcase

– Memory – Life is Good!

– Q&A


Pinewood Derby Myths

(An imaginary conversation between two Cub Scouts a month before the pack pinewood derby race).

Johnny: What ya’ got in that baggie in your pocket?

David: These are my pinewood derby wheels. I’m “marinating” them in graphite so they will go faster.

Johnny: That’s silly! What you really want are grooved axles. They reduce friction.

David: No they don’t! But you can reduce friction with a raised wheel.

Johnny. I don’t think that reduces friction, but I think if you angle the axles so that the wheels run on one edge, you’ll reduce friction and go faster.

David: Hah, where did you hear that one? On Car Talk? Really, I think the main thing is “aerodynamism”. You know, like race cars.

Johnny: You mean “aerodynamics”. But that doesn’t do anything at slow speeds. But we do have a super secret lube we are going to use this year that will let us win the council race.

David: Oh really! There’s no such thing — you know that “Lemon Pledge” isn’t the silver bullet don’t ya’?

Johnny: It’s not Lemon Pledge, trust me. But we’re also going to put the weight in the front of the car so that it gets moving faster.

David: That won’t help. Lightweight wheels are what you need to get the car going faster. Besides, my dad is a science teacher, and he says that weight doesn’t matter because of some guy named Newton.

Johnny: Well my dad’s an engineer, and he says that weight does matter. We’ll just see whose dad knows more after “I” win the race.

David: You mean after “I” win the race!

Well, that conversation was a bit confusing, wasn’t it? Although the boys seemed confident of their “speed tips”, in my mind I now have more questions than I started with. For example:

  • Which of the boy’s statements are true, or are they simply a myth?
  • Is Johnny or David’s dad smarter?
  • Who will win the race?

I can’t answer the last two questions, but I can certainly take a crack at whether any of Johnny or David’s statements are fact or fiction. Over the past several years, I have run across quite a few pinewood derby myths, and have experimentally confirmed or busted many of them. So in today’s article, we will review the main pinewood derby myths and label them as confirmed, plausible, or busted.

Marinating Wheels In Graphite
Graphite reduces friction when applied to the wheel to axle contact surfaces (wheel bore, inner hub and outer hub). There is also a slight benefit to coating the inner edge and tread surface of the wheel with graphite — see Volume 8, Issue 2 – October 15, 2008. Obviously, there is no benefit to coating the non-contact surfaces such as the inner and outer walls of the wheel.

So, the question is whether immersing the wheels in a bag of graphite is more or less effective than purposefully placing the graphite on the contact surfaces. In my testing I have found that graphite is most effective when it is worked into the contact surfaces by repeated spinning (or similar). Just placing graphite on the contact surfaces is not sufficient; the graphite must be worked into each surface.

So, simply placing the wheels in a bag of graphite (even if the bag is massaged around the wheel) is a less effective technique than purposeful application of graphite.

Busted – One point to Johnny

Grooved Axles
In Volume 8, Issue 6 – December 10, 2008 we discussed grooved axles at length. From that discussion we learned that grooves do not reduce friction (the friction is just relocated). However, we did find that grooves can be of benefit in specific situations.


Figure 1 – Grooved/Non-Grooved Experimental Results

When running on BSA-type nail axles, grooves were of benefit with both graphite and liquid lubes. But when running with oversized axles, the advantage/disadvantage of grooves was indeterminate.

Plausible – One point to David for knowing that grooved axles don’t reduce friction. One point to Johnny for knowing that grooved axles can be of benefit

Raised Wheel
Contrary to David’s statement, raising a wheel does not reduce friction (the frictional forces are just increased on the other three wheels). However, there are other benefits to a raised wheel including a reduction in wheel inertia.

In Volume 4, Issue 14 – April 6, 2005 a raised wheel experiment was conducted which showed a significant benefit to racing with a raised front wheel (see Figure 2).


Figure 2 – Effect of Raised Wheel on Performance

Confirmed – One point to David for knowing that it helps, one point to Johnny for knowing that it does not reduce friction.

Canted Axles
The term “canted” means an object set at an angle, thus “canted axles” are axles which are attached to the car at an angle. Sometimes this is done accidentally, but usually car builders cant axles in an attempt to reduce the amount of contact between the wheel tread and the track.

In Volume 8, Issue 8 – January 8, 2009 a canted axle experiment was documented. The results show that up- canting the rear axles on an aluminum track may provide a very slight benefit. In Figure 3 the amount of change between the data points is within the statistical variation of the heat times, so the data is inconclusive.


Figure 3 – Effect of Canted Axles

Plausible – One point to Johnny

Aerodynamics
As it applies to pinewood derby cars, aerodynamics refers to the affect of air flow on the movement of the car. Johnny is correct that the effect of air flow on a vehicle does increase at higher speeds, and decrease at lower speeds. But does the effect go away at pinewood derby speeds (10 to 15 MPH average)?

In Volume 3, Issue 9 – January 21, 2004, an aerodynamics experiment was documented. In this experiment, the frontal surface area of a car was varied with a removable air dam. The results are shown in Figure 4. As you can see, an increase in frontal surface area does reduce performance for a pinewood derby car.


Figure 4 – Effect of Aerodynamics

Confirmed – One point for David

Super Secret Lube
The use of an effective lubricant is critical to car performance, and there are certainly a vast number of possible lubricants that can be used. These include dry powders, liquids, and liquids that become dry to the touch.

Over the years I have tested a large number of these lubes, including but not limited to:

Dry

Graphite (at least fifteen blends)
Molybdenum Disulfide (several particle sizes)
Tungsten Disulfide
Boron Nitride
Powdered Teflon

Liquid

Krytox 100
NyOil II
SB-10
Several exotic oils, both synthetic and petroleum-based

Wet to Dry

Silicon Spray
Emery’s Slide All
Several graphite suspensions
Several boron nitride suspensions
Spray and non-spray waxes, including Lemon Pledge

After all of these experimentation, I have found that a good quality graphite (such as Max-V-Lube) or a good quality synthetic oil (such as Krytox 100) gives the best performance.

So, is there a super secret lube? I can’t absolutely confirm or bust this myth, but I don’t believe there is a secret lube. If there was, it would not remain secret for very long, as it would be publicized on the Internet and be available from pinewood derby stores such as ours. There are likely other lubricants that rival the performance of Krytox 100 and Max-V-Lube, but I don’t believe there are lubes that are significantly better.

Unconfirmed – No points awarded

Weight In Front
The location of the ballast weight on a pinewood derby car affects the center of gravity (generally referred to as the “balance point”). The optimal balance point varies from track to track, but that position is somewhere between the center of the car and the rear axle location (1 to 1-1/4 inches in front of the rear axle location is a good rule of thumb for most tracks).

In Volume 3, Issue 14 – March 31, 2004 a weight experiment was documented. In this experiment, the balance point was adjusted from the front to the back of the car. The results are shown in Figure 5. As you can see best performance was attained with a rearward balance point.


Figure 5 – Effect of Balance Point Location

Busted – One point for David

Lightweight Wheels
In recent years, lightweight speed wheels have become readily available. These wheels are weight-reduced by removing excess plastic from the interior of the wheel.

Reducing the weight of the wheel reduces wheel inertia – the tendency of a wheel to not spin. So, lighter wheels should provide a faster start for a car.

In fact, this has been proven to be true. In Volume 7, Issue 3 – October 31, 2007 a wheel weight experiment was conducted. The results of the experiment show that reducing the weight of the wheels (and adding that weight to the car) does improve performance (see Figure 6).


Figure 6 – Effect of Wheel Weight on Performance

Confirmed – One point for David

Amount Of Weight
While Sir Isaac Newton is credited with the “discovery” of gravity, it was Galileo that showed that the mass of the object did not affect the acceleration of the object due to gravity (true in a vacuum). However, on a pinewood derby track there are other factors at work. Most pinewood derby tracks today have a sloped section (where gravity accelerates the car), and a flat section. On the flat section, the momentum of the car, aerodynamics, and friction are among the factors that affect how fast the car slows down. Momentum is based on speed and mass, the heavier the mass, the greater the momentum. So, heavier cars tend to hold their speed for a longer period of time, and thus tend to be faster.

In Volume 3, Issue 14 – March 31, 2004 a car weight experiment was conducted. The results of the experiment show that increased weight improves the performance of the car (see Figure 7). A similar test with weight beyond five ounces was documented in http://www.maximum-velocity.com/pinewood_derby_times_v7_i5.htm olume 7, Issue 5 – November 28, 2007.


Figure 7 – Weight versus Performance

Confirmed – One point for Johnny

Conclusion
Well the debate between Johnny and David ends in a five to five tie. But now that you have the facts, you will be better armed for your next race (or pinewood derby debate). Good luck, and may the best car win!


Pinewod Derby Car Showcase

WALL-E Tandem: Kaz Terada


To build the WALL-E tandem car, I used a standard size pine wood block and cut it into two cubes. I kept the original axle slots for mounting the wheels, and attached parts from a toy caterpillar with 1-1/4″ wheel cut-outs (made with poplar). Most of the other parts (head, neck and arms) were made of poplar. After completing the two identical WALL-E’s, I connected them with two dowels. Some weight was added to the back and bottom of each Wall-e. Since the two parts were connected together, there was an alignment problem so it wasn’t very fast. But it was a fun project!

Batmobile: Andy Holzer


Last summer Noah (my son) and I went to the MotorBooks car show, in Osceola Wisconsin. At the car show there was a replica of the Batmobile. While we were discussing the Batmobile he asked if it was possible to build a Batmobile for his pinewood car for next year. I love when he comes up with these ideas on his own so of course I said yes (not even thinking how hard it would be to create the Batmobile in pine).

The windshield is made from the top of a 500ml (16.5 fl. oz.) Aquafina bottle. The plastic is recessed into the body, via a knife cut line and attached with a small amount of glue.

During the racing I did not have a lot of time to view the races, but this year there was a lot of fast cars. When it came time for the awards Noah received 3rd place (technically 2nd for Webelos 1, as all Webelos raced together-10 racers total). This was the first year our pack gave out design awards (picked by all of the race spectators), and Noah received two – Coolest Looking Car & Best Painted and/or Decorated Car.


Pinewood Derby Memory

Life is Good!

Yesterday was Derby Day for our Pack here in St. Louis, Missouri. My son, Max, is a Webelos II and this was his last derby. Last year we had the pleasure of coming in First Place in the Webelos I race and winning First Place Overall in the Pack Finals. We have used your products for the last four years counting this year.

This year was a little different. We have a Webelos II scout who lost his father a little over two years ago to cancer. He’s a quiet young man, but nice as can be. The last two years his uncle, and then another father, helped him with his cars. They were much more into design than speed and he finished well back in the pack so to speak. Sometime after my son won the derby last year, I asked Max if he would mind if we helped Eric build a car this year. I told him there was no assurance that I could guarantee which car would be faster and he might not do as well. I waited for his answer and it was more than I had hoped when he said, “It’s OK dad, we won this year and maybe Eric will win next year. Let’s do it!” Several months later we asked Eric and his mother if he would like our help, and he and his mother consented to this. Two other fathers offered also to help him, not to suggest this was any grand gesture on my part — although, I thought it was pretty special on my son’s part.

Well, I helped the boys build two cars using the Maximum Velocity tools and parts we’ve acquired. We shaped the standard BSA block. When they were complete, other than the full body decals and the numbers on the cars, you really couldn’t tell them apart. We don’t have the opportunity to run the cars in advance in our pack, so we had no idea how they would perform.

Well, Max won 2nd Place in the Webelos II Division and 2nd Place in the Overall Pack. There were 57 cars in the Pack races and 13 in the Webelos II Division.

Now about Eric …

It was almost like watching a made for TV movie during the racing as Eric never lost a race and came in 1st Place in the Webelos II Division, and 1st Place in the Overall Pack. He was one excited and happy young man. His mother told us later that when he climbed into the van to head home with his trophies, he closed the door and he yelled at the top of his lungs, “Life is Good!”

So to all you fathers out there, build them fast with Maximum Velocity parts and tools, but take time to share your knowledge. I believe my son has discovered the true meaning of being a Cub Scout and I hope your sons do also.

Mark G. Bredenkoetter


Q&A

All things being equal, can I build a faster car using tungsten instead of lead? For instance, using the basic wedge design, can we place weight in a more favorable position with tungsten?

The goal of weighting is to get to the maximum weight, to get the desired balance point, and to focus the added weight in one spot (as much as possible). If you are using a more full-bodied car (including a wedge), these three goals can generally be achieved with lead.

However, if you have a low-profile car will minimal wood, then generally tungsten is needed to achieve the weighting goals.

Just substituting tungsten for lead will not create a faster car.

Is there anything that would cause a car to start more slowly than others, but run faster at the bottom of the track?

There are several things that can make the car start slower than others. Without knowing more about the situation, here are some ideas:

  1. Other cars are using weight reduced wheels, and your car has full- weight wheels,
  2. Other cars have a high nose or cheater bar (advantage if the gate drop is not consistent, or is consistently slow),
  3. Other cars have a raised wheel, and your car has four wheels on the ground,
  4. Your car is staged with the wheels touching the car body, and/or touching the guide rail,
  5. Your car is staged crooked,
  6. Your car is using a different lubricant than the other cars (some lubes start slow but work well once moving).

Pinewood Derby Times Volume 8, Issue 11

– Feature Article – Raising the Performance Bar

– Pinewood Derby Car Showcase

– Memory – A Crashing Halt and a Great Finish!

– Q&A


Raising the Performance Bar

(This is an updated version of an article that first appeared in Volume 2, Issue 7 – December 24, 2002)

Most people have a sense of fair play. When two mismatched teams or individuals compete with each other, interest usually wanes, and from a sense of sympathy oftentimes the underdog is the crowd favorite. But when inferior equipment, questionable coaching, or unawareness of the rules disadvantages one competitor, most people hardly consider the event to be a truly fair contest.

People generally prefer to watch an event where the teams or individuals are evenly matched. When skills, equipment, coaching, and officiating are all relatively even, then a sense of fairness prevails and — because the outcome of the event is uncertain — the interest level of the spectators remains high.

Similarly in pinewood derby racing the most exciting events are those in which many of the cars are closely matched in performance. Since the outcome is uncertain, everyone will be on the edge of their seats until the races are concluded.

Due to mistakes, inexperience, shoddy work, etc., there will always be some cars that are out-classed. But the goal of the race organizer should be to give each entrant a full opportunity to perform at a high level.

How is this done? In today’s article I will share several ideas for leveling the playing field, not by penalizing the best cars, but instead by raising the performance bar.

Equal Access To Information
The first way to level the playing field is to provide clear and complete rules for the event. The rules should clearly state what is, and what is not allowed. Rules that require interpretation will result in entries using performance-improving techniques that others had assumed were disallowed. This can only result in disappointment or disillusionment.

Please note that I am not advocating highly restrictive rules. On the contrary, I prefer to allow car designers to use their creativity and ingenuity to increase performance. But to do this, the rules must clearly state what is in bounds, and what is out of bounds.

Another kind of information to distribute is performance tips. Although veterans of your event will likely know the tips already, this information will most certainly be an eye opener to newcomers.

Equal access to performance tips could consist of distributing:

  • a list of the better pinewood derby-related web sites,
  • a locally-developed tip sheet, a tip sheet from a web site, or
  • a commercially available speed tip booklet.

In any case, all participants should receive the race rules and the performance information at the time when the car kits are distributed.

Equal Access To Tools
To raise the performance bar, participants should have equal access to the required tools. In every organization there are some folks with an extensive workshop and with skills to match. Others may not even own a hand saw. Clearly, this leads to lopsided events.

A simple way to provide equal access to tools (and skills) is to hold one or more workshops prior to the event. Of course workshops are more than just an opportunity to share tools. These events provide opportunities for comparing/learning techniques, collaborating on design ideas, and in general becoming more competent in car building. In recent years, we have held a workshop for our group on two consecutive Saturdays at Maximum Velocity. Kids and parents use the tools, seek advice, test cars on the track, and collaborate with the other participants. For those with little pinewood derby experience, attending a workshop can make a big difference in car performance.

In particular I remember two boys and their single mom who attended a workshop for some assistance. I helped them add weight to the car, prepare the wheels and axles, and loaned them some graphite. They ended up taking first and second in their age category — not bad for their first event!

Equal Access To Practice Time
Another way to raise the performance bar is to allow practice time on a derby track. This gives participants the opportunity to test their cars, and thus recognize if changes are needed.

One concern with allowing practice time is that some competitors may become disillusioned if they are continually bested during practice. To avoid this issue, disallow racing between competitors during the practice time. Instead, each entrant may run their car alone (sufficient if the track has a timer), against the entrant’s car from a previous year, or against a “benchmark” car. This minimizes comparing cars during the practice time, but still allows the entrants to ascertain how their car is performing.

Competition Levels
Would you consider it a true competition if the New York Yankees were pitted against a college baseball team? Not likely. But a similar mismatch does occur in some pinewood derby events. If your derby has rather flexible car design rules (e.g., allows modified wheel bases, machined wheels, or similar), then likely the event will end up with some high-performance cars leaving the more traditional cars in the dust.

Obviously, the rules could be tightened to disallow certain modifications, but I suggest an alternative. Instead of reducing design options, consider offering different entry classes. How about a “Stock” class race for cars with standard wheel bases, unmodified wheels, etc., and an “Open” class race for cars with extended wheel bases, modified wheels, etc? This will require more awards, and a little more time. However, I believe you will find the increased competition and excitement will more than compensate for the additional cost.

Conclusion
Raising the performance bar can help to make for a more memorable pinewood derby event. By providing equal access to information, tools, and practice time, and by possibly having multiple event classes, the races will be closer and more exciting.

By the way, what I have included in this article certainly does not exhaust the possibilities for raising the performance bar. If you have other ways to raise the level of competition, please share them with me. Thanks!


Pinewood Derby Car Showcase

The Hive: Scott Morrill

We held a derby as the main event at our family reunion this past summer. My grandfather was a beekeeper, so in his honor I created “The Hive”. The hive itself is an empty shell of balsa which also hides the tungsten weight. The bees were individually created with beads and wire to form the wings and stingers.

Wayne: Bob Kirmis


I am not a scout but rather a mid-forties guy who is part of an annual pinewood derby race at my place of employment. This “car” is a City of Fargo, North Dakota “Wayne” street sweeper. As you can probably guess, I am from Fargo. The guy driving the street sweeper is my dad (who is coincidentally named Wayne).

The two back wheels are glued together to create one wide wheel. The car is elevated about a quarter inch so that it would fit on our track. As you can guess, the car didn’t do real well in the speed category.


Pinewood Derby Memory

A Crashing Halt and a Great Finish!

To start with, at forty-nine, I’m a fairly old Dad to have three sons aged eight, seven, and five. My two oldest sons are Cub Scouts and my youngest son will start scouting in the fall. My middle son won our overall Pinewood Derby championship last year. I compete in the open class of our Pinewood Derby.

I was a Cub Scout way back in the 1960’s and early 1970’s. The Pinewood Derby was a big deal back then too! When I was a Bear Cub, I was entered in our Pinewood Derby. It was Cub Scout Pack 27 in Fort Worth, Texas. I can’t recall what the track was constructed of, but it was the coolest thing that I had ever seen! They had created awards out of coffee can lids, leather, and gold glitter. Those simple awards looked like Olympic Gold Medals to me!

I think my Mom and Dad did more than their “fair share” of work on my car. My Dad could build anything out of metal or wood and he was very competitive. So was my Mom as my car was awarded, “Best Paint Job”. I still have that race car and you can tell by looking at it that no little kid built this by himself.


We had our pre-race ceremonies and the excitement built up even more for me. I was very excited about getting a chance to race my car. My car looked like it would be fast and I was very proud of it. Both my parents kept telling me over and over again to be very careful with my car and to not drop it. As with any kid, I could not put my race car down. I carried it with me everywhere.

Well, we started the race and my Pinewood Derby car was a speed demon! I don’t remember how many boys were in our Pack, but I was beating everyone from the Webelos to the Bobcats. After every heat that my car was in, I snatched it up and pranced around with it. I remember looking at my Dad a couple of times and he was smiling and laughing along with me. Those were very special moments for me as my Dad was “old school” and he didn’t let on too often that he was pleased. I can still hear my Mom and Dad saying, “Be careful with your car and don’t drop it.” Those same words haunt me to this very day.

Our Pinewood Derby was finally winding down and I was still undefeated. I had just finished grabbing my car off the track after another victory when disaster struck! I can still recall that exact moment like it happened yesterday. I still see it in slow motion. I was holding my race car when suddenly, I wasn’t holding it anymore! It seems like it took two minutes for my car to hit the floor. As it smashed down, the two front wheels shot outwards away for my car. The wheels and nails went rolling and spinning away.

I remember the room went quiet and I looked towards my Dad. That in itself was a memorable moment. The expression on his face was a mixture of sadness, anger, and defiance. He came over and gathered the wheels and nails. I was upset and he told me that it would be all right; he could fix it. I was in shock as I thought the car was ruined!

Pinewood Derby cars were way different than they are these days. The axles were mounted into glued-on wooden struts. The front axle strut on my car had actually shattered and was gone! So my Dad laid the car on it’s side and with the palm of his hand, he actually pushed the nail axles right into the side of the wooden car body!

The race continued. Two other cars had only one loss each and they ran their race. Now, it was just me and my repaired little racer versus another car we had already beaten once. Well, not all stories have a happy ending, but this one did. My little broken car beat the other Scout just barely and we won the final race! That is still one of my proudest days as a Cub Scout.

If there is a moral to this story, it’s leave your race car alone and listen to your Mom and Dad. Sometimes, they are actually right about stuff!

Carl “Crash” Wilson


Q&A

Is there truth to reducing friction by only having 3 wheels touch the track surface or is there a negative effect?

The friction isn’t reduced, but there are several advantages to a raised wheel:

  1. Less inertia to start the car rolling,
  2. Easier to align,
  3. Front wheels don’t fight each other if the alignment isn’t perfect,
  4. A wheel that doesn’t spin as well can be used as the raised wheel,
  5. Car sits with more stability on three wheels than on four (as long as the added weight is placed towards the rear of the car).

I was able to get my son’s car to roll straight, but it zigzags in the flat section of the track. How do I correct this?

This is a common problem, often attributed to the wheels and axles. But in most cases the problem is that the car is too back weighted for the track.

Lay a ruler on it’s long edge (or use a Balance Stand), then balance the car on the ruler (front to back). Determine the point at which the car balances, then measure the distance from that point to the rear axle.

On most tracks a good distance is 1 inch in front of the rear axle. On a very smooth metal track you can sometimes push this to 3/4 inch in front of the rear axle. But the further back you go, the greater the risk of the “death rattle” that you are experiencing.

To correct the zigzagging, you will need to move some weight forward on the car until the car stabilizes, or implement rail-riding alignment.

Pinewood Derby Times Volume 8, Issue 10

– Feature Article – Lubricant Testing

– Pinewood Derby Car Showcase

– Memory – Sons of Engineers

– Q&A


Lubricant Testing

If you have done any pinewood derby research on Google, or looked at derby products for sale on eBay, then I’m sure you have run across statements such as:

– “Tungsten Disulfide (WS2) has an extremely low coefficient of friction of 0.03 — lower than that of Teflon, Graphite, or Molybdenum Disulfide”

– “Molybdenum Disulfide (MoS2) has a lower coefficient of friction than graphite. This means (brand name removed) is a better lubricant than graphite.”

If you are looking for better derby performance, then statements such as these are quite intriguing, especially when accompanied by a graph comparing the coefficient of friction of each substance (see Figure 1).


Figure 1 – Lubricant Comparison from BryCoat, Inc.
Graphic from BryCoat, Inc. web site
When viewing statements and graphs such as these, it pays to take a careful look at the details. In Figure 1, the range of the data is between one and three hundred thousand PSI. This is an extremely high pressure condition. Most importantly, note how the coefficient of friction of the three materials appears to be the same at the low end of the data.

An important question to ask oneself at this point is, “What happens as the pressure reduces further, especially at a pressure that would occur in a pinewood derby car?” Clearly, for MoS2 or TS2 (or any other lube for that matter) to be of value, it must have a lower coefficient of friction than graphite at the pressure found in pinewood derby cars. So, let’s test these lubes in that pressure range.

Background
The coefficient of friction is the ratio between the mass of an object and the amount of force required to move the object. Normally, the coefficient of friction is indicated by the Greek letter “µ”. So the mathematical formula is:

F = µM or µ = F/M

Where F is the force required to move the object, µ is the coefficient of friction, and M is the mass (weight) of the object1.

As an example, if you were to push a heavy box on a rough road (asphalt) and then on smooth sidewalk, pushing it on the sidewalk will be easier because the µ of the sidewalk is lower. If you then pour oil on either surface, it will be easier to slide the box because the oil has lowered the µ.

The coefficient of friction can be measured in any of several ways. For our purposes, we are going to use the “Tilted Plane” method. In this method, an object will be placed on a smooth surface which can be incrementally tilted. At some point, the object will slide on the surface. The angle at which the object slides is called the “friction angle”, and is notated as ø. We can then calculate µ as follows:

µ = tan(ø) (See note 2)

Experiment Setup
The main piece of equipment for the experiment is a tilting apparatus (Figure 2). It consists of a piece of glass on a tilting frame, which is moved when the crank winds the string around a rod. An angle measuring device shows the current tilt angle.


Figure 2 – Tilted Plane Apparatus
The sliding blocks are also critical components. Eight blocks of Delrin3 were machined to the same dimensions, and provided with two smooth surfaces. Delrin is not as consistent in density as some other plastics, so there was a slight weight variance between the blocks. So, the lightest block was found, and then small holes were drilled in the sides of the other seven blocks until all of the blocks weighed the same. The resulting weight of each block was 2.05 ounces. This is the typical load for one of the rear wheels on a pinewood derby car.

Experimental Procedure
Three lubes were tested: TS2, MoS2, and Max-V-Lube Graphite. Two blocks were used for each lube, and the last two blocks were used without lube as a control.

The glass plate on the tilting apparatus was first cleaned thoroughly with a glass cleaner. This cleaning was repeated each time the lubricant was changed.

A quantity of each lubricant was placed on a sheet of clean newsprint. One side of a block was then rubbed on the lubricant until thoroughly coated (Figure 3). The block was then placed on the glass and slid back and forth to distribute some of the lube onto the glass. The block was then recoated with the lube and placed on the uphill side of the glass. The glass was then slowly tilted until the block slid to the downhill side of the glass. The tilt angle was then recorded. This test was repeated five times for each block.


Figure 3 – Lubricant Application
Experiment Results
After all of the tests, the high and low angle measurements were removed and the remaining three were averaged. µ was then calculated for each of the lubricants and for the control test. The results are shown in Figure 4.


Figure 4 – Coefficient of Friction for Pinewood Derby Lubricants
As shown by the data, both MoS2 and TS2 have a higher coefficient of friction than Max-V-Lube graphite at 2.0 ounces.4 Thus, these lubricants will be less effective than graphite as a pinewood derby lubricant.

1Oftentimes, F(normal) is used instead of M in the equation. These are essentially the same.

2If you are interested in why this is true, there are several good discussions of this on the Internet. Just search for “measure friction angle” on Google.

3A brand name of an engineered plastic.

4In a previous test using this apparatus, I compared many of the top graphite brands with MoS2 and TS2. In all cases, graphite had a lower µ than MoS2 or TS2. At that time I also tested “Dry White” Teflon lube. Not surprisingly, the µ of “Dry White” was higher than MoS2 or TS2. Note also that spin tests were performed on all of these lubes with compatible results.


Pinewood Derby Car Showcase

Modified Detonator: John Cerrone

This car was one my son and I built, slightly modifying the Detonator design. The only rules for this particular derby were to use the wheels and block supplied with the BSA kit and not exceed five ounces. So we extended the wheel base and rear weighted with tungsten to achieve a COG at 3/4 inch. We cut down and used a dome to cover the rear cylinder weights, and molded the sides and rear of the car to conform to the outside edges of the dome. We painted the inside of the dome black and then used epoxy to fill in the gaps between the dome and the car body, then finishing it with a fine pin stripping around the dome. The car took first in class, second overall in the pack race, and took first in class at districts. We also received the Best and Fastest looking car awards at both the Pack and District event.

Iwo Jima: Scott Morrill

My son enjoyed helping with this car which was created for an adult race. We used Tannin’s army men, and cut the bases off the feet then used heat to allow us to bend their legs and arms. The rocks are Styrofoam, and the large rock which holds the base of the flag pole hides the weight. The flag is a miniature fabric flag that was starched to hold the shape. Due to the height, the flag was just for display and not in place during the race.


Pinewood Derby Memory

Sons of Engineers

My son just entered his first pinewood derby. At the night of the weigh- in, I overheard one of the leaders talking with another parent as they were looking at a car submitted by another scout. The leader was saying to the parent that the car was from the same boy who had won the previous two years, and that his father is an engineer. After leaving I told my wife about the conversation I overheard. We both got a good laugh because I am an engineer as well.

On the day of the race my son ended up winning the overall championship. After the race, I wet up to the leader and laughingly told him that I had overheard the conversation at the weigh-in, and that I too was an engineer. He laughingly responded with, “Son’s of engineers have an unfair advantage”.

Steven Ward

Editor’s Note: Son’s of engineers don’t have an unfair advantage. The boys in this story were just fortunate enough to have a dad that was willing to work with them and apply the principles that are readily available on the Internet.


Q&A

I was wondering if you have experimented with other lubes like Tungsten Disulfide? I have read about the nano lubricants that are being developed. Have you tried any of those?

The results for Tungsten Disulfide are shown in the feature article. I have also tried a nano product known as “Bucky Balls” (technically C60, a member of the Fullerene family). Basically, these are carbon molecules in the shape of tiny spheres. Unfortunately, they don’t behave like ball bearings; instead the product lubricates similar to sand.

Which is more important: properly weight balanced car or a car with special designed axles?

Really, all the factors are important. But I believe that getting the car to 5 ounces and having the balance point set for the type of track would be more important than a specific type of axle. Of course, you still want to have your axles defect free, and polished.

Pinewood Derby Times Volume 8, Issue 9

– Feature Article – The Derby Worx Story

– Pinewood Derby Car Showcase

– Q&A


The Derby Worx Story
By Bill Launius Jr.

I have always been fascinated by pinewood derby racing! From the time my neighbor came home with his first kit, I could not wait until I was old enough to join the Cub Scouts so I could build a car too. So when I became a Cub Scout in the fall of 1975 my Dad and I went to the local scout shop to pick up a kit and get an early start on the car; we just couldn’t wait for that race! That car was gold and black, and it was the coolest car ever because my dad and I built it. As cool as it was it was also fast, faster than everyone’s that year. But little did I know in 1975 what would eventually happen.

As the years went by we were involved with many cars. Several were mine, but others belonged to cousins, neighbors and friends that we helped over the years. When my son, Trey, became a Cub Scout it was even more exciting than ever. With the information age in full swing and the Internet starting to contain pinewood derby information, we could see there was a thirst for more racing information and supplies.

We had several items we had made over the years for building our cars. They were our little secrets, but I could see one guy on-line, Randy Davis of Maximum Velocity, was forging ahead in this new industry and I wanted to share a little of what we were doing. After testing our items, Randy said that they worked well and wanted to know if we would be interested in marketing them. My first thought was, “Wow, this could be a way to make a little racing money!” My second thought was, “We are a marketing firm who works with manufacturing, so I do know a little about sales.” I told Randy that I was interested in his proposal. Once again, I didn’t realize what was about to happen.

Maximum Velocity launched the Derby Worx Pro Body Tool, Pro Hub Tool and Pro Axle Press in October of 2002. We had no idea how they would sell, but with Randy’s hard work and great reputation, the tools took off, and Derby Worx was born.


The Derby Worx Facility
In 2005, we moved into a new facility in Millstadt, Illinois to help support Derby Worx’s growth. We added a few more products, and with the addition of an Okuma CNC1 lathe we started the Derby Worx Pro RS and SS wheel lines. In June and November of 2005 Derby Worx was granted United Stated Patent numbers for the Pro Hub Tool and Pro Body Tool. This was followed by a patent number for the Pro Wheel Shaver in 2007, and two U.S. Trade marks in 2008. Currently Derby Worx has six patents in different stages.


Okuma CNC Lathe at Derby Worx
In 2007 we partnered with Jay Wiles and Warp Speed Inc. to expand our BSA wheel and axle line up. Jay’s NASCAR background brings the passion and precision to build the best, and both companies complement each other quite well. The Warp Speed facility is equipped with two Haas CNC’s that exclusively turn out pinewood derby wheels and axles. In 2007 DerbyWorx added an Okuma CNC mill for machining additional items like the Pro Rail Rider Tool.


Haas CNC Lathe #1 at Warp Speed

Haas CNC Lathe #2 at Warp Speed

Okuma CNC Mill #2 at Derby Worx
In this current 2008-09 season, Derby Worx has brought several new items to the pinewood derby market. We now have thirty-four different pinewood derby specific products. The six new products this season are the Pro Rail Rider Tool, the Pro Body Jig, Pro Awana Lite wheels, Pro Pine Car Lite wheels, Pro RS-X wheels, and Pro SS-X wheels. We are also very excited in having gained the endorsement of the Boy Scouts of America. Derby Worx supplies the Pro Hub Tool, Pro Wheel Mandrel, Pro Axle Press and Pro Axle Guide to the BSA. But the real success of Derby Worx is driven by our customers, who have accepted our products from the very beginning and have been very helpful with everything from tool applications and improvements to new ideas. Thanks!

Bill Launius Jr.
President, Derby Worx, Inc.

Derby Worx is a leading innovator, manufacturer and distributor of pinewood derby supplies. They are located in Millstadt, Illinois

1CNC stands for Computer Numerical Control. Basically this indicates that the machine is computer driven.


Pinewood Derby Car Showcase

Guitar Car: Mark Robison

This is one of the more recent cars I have made. I downloaded a picture of a fender guitar, worked it into a pattern, used a little intuition, and voila … a Fender guitar car! This will surely be a hit among the kids (especially Guitar Hero fans — like my wife).

Cobra: Mike McBride

I always try to do a theme car every year that I don’t intend to race. I’ve got many interesting pieces of art on wheels, like this fluorescent cobra car that I did for a Halloween race this year.


Q&A

After sanding with the finest sandpaper, what is the best way to use pumice to finish polishing the surface?

Pumice is generally rated about 1500 grit, so if you have already polished with a paper rated at 1500 grit or finer, don’t use pumice.

If you do use pumice, then you will want to take a small amount, add water, and mix into a slightly runny paste. Then put some of the paste on a clean, soft rag and polish the spinning axle for about 10 seconds. Then buff off the residue with a clean, soft rag.

To get a finer finish than pumice, you can use jeweler’s rouge, and/or a metal polish such as Brasso, or Mother’s Chrome Polish.

Twice, I’ve chipped the wood of the car when I was putting my axles into the slots. Is there a recommended way to do this without chipping the wood?

If you are using a BSA or BSA-compatible block, then our “Pro-Axle Guide” tool solves this issue.

To make sure nothing chips you can pre-install spare axles into the blank block. Then twist and pull the axles out with a pair of pliers. When you put in the real axles, they should go in without difficulty.

Pinewood Derby Times Volume 8, Issue 8

– Feature Article – Canted Axles Revisited

– Pinewood Derby Car Showcase

– Memory – Magic Car

– Q&A


Canted Axles Revisited

The term “canted” means setting an object at an angle. Thus, “canted axles” are axles which are attached to the car at an angle. Sometimes this is done accidentally, but usually car builders cant axles in an attempt to reduce the amount of contact between the wheel tread and the track.

When discussing canted axles, the following questions must be asked:

  1. Is there an advantage to canted axles? We will attempt to determine this with an experiment.
  2. Which type of canting (up or down) would provide the most benefit? (see Figure 1) Generally, up canting is chosen as the wheel to car body contact is eliminated, and the car body is lowered. However, the guide rail contact is increased with up canting.
  3. What is the optimum canting angle? We will attempt to determine this with an experiment.


Figure 1 – Canting
Previous Experiment
Back in December of 2003 I conducted an experiment measuring the effect of canted axles (see Pinewood Derby Times, Volume 3, Issue 6, “The Big Debates Part 4: Canted Axles”, December 10, 2003). The results of that experiment were that, in general, up-canted axles were not beneficial. These results were supported by an experiment from another person, as well as from mathematical models.

Since then, I have had many discussions with various people regarding the results of this experiment versus the anecdotal support for canting. So I decided to rerun the experiment with some key changes. The main changes to the experimental method were:

Original experiment

  1. Four wheels on ground,
  2. Front and back canted equally,
  3. Cant angle adjusted by using multiple axle holes (axles had to be pulled and then reinserted to try a different angle. Unfortunately, this introduced experimental error.

New experiment

  1. Three wheels on the ground,
  2. Front dominant wheel not canted, but shimmed to cause rail-riding,
  3. Cant angle of rear axles synchronously adjusted with a mechanism (eliminates error introduced by pulling axles, and using multiple axle holes).

New Experiment

Equipment
The main equipment for this experiment is a car with an adjustable rear cant. Figures 2 through 4 show this car.


Figure 2 – Full Car
Note the fork of brass protruding out of the car. The fork is held in place by a screw into an L-bracket mounted on the car. When the screw is loosened, the fork can be moved up or down, adjusting the cant angle.


Figure 3 – Undercarriage
The fork from Figure 1 is connected to two aluminum tubes, which are press fitted into a slot milled into the bottom of the car. As the fork is moved up and down, the aluminum tubes synchronously move up and down. The axles are pressed into the aluminum tubes. (Note that the chip on the upper left is cosmetic; it doesn’t affect the mechanism).


Figure 4 – Side support
To force the aluminum tubing to move up and down at an angle, the end of each tube is supported by a washer. The screws hold the washer in place (I wasn’t sure if epoxy alone would hold the washer). The washer has a close fit with the tubing, so it does limit the amount of cant that can be applied to approximately 6 degrees down or up.

To set the desired cant angle, a little trigonometry is used. First, the length of one aluminum rod is measured (L). Then the up-down offset of the center part of the rod is measured (O). With this information, the following formula provides the cant angle:

Angle = arcsin(O/L)
This can also be worked in reverse to calculate the desired offset:

O = sin(desired angle) x L

Additional equipment for the experiment includes:

  • 32 Foot Aluminum Freedom Track, the track was leveled with a bubble level and shims.
  • Rear weighted extended wheelbase wedge weighing five ounces, front- left wheel raised
  • Max-V-Lube Graphite
  • Ultralight Speed Wheels from DerbyWorx
  • Speed Axles from Maximum Velocity

Procedure
The car was first aligned to rail-ride (see Volume 8, Issue 4), and then a few break-in heats were run. Then the following sequence was followed.

  • 5 runs, 0 degrees cant
  • 5 runs, 3 degrees up cant
  • 10 runs, 5 degrees up cant
  • 5 runs, 3 degrees up cant
  • 5 runs, 0 degrees cant

After the heats were run, the high and low times were removed and the remaining heats averaged.

Results The results of the experiment are shown in Figure 5.


Figure 5 – Experiment Results
Note the time scale on the left is in milliseconds. The results indicate that there is a very small improvement in performance by up-canting the rear axles. However, note that this is not an absolute conclusion as the statistical variation of the heat times is greater than the 3 milliseconds absolute difference in times. So, there may actually be no real improvement.

Conclusions
We can certainly say that accurately up-canting the rear wheels on a smooth aluminum track is not a disadvantage, and may provide a slight advantage. However, the benefit of canting on a rough track is unknown, but may provide a more noticeable advantage.


Pinewood Derby Car Showcase

iPhone: Hope Wallace

I know most of your cars are made by boys, but this was my car at our Girl Scout Troop’s first Powder Puff Derby. Although I raced at another troop’s Powder Puff derby five years ago, it was a lot more fun having our very own. I worked on the faceplate design, and my Dad taught me how to cut the block, polish the axles, and place the weights. Thanks to your tungsten weights, slim designs like this are possible … and pretty.

Silver Dollar: Bryan Solby

This car was a prototype and never actually raced. It was an idea we came up with and wanted to see if it was doable. The “S” body is made of 3/4 inch pine, cut on a band saw. The rods are 1/4 inch steel, approximately 7 inches long. The car, wheels, axles, and rods weigh just under 5 ounces. Originally it was painted green — because dollars are green — but later was repainted sliver and named the “Silver Dollar.”


Pinewood Derby Memory

Magic Car?

Our local church race was interesting this year — for me anyway. I usually try to build a nice car, but since I started hosting the event I haven’t been very careful to make it fast so that someone else can win. This year I was so rushed I didn’t even sand my car — only rough cut. About a half hour before I had to go to the race, I cut the tab off the Awana wheels, sanded around the edges to make sure they were smooth, and placed several drops of NyOil II on each axle (contrary to instructions). I then installed the axles in the original holes, made sure they had some side clearance (but I didn’t measure it), and added weights (not too accurately). The car weighed in light at 4.7 ounces.

So, what a surprise it was to see my car running first! Not only was it faster than the stock cars I raced, but it was faster than the times posted by the modified cars. I saw the car fishtail on a couple of races, so I can only imagine what the car could have done with tighter tolerances and more weight. Luck? Hmmm.

Corey
NC Awana State Grand Prix Open Coordinator


Q&A

Riding the Rail would not seem to be a winning strategy if the goal is to reduce friction? How does this work?

If you could get a car to roll down the track without contacting the guide rail, that of course would be best. But in reality, the car will contact the guide rail multiple times. The intent of the Rail Riding is to control which wheel contacts the rail, and how much contact is present.

A few key points:

  • If you use a raised wheel, to get the benefit that wheel must not contact the rail.
  • If your weight is in the back of the car, contact with a front wheel has less affect on performance than contact with a back wheel (more weight on the back means that rear wheel contact has more impact force than a contact with a front wheel).

So, the idea is to make the car contact only the front dominant wheel.

Did I read someplace that tungsten putty has about the same density as melted lead?

Tungsten putty (7.9 g/cm3) is denser than lead putty, but less dense than melted or solid lead (11.3 g/cm3). Please note that melting lead is a very risky. I strongly recommend using solid lead, or another metal such as tungsten.

Pinewood Derby Times Volume 8, Issue 7

– Editor’s Notes

– Pinewood Derby Car Showcase

– Memory – Nathan

– Q&A


Editor’s Notes

Christmas Issue

We’re taking a break from article writing, so there isn’t a feature article in this edition. Instead, we are including an an extended Car Showcase.

Reader Feedback
From Shawn Stebleton: Regarding your article on unusual tracks (Volume 8, Issue 5), the first of the two loop tracks shown (the red one with the jump following) is from our pack, Pack 207 in Murrysville, Pennsylvania. Our Cubmaster built it about ten or twelve years ago. We use it every year for our pinewood derby “Fun Day”, a build workshop combined with lots of fun. Not viewable in the picture you have is a net through the center of the loop to catch most cars that are unable to complete the circuit. Ironically, only the fastest cars — those with proper weight placement, good alignment, and polished axles/wheel bores — can make it through the loop successfully, and those are the cars the good builders don’t want to risk on such a track. I don’t remember exactly the story, but our Cubmaster said that someone from Canada had seen or heard of his track and wanted to build one similar to it. The picture of the other one is the result.

Operated as a pack fund raiser, the Fun Day is open to all scouts from not only our own pack but neighboring packs too. We have a station for cutting cars, including band saws (parents operate these), coping saws, rasps, sandpaper, etc. Weights, extra car kits, craft display stands, food, and other items are for sale. Parents bring lots of tools too, (I bring my Dremel and plunge router attachment, among other items) and freely share them and help any scout that asks. Teaching a scout how to use a tool (and understand the why behind it) is a great feeling. It’s held on a Saturday in early January, usually two weeks before our pack Pinewood Derby, and runs from about 8:30 am until 3:30 pm. Our next one is coming up January 10th, 2009.

The scouts can work on building their cars, test them, and enjoy running them. Cars from previous years are welcome on the loop-and-leap track, as most boys don’t want to use their new cars in such a way, for fear of damage. We also have a Demolition Derby track (our pack supplies cars to be smashed up) and a seat-belt demonstration track, with raw eggs as “passengers” and removable elastic straps that represent seat belts. We make some runs head-on with another egg car, and some head-on into a brick, both with seat belts and without. The scouts love it when eggs get smashed in a collision! It drives the point home about not getting your head smashed like the egg.

Here are some pictures from a previous year’s Fun Day event. We typically have about 100+ Scouts (accompanied by parents) throughout the day, some for a few hours, some all day.


Event Overview

Looking Down the Loop and Leap Ramp


Egg Car Without Seatbelt Crashing Into a Brick


Egg Family Cars After Head-on Collision


Pinewood Derby Car Showcase

Today’s showcase cars are from Chad Thorvilson.

I have been involved in the Cub Scouts since my son, Ryan, first started in 2000. The second year of the pinewood derby I made a new four lane Formica track for the pack. He is now in Boy Scouts, and he and I still help run the track. We have always enjoyed making cars and other projects in the shop. We no longer race, but we still make cars every year. The last few years I have been making trick cars.

This white and red car has a trigger on the bottom that releases the sides and roof. A small wedge is put on the track and when the car crosses it the sides and roof pop off.



The light blue speckled car leaves the cab behind as the tires and frame go down the track.




This blue car has a piece of radio antenna that I pull out to hold the competition back.



The red and blue car has a nose attached to a radio antenna. I pull out the nose and tell the boys that I will beat them by this much.




I also have a car with a small motor geared to the tire to make it run very slow (not shown). Here is my fan powered car and string/motor car.



We have also made some nice cars. We were finalists in the Lowes/Dremel contest one year and grand prize winners the last year they had the contest.


We look forward every year to the pinewood derby and working in the shop together. I get excited when the first Pinewood Derby Times arrives in my inbox.


Pinewood Derby Memory

Nathan

When Nathan (name changed) came to us two years ago (second grade then), he would not talk to us much, and when he did he kept his head down and wouldn’t look up to speak to us. He hadn’t experienced love from his parents; basically they have checked out. His self confidence and self-esteem were very low and he had a lot of pent-up anger and frustration. Nathan lives with his Grandparents, and his Grandmother sees to it that he gets to attend the weekly Ranger meetings. We have continually prayed, and worked with Nathan to obtain any change.

This past race season, Nathan designed a car and painted it with some help. I was thrilled to see him receive trophies (1st Place) for the design and speed of his police car at our sectional pinewood derby race. In fact all of the Ranger Commanders were excited for him and his win. He had a big smile on his face and I did too!

Lately he talks to me and the other commanders quite a lot, and he is coming out of his shell a little at a time as he learns to trust us. Recently, Nathan told his Grandma that what she needed was some hugs. It seems that he was being disobedient and didn’t want to follow her direction, so he tried to side track her with that comment. She was laughing when she told me about this, saying that we had been the reason for him to think about having and giving a hug.

Paul R. Mark, Senior Commander, Outpost #348


Q&A

Your book (as well as many others) focuses on lead or tungsten for weight. I have used large washers and buckshot with great results. Have I just been lucky?

There are many factors that affect performance, and weight is just one of them. Clearly you want to be at maximum weight, which can be accomplished with many materials. But the type of weight does affect the performance in a few ways:

  • Denser weights permit the achievement of a desired balance point with a low-profile design,
  • Denser weights allow the weight to be focused in one area, which appears to have some benefit in performance (I plan to run tests on these over this coming summer).

The Pro-Body Tool doesn’t fit on the BSA Pinewood Derby block that we have. It is just a few microns too narrow. Is the tool defective? Do I need to sand the block?

BSA blocks vary a bit in size depending on the setup at the mill. So some are a bit too big, while some are a bit too small. If the block is too big, then sand a little bit off of one side to get it to fit. If the block is too small, then insert paper on one side to tighten up the fit.

Pinewood Derby Times Volume 8, Issue 6

– Feature Article – Grooved Axles

– Pinewood Derby Car Showcase

– Memory – Ugliest Car in Derby History

– Q&A


Grooved Axles

One of the major areas of debate in pinewood derby racing is the benefit of grooved axles. This technique calls for placing one or more grooves in the axle shaft near the axle head. These grooves are thought to:

  1. Reduce friction,
  2. Serve as a reservoir for graphite,
  3. Reduce contact with a non-perfect axle surface (nail-type axles).

We’ll will discuss these points a little later.

Anecdotal (and thus questionable) evidence for the benefit of grooved axles abounds. Statements such as, “I used grooved axles and won, therefore grooved axles are better than non-grooved axles”, are commonly made, but cannot seriously be used to prove the benefit of grooving. In this example, any number of factors could have led to the victory; whereas the grooved axles may or may not have been of benefit (they could have actually made the car slower).

Theorizing
If grooved axles provide any benefit, there must be some scientific basis. Let’s first look at the three points given above, and then consider some additional possibilities.

    1. Reduce Friction – The use of grooves does not reduce friction. The amount of friction present in a system is based on mass and the coefficient of friction (F = mass x COF). The amount of surface area contact does not figure into the equation. So, when grooves are used, the amount of friction is not reduced, but instead the mass of the car is focused on smaller contact patches.
    2. Graphite Reservoir – Graphite is most effective when it is thoroughly worked into the wheel bore, and any excess graphite is shed from the system. The introduction of raw graphite (from grooves or otherwise) tends to slow down the car until the break-in and shedding is completed again.
    3. Reduction in Axle Contact – There may be merit in this theory. Since nail axles are not perfectly straight, round, and smooth, reducing the contact patch could be of benefit.Here are a few more possibilities, especially as it pertains to liquid lubes:
    4. Lube Channeling – Excess liquid lube tends to slow down a car (due to the viscosity – thickness – of the oil. If excess lube is used, the grooves provide space for any excess liquid, minimizing the amount of lube that is actually working to reduce friction.
    5. Lube Thinning – As discussed in point 1, grooves cause the mass of the car to be focused on small contact patches. This tends to thin the oil between the wheel bore and axle (reducing viscosity), which could lead to better performance in the short term.

So, if grooves are of benefit, the reason for the improvement will likely be due to points three through five.

Experiment Time
In order to prove/disprove the benefit of grooved axles, a controlled experiment must be conducted which eliminates as many variables as possible. Under these controlled conditions, the effect of grooves on axles can be ascertained.

An experiment of this type was performed in 2003 (updated in 2004) by Bob Barga.1 The results of this experiment generally showed that grooves were of benefit when using a liquid lube, but were detrimental when using graphite. This experiment also tested the effect of various polishing treatments. In our experiment we will focus entirely on the effect of grooved axles.

Apparatus
To eliminate variables, the performance of a wheel on an axle will be measured with a weighted-wheel spin jig (see Figure 1). This apparatus consists of a machined steel ring which is sized to fit snuggly over a machined BSA wheel. The ring weighs two ounces, which is essentially the load on a rear wheel of a pinewood derby car.


Figure 1 – Weighted Wheel Spin Jig
After sliding the ring over the lubricated wheel-axle assembly, the axle is mounted onto the apparatus. A length of fishing line with a weight on one end is wound around the ring (there is a small pin on the ring not seen in Figure 1, to which the non-weighted end of the string is attached). On each test, the string is wound until the weight touches the eye hook. The weight is then released and a stopwatch is used to measure the spin time. The string is sized such that it is released from the ring before the weight reaches the ground.

To ensure consistency:

  • A mark is placed on the head of the axle, and that mark is oriented at the 12:00 position when the axle is mounted onto the jig, and
  • The jig is shimmed such that the wheel runs on the axle without touching the axle head or the jig.

Wheels, Axles, Lubes
A set of DerbyWorx Precision Pro Stock Wheels were used. Two of the wheels were used with graphite, and two with Krytox 100. The results of each pair of wheels were averaged. Two of each of the following four axles were used:

  • BSA Speed Axle – Standard BSA nail axle that has been machined to create a smooth shaft.
  • Grooved BSA Speed Axle (4 groove) – Same as above but with the four grooves.
  • Super Speed Axle (smooth) – an oversized (0.091), nickel plated, machined axle.
  • Grooved Super Speed Axle (1 large groove) – Same as above, but with a single wide groove.

One of each of the above axle types was lubed with Max-V-Lube Graphite, and the other with Kryox 100. The recommended lubrication method was used in all cases.

Pairing
Referring to Figure 2, the wheels and axles were paired as shown. Thus, wheels one and two were only lubed with Krytox, while wheels three and four were only lubed with Max-V-Lube.


Figure 2 – Wheel Axle Pairing
Experiment Results
Each wheel-axle combination was given several “break-in” spins, and was then given ten timed spins. The high and low times were removed, and then the times were combined and averaged. The results are shown in Figure 2. Note that longer spin times mean better performance.


Figure 3 – Grooved/Non-Grooved Experimental Results
Test Conclusions
Here are the conclusions that I draw from these tests:

  1. With Krytox 100, grooved BSA axles provide a slight benefit. This is likely due to lube thinning. With oversized axles there appears to be no difference between grooved and non-grooved axles.
  2. With Max-V-Lube Graphite, BSA grooved axles provide significant benefit. This is likely due to a reduction in the contact patch. With oversized axles, grooves provide no benefit (or slightly negative benefit — the difference in times is within the experimental variance so a solid conclusion cannot be drawn).
  3. Although this was not the intent of the experiment, the data clearly shows that oversized axles perform significantly better than BSA axles.

1The results of the experiment are posted Here.


Pinewood Derby Car Showcase

Chilly Willy: Rob & Blake Overton

Attached is a picture of my son, Blake’s ice cream sandwich car which he named “Chilly Willy”. It won crowd favorite and took 3rd place in speed. We had to take the photo from the right side to see the bite (which is actually from Blake). He bit into a piece of foam and we traced it to the wood.

Photo Finish: Gary Kranston

This car competed in my daughter’s Indian Guide Pinewood Derby last year. Since my daughter is getting older and she likely won’t do this many more times, I wanted to create a special keepsake for her. I used clear acetate, and applied a decal I created to look like a filmstrip with some special pictures of our camping adventures together. Also, I used some small watch batteries to power a flashing yellow LED light at the front of the car and two white LED lights beneath the filmstrip. Not only was the car fun to look at, we raced it with outlaw wheels and won!

Flex Car: Tom Bybee


I compete in the open class in our pack which was designed mainly for adults and has very few restrictions. However, there is still a restriction of no external springs. Since we use an older wooden track that is pretty rough in places, cars lose a lot of energy because the entire weight of the car has to go over every bump. This year I tried a flex design. By doing some clever cutting and a lot of sanding, the car has four-wheel independent suspension — each wheel can flex and move more than 1/4 inch. With this design I was able to move the weight further back on the car (the wide area at the back is filled with lead) without fear that it would “pop a wheelie”. It also absorbed track bumps without losing much energy. Although from the picture it may look fragile, it is actually quite strong and won every race by well over a car length.


Pinewood Derby Memory

Ugliest Car in Derby History

When I was a young boy in cub scouts, derby time came. So like many other kids my dad helped me build my car. Because of my health problems, my dad worked two and sometimes three jobs, so spare time was a rare thing. As a young kid I didn’t understand why it seemed like I was having to build the car on my own (besides, I wasn’t doing such a good job of it). I didn’t know it then, but I had the very best in fathers. He helped me every chance that he had, but like I said, his time was in short supply. Anyway, the car finally was built and ready for paint. I was sort of on my own again for this, and I really messed it up bad. My dad saw it and said it wasn’t so bad, he would just sand it off and I could start over again. Nobody told me how to paint though, so it came out worse the second time around, and I also had run out of paint. As ugly as it was, things got even worse.

Race day came and I wasn’t going to take that ugly car to the derby. I am not sure which of my two older sisters or my mom came up with the idea that fingernail polish might cover the bad paint job — and that it dried really quick. Just as soon as I got home from school I started trying to make things better with some horrible color of fingernail polish that one of my sisters had given me. It got worse and worse. I kept piling on more of that thick gooey stuff. The polish would dry and I would put on more. It looked horrible. Nothing more could be done at that late date and even though I was very unhappy with the final results, we had to go race it anyway.

One of the first things I can remember when we got to the race was the cars that two friends of mine had brought. They were absolutely beautiful, formed so well and the paint was perfect on both of them. But both of those cars were eliminated before the race because that had not complied with rules and had used really trick slot car wheels instead of the plastic wheels required by the rules.

During the race, my car won races up to one of the very last rounds. The little ugly car smoked so many others, and not by just a little. I was so proud of it then even though it was hard to look at. This is not the end of the story, although I guess it could be.

Years later, derby time came around for one of my nephews. I helped him build his car (in other words I did almost all of it myself). It was perfect, sanded with 1000 grit paper, weighted perfectly on a digital scale, and the paint was so perfect. The car turned out great.

Race day came for my nephew and as we were having the cars inspected before the race someone doing the inspections mentioned to the crowd that these were some very good-looking cars that the “boys” had built. Then he looked right at me. He knew that this was my creation, not my nephews.

The race came and went and we were almost happy with the results. It turns out that the fastest car that night turned out to be the second ugliest car in derby history. Right behind the one I built when I was young.

Terry Graham


Q&A

In your opinion, what is the fastest axle for RA Racer wheels? We have tried the Super Speed Axles, but the width of the RA Racer wheel hub is a little short for these and doesn’t ride well across the grooves.

Assuming that your rules allow you to use axles other than those supplied with the kit, you can use Awana Axles. They are straight and defect free, and similar in diameter to the RA Racer axles.

I have a stock block with your axles and wheels — the light weight BSA wheels. I aligned the axles with your tool. I have your basic speed kit and Speed to Finish booklet. I used graphite as recommended. The car is running a consistent 2.68 second down the track, I only varied from 2.65-2.69. The problem is I need to be about 2.5 seconds to dominate the field. I’m limited to stock wheel base. Can you turn me on to any hot tricks?

If you are running 2.65 to 2.69, it may not be feasible to get to 2.50. However, you might get close using the “Rail Riding” technique. For information on this technique, take a look at the main article in the newsletter posted Here.