Wayne Schmidt's Awana Grand Prix Race Car Page: How to build the fastest Awana pinewood race car.

 
Introduction:

My interest in Awana Grand Prix racing began when my grandson asked me to help him build a race car for a Spring competition. My only previous experience with pinewood-type race cars was 25 years earlier with my son. Since we didn't do very well back then I decided a little study was in order to learn how to build the fastest possible Awana car. This proved be a frustrating venture because while there are a dozen books on the subject of pinewood racers and hundreds of web sites, the problem with all of them is that while they told me what to do and offered some explanations why it should be done that way none provided experiments to verify that the advice they provided was valid. This is critical because many sources offer conflicting advice. (The one exception to this is the excellent DVD titled Physics and the Pinewood Derby by Dr. Scott Acton, a physicist at Ball Aerospace Laboratory. This video provides the science behind building lightning fast pinewood race cars in a thoroughly entertaining and enlightening mix of experiments and practical advice. While I reference this DVD many times on this page, this video covers a wealth of additional information not mentioned here that is worth the purchase price many times over. I strongly recommend that anyone seriously interested in building a fast Awana Grand Prix race car, or any pine wood race car, purchase this DVD. It's available from many sources including Dr. Acton's web site at www.pinewoodphysics.com.) Note: On 6 May 2014 I attempted to order another DVD from Dr. Acton through Amazon and never received it. He failed to respond to three emails to find out what happened to the order. This suggests that he is no longer interested in marketing this DVD.

Before we start building the ultimate Awana Grand Prix racer, a little background is appropriate.

Awana, (Approved Workmen Are Not Ashamed) is a non-denominational, Christian youth organization similar to the Boy Scouts of America in that it strives to promote responsible development in children. One of the programs they support is the Awana Grand Prix race every Spring. Participating children purchase Awana Grand Prix car kits, build their cars with the help of their parents or other relatives and race them at a church participating in the Awana program. The car kits are almost identical to Boy Scout pinewood derby kits in that they consist of a pine block measuring approximately 7-inches long, 1.75-inches wide and 1.25-inches tall, four wheels embossed with the Awana Grand Prix logo and a set of axles.

The biggest difference between Awana Grand Prix car kits and all the other variations of pinewood race cars is that while many programs use simple nails for axles, the Awana car kits use small hinge pins. This has a profound effect on one of the critical aspects of car construction: axle polishing. This topic and many others will be researched and discussed in detail further down the page.

A lot of what follows is painfully detailed so let's start off with something lighter. The following video shows the favorite cars in my collection. I hope you enjoy them.

Here's one more you might enjoy:

So much for fun. Let's get started!

 
Methodology:

The times reported in the various tests on this page are for cars running on my track at home and are for comparison purposes only. If they appear slow that is because the vinyl surface on the track has a slight texturing that causes it to run slower than polished plywood tracks and much slower than aluminum tracks. Additionally, while most 32-foot tracks have actual run lengths of 30 feet or less, mine has a run distance of 31.1 feet. Finally, the start end of most tracks is 48 inches high. Mine is only 44. All these factors add up to a very slow track. For comparison, I made a car identical to one used by Dr. Acton for his DVD and discovered it ran 0.030 seconds slower on my track than on his. The conclusion is that if some of the times reported for what I consider a very fast car sound slow, it's because of the track.

It is my intent to provide experimentally verified information to help people construct the fastest possible Awana Grand Prix car. Readers are provided with the raw data as well as the experimental methodology so they can decide for themselves if the conclusions are valid.

The methodology used to compare speed techniques was to run a set of ten runs with the car in its normal configuration, make the change to be tested being careful to keep everything the same, particularly alignment, then run a second set of ten runs. The times for the two sets are averaged to determine if there is a significant difference. The track is vacuumed before every set of ten runs to avoid dust buildup, which can effect times. For the same reason, wheels were wiped off to prevent imbedded grit from slowing the car by roughening the wheel surface. As an example, the following experiment determines the error between tests:

The same car was raced with no changes made between sets except that fresh graphite was added at the beginning of each set of ten runs:

Run Set 1.....................Run Set 2

2.542 seconds..................2.531
2.569..............................2.563
2.558..............................2.545
2.553..............................2.557
2.564..............................2.540
2.544..............................2.564
2.547..............................2.541
2.550..............................2.560
2.553..............................2.551
2.542..............................2.553

2.552 seconds average....'..2.550 seconds average

The 0.002-second difference suggests that when comparing speed techniques, unless the technique being tested shows an improvement greater than this then it is impossible to claim whether it works or not. This criterion is used throughout this page to judge whether a technique is worth applying. I'll be the first to admit that larger test runs should be used but I had to compromise some accuracy due to time constraints. It's important to understand that the test results reported are for my cars running on my track. Other people using different equipment may obtain varying results.

The biggest source of inaccuracy with this technique is axle alignment changes in those tests where the wheels have to be removed. Marking the axle heads helps return them to their original alignment.


 Painting the axle hub white makes placing an alignment mark on it easy. This
records where the axle is aligned, which allows removing and replacing
the same axle without affecting the car's alignment.

 
I always test the alignment by running the car down an inclined flat board. If the car swerves off a straight line it is realigned so that it tracks as straight as it did before the axles were removed. Test runs confirm that the average change in run times before and after axle removal is 0.004 seconds. If a speed technique produces a change that is smaller than this then no judgement can be made regarding its efficacy.

The timer used for the experiments was a Timestopper TS100-2 running 3.0A software. It measures to 0.0001 seconds and rounds to display to 0.001 seconds.

Sometimes there are changes in run times between large groups of tests. For example, run times increase between the sequence of test runs comparing Max-V-Lube, Hillmand and Hub-E-Lube and the follow-on sequence of test runs comparing Max-V-Lube, Super-Z Graphite and Super-Z Graphite with oil. The cause of this was a change in the configuration of the track. For this reason comparisons across different groups of tests should be approached with care.

Major topics are bookmarked so that visitors may quickly skip down to the article they want. The first line in each article is a summary of results so readers can get the answers to their questions as quickly as possible. Following this summary are the experiments and analysis that provided the conclusions in the summary.

Several products are mentioned on this page. I have no connection with any of these products or the people who market them. No one is has paid or asked me to mention them.

The topics are ordered with the most important speed hints listed first. I hope you find them helpful and wish you all good racing!

 

Topic List:

Graphite: Why it's the single most important factor, what types to use and how to apply it.

Axle Alignment: How two wrongs make a right.

Center of Mass and Moment of Inertia: Understanding these two concepts is essential to building the fastest car.

Axle Treatments: How much polishing helps, what about hub coning and do slots really reduce drag?

Wheel Treatments: The dangers of wheel mandrels, does bore polishing help, graphite coated wheels, rim smoothing, the spin-up myth, hub coning, and are $40 lathed wheels worth it?

Three Wheel Cars: How much faster are they?

Extended Wheel Bases: How much do they increase speed?

Rail Riders: Do they really make the fastest cars?

Hub Huggers: Myth or fact?

Quick Start Wings: Do they really provide 0.010-second head starts?

To Bake Or Not To Bake?: Cooking your car may reduce it's weight, but is the risk worth it?

But Dad, I really want fins: A hard look at aerodynamics.

The Shock Absorber Design: Do flex-bodies really help cars run smoother and faster?

Rules: A typical set of rules for Awana Grand prix races.

Putting It All Together: My fastest car.

How Fast Is Fast?: How fast they go.

When Good Cars Go Bad: How a speed demon can turn into a dog.

But I Was Winning!: The dynamics of racing.

Building a Super-Cheap Track for Home Use: Would you believe a 32-foot track for $20?

Want a Super-Cheap Timer to Go with that Super-Cheap Track?: It'll cost another $30.

Odds and Ends: Useful bits and hints.

2013 RACE RESULTS!!!

Are Dr. Scott Acton's Cars Really the Fastest Cars?

Treadmill Tuning: Does it really help?

Bibliography: The sources referenced in creating this page.

Graphite:

Summary:

a. Using graphite is the most effective way to increase car speed.
b. Max-V-Lube gives the best times.

Nothing is more important than having a good layer of graphite on your car's axles. I've had cars that were out of alignment, had bent axles, wobbly wheels, poor centers of gravity and insufficiently weighted, but as long as they had a liberal coating of graphite they somehow managed to make it to the end of the track. I've also had class-A speedsters that rolled to a stop halfway down the course because I failed to graphite their axles.

The two big questions are: What type of graphite is best and what is the best way to apply it?

To answer these questions I drafted my oldest grandson's car to test three common brands.


Joshua named his car Lighting Quick, and it's an appropriate name.
It's been the Grand Champion at several family races.

The first three graphites tested were: Hillman (graphite for locks), Hob-E-Lube (graphite and molybdenum mix) and Maximum-Velocity's Max-V-Lube (pure graphite.)

Max-V-Lube was many times finer than the other two and the container comes with a long thin tube that makes reaching into tight area around axles easy.

 
How To Apply Graphite:

There are six surfaces that have to be coated with graphite: the axle, the wheel bore, the area of the car body that contacts the inside hub of the wheel, the inside wheel hub, the outside wheel hub and the inside face of the axle hub. To insure that all six surfaces get the same treatment I adopted the following routine:

1. With a wheel down to expose the inside section of axle, I build up a fillet of graphite all the way around the inner wheel hub.

 

I then press the wheel up against the car's body and twist it back and forth four times to work graphite into the body's surface and the inner hub face.

2. I build up another fillet and this time tap the wheel lightly with a fingernail ten times to enable graphite to work into the gap between the axle and wheel bore.

3. The car is turned over and both steps repeated for the outside of the wheel.

 
For the test I began by removing the wheels, scrubbing the bores clean with a cotton pipe cleaner, wiped off both wheel hubs and the hub contact point on the car's body and carefully cleaned all traces of graphite off the axle. This process was repeated for all four wheels then they were regraphited with the graphite to be tested. Then the car was run down my test track 10 times, recording the time of each run.

Here are the results of the graphite tests:

Hillman ..........................Hob-E-Lube .....................Max-V-Lube
2.564 seconds....................2.544..............................2.542
2.550................................2.528..............................2.554
2.537................................2.527..............................2.539
2.541................................2.532..............................2.533
2.547................................2.546..............................2.510
2.516................................2.559..............................2.535
2.529................................2.550..............................2.537
2.547................................2.570..............................2.542
2.552................................2.561..............................2.541
2.577................................2.551..............................2.547

2.546 seconds average......'..2.547 seconds average...'...2.538 seconds average

 
It may not seem that Max-V-Lube's 0.008 and 0.009-second advantages are significant, but at an average speed of 13 feet per second this corresponds to a lead of 1.2-inches at the end of a race, more than enough for an electronic timer to signal the Max-V-Lube car the winner.

Shortly after finishing the test above I read an article about Super-Z graphite and Super-Z oil which, when used together, were claimed to produce a super low coefficient of drag and therefore very low race times. Carefully following the manufacture's instructions for using these products I conducted the following tests:

Max-V-Lube ................Super-Z Graphite ....Super-Z Graphite and Super-Z Oil
2.766 seconds....................2.785..............................2.931
2.740................................2.812..............................2.925
2.740................................2.827..............................2.933
2.740................................2.835..............................2.891
2.753................................2.822..............................2.901
2.745................................2.837..............................2.918
2.747................................2.812..............................2.875
2.744................................2.823..............................2.867
2.736................................2.816..............................2.894
2.739................................2.832..............................2.900

2.745 seconds average........'2.820 seconds average......2.903 seconds average

These tests strongly suggest that Max-V-Lube is superior. The very large flakes of Super-Z Graphite were extremely difficult to use and the application process much more involved than that of the other graphites tested. (Note: The increased times over the first set of tests were the result lowering the starting end of the track. Also, even if the Super-Z oil had worked, most Awana Grand Prix races only allow graphite.)

 
Graphite Types:

From left to right: Hillman, Hob-E-Lube, Max-V-Lube, AGS Ultrafine Graphite, 0.6 micron Tungsten Disulfide, Super-Z Graphite

Smearing each with a finger disclosed some interesting comparisons. Hillman, Hob-E-Lube and Max-V-Lube all smeared smoothly. (Max-V-Lube has a granular, almost crystalline appearance.) AGS Ultrafine looked clumpy and felt a little gritty. Where I first pressed my finger it left a clump of compressed material that was hard to dislodge. The tungsten disulfide looked extremely clumpy but smeared the smoothest of all. (It's reported to be twice as lubricating as graphite.) Super-Z had very large, hard to control flakes that nevertheless smeared smoothly.

 
Comparing Max-V-Lube to AGS Ultrafine Graphite and Consolidated Chemical's 0.6 micron tungsten disulfide lubricants:

Max-V-Lube .................AGS Ultrafine ................Tungsten Disulfide
2.712 seconds....................2.785..............................2.921
2.701................................2.813..............................2.911
2.698................................2.804..............................2.924
2.710................................2.818..............................2.930
2.704................................2.797..............................2.917
2.709................................2.806..............................2.898
2.713................................2.811..............................2.904
2.707................................2.798..............................2.911
2.698................................2.801..............................2.916
2.704................................2.810..............................2.902

2.706 seconds average......'..2.804 seconds average...'...2.913 seconds average

AGS Ultrafine and tungsten disulfide did very poorly in part because they were so fine they clumped and were impossible to coat the axles. I repeated the test, this time breaking the established application protocol by removing the axles and rubbing AGS and Tungsten disulfide directly onto the axle shafts and wheel bores. That did not change the results. After completing these tests I found another ultrafine graphite sold by Consolidated Chemicals. Like the AGS Ultrafine, it did very poorly when compared to Max-V-Lube. Another problem with ultrafine graphites is that they are so fine that if spilled on almost any surface they get pulled into microscopic pores and become messy and difficult to remove.

Max-V-Lube has proved itself superior to seven other lubricants so it's the one I'm using from now on.

Axle Alignment:

Summary:

a. The axle slots and predrilled holes in commercially produced Awana or pinewood derby blocks are not accurate enough for optimum performance.
b. Pro body tools for guiding drill bits for drilling axle holes are far too inaccurate.
c. The best way to mount axles is in holes drilled with a drill press that's been set up to create holes that are within 1/4-degree of perpendicular.

When I began making Awana Grand Prix cars I just about went crazy. My cars always swerved off to one side or another. My only recourse was to go through an arduous process of axle bending to get them to track straight. After countless hours examining the problem I discovered that the predrilled axle holes and precut axle slots in the blocks I was buying were as much as 2 degrees off perpendicular, even on the high-end precision-cut blocks available on-line.

I tried using a pro body tool to act as a guide for drilling holes that were more perpendicular to the sides of the block. It made things worse.


Pro Body Tool

The hole for guiding the drill was large enough that the drill bit could lean two degrees off perpendicular.

I decided that the only thing to do was buy a drill press. It didn't help. I quickly discovered that the adjustments on it were far too coarse to achieve the 1/4-degree accuracy required. But at least the drilling surface was stable and the drill head fixed. I learned that by using layers of tape on the drill bed to shim the back and sides of a wood base I could finally get the press to drill axle holes that were almost perfectly perpendicular to the sides of the block. I grabbed a block, threw on the press's switch and drilled four beautiful holes. Two minutes later I'd mounted wheels on it and let it roll down the alignment board (a 10-foot long by 6-inch wide piece of vinyl coated molding with one end elevated 5 inches) and watched in horror as the car swerved sharply to the left and fell off the board before it traveled three feet.

After examining the problem I discovered that even the best Awana and pinewood derby blocks don't have truly perpendicular edges. They all have slight tapers that give them trapezoidal cross sections. Even though the holes on one side were perpendicular to that side, because that side wasn't parallel to the opposite side the axles on the second side aren't parallel the axles on the first side. I was about to give in to the inelegance of bending axles to achieve alignment when inspiration struck.

If I mounted a wood fence on the drilling base that was perpendicular to it then held the bottom of the car block against it, rather than the side of the block against the bottom of the drill press platform which is more typical, then all four axles would be drilled relative to the same surface: the bottom of the block.

To check the accuracy of the holes, something I do using a test block before drilling the real holes in a car, purchase a 3/32-inch brass rod from a hobby store. After a little sanding on one end with 400-grit paper it should slide down very snuggly into an Awana-sized hole. Using one edge of a very accurate architect's triangle, hold it against the base of the block and check to make sure that the separation between the rod and triangle is constant all the way up the rod's 12-inch length. Then use the right angle of the triangle with one side parallel to the long edge of the block and check that the rod is perpendicular that way as well. (Check the rod's straightness by rotating it in the hole. If the angle relative to the edge of the triangle remains constant it's straight. I'm always careful to hold the block so the rod points straight up. If it's leaning the rod could flex enough to throw the check off.) If the rod shows the hole is straight you're good to go. If it shows an angle then add or remove shim tape to correct it. As simple as this system is it can repeatedly drill holes that are with 1/4-degree of perpendicular.

It worked... almost.

The first car I built using this system rolled down the alignment board swerving just 2-inches in ten feet. Good, but not good enough. I thought I was doomed to descend into axle bending when inspiration struck for the second time. This time it was the realization at at least as far as pinewood race cars are concerned, two wrongs really do make a right.

The first "wrong" is that no axle hole will ever be perfectly perpendicular. The second is that no axle is perfectly straight. Realizing that the very small amount of bend in all axles is on the same scale as the very slight off angle of the axle holes, I realized that if the axle was rotated so that its bend turned the axle in the opposite direction that the axle hole pointed it then the two defects would cancel.

It worked. I began turning the front right axle a quarter turn at a time and on the second turn the car ran straight down the alignment board. It was beautiful. I made two more cars the same way. The first tracked straight the first time I tested it and the other only took three twists to get it to run straight. I was riding high thinking I'd conquered crooked axles forever. Then everything went horribly wrong.

I drilled the holes for a new car, put it on the alignment board and watched in horror as it swerved sharply right. No amount of axle turning would solve the problem. What had happened?

Nature happened. Wood blocks have grain: alternating layers of soft, light wood and hard, darker wood. If the drill hits a layer of hard grain at a small angle the bit will bend as it slides along the hard wood and drill a curved hole.


The white line represents the path of the drill as it's deflected by a layer of harder wood.
Normally this isn't an issue but the thin drills used for Awana axles bend very easily.

When an axle is inserted in such a hole it'll end up coming out at a slight angle. You can feel this when inserting an axle because instead of sliding in snuggly it has to be pressed in very firmly.

To reduce this problem, stub bits short in the chuck so that only the absolute minimum needed to drill the axle hole is exposed. This effectively makes the drill stiffer. Select wood with the grain as close to perpendicular to the direction of the drill as possible. Drill with a high rotation speed so the drill has more cutting strength to help it pierce the hard layer. Finally, drill very slowly so the bit has enough time to grind through hard layers. I usually take one minute to drill an axle hole that's only 1/2-inch deep.

Another useful trick is to avoid drilling axle holes right next to the edge, as pro body tools do. The problem is that wood is flexible enough that while drilling it will actually bulge out. You can feel this happening if your finger is over that spot. By moving the axle hole 1/8-inch from the edge the extra thickness provides enough strength to prevent this and yield straighter holes.

Once the axle holes are drilled it's time to align the axles in them so the car runs straight. Rough out the shape of the car first to relieve any internal strains that might throw alignment off. Polish and lube the axles before alignment because axle drag can be enough to turn the car even if the axles are perfectly aligned. Place a weight on the car near the rear, remove one of the front wheels and roll the car down the alignment board. If it curves, rotate the axle 1/4-turn and try again. Usually, before you get back to where you started you'll find a position where the car tracks straight. Don't be afraid to play with the rotation. Sometimes a tiny fraction of a turn makes the difference between a car running arrow straight and curving. Use a permanent marker to make a mark at 12:o'clock on the axle head so you know that axle's alignment position and remove it. Repeat the process with the other front wheel then test them together. When they are done turn the car around, move the weight to the new rear end and repeat the alignment with the rear (now front) two wheels. Replace all the wheels using the axle marks to get them back to their properly aligned positions. Check the car one more time and you should be good to go. Remove the wheels and finish the car. The alignment needs to be repeated after the car is finished because all the handling might warp the wood slightly.

Cars can be made to roll straight by leaving all four wheels on and playing with the axle rotations. This saves the hassle of aligning each wheel by itself but it may end up being a car that rolls very straight... and very slow.

What can happen is that two wheels can be off angle by the same amount but in opposite directions. In other words the car is pigeon toed. One wheel wants to turn the car left while the other wants it to go right, both by the same amount so they cancel each other and it goes straight. The problem is that because the wheels are pushing against each other the wheel drag goes sky high and the car never runs as fast as it should. (Dr. Acton's DVD shows how to make a jig for testing axle alignment.)

If you find that axle rotating doesn't quite achieve the alignment needed, try using a different axle. There is always some variation in manufacturing error and a different axle may have enough natural bend to get the car running straight.

Once in a while I end up with a hole that's just too crooked to deal with by rotating the axles. The best course of action is to start over with a new block and hope for straighter axle holes. But if you've invested a lot of time and money in the existing car then there is no other course other than axle bending. After aligning all the other wheels, remove the offending axle and wheel. Hold the axle in a pair of long nosed pliers just below the area where the wheel rides and using a second pliers, bend the bottom of the axle "very slightly." You shouldn't be able to see the bend. Reinsert the axle and wheel and continue the alignment. Bending is a very powerful technique. Usually, the amount of bend is many times what's needed so the angle over which the wheel is aligned is very small. It can be frustrating when a tiny rotation of the axle results in the changing the car from swerving hard right to hard left.

 
All of the above has worked great for me for building many solid body cars like this:


 
It doesn't work as well with more complex high performance cars like this:


Grandson James' Dale Sr. blows past even the very fast Lightning Quick.

 

The reason is that so much wood is removed after the axle holes are drilled that the wood that's left invariably warps. Drilling the holes after final shaping isn't always possible because there's not enough left of the base of the car to act as a reference plane. This is one of the frustrating aspects of building a top performer, as the following car demonstrates:

 

 
After drilling the axle holes and epoxying the tungsten weight in the car above, I carefully aligned it. Going forward or backward it tracked perfectly straight. Then I proceeded to gently remove all the wood I could to make it the high performer I hoped it would be. After it was complete I placed it on the alignment board and as expected, it failed to track straight even though I'd positioned the axles using marks I'd put on them after the first alignment. I had expected as much and started realigning it. In the end I got it pretty good... but "pretty good" isn't good enough for a car intended to be a winner. No matter how much I played with the axles the best I could do was reduce a swerve to the right to 1.5 inches over ten feet, as indicated by the black arrow. I was about to resort to the brute-force technique of axle bending when it occurred to me that the amount of misalignment was so small that there might be enough flexure in the wood itself to fix the alignment. I held the car body in my left and and with my right grabbed the front axle section, gently twisted it in the direction of the green arrow and held it there for a count of 20. It worked. The car now tracked absolutely straight. Better still, half an hour later it was still running straight so it seems this is a long term fix.

For cars with bodies whittled away enough to have some bendability, gently twisting the front in the opposite direction of a persistent swerve might help provide a final touch-up to alignment. But be warned, the front ends of such cars are extremely fragile so don't use too much muscle or you may break it off. Also, be sure to check the alignment right before a race to verify that it's held. The front end's flexibility should be kept in mind when handling the car. Carrying it by the front may throw the alignment off.

In rare cases a car will start swerving one direction, straighten out, then turn in the other direction. I believe what is happening is that a misalignment is turning it one way but as it gets into the bottom half of the alignment board a speed related friction factor on one side begins dominating the car's motion and turns it back the other way. Try using a new set of axles and wheels to correct the problem. If it persists it might be best to start over and build a completely new car.

(Note: Always keep a log for each car recording how each axle affects alignment. If you get the chance to test your car on the track before a race you can use the log to fine tune the car. Also, in his DVD Physics and the Pinewood Derby, Dr. Acton presents an outstanding way to build cars with an adjustable alignment system.)

Conclusion: Thorough wheel alignment can be a challenging task, but one that is absolutely essential for building the fastest possible Awana Grand Prix race car.

 

Center of Mass and Moment of Inertia:

Summary:

a. Build your car so that it balances 0.9 inches in front of the rear axles.
b. Concentrate as much weight as possible in as small an area as possible.

&n