Pinewood Derby Times Newsletter Volume 12 Issue 11

Pinewood Derby Times
Volume 12, Issue 11
February 20, 2013
In this Edition:

- Editor's Notes

- Feature Article - Eliminating Race Variation

- Humor

- Product Showcase - BSA Speed Axles: One Set Free

- Pinewood Derby Car Showcase

- Q&A

Editor's Notes

MV Basic & Wedge Car Kits

If you are planning a race and are not required to use a specific kit type, our MV Basic or Wedge Car Kit are just what you need. These attractively priced kits are equipped with:

Quality Block - Unlike the blocks provided by some organizations, our blocks are soft, northwestern pine blocks, cut precisely to 7 inches long, 1-3/4 inches wide, and 1-1/4 inches tall. These dimensions, as well as the axle slots accurately duplicate the dimensions of standard pinewood derby blocks from BSA and PineCar.
Simple Axle Preparation - Don't worry about filing off flaws, or losing hub caps. Our Speed Axles have no burrs or crimp marks, and install without hub caps. With or without polishing, they are ready to go. We supply five, so you have a spare.
Quality Wheels - Forget cheap, out of round wheels. Our MV wheels are top-quality wheels. You will not be disappointed with the quality of these wheels.

So, if your organization does not mandate a particular kit type, consider our MV Basic Car Kits or MV Wedge Car Kits.

Can We Help? If we can help you in any way with your pinewood derby project, or if you have any feedback regarding this newsletter, please contact us at: [email protected]

Feature Article

Eliminating Race Variation
By Randy Davis

Have you ever looked at heat times for pinewood derby cars? If your event uses an electronic timer, then the heat times are available and can provide important insight on race performance.

Quite often the heat times vary considerably, while in some cases the heat times are quite close. This difference in heat times is sometimes called "race variation". Today we will look at what causes race variation, identify what can and what cannot be controlled, and then suggest ways to minimize race variation.

Uncontrollable Factors
Some factors that cause heat variation cannot be directly controlled by the car builder, however, in some cases they can be minimized by adjusting the car design. The main factors in this category are: Lane Variation, Staging Variation, and Finish Line Variation.

Lane Variation Under racing conditions, race variation will be introduced due to lane differences. On many tracks there are fast lanes and slow lanes. This lane variation can be due to defects in the track surface and lane guides, and/or warping of the track due to poor setup, improper storage, or exposure to heat or moisture. Although the race participant cannot directly control these factors, lane variation can be minimized by:

Setting the balance point of the car - If the track is known to be rough or warped, then setting the balance point to be less aggressive (more stable), will help the car to stay on a more true line as it runs down the track.
Setting the alignment - As long as the track guides are reasonably smooth, setting the car to rail-ride will minimize variation because the car will hold a straight line. Also, when rail-riding, the balance point of the car can generally be set more aggressive to improve performance.
Running on three wheels - keeping one wheel off the ground reduces track contact, which can help minimize variation.

Staging Variation Variation in heat times is also introduced by differences in the way the car is staged from heat to heat. If the car owner places their own car on the starting line, then variation can be minimized by staging the car consistently. But if a race official stages the car, then little can be done (other than to make sure the official knows which end of the car is the front end!)

Finish Line Variation The finish line can also introduce variation. If the front of the car is quite narrow, then the point at which the finish line sensor is tripped can vary depending on whether the car is centered, or is shifted left or right as it passes the sensor (see Figure 1). To minimize this source of variation, make sure the front of the car is a minimum of 1/2 to 3/4 inch in width.¹

Figure 1 - Finish Line Variation
Controllable Factors
There are many factors that can cause race variation which can be controlled by careful car design and construction. Some of these which have already been mentioned are weight position, alignment, and 3 versus 4 wheels on the ground. Additional factors include: precision components, better fitting components, aerodynamics, and lubricant choice.

If there are no limits on components and if the track is very smooth, then heat variation can virtually be eliminated. In an experiment using needle axle outlaw wheels, and Krytox 100 lube, the heat deviation was measured at .0016 seconds (standard deviation).² But even with more stock components, the heat deviation can be kept to .0030 seconds (standard deviation).³ So, proper design and construction can make a huge difference in heat variation.

Precision Components Regardless of the kit type, stock wheels and axles are not perfect. Wheels can be out of round, have a left-to-right wobble, and/or out of round bores. Axles also have defects and variation. To minimize heat variation, the wheels are axles should be as accurate as possible. Some possible remedies include:

Wheels

Truing wheels on a lathe or with a Pro-Wheel Shaver XT.
Measuring wheels and using the most accurate ones.
Polishing the bore of the wheel.
Purchasing trued wheels.

Axles

Polishing axles to a high shine.
Beveling the axle head.
Grooving the shaft.
Purchasing accurate replacement axles.

Better Fitting Components When wheels and axles have a sloppy fit, then the wheels have an opportunity to move in undesirable ways in response to track defects. So, to minimize heat variation, the wheels and axles should be sized to fit. This may not be possible due to rule restrictions, but if allowed, size the axle to be no more than 5 thousandths of an inch smaller than the bore. After-market axles with larger diameters are available for BSA and other wheels with a sloppy wheel/axle fit.

Aerodynamics Low-profile cars and narrow wheels both reduce aerodynamic drag and turbulence. Although these are minor factors, some improvement in heat variation can be achieved by reducing the cross-section of the car.

Lubricant choice Another possibility for reducing heat variation is the lubricant choice. Although I do not have firm results, it appears that Krytox 100 produces slightly less heat variation than graphite.

Conclusion
So, if you want to improve heat variation - and performance as well - consider implementing some of the options discussed above. You will find that your car is more consistent, and consistently faster than most (if not all) of the entrants in your race.

¹For more information on finish line variance, see Is Your Finish Line Providing Accurate Results?

²See Solenoid Start Gate: Are Races More Consistent? Although this article is not specifically on reducing race variation, it does show how consistent cars can run with precision components.

³See Cheater Bars - Do They Work? Again, this article is not on reducing race variation, but it does show how consistent cars can run with stock components.

Humor

Kathryn's 5-year-old developed a strong interest in spelling once she learned to spell STOP. After that, she tried to figure out her own words. From the back seat of the car she'd ask, "Mom, what does FGRPL spell?"

"Nothing," Kathryn said.

Sitting at breakfast she'd suddenly ask, "Mom, what does DOEB spell?"

"Nothing," Kathryn answered.

This went on for several weeks. Then one afternoon as they sat coloring in her room she asked, "Mom, what does LMDZ spell?"

Kathryn smiled at her and said, "Nothing, sweetheart."

The 5-year-old carefully set down her crayon, sighed and said, "Boy, there sure are a lot of ways to spell 'Nothing'!"

Product Showcase

BSA Speed Axles - One Set Free

Our BSA Speed Axles are precision-made to replicate the official BSA nail, but without the burrs and crimp marks. You can use these axles as is, or give them a light polishing if desired.

Through March 5, 2013, you can get one set of BSA Speed Axles at no charge. To take advantage of this limited time offer, Click Here and use coupon code 20FEBNL during checkout.

Car Showcase

Help, we are almost of cars for the showcase. Please send us your photos. Thanks.

CUDA - James White

This car named "CUDA" was built for my grandson's (Aaron Shain's) 2013 pinewood derby races. The rear fenders are made from a portion of the plastic bottle that the BSA wheels come in, and the cockpit canopy is made from a slice off the side of a small shampoo bottle.

Finn McMissile - Caleb Tachick

At my son Caleb's first Awana Grand Prix, he and Finn held their own most of the day, but ended up around 6th or 7th. But since it was our first year, the real goal was the design award. He came home with 2nd place; he would have had first but his sister's Cancer Survivor Ribbon car took first. They never raced each other until after the event when the track was open for fun runs. They ran neck and neck. Finn McMissile is shown here with the BSA wheels we swapped over to for the Home Depot race a month later, where he took 4th place -- not bad for a full bodied car.

Cancer Survivor Ribbon - Kailyn Tachick

Here is my daughter Kailyn's 1st place Awana car in the design category. This car was in honor of her grandma, who within the last year underwent treatment and surgery for cancer. We thank the Lord she is doing OK today. We did not hollow out the nose (my first year to build), but did incorporate rear fenders, reduced midsection as on supersonic jets, a concave tail end like a Shelby Daytona coupe, and speed axles from Maximum Velocity. After losing her first heat(in a double elimination race format), she continued to terrorize the loser's bracket to within a few heats from the end!

Share Your Car With Our Readers
Do you have a car you would like to "show off" to our readers? If so, send us a photo of your car along with a brief description of any special features. Also, please include your full name. If selected, we will include the photo and description in this newsletter.Please e-mail photos to:
[email protected].

Photos must be sent by e-mail in JPG format (minimum size of 640x480, maximum size of 1280 x 960). Please shoot photos from the front left of the car, similar to the orientation of this car:

For better focus, keep the camera four or five feet away from the car, and then use the camera's zoom to fill the frame with the car.

Send only one photo per car, unless an additional photo is needed to adequately show a feature. Also, only one car per subscriber per year please. Thanks!

Q&A

Do you have any advice on cutting an axle groove on a block with pre-drilled axle holes? Could I just take a hacksaw and cut a groove between the axle holes?

I wouldn't cut slots into a block with drilled axle holes unless your rules specifically state that axle slots are required. If you must have slots, then put two hacksaw blades together (most hacksaw frames will hold two blades), and cut down to the axle holes. If the blades don't stay together use one or more binder clips to hold them together.

I am interested in both the Pro-Axle Guide and Pro-Body Tool, and was wondering which you have found is more effective? Both seem as if they would work but I didn't know if one was more reliable.

If you are using axle slots, the Pro-Axle Guide will help you insert the wheels into the slots. But if the slots are not perfectly straight, then the axles will be crooked.

To get more accuracy, the Pro-Body tool will let you drill new axle holes, or put pilot holes in the axle slots. This will tend to correct slightly irregularities in the axle slots.

How does using lighter wheels help make the car faster? Common sense would indicate the total weight of the car would be the deciding issue here. So if I use lighter wheels, but ALL the parts together weigh 5.0 ounces, isn't it a zero sum game?

Lighter wheels generally improve the speed of the car, because lighter wheels take less energy to start rolling. So cars with lighter wheels tend to jump ahead as the starting gate opens. On normal length tracks, they can keep the lead through the finish line. If the track is exceptionally long, then cars with heavier wheels may catch up, as heavier wheels tend to roll longer.

Do You Have Questions that Need Answers? Do you have a pinewood derby-related question? If so, send your question to: [email protected]. We answer all questions by e-mail, but not every question will appear in the Q&A section of the newsletter.

Back Issues

Are you a new subscriber, or have you missed some of the previous newsletters? Don't miss out! All of the issues for Volume 5 through Volume 11 are posted on our web site and can be found using our Newsletter Index.

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Randy Davis, Editor, Pinewood Derby Times
E-Mail: [email protected]
Copyright ©2013, Randy Davis. All rights reserved. Please do not reprint or place this newsletter on your web site without explicit permission. However, if you like this newsletter we grant permission, and encourage you to e-mail it to a friend.

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