Stallion

Stallion

Pinewood Derby Times
Volume 7, Issue 3
October 31, 2007

In this Edition:

- Editor's Notes

- Feature Article - Effect of Wheel Weight on Performance

- Tip

- Humor

- Product Showcase

- Car Showcase

- Memory - Mrs. Bubba's Do's and Don'ts

- Q&A




Editor's Notes
Reader Feedback

From Stan Pope: "Good feature article in Volume 7, Issue 2, 'Is Your Finish Line Providing Accurate Results?' A trouble source not mentioned is that the light source can be too wide. I saw one with a 9-inch diameter metal reflector around a lamp. When combined with a narrow car nose. the umbra (totally shadowed portion) is smaller than the car's nose. The wide light source instead creates a penumbra (partially shadowed portion) which may fail to trigger the sensor.

Wide light sources can also cause car nose height to make sensor triggering less accurate. If the sensor is very sensitive, a high nosed car (barge nosed) may trigger the sensor early. If the sensor is much less sensitive, that same barge nosed car may trigger the sensor late.

A routine practice of requiring multiple judges (one of which is electronic) will catch finish placement exceptions -- most of the time. The human judges may keep the electronics honest for determining place, but they don't help when the competition is by time. Then the human judges will only be able to detect problems that involve very close finishes. Then there is the issue of overriding the mechanically recorded results!"

Inventory Clearance Sale

We also have several items on Inventory Clearance. Supplies are limited so make sure to get these discounted products before they are gone!

Maximum Velocity Car Kits
New Lower Price

If you are planning a race and are not required to use a specific kit type, our MV Basic Car Kit is 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. We supply top-quality, PineCar-brand wheels to give great performance.
So, if your organization does not mandate a particular kit type, consider our Maximum Velocity 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: info@maximum-velocity.com



Feature Article

Effect of Wheel Weight on Performance

One of the major changes to pinewood derby racing during the past year was the wide-spread availability of light-weight speed wheels. For BSA, wheels ranging from 3.3 to 1.0 grams were offered by various vendors including Maximum Velocity.

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

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

Experiment Equipment

The experiment used the following equipment:

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

Figure 1 - Wizard Body Weighted for 1.0 Gram Wheels

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


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

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

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

Experiment Procedure

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

  1. Three heats were run with the 1.0 gram wheel weight. An o-ring was then added to each wheel, and tungsten beads were removed symmetrically to maintain the 5.0 ounce weight and center balance point.


  2. Three heats were run with the 1.9 gram wheel weight. A second o-ring was then added to each wheel, and the weight adjusted to 5.0 ounces.


  3. Six heats were run with the 2.9 gram wheel weight. One o-ring was removed from each wheel, and the weight was adjusted.


  4. Three additional heats were run with the 1.9 gram wheel weight. The last o-ring was removed, and the weight was adjusted.


  5. Three heats were run with the 1.0 gram wheel weight.
Experiment Results

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

Figure 3 - Experimental Results

Conclusions

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

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

1Pro-Ultralite Speed Wheels are available
Here

2Speed Axles are available Here (scroll down to part #5095)




Tip
Colored Spokes

Everyone likes the way the spokes look when they are painted with a silver color. But how do you achieve the fine detail without making such a mess?

Answer: A Prismacolor silver colored pencil. The colored pencil is soft enough to leave the silver color on the spokes without having to worry about paint running down in between the spokes. It also gives a child better control than when using a paint pen or a felt tip Sharpie marker. Best of all, if there is a mistake just erase it!

Jim Leehy

Speed Tips, Web Site or Product Reviews?
If you have a speed or construction tip, a web site review, or a product review that you would like to share, please send it to:
info@maximum-velocity.com

If your submission is used, you will receive a $10 coupon in May of 2008. Don't worry about literary polish. We will edit it as needed before publishing. Also, please read our Submission Policy.




Humor

A Texas rancher was visiting a farmer in Israel. The proud Israeli showed him around. "Here is where I grow tomatoes, cucumbers, and squash. Over there I built a play set for my kids, next to the doghouse," the farmer said.

The land was tiny, and the Texan was surprised by its small size. "Is this all your land?" he asked.

"Yes," the Israeli said proudly. "This is all mine!"

"You mean this is it? This is all of it?" the Texan said incredulously.

"Yes, yes, this is really all mine!"

"Well, son," said the Texan, "back home I'd get in my car before the sun'd come up and I'd drive and drive and drive, and when the sun set, why, I'd only be halfway across my land!"

"Oh, yes," replied the Israeli farmer wistfully, "I used to have a car like that."

Amir Rosenbaum
Milpitas, California




Product Showcase

Grooved Official BSA Speed Axles

The nail axles supplied by BSA in the Cub Scout kit are notorious for their flaws, bent shafts and out of round heads. This results in considerable effort to create a precision axle.

If you have the tools to work on these axles, then we encourage you to do so. However, if you don't have the tools, then we offer a solution.

Grooved Official BSA Speed Axles are official BSA nail axles with:

These axles can be used without any preparation, but a light polishing is recommended.

Grooved Official BSA Speed Axles - $2.00 Off!

Until November 13, 2007, you can purchase Grooved Official BSA Speed Axles at $2.00 off the regular price. To take advantage of this limited time offer,
Click Here.



Car Showcase

Cub Scout Theme Cars: Bill & Zachary Williams


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

By the way, for the first time this year we used the new Tungsten Plates1. This is a GREAT product!!! We used 6 of them (3 oz. total) under the rear section of the car. Three of them were recessed into the bottom of the car as to make them flush with the bottom of the car. The other three were mounted on top of these and hung below the bottom of the car. We still have plenty of clearance under the car. Our body was very light, about one ounce, and very light in the front of the car. These tungsten plates added an ENORMOUS amount of stability to the car. We only had to add about 2 tungsten cubes more weight to get to five ounces. This is one of the best new products I have seen come on the market.

Formula One: Chris & Jacob Holan


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

Mack Truck: Roger & Cole VandePoel


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

1Tungsten Plates are available
Here

Share Your Pinewood Derby Car Creation
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:
info@maximum-velocity.com.

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 the cars shown above.

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!



Pinewood Derby Memory

Mrs. Bubba's Do's and Don'ts

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

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

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

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

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

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

Do - allow your younger ones to watch "Down and Derby" - mine think it's hilarious.
Don't - allow them to badger their mother about watching it again and again.

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

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

Share Your Pinewood Derby Memory!
I am sure there are many stories to share. Please jot down your humorous, unusual, sad, or heart-warming pinewood derby tale and send it to: info@maximum-velocity.com

If your memory is used, you will receive a $10 coupon in May of 2008.

Don't worry about literary polish. We will edit as needed. Also, please read our Submission Policy




Q&A

I have run out of fresh questions, so these are recycled and updated from Volume 1 of the Pinewood Derby Times published in the 2001-02 season.

I was just at my sonís first race and noticed the other guys really examining the placement of their cars on the track. Does exact placement make a great difference?

In a close race the car position at the starting line can make a difference. The goal is for the car to roll as far as possible before bumping the guide rail. So it is best to center the car over the guide rail and point it as straight as possible down the track.

Some people pull the wheels all the way outward towards the axle heads. The idea is to minimize the wheel hub rubbing on the side of the car, which generally is worse than rubbing on the axle head.


I know that everyone tells you that the maximum weight of a car is five ounces. But at our pack weigh-in the scale measured in grams and it was confusing. Why would they do this? Is grams or ounces the official unit of measurement for BSA?

The rules with the BSA kit specify five ounces, so that is the official maximum weight and official units. Most race leaders use a postal scale that measures in ounces. But some race leaders use a scientific scale that measures in grams. This was evidently the situation at your race.

Either type of scale can be used, and the type of scale used is oftentimes simply the type that is available to the race leader. However, there is a slight advantage to the scientific scale as it usually has greater accuracy. Postal scales typically measure to the nearest 0.1 ounce (2.835 grams), while scientific scales measure to the nearest fraction of a gram.

I suggest that if cars will be weighed in grams, then that fact should be clearly stated in the local rules. The rules should also state the maximum weight in grams and the conversion factor from ounces to grams.

By the way, there is sometimes confusion as to the correct conversion factor as there are two types of ounces, avoirdupois and apothecary (troy). In the United States we use the avoirdupois ounce for weighing most goods. Conversion from ounces to grams is accomplished by multiplying the number of ounces by 28.35. Thus, a five-ounce car would weigh 141.75 grams.

Be aware - if you have a scale used for weighing pharmaceuticals, it will likely weigh in troy ounces; a five ounce car will not weigh five ounces on a pharmaceutical scale! I have had a few calls from customers insisting that our 5 ounce weight was way off. After some discussion, we discovered that the scale being used was a pharmaceutical scale and was weighing in troy ounces. Note that the conversion from troy ounces to grams is 31.10.

Recently my son had the opportunity to compete in his first pinewood derby. At the weigh-in, his Cub Scout troop provided Play-Doh to add to any cars that needed extra weight. One child added his Play-Doh to the front of the car, and on almost every run down the track the weight came off when it hit the stopping block. An official replaced the Play-Doh after each heat. Finally, in an attempt to keep it from coming off, the official changed the position of the Play-Doh from the front to the rear of the car, and gave it a more aerodynamic shape. My son lost the den championship to this car by a very small margin. Is it common practice to replace weight after it falls off? What about changing the position and shape of the weight after it has already run a race?

Before I answer your question, let me ask you one. What do your local rules say about attaching objects to the car, replacing lost parts, and making modifications after the weigh-in? If your rules address these issues, and the official violated them, then there is some room for discussion regarding the outcome of the race. However, if your rules do not address these issues then consider working with the pinewood derby committee to update the rules for next year. Here are some suggestions.

Attachment of Weights
Most rules state that all objects must be firmly attached to the car (with screws, permanent glue, etc.). This rule virtually eliminates occurrences such as the one you experienced. Clearly, placing Play-Doh on the car would violate this rule. Play-Doh might be acceptable as weight if it were firmly embedded in a hole or pocket in the car. One reader states that a small groove can be created in the bottom of the car and filled with clay. The clay can then be adjusted at the weigh-in. Clay is likely superior to Play-Doh for this application as clay takes longer to dry out, and does not shrink as much.

Parts Falling Off the Car
Generally, parts falling off a car may only be replaced if they are critical (i.e., wheels and axles). In our race if accessories or weight fall off, we do not replace them. But because of rule one above, this rarely happens.

Moving the Weight After the Weigh-in
Every set of rules I have ever seen prohibits car modifications after the weigh-in. Moving weight from the front to the back of the car is clearly a modification as it affects performance.

Do You Have Questions that Need Answers?
Do you have a pinewood derby-related question? If so, send your question to:
info@maximum-velocity.com. 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!

We have just added an index of all newsletter articles since the first edition in October of 2001. We hope this helps you find information more quickly. To view the index Click Here

All of the issues for Volumes 5 through 7 are posted on our web site:

Volume 7

  1. Volume 7, Issue 3

  2. Volume 7, Issue 2

  3. Volume 7, Issue 1
Volume 6

  1. Volume 6, Issue 1

  2. Volume 6, Issue 2

  3. Volume 6, Issue 3

  4. Volume 6, Issue 4

  5. Volume 6, Issue 5

  6. Volume 6, Issue 6

  7. Volume 6, Issue 7

  8. Volume 6, Issue 8

  9. Volume 6, Issue 9

  10. Volume 6, Issue 10

  11. Volume 6, Issue 11

  12. Volume 6, Issue 12

  13. Volume 6, Issue 13

  14. Volume 6, Issue 14

  15. Volume 6, Issue 15
Volume 5

  1. Volume 5, Issue 1

  2. Volume 5, Issue 2

  3. Volume 5, Issue 3

  4. Volume 5, Issue 4

  5. Volume 5, Issue 5

  6. Volume 5, Issue 6

  7. Volume 5, Issue 7

  8. Volume 5, Issue 8

  9. Volume 5, Issue 9

  10. Volume 5, Issue 10

  11. Volume 5, Issue 11

  12. Volume 5, Issue 12

  13. Volume 5, Issue 13

  14. Volume 5, Issue 14

  15. Volume 5, Issue 15
Issues from the four previous seasons are available in four formatted volumes, ready for immediate download. To find out more, Click Here.





Newsletter Contributions

We welcome your contributions! If you would like to contribute an article, a web site review, or a speed tip, please send it to: info@maximum-velocity.com.

Please read our submission policy.




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Randy Davis, Editor, Pinewood Derby Times
E-Mail: info@maximum-velocity.com


Copyright ©2007, 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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