The Missile

The Missile

Pinewood Derby Times
Volume 6, Issue 12
March 7, 2007

In this Edition:

- Editor's Notes

- Feature Article - Scaling Up: Design a Pinewood Derby Car from a Toy Car

- Speed Tip

- Newsletter Subscriber Specials

- Car Showcase

- Memory - Second Place in Speed Goes to ...

- Q&A




Editor's Notes
Reader Feedback

I received several comments on the article, "Points or Times: Which Method Should I Use?" in Volume 6, Issue 11 - February 21, 2007.

From Mike Ruhl:
I just read your Feature Article on Points vs. Heat Times, and I'd like to point out something that is probably obvious to you, but wasn't really accounted for in the article itself.

If you had advanced just 7 cars to your finals, instead of 10, then you could have run a perfect round-robin, in which every car runs once in each lane and runs once against every other car (assuming a 4-lane track). Your son's car probably would have finished 3rd in this case, instead of 4th.

This is how we run our Grand Prix. In the interest of time, our qualifying rounds are imperfect round-robins where each car runs once in each lane. We have as many heats as there are cars. We track points, and the top 7 cars advance to the finals, as described above.

If the qualifying round produces more than 7 cars tied for the top 7 places, then we have a run-off from the bottom up to determine the 7 top cars. With anywhere from 40 to 60 cars in the qualifying round, we usually end up with 10-12 cars in the top 7 places. Most often, we'll have one, two, or three cars at the top, with 3 or 4 tied for 3rd, 4th, and (sometimes) 5th place.

Let's say that after our qualifying round we end up with a distinct 1st place car, two cars tied for 2nd, 3 cars tied for 3rd, and 4 cars tied for 4th (actually pretty close to reality most years). That's a total of 10 cars. In order to end up with 7 finalists, we'll take the 7 cars that tied for 3rd and 4th places, and run them in a perfect round-robin to come up with 4 finalists. These 4 will run against the top 3 from the qualifying round in the finals.

The only problem is that some cars end up running more heats than others, but no one has ever complained about it. And some years we've ended up with 8 or 9 tied for 3rd and 4th, 3 or 4 tied for 2nd and 3rd. I keep copies of racing charts for every potential outcome, so we can plug them in as needed. But on average, the scenario described above is what we usually see.

From Stan Pope:
Cory Young and I have often abbreviated the Perfect-N chart variations as PN (Perfect-N), CPN (Complementary Perfect-N), and PPN (Partial Perfect-N).

Your case demonstrates the problem inherent in the selection of finalists. PN and CPN charts are relatively rare; PPN are almost common. PN has both lane equality and opponent equality. PPN by definition narrowly misses full opponent equality.

In selecting finalists, the number of finalists is important so that the more accurate PN or CPN charts can be used. Ten finalists requires either an exorbitant number of rounds or at least a 9-lane track (fit that one in your budget!) to run a PN chart. So, I recommend either a 7-car or a 13-car finals chart since these have PN and CPN solutions on 3 and 4 lane tracks. (A single "bye" in either of these does not affect the results, so those charts are applicable to car counts of 6, 7, 12, or 13.)

The nature of PPN charts limits how accurately PPN can rank the top cars. But PPN is excellent at ranking the N best cars among the highest scoring 2*N places. So, the number of finalists needs to be about twice the number of places that need to be determined.

Points racing has another problem that occurs when the cars are more equal than the lanes. If heat results are "true to form", PN and CPN charts will usually produce ties in the final standings for these cars. Unless you can find two lanes on the track that are more equal than the cars, the tie might have to be left to stand or be broken with a coin toss.

From Ed Phillips:
Your article shows a bias towards "Points" as evidenced by the minimal number of advantages in "Times", and many more "disadvantages". ... I really don't care if someone prefers "Points" over "Times", but I believe this article could unfairly bias someone trying to figure out which is better for their pack. My view (somewhat also stated in the article) is that it really depends on what is important to your pack. Number 1 is fairness, which as you know double elimination is sorely lacking. Number 2, for us at least, is how can you keep everyone interested for the full race, so how long it takes is also important. ...

(Editor's Note: I do prefer "Points", and I guess that did translate into some bias in the article)

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

3/16" Tungsten Cubes
Special Price

We made a large buy of 3/16" Tungsten Cubes and are offering them to you at a special price. Great for making thin cars! You can get these cubes by Clicking Here


Stock Car Pre-Cut Kit

Do you want to go for the NASCAR look? Then take a look at our pre-cut stock car kit. Just add weight, sand, and paint. The Stock Car Kit is the Newsletter Special for the next four weeks.


Feature Article

Scaling Up: Design a Pinewood Derby Car from a Toy Car

I generally build pinewood derby 'cars' that don't look like real cars. Oftentimes it is awkward to coerce a real car design into the pinewood derby car form factor. However, many people like to use a real car as the basis for a design, and in fact, I have done so a few times. So in this article I will explain how this conversion is accomplished, and the design decisions that will need to be made. Although I will focus on scaling up from a toy car, the same principles apply when scaling down from a full-size car.

What Is The 'Scale' Of A Pinewood Derby Car?

When building models, the 'scale' refers to the size of the model relative to the original. For example, many people have heard of 'HO Scale', a popular scale for model railroading. The HO scale is 1:87. That is, for every 1 inch in length (also width and height) of the model, the real train is 87 inches. Thus a train car that measures 44 feet long would be a little over 6 inches long in HO scale (44 feet, times 12 inches per foot, divided by 87).

Pinewood Derby Cars do not have a specific scale factor, as they are forced to be 7 inches long by 1-3/4 inches wide (instead of varying in size based on the size of the original). For many standard automobile sizes, 1:24 is pretty close, and in fact 1:24 scale decals generally work pretty well. However, the scale would be reduced when modeling a compact car, while the scale would be increased when modeling a large vehicle. So, instead of using a specific scale the designer must calculate a scale factor for the given original.

Calculating The Scale

To determine the scale, measure the length of the original vehicle, and then divide that number into 7 (inches). For example, let's consider modeling a toy car that measures 3 inches long, 3/4 of an inch wide (excluding wheel wells), and 11/16 of an inch tall (see Figure 1). With these measurements, dividing the length (3) into 7 gives 2.33.1 Thus, for every 1 inch dimension of the toy car, the pinewood derby car will be 2.33 inches. Therefore, the pinewood derby car will be 7 inches long (2.33 times 3), 1-3/4 inches wide (2.33 times 3/4), and 1.6 inches tall (2.33 times 11/16). All other dimensions, such as the placement of the cockpit and engine, the location of the body curves, etc. are calculated using the same scale factor.


Figure 1
Hot Wheels Sweet 16 II

At this point, a tradeoff may need to be made. In this case, the width is fine, however, 1.6 inches is quite tall for a pinewood derby car. If realism is the primary goal, then maintaining the 1.6 inches is okay. However, if speed is the primary goal, then it is best to reduce the height of the car as much as possible.

If the width is too narrow, then it would need to be arbitrarily increased to 1-3/4 inches. If the width is too wide, then two options exist:

Wheelbase Considerations

The next design issue that must be resolved is the wheelbase. When the wheelbase of the toy car is scaled up, almost certainly it will not match the wheelbase required by your local rules. For example, on the toy car in Figure 1, using the 2.33 scale factor, the front wheels would be 0.73 inch from the front of the car, and 1.16 inches from the rear of the car. Obviously this does not match the BSA wheelbase (nor any other for that matter). At this point, the following options could be implemented (based on the rules for your race).

  1. If your race rules require a wheelbase distance AND a wheelbase position, then adjust the wheelbase to meet the regulations. This will certainly skew the resulting car, but there isn't really a choice in this case.


  2. If your race rules require a wheelbase distance, but does not require a relative location then adjust the wheelbase to meet the required distance, but position the resulting wheelbase as close as possible to the position calculated with the scale factor. The resulting car will be skewed, but less so than in option 1.


  3. If your race rules do not specify a wheelbase, then use the wheelbase calculated with the scale factor.
Wheel Wells

Another design issue is that of wheel wells. Many toy cars have wheel wells, so to accurately model the car the wheel wells must be included. This will require the addition of material to the sides of the car, followed by shaping the wheel wells to accommodate the pinewood derby wheels.

But wait; now we may have another issue. Measure the diameter of the wheels on the toy car, and then multiply the diameter by the scaling factor. Does the result closely match the diameter of a pinewood derby wheel? If not, the wheel wells will need to be adjusted to fit the pinewood derby wheels, which could skew the car.


Figure 2
Hot Wheels Silver Bullet

As an example, for the car in Figure 2 (which also has a 2.33 scale factor), the rear wheels scale up to 1.16, but the front wheels scale up to 1.02. Since the standard BSA Speed is about 1.18, the wheel wells (mainly the front wheel wells) would need to be increased in size to accommodate the pinewood derby wheels.

Selecting A Car To Model

When choosing a car to scale, you will need to consider the following factors before doing any wood working:

  1. Given the rules for the local race, when the toy car is made to fit within the required dimensions, will it maintain the 'look' of the original toy? With strict wheelbase rules, try to find a toy car that will fit well within the local wheel base restrictions.


  2. If you don't want to deal with wheel wells, choose a car without them.


  3. Make sure to consider car weighting. You will likely need to add 2 to 3 ounces of weight, so space must be available on the car to accommodate the weight.


  4. Some toy cars are quite complex. Consider whether the car can be built with your tools, or whether the design can be simplified without sacrificing the original look.


  5. Actually, if you have a young boy like mine, the most difficult problem will be finding a toy car that is still intact!
Examples

Here are three examples of modeled cars:

Humvee
This Humvee in Figure 3 was modeled from a drawing on the internet. To model the wheelbase as accurately as possible, and to meet the BSA wheelbase specification, the car was shortened to 6.2 inches (see Figure 4 - blue lines show original body location, red lines show shortened location). The result is a wheelbase that matches the BSA wheelbase length, but is moved slightly forward from the standard location.

The body is made from three parts (you can see the glue lines running front to back). Before the parts were glued together, much of the middle part was cut away to eliminate weight. Even so, the final car required little to no added weight.


Figure 3
Humvee Body

Figure 4
Humvee Drawing Showing Shortened Body

Hot Wheels Car
This race car was modeled by a customer (see Figure 5). As you can see, the wheelbase was lengthened, the wheel wells were enlarged, but the general look was maintained.


Figure 5
Hotwheels Car

Stock Car
This (unfinished) Stock Car body is for sale on our web site. The wheel base is lengthened to match the BSA wheelbase, but is offset to maintain the NASCAR look. The height of the car is slightly lowered (looks slightly mashed, but not overly so). 1:24 scale decals are used, but they had to be trimmed slightly as the actual scale factor is slightly larger than 1:24.


Figure 6
Stock Car

Conclusion

If you need inspiration for a pinewood derby car design, your child's toy box (or the local toy store) can provide a lot of great ideas. Then, by calculating a scale factor, creating a pinewood derby car from the toy car is not as hard as it may first appear. Just make sure to consider the overall dimensions, the wheelbase, wheel wells, and the overall complexity of the design before making any sawdust.

1Most 'Hot Wheels' brand cars are 3 inches long, resulting in a 2.33 scale factor.




Speed Tip
Top Ten "DO NOTS!"

By William Beaver

(In reverse order)

10. DO NOT tell your child that his car "could be the fastest in the race" before the race.

9. DO NOT do all of the work on your child's car.

8. DO NOT "over work" on the car. Quickly made, simple cars often win! Go figure.

7. DO NOT get in a hurry painting the car, or especially mounting the wheels and axles.

6. DO NOT think a winning car and trophy is what makes your child most happy.

5. DO NOT overuse super glue, NyOil II, or Krytox.

4. DO NOT glue more than $3.00 in coins underneath your car.

3. DO NOT focus all attention and praise only on the fastest car during the derby.

2. DO NOT make your car too thin, wheels too thin, axles too thin, or wallet too thin.

1. DO NOT whine or cry "foul" when you lose.

(Editor's note: Not exactly 'Speed Tips', but good food for thought.

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 2007. Don't worry about literary polish. We will edit it as needed before publishing. Also, please read our Submission Policy.




Special Offers for Newsletter Subscribers



Stock Car Kit
$2.00 off

This pre-cut kit effectively mimics the styling of a NASCAR entry. Just sand, paint, and apply 1/24 scale decals for you favorite driver.

For more information, Click Here

but make sure to Purchase Here


Pine Block Blowout
$0.95 off

If you have plans to build several cars in the future, now is the time to stock up on these BSA-spec pine blocks (1-3/4 x 1-1/4 x 7 inches). The blocks are equipped with BSA slots (we did not cut the slots). You can use the slots, or turn the block over and make your own slots or holes.

You can Purchase Here

These specials are valid through March 20, 2007.



Car Showcase

Bear-ly Finished: John & Heidi Row


This is my wife's car (Heidi). Named appropriately "Bear-ly Finished". She was up until 2 AM the morning of the race! The car is hand-chiseled with Exacto blades and Dremel bits. I lubed the wheels and aligned them (Max V Official BSA Matched Speed Wheels & Axles). Because we were running late I only spent about 3 to 4 minutes on the wheels. Despite the lack of time they ran straight as an arrow, and the car was the second fastest of all cars participating. This car goes totally against all reasoning of physics! The COG is 21/4 inches(!!!) in front of the rear axle and only weighed in at 4.90 ounces!

Champ Car: Chuck Baum


This car was never raced, it was just made for show. It was constructed from a standard BSA kit. The wings are made from tongue depressors and popsicle sticks, and the side pods from 3/8 inch thick pine. My son and I are open-wheel (Champ Car) race fans and I believe that this car was modeled after a car that Michael Andretti was racing circa early 90's. We continue to get together for Champ Car races.

Rollin' Rattler: Lisa & Ryan Ford


Attached is a picture of my son's Pinewood Derby car from this year. He has won two first place overall trophies with a Wedge and the Formula 1 from your car plans. This year he wanted the Most Creative trophy, so we purchased the Extreme Car Plans booklet and attempted the Rollin' Rattler. This is his version; I helped with the Dremel work and wheel polishing and he mixed the paint to get the right colors. He did take home the most creative trophy and came in 6th overall.

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 please. Thanks!



Pinewood Derby Memory

Second Place in Speed Goes to ...

My son Connor is now a Bear Cub. When he was a Tiger Cub he won for most unique. I also thought he had a fast car. Since then he has been bitten by this bug and has gone for unique designs instead of speed. Last year he made a 'Tank' which was pretty cool. It didn't win anything, but he still enjoyed building and racing the car. This year I decided that no matter which car he built, it would also be fast!

He again came up with a unique design: a tombstone. He carved it and painted it to look really nice with a stone paint finish. I had some leftover tungsten weights from building a car for the adult race, so we used them in Connor's car.

I think these tungsten weights made a difference because of their density and small size. I was able to create a small hole to put them in (over the rear wheels). Then I was able to carve out some wood underneath to make the 5.0 ounce limit.

During the time trials the night before the derby we got excited. His car beat most that he went against. His time was also competitive with the adult cars. We had done something right! On the day of the big race he was very excited. We had a fast car and a unique car. Most of the other scouts liked Connor's design. Everyone wanted to touch it and feel the stone finish.

When the race started everyone, except me, was surprised that this 'rock' was so fast ! It was not aerodynamic at all. It did not look fast, but it was. In his heats he had two first place finishes and two second place finishes. Connor was so thrilled just to win two heats that he would have been happy just with that.

When they called the third place winner in speed, it was not Connor. I felt like he would at least get third. "What went wrong," I thought.

Next ... "Second place in speed goes to ... CONNOR." Yes, he won second place in speed! WE ARE GOING ON TO THE DISTRICTS RACE IN MARCH!

I think the speed of the car has a lot to do with the tungsten weights we got from you and where we placed them. I recommended these weights highly!

Kyle & Connor Wilson

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 2007.

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




Q&A

Another question for you. My son is interested in lightening his BSA wheels in order to maximize weight placement back. We can get them down to about 1.5 grams. With the mass loss, does the 20 to 30 second spin rule still apply? The reason I ask is that we have lost a couple of seconds off the wheel spin time.

As the weight of the wheel is reduced, the spin time of the wheel will be reduced accordingly. The momentum of the wheel is what keeps the wheel spinning, and momentum is based on the weight of the wheel and the velocity of the spin.

If my son's car wins and goes on to the next level, before the next race we want to re-lubricate the wheels. We put two drops of white glue in each axle slot to hold the axles in place. How can we pull the wheels and axles out of the slots without damaging anything?

With white glue, you should be able to grasp the axle head with a pair of pliers, then gently twist and pull the axle out. The glue bond should release when you give the axle a slight twist. After removing the axles, clean out most of the glue from the slot, then re-glue after you re-install.

We have a car body with drilled axle holes, and one front wheel is drilled higher. What is the best way to make all four wheels touch the ground?

First, verify that the rules for your race do require four wheels touching. If you don't need four wheels touching, then I would leave the car as is (better performance).

To get four wheels touching, there are two options.

  1. Plug both front axles holes with round toothpicks, then re-drill the front two holes with a drill press, or with the Pro-Body Tool. A #44 or #43 bit is required. Don't try to just plug one hole and re-drill. It is extremely difficult to drill a new hole that matches the others.


  2. Plug both front axle holes with round toothpicks. Then use a saw to cut a slot at the front axle position. A radial arm, or table saw work best. Just make sure that the width of the blade is the correct size (test this on a scrap piece of wood). In a pinch, you can use a band saw or hand saw, but these tools are not as accurate.
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! All of the issues for Volumes 5 and 6 are posted on our web site:

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
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.





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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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