Allowed to drill holes in wheels. Anyone else have rule?

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PWD
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Allowed to drill holes in wheels. Anyone else have rule?

Post by PWD »

My sons compete in the boy scout pinewood derby. Our rules on most things are very conservative. But we do have a rule where we are allowed to drill holes in the sidewall of the wheels.

I read everything I can on the Internet about Pinewood derby car building and I have never seen information on drilling holes in the wheels.

Does anyone have this rule?

I assume:

1) If you are allowed to then your son should do it.
2) They should get rid of as much as they can without breaking the wheel
3) You would want to keep the wheels as balanced as possible.

The thinking is that lighter wheels can get started more easily. Also lighter wheels take less energy to roll.

Wanted to know what others thought about this.

-Stev-
Last edited by PWD on Fri Dec 05, 2003 8:53 am, edited 1 time in total.
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Re: Allowed to drill holes in wheels. Anyone else have rule

Post by Darin McGrew »

PWD wrote:1) If you are allowed to then your son should do it.
Not necessarily. You're allowed to enter a car that weighs only 2oz, but most people still get as close to the 5oz maximum as possible.
PWD wrote:2) They should get rid of as much as they can without breaking the wheel
3) You would want to keep the wheels as balanced as possible.

The thinking is that lighter wheels can get started more easily. Also lighter wheels take less energy to roll.
Lighter wheels will have a lower moment of inertia, so they'll take less energy to bring up to speed. It's basically the same idea as having only 3 wheels touching the track. Less energy is used to spin the wheels, so more energy is available for the car's forward motion.

But this is a relatively minor factor, compared with more important factors like wheel alignment. Don't be penny-wise and pound-foolish.

Also, if the car no longer tracks properly because the wheels are now unbalanced, then you'll lose far more than you might have gained. It might be worth keeping a set of unmodified wheels, and running a simple test to compare the performance of the modified wheels against the performance of the unmodified wheels. Then use the wheels that perform the best, even if that means using the unmodified wheels.
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Re: Allowed to drill holes in wheels. Anyone else have rule

Post by Stan Pope »

PWD wrote:My sons compete in the boy scout pinewood derby. Our rules on most things are very conservative. But we do have a rule where we are allowed to drill holes in the sidewall of the wheels.

I read everything I can on the Internet about Pinewood derby car building and I have never seen information on drilling holes in the wheels.

Does anyone have this rule?
Most local Cub Scout rules prohibit such major alterations to wheels. Other commonly prohibitted practices include excessive tread removal and undercutting the tread and sidewall to thin the portions of the wheel away from the center and shaping the tread profile to reduce the wheel's track contact.

The sidewall holes modification can be beneficial when allowed and when done with precision. Most "tips lists" don't mention the issue, although at least one booklet does. (One booklet even shows holes drilled through the tread! That is really pushing the envelope!)
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Re: Allowed to drill holes in wheels. Anyone else have rule

Post by PWD »

BTW, we are only allowed to dril holes in the sidewalls. We are not allowed to do any other alterations.

I have always found the rule strange and out of character of the other rules which are very conservative.
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Re: Allowed to drill holes in wheels. Anyone else have rule

Post by Jungle Jim »

One of the modifications to our Council-wide rules this year was the words, "No drilling holes in the side of the wheels". Why, because no matter how many times you tell someone or how well you "think" you've set the rules, someone will always find a way around your good intention. So this year we spelled it out.

Personally, it wasn't a problem for a few years, and then I was told at the Council race last year there would be a car there that had holes in the sidewall (he had already been to his Pack and District races). I informed the Chairperson that since this was a gray area I would implement my "test". If passed - OK. If not, I would impound the car and it would be voted on. The car showed up, the test was failed, it was put to a vote (5 people {the comm.}, secret ballot) and decided (3 to 2) it would be allowed to race. It did not place well.

And just like Darin and Stan pointed out, any gains in weight may well be lost in creating an out-of-balance condition. Also, since their is no suspension on these cars, lighter wheels = higher vibration susceptibility.
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Re: Allowed to drill holes in wheels. Anyone else have rule

Post by ExtremePWD »

Stan Pope wrote:My sons compete in the boy scout pinewood derby. Our rules on most things are very conservative. But we do have a rule where we are allowed to drill holes in the sidewall of the wheels. (One booklet even shows holes drilled through the tread! That is really pushing the envelope!)
I haven't seen that book but we tried drilling holes in the tread a couple of years ago. It was not a controlled enough experiment to make any recommendations. The car wasn't a slouch but it wasn't the fastest either. The sound was quite a bit different. The acoustic response of the wheel was altered with the holes. If I recall correctly it had a much higher frequency ring as it went down the track. The likely imbalance probably helped to excite it. Our standard rules do not allow drilling holes in the sidewalls or tread. This was an open class experiment.
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Re: Allowed to drill holes in wheels. Anyone else have rule

Post by gpraceman »

Jungle Jim wrote:One of the modifications to our Council-wide rules this year was the words, "No drilling holes in the side of the wheels". Why, because no matter how many times you tell someone or how well you "think" you've set the rules, someone will always find a way around your good intention. So this year we spelled it out.
Why have such a rule in the first place? Anyone with a drill can put the holes in the sidewalls. As pointed out in this forum, you run the risk of making things worse than better, so why not allow it?
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Re: Allowed to drill holes in wheels. Anyone else have rule

Post by Colibri »

You could try to rebalance the wheels the same way model airplane guys balance their props. I don’t know if any of you have seen a balancer in the hobby shops. I has two vertical posts. At the top of each there is a magnet. The prop is placed in a jig that holds the prop and suspended it between the two magnets. The prop is then spun and allowed to slow to a stop. The heavier of the blades move to the bottom. Weight is then removed off the heavier blade. Has anyone tried this with pine wood derby wheels? The weight would be removed from the inside of the wheel.
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Re: Allowed to drill holes in wheels. Anyone else have rule

Post by PWD »

This is a district rule and not just a pack rule in my area. At districts most have wheels drilled out. I would say it is 80%. But I have seen very fast cars where the wheels were not drilled out. I have done some testing but it is inconclusive. IMO, wheels drilled out does not give a consistent advantage. I have suspect that you get them more out of balance.

Two years ago at districts one of the boys cars had the sidewalls drilled out such almost nothing was left. It looked really, really cool. His car was very fast and I believe he finished top 5 out of 400. You don't know if it was the wheels being drilled out that made the car fast or other factors. If someone is going to spend the time to drill out the wheels so completely they probably are doing to do lots of other things.

The technique to completely drill out the wheels would probably help with the balance issue. Most just start drilling holes in the sidewall and it looks very bad for balance.

How balanced are the wheels to begin with? I would doubt they are. If I get some time this year I will try to compare drilled out wheels versus not drilled out. I will also try to balance.

-Stev-
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Re: Allowed to drill holes in wheels. Anyone else have rule

Post by TurtlePowered »

Our district does not allow any reshaping of the wheel which would include tapering the wheel, coning the hub, or drilling of any holes in the wheel. If you can do this much, you might be better off sanding down the interior of the wheel while spinning it on a mandril. That way it should be balanced.
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Re: Allowed to drill holes in wheels. Anyone else have rule

Post by PWD »

You can't do anything to the wheels except drill holes in the sidewall. We can't sand or anything. I think it is a weird rule.

-Stev-
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Re: Allowed to drill holes in wheels. Anyone else have rule

Post by Barga Racing »

Jungle Jim wrote:One of the modifications to our Council-wide rules this year was the words, "No drilling holes in the side of the wheels". Why, because no matter how many times you tell someone or how well you "think" you've set the rules, someone will always find a way around your good intention. So this year we spelled it out.
Jungle Jim,
What council are you in? Last year we drilled holes in my son's wheels but not before I consulted the chairperson. They said that since drilling holes was not reshaping and I was not drilling them in the tread that we would be allowed but the following year we would not be allowed. When we got to council we were told that someone had checked in previously with holes also. We were then told that next year the rules were going to be rewritten to address this. We were not planning on doing it this year because I am not really sure it helped. My son got 2nd and had it not been for another car jumping the track and bending an axle he would have gotten 3rd. And neither of those cars had drilled sidewalls.
I also am in agreement that alignmet is the most important thing. We have always raised one front wheel and then bent the other one to get the car to go straight, not really being concerned with what the back wheels were doing. This year we are going to spend lots of time trying to achieve dead-on alignment. This is my son's 3rd year and so far he has gotten 3rd and 2nd at council. Maybe this year with better alignment he will be even faster.
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Re: Allowed to drill holes in wheels. Anyone else have rule

Post by Stan Pope »

Wooden Wonder wrote:I also am in agreement that alignmet is the most important thing. We have always raised one front wheel and then bent the other one to get the car to go straight, not really being concerned with what the back wheels were doing.
This is a common misconception. Do you know why aligning the rear wheels is important, too?
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Re: Allowed to drill holes in wheels. Anyone else have rule

Post by Colibri »

I would think that if the rear wheel were out of alignment they would tend to pull the rear of the car to one side or the other. The rear set of wheels would act like another steering mechanism. The Honda Prelude of the late 80’s that had four wheel steering needing to have a four-wheel alignment. I also assume that the new Chevy trucks that have four wheel steering will need four-wheel alignment. Last time I had new tires put on my car they offered four wheel alignment. If all of the wheels are aligned together the car will run truer with less vibration.
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Re: Allowed to drill holes in wheels. Anyone else have rule

Post by Barga Racing »

Colibri wrote:I would think that if the rear wheel were out of alignment they would tend to pull the rear of the car to one side or the other. The rear set of wheels would act like another steering mechanism.
This would be true if the rear axles were parallel with each other but not parallel with the front axles. If the rear axles are not parallel with each other then you will have toe in or toe out, which will cause the wheels to be forced against the nail head or car body. Either way you get more friction than if the axles are neutral. Also since the wheels will not be square with the world there would be some sideways sliding. Even though it would be very small it is still a speed scrubber.
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