New Rules, New Challenges

Secrets, tips, tools, design considerations, materials, the "science" behind it all, and other topics related to building the cars and semi-trucks.
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Gregg H
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Location: Washtenaw County, Michigan

New Rules, New Challenges

Post by Gregg H »

Hello everyone:

'Tis the season - Pinewood Derby time again. Last winter, with the help of several years worth of research, my son and I built a very fast car that ended up taking third at our council race. It seems the council rewrote the rules, yet again, to be even more conservative than they were before. So now we need to build a car, which will undoubtedly be slower than other cars given the new rules, to get the most we can out of it, with more restrictive rules.

The gist of the rules are as follows:
-Standard items: 7" max length, 5oz. max weight, 2 3/4" max width.
-must use slots, maintain stock wheelbase of 4 3/8", and cannot adjust the position from the nose (cannot cut 1/4" off the back and move to the front)
-must have all wheels touching equally on a flat surface.
-wheel track must be between 1 3/4" and 1 7/8".
-axles cannot be covered (entire axle must be visible), and only lightly sanded to remove the burr marks. They cannot otherwise be altered. They must also be the kit axles and they plan to check them with a magnet. (?? never heard that one)
-wheels must be from the kit (specifically says no hobby shop modified wheels are allowed) and cannot be modified other than removing the ream mark (must be old rules)
-only dry lubricant can be used.

So given these parameters, is making a rail rider even possible? I have to believe alignment will be really tricky with a shorter wheelbase and needing to have all four touching. I don't know how they plan to check that one (paper test maybe?).

I also wonder just how aggressive a COM can be used. Three rows of 1/4" tungsten cubes could fit behind the rears, considering the slot is 1" from the rear of the car, but that could make for the death wiggle I am thinking. Just wondering the best weighting scheme that people have found. I know it is better to be bunched together, but with all four touching this might change what I do.

Any advice some of the experienced builders have who have built cars under the rules above?

Cheers,
Gregg
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sporty
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Location: rockfalls, Illinois

Re: New Rules, New Challenges

Post by sporty »

Call me. I'll chat over the phone w ya.
pm sent
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pwrd by tungsten
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Re: New Rules, New Challenges

Post by pwrd by tungsten »

Does not get any better then that. I would call Sporty, he had very similar rules. The most painful being all 4 wheels touching. :-) Hi Sporty!
W Racing!!!!
Speedster
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Re: New Rules, New Challenges

Post by Speedster »

I'm working with a scout in a District that has those exact rules. In an effort to make it fair, well meaning folks do the opposite. The skilled builder gets the advantage and the unskilled builder gets hurt.
For $4.90 you can buy 100 BSA axles from Derby Evolution. You now have some bent axles. We recently finished a car. We used the "screw" technique on the rears where we can put Negative Camber on the wheels and still have the wheels sit flat. There's slop between the nail and bore. The same goes for the DFW. We saved the 4th wheel for last. Ours happened to be off the ground when inserted straight with the Derbyworx tool. We took a very thin straight pin, cut the point end back 5/8", cut the pin, bent the pointed end to a 90 degree angle about an 1/8th inch, drilled a tiny hole in the axle slot and inserted the pin. When we inserted the axle the wheel was on the ground. With the bent axle we were able to set the wheel with Negative cant and a slight toe-out. There is no weight on the 4th wheel but it rolls. It has been suggested 1 1/2 ounce of weight behind the rear axle slot.
Much of the above I learned from Sporty.
Best of Luck in your Teams race.
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sporty
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Re: New Rules, New Challenges

Post by sporty »

Ya have not heard from him yet.
it's to much to type. Re type. And much easier to discuss over the phone.
Speedster
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Re: New Rules, New Challenges

Post by Speedster »

Gregg H, the reason the axle is checked with a magnet is to see if they are stainless steel. It's probably a waste of their time. I have many stainless steel axles from the Mid America race that are drawn to a magnet.
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