Rail Riding - "How To Guide"

Secrets, tips, tools, design considerations, materials, the "science" behind it all, and other topics related to building the cars and semi-trucks.

Have you had success with a "rail rider"?

Yes
93
50%
No
8
4%
Somewhat
12
6%
Haven't tried yet
73
39%
 
Total votes: 186

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Vitamin K
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Joined: Sat Apr 20, 2013 7:26 pm
Location: Spotsylvania, VA

Re: Rail Riding - "How To Guide"

Post by Vitamin K »

The DFW should have positive camber, as such, the lower edge of the wheel should be closer to the rail and the upper edge of the wheel further from it.
zahnarzt wrote: Tue Jan 28, 2020 3:18 pm OK, so I have to ask. Front dominant wheel bend DOWN or UP? My boys are 4 years into this and have done really well bending it about 1.5deg UP. I don't believe they've tried bending it DOWN. Strong opinions here?

Thanks in advance.
Speedster
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Posts: 1972
Joined: Sat Feb 18, 2012 1:48 pm
Location: Toledo, Ohio

Re: Rail Riding - "How To Guide"

Post by Speedster »

The nail on the dfw is bent down 1 1/2 degrees and the wheel now has Positive camber. The car is adjusted to drift 2" in 4' on a test board. The car is then taken to your Best track if you have one and the final tuning is made. The main advantage for Positive camber is if the wheel hits a misalignment in the track it will bounce over it and go back to the rail. If it has Negative camber the wheel is riding on the top edge of the rail and a misalignment can literally tear a hunk out of the wheel and the car might even leave the track. It's been reported the Positive camber reduces friction. I don't know if that's true or if the friction is simply moved to a smaller area. A very critical thing is to make sure the rear wheels are absolutely parallel to the body of the car. The recommended amount is 2 1/2 degrees Negative Camber. Our rules do not allow that but 1 1/2 degrees will also work. The wheels will ride on the inside edge and migrate to the axle heads and stay there. If there is any defect on the surface of the wheel that was touching the track it will no longer be involved. The car will run very straight and actually run a shorter distance then a car bouncing back and forth and possibly dragging both wheels on one side all the way down the track.

If the raised wheel is any concern simply double the space of the clearance and stick a tiny bit of tungsten putty in the bore. It won't be able to bounce to the car. The savings of the raised wheel is 25% of the" rotational energy" formerly shared by all 4 wheels is now available and the linear velocity increases. Between 2 Perfect cars a 3 wheeler will beat a 4 wheeler by 3 1/2". Raising a wheel does not reduce friction, It actually increases friction on the other 3 wheel/axle assemblies. Doc John Jobe, Author of The Big Green Book, The Physics of the Pinewood Derby.

I highly recommend Troy Thorne's 2013 Edition, Build a Winning Pinewood Derby car. They are available from Fox Chapel Publishing for $9.99. If you are in scout racing for 5 years the book will cost you $2.00 per year. After you leave racing you can sell the book for $10.00. The book has cost you Nothing.

I am so very HAPPY just yesterday I was notified the Lucas County Library will have Troy's book available soon. I urge everyone to contact their library and tell them about Troy's book. There are no Secrets and no such thing as Luck. All the Physics of the Pinewood Derby is in Troy's book and there are No pictures of Big, Bulky cars. Learn the science of Matter and its Motion in a couple of hours and then ask any questions you might still have on Derbytalk.
Best Wishes for your Racing Season
Speedster
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