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Taking great liberty with the limits of our restricted subject material, I'm
asking a scientific question regarding acceleration.
Ok this is going to sound a little silly, but ever seen valve cover races?
Well, this is what were are dealing with here! lol This is something
usually held for the kiddies at vehicle shows. My Grandson (6) and I are
going to build one of the racers and we would like it to be pretty darn
quick, using a mil-veh valve cover of course all done up in camo colors.
( If you haven't seen one of these races before, let me explain. Its fairly
simple, usually a smooth surfaced wooden track, laned off, being about 40
feet long and of a mild grade, possibly 15%. Contestants use any standard
size engine valve cover modified with four wheels of any size or composition.
They cannot be aided by any mechanical drive device. They are launched like
a soap box racer and gravity takes them to finish line.)
So to all our engineers out here who don't mind helping, here is the problem.
Given a simultaneous mechanical release from a dead stop, to the fastest
possible speed in a given distance ( 40 feet ) with a 15% grade. Which model
will reach the finish line first, given equal axle friction and similar tire
width and composition:
1. Light body
2. Heavy body
3. ( H or L ) Equipped with smaller dia. wheels
4. ( H or L ) Equipped with larger dia. wheels
5. Weight and wheel size have no effect on speed attained
Any opinions, as always, will be much appreciated.
Jack
P.S. My theory is......
Weight of vehicle is relevant to initial accelerating and therein is the key.
Lighter, accelerates faster at the very beginning, but both reach identical
max. speed (based on a coefficient of friction and gravity). Heavier object
will generally finish behind lighter because of slower start, otherwise not
difference.
Theory......best ways to increase speed, all other factors being equal:
1. Ball bearings - light coat graphite dust
2. Small, narrow wheels - less drag & less friction
3. Hard wheel surface - less energy to move
This archive was generated by hypermail 2b29 : Thu Jun 01 2000 - 22:37:11 PDT