Copyright © 2009 by Stan Pope Page 1
Pinewood Derby Performance
BasicsAn introduction to
making a high performance
Pinewood Derby car
Copyright 2003, 2009 by Stan Pope, all rights reserved.
Copyright © 2009 by Stan Pope Page 2
Pinewood Derby Design http://stanpope.net/pwdesign.html
Learn to Build a Winner http://stanpope.net/lbw_apl.html
Based on information presented at the author's website at ...
Copyright © 2009 by Stan Pope Page 4
To win a pinewood derby race,your car must get from the startingline to the finish line before the other cars.
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Quickest:
Accelerate earlyAttain maximum velocityHold speed through finish line
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Follow your district's rules.
If you can't pass inspection,
you can't race.
If you can't race, you can't win!
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Assure Ground Clearance.
Failure:
Grinding stop
Dramatically flying off the track
If you can't get to the finish line,
you can't win!
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Assure that the car will "run" on the track.
A narrow or pointed nose may not stage correctly on the starting mechanism and may not trip the finish line sensor correctly.
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Make sure that the wheels are
in balance,
in round,
moving freely,
well lubricated,
minimum turning weight, and
correctly aligned.
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Optimize weight distribution.
As the center of gravity moves farther back in the car, there is more energy available to be converted into speed.
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Car as long as rules allow
Rear wheels as far back as rules allow
Front wheels forward almost as far as rules allow, without affecting rear wheel location
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Car's center of mass as far back as car stability allows, and car's center of mass as low as possible, but "as far back" is more important (maximize potential energy)
Wheel alignment "dead-on"
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Weight as close to maximum allowed as possible
Car's cross section as small as possible
Wheels "in round", balanced, and all sliding contact surfaces polished and lubed (hub, bore, and inside wheel edge)
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Axle contact surfaces polished
Hub contact area as close to wheel axis as possible (minimize breaking torque due to wheel-body and wheel-axle friction)
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Fundamental Energy Equation
Potential Energy at start minus Lost Energy leaves Kinetic Energy at finish
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In other words ...
Start with as much potential energy as you can, and waste as little of that energy as possible.
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Losses from:
Friction between wheel and axleFriction between hub and carFriction between hub and nail endAir frictionWheel vibrationBody oscillation (wheels out of round)Wheel rolling frictionWheel sliding friction on track or railAngular acceleration of wheels
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Lead:
Lead is PoisonousLead often has nasty additives
Minimize contact.
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Melting lead is discouraged!
Supply your builders with lead slugs.Hold lead slugs in pliers. Pound lead slugs into desired shape with hammer. Glue in place with 5-minute epoxy.
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Rules change from time to time.
Review the rules carefully each year.
Especially check the “boundary conditions.”
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Don't believe everything the “experts” tell you!
Smile, say “Thank you,” and go home and check it out!
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Help your builders get the mostout of their efforts.
Share what you have learned.
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