Copyright © 2009 by Stan Pope Page 1 Pinewood Derby Performance Basics An introduction to making a...

Copyright © 2009 by Stan Pope

Pinewood Derby Performance

BasicsAn introduction to

making a high performance

Pinewood Derby car

Copyright 2003, 2009 by Stan Pope, all rights reserved.


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 ...


Basics


To win a pinewood derby race,your car must get from the startingline to the finish line before the other cars.


Quickest:

Accelerate earlyAttain maximum velocityHold speed through finish line


Make or Break


Follow your district's rules.

If you can't pass inspection,

you can't race.

If you can't race, you can't win!


Assure Ground Clearance.

Failure:

Grinding stop

Dramatically flying off the track

If you can't get to the finish line,

you can't win!


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.


Top 10 in district


Make sure that the wheels are

in balance,

in round,

moving freely,

well lubricated,

minimum turning weight, and

correctly aligned.


Maximize weight vs. wind drag.


Optimize weight distribution.

As the center of gravity moves farther back in the car, there is more energy available to be converted into speed.


Some Guidelines


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


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"


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)


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)


Fundamental Energy Equation

Potential Energy at start minus Lost Energy leaves Kinetic Energy at finish


In other words ...

Start with as much potential energy as you can, and waste as little of that energy as possible.


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


Closing


Admonitions


Hot Lead:

Severe burns possible


Lead:

Lead is PoisonousLead often has nasty additives

Minimize contact.


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.


Rules change from time to time.

Review the rules carefully each year.

Especially check the “boundary conditions.”


Don't believe everything the “experts” tell you!

Smile, say “Thank you,” and go home and check it out!


Help your builders get the mostout of their efforts.

Share what you have learned.


Good Racing!


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Copyright © 2009 by Stan Pope Page 1 Pinewood Derby Performance Basics An introduction to making a...

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