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Winning Pinewood Derbies - Center of Gravity

I see a lot of advice out there about where the center of gravity should.  Some say it should be all the way in the back so the weight is spending more time on the slope to gather more speed going into the flat portion of the track.  Others say it should be balanced or at least in front of the back wheel.  So I ran a series of tests changing the center of gravity to find the optimal position.  Stop listening to the pundits and look at the data.

Below is a table of the runs.  This is one of those times I wish I had more data due to the curving of the data.  However, I think we can still extract useful information.  You can certainly see if the center of gravity is too far forward or to far back the car performs worse.  In fact, if it is too far back the front wheels begin to wobble and chatter.  Certainly not a good condition if you want a winning car.

My recommendation is to have the center of gravity about 4 1/2 - 5 inches from the front of the car.  This looks to be the optimal area.

 

Center of Gravity*     Trial (sec)        
1 2 3 4 5 Avg STD
2 2.458 2.43 2.443 2.444 2.473 2.450 0.02
3.5 2.386 2.384 2.378 2.38 2.366 2.379 0.01
4 2.349 2.347 2.314 2.314 2.33 2.331 0.02
5.5 2.4 2.371 2.404 2.367 2.363 2.381 0.02
* - (inches) measured from front of car        
5.5 - noticeable wobble in front of car.        

 

Chart of the data with a polynomial fit.

May your car run fast and true.