WHEELS, WHEELS, WHEELS! - Derby Tech - May, 1987

by John Knox and Guy Steward


Many questions have been raised in regards to the variation of the Z-glas wheels as they have been used in the All-American Soap Box Derby. Racers and their families have expressed concern about the use of uncalibrated wheels to run the Big Race. As a result of the Akron Suburban Local, running on Z-glas wheels, we now have evidence to support our fears.

The Akron Local changed from calibrated steel wheels to uncalibrated Z-glas wheels for this year's local. This was done to allow the fastest cars and drivers on Z-glas wheels to advance to the All-American Instead of cars that take advantage of steel wheels. There was not sufficient time for calibration of the new wheels so the race was run with four wheels, "out of the same box". All wheels had screws tightened and the bearings lubricated. Basically, this same treatment is used to prepare championship wheel sets for the All-American race.

The weather conditions for the Akron Suburban Race were less than ideal for racing, but provided excellent data for testing wheel sets. Due to rain delays, many first phases had to be rerun. When first phases were rerun, wheel sets had already been reversed in preparation for phase two.

As you can see In the following table, all first phase winners were reversed by the wheel swap with the exception of one double-phase winner. (Byes and mishaps were omitted from the table.) This shows that the fast wheels would be the winner in any All-American style race. If we follow through the heat sheet in a single elimination, using only first phases, the fourth place car would have won and the winner would have lost her first heat and had been eliminated from the race.

Heat # Car # 1st Phase 1st Phase rerun 2nd Phase
1 33 .411   .420
  21   .521  
2 31 .745   .803
  22   .686  
3 32 .296 .450 .387
  27      
4 30   .217  
  29 .246   .222
5 161   .006  
  171 .158   .334
6 166 .217   .225
  158   .125  
7 165 .987   .970
  164   .434  
8 157 .557   .649
  160   .569  
9 152   .444  
  168 .392   .385

Examining phase differentials provides more data that reinforces the need to use calibrated wheels. The average phase differential was .392, which is more than two car lengths. The professional photographer had difficulty photographing both cars professional at the finish line because the margins of victory were so large.

According to the All-American rule book, the National Control Board of the All-American Soap Box Derby has stated, 'We believe that all competitors should have an equal chance based upon their own abilities.. The data has shown that uncalibrate wheels will not give competitors an equal chance based upon their own abilities. The obvious solution is to have calibrated wheel sets.

Since the Z-glas wheels need to be calibrated, the All -American Soap Box Derby needs to address this problem while there is still time to provide an equitable race. The question is: why can't championship wheels be calibrated? If a family spends hundreds of hours building a car, can't the Control Board delegate fifteen minutes per set to calibrate wheels? How can the Control Board guarantee a competitor an equal chance without calibrated wheels? We are anticipating a response from the National Control Board and anyone who is concerned with the All-American Soap Box Derby becoming a more equitable race.


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