The Nagel-Crossett ZipZap Speed Calculator

Radio Shack® ZipZap and ZipZap Special Edition
motor speed, rpm

e.g., 10000, 21500, 34000
 rear ratio

e.g., 12.00, 9.86, 8.25
 actual speed, mph

scale speed, mph
these computations assume a stock tire circumference of 1.73228 in.1
Radio Shack® ZipZap Monster Truck
motor speed, rpm

e.g., 8000, 14500, 21000
 rear ratio

e.g., 24.00, 20.85, 16.22
 actual speed, mph

scale speed, mph
these computations assume a stock tire circumference of 3.464947 in.1
generic speed calculator
motor speed, rpm

e.g., 10000, 21500, 34000
 gear ratio

e.g., 12.00, 9.86, 8.25
 tire circumference

 
 actual speed, mph

scale speed, mph
you must enter your own tire circumference data

1Thanks to Rich Nagel for his contribution of the tire circumference data.  See his text version of computations.

Yet to come:  Monster truck speed results computed as seconds per foot (for the crawler guys).