fxgeorge
01-21-2009, 07:08 PM
Monty, I thought you might have access to a table that would show the overall ratio of gear and tire diameter. I remember seeing such a table long ago. I've been putting a lot of time into testing the gearing of Contender/Stinger motors in flexi cars, AKA USRA LMP...all on SCR's road course. Currently I've jigged the rear axle using 40 tooth 72 pitch gears (Dia=.579"), car techs with nominal .640" tires, gets around Frank's Road Course ridiculously fast (let's just say we broke the 4 second barrier with Jerry Herbert's TQ at last year's Nats a 4.1), but the motor peaks out just past halfway down the straightaway. The motor is really wound up and although it goes fast, I'm concerned about longevity for a whole race. I'm considering my next step is to jig my rear axle using 72 pitch 41 tooth spur (.593") and run a 7:40 gear ratio...that gives a .655" tire, but stay with the 40 tooth spur. This means the motor is working against a higher ratio and should theoretically peak out further down the straightaway. The next move would be the 42 tooth gear (at .602") for the .665" tire, again staying with the 40 tooth spur. Of course the gear ratios are easy to compute, but is there a way to compute the overall ratio including rear tire diameter to make the numerical comparisons? Of course after all this is the exercise of bumping up to an 8 tooth pinion, or possibly go to 64 pitch gears using a 7 pinion and 35 or 36 tooth spur. Test, test, test....but also compute, compute, compute.:eek: