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Title: the magic formula Post by: bandit5050 on July 29, 2013, 07:12:24 PM got a gsxf750 trike with standard cog on front with chain going to a beval box onto the propshaft of a reliant axle? is there a way of working out what wheel and tyre size to use.also what cog size on the beval box?.......think that makes sence ;D.cheers ady
Title: Re: the magic formula Post by: tbone on July 29, 2013, 08:55:33 PM Need a lot more information than you have supplied but the formula is
MPH = RPM x ERWR / GR x 168 ERWR is the Effective Rear Wheel Radius, that is, the wheel radius + height of the tyre GR is the Gear ratio and that`s the total gear reduction. Most bikes have a secondary reduction to the input shaft as well as the primary + (in your case) the bevel box reduction + the axle reduction. so working the other way, ERWR (that`s wheel and tyre size) = MPH x GR x 168 / RPM I forgot to add that you really want your bevel box output 1:1 with the engine output shaft cos then you can eliminate it from the equation. |