Since the sum of the number of revolutions of the rear wheels = 2 times the
number of revolutions of the driveshaft divided by the diff ratio, the rear
wheels would move a total of 9.756 revs in Allen Nugents example since he
rotated the driveshaft through 20 revs. If both wheels were allowed to move
freely, the result would be 4.87 revolutions of each rear wheel. The
problem with leaving both wheels free to rotate and, consequently, having
to measure how far each has turned can be resolved by locking one wheel;
either by leaving it on the ground or some other means. Now the sum of the
number of revs of the rear wheels =s the number of revs of the free wheel
since the locked wheel revs will be zero. Now rotate the free wheel one
rev while counting the drive shaft revs. The diff ratio will be 2 times the
number of driveshaft revs you just counted. If you wish more resolution,
rotate the wheel 10 times, rather than once, but don't forget to divide
your answer by 10.
Examples: With one rear wheel prevented from moving, a 4.1 ratio will cause
the driveshaft to rotate 2.05 turns when the free wheel is rotated once.
Similarly, a 3.7 ratio will cause the driveshaft to rotate 1.85 turns.
Since we're not looking for any ratios between 3.7 and 4.1, less than 2
turns of the driveshaft indicates 3.7, more than 2 indicates 4.1.
If you choose to rotate the wheel 10 times, you will count 20.5 turns of
the driveshaft for 4.1 gears; 18.5 turns for 3.7 gears.
Fog One
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