Gear Box

" snipped-for-privacy@gmail.com" wrote in news: snipped-for-privacy@z14g2000cwz.googlegroups.com:

You need an angle disk, similar to those used by engine builders to set the camshaft timing. Lock the output shaft so it cannot move (collar or whatever). Install the angle disk on the input shaft, with a fixed pointer. Rotate the shaft counter clockwise until it does not move (may wish to set a 'standard' torque measurement for this). Zero the angle disk at this point. Move the shaft in the clockwise direction until the same torque is reached...and read the degrees of freedom. Now, to get the actual free play distance between the gears, you would have to know the actual gear specifications, centerline distances, etc and do some math. This is but one method...

Hold the reduction shaft, and attempt to rotate the higher-speed shaft. The angle turned due to lost motion is called 'backlash"

You will readily see how to calculate this value given the gear tooth mesh gap, and shaft float if any.

Brian W

Plastigage - you need to measure both largest and smallest lash. do it at 0 degrees, 120 degrees, and 240 degrees so you can find the minimum lash point on the circumference- you can break a shaft if you use any old point on the gear and happen to set lash at the largest gap instead of the smallest. With most gear types and with experience, you can read the face to see where it is to start the process. And if the largest and smallest are outside of spec, you have a worn bearing