DLB wrote
dusty wrote
Please - if you see an error in my thinking say so. I would very much appreciate being shown the light.
Previous results, both measuring RPM and measuring minimum radius, suggest to me that there is an error in your modeling that suggests a 2.75" large radius corresponds with a 1.25" small radius.
Since I don't know the logic that ties these together I can't guess. I consider the 2.75" to be correct for slow speed. My best estimate of minimum radius, measured at the datum line (also best estimate) is 0.916" for standard belt, fully closed Idler sheaves, proper eccentric adjustment, typical upper belt, etc. (sample of one, YMMV cuz this obviously vary a bit). So I think your error is in the small radius that corresponds with max radius: 1.25" Vs 0.916".
In an earlier post where I corrected my minimum radius value to 0.916", calculated RPM and measured RPM were within 1%. I'm pretty satisfied that this is an accurate number
for the one machine I measured it on.
- David
What tied those two numbers together was not based on logic. In fact, 4" being the sum of the two radii is not even correct. When I wrtongly came to that conclusion I was doing calculations with no decimal accuracy. Carrying the calculations to two or three decimals immediately reveals that. Also, I had been working on the numbers assuming belt length of 27" and with idler speed equal to motor speed. Under all other conditions, my error becomes obvious.
However, the sheave radii do add to a number very, very close to 4". Deviation greater than about 3/32" indicates a problem in the model.
With the testing and modeling that I have now done, I am totally convinced that the sheaves move in
"equal" and opposite directions unless there is something not working correctly. Making this happen is the primary task of the motor spring. If belt tension is retained when the
control sheave makes a change the floating sheave will move in the opposite direction and by the same amount.
