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MarshSt
02-11-2015, 03:32 PM
I have a Logan Powermatic 11 x 30 that has had the original motor replaced with a 1725 RPM 240VAC motor. I just did some repair work on the vari-drive (keys and bearings etc.) and installed a new belt. The manual describes how to adjust the speed adjust travel stops and I have the low end (250 rpm) set correctly according to my tach, but the rest of the speeds are only about 75% of what the indicator shows as I go up the speed range. The original motor was 1800 rpm so I should only be seeing a linear reduction to 95% if I calculated correctly. Has anyone checked their actual spindle speeds compared to the selector dial? Is there another adjustment I need to make?

Thanks,
Steve

Richard P Wilson
02-11-2015, 07:09 PM
I don't have a Logan, but I've had Raglan and now got a Denford, both UK built lathes with varispeed pullies, and on both of them the manufacturers claimed speeds are garbage. I set both of mine to get the bottom speed right, but the claimed higher speeds just are not attainable, especially with the Denford. The claimed range is 70 -1650, best I can get is 70 -1350, but thats fine for what I do. I've checked with a good rev counter.

J Tiers
02-11-2015, 10:09 PM
No common motor IS "1800" rpm.... that would be a synchronous motor, not an induction motor. Most induction motors will fall into the 1725 to 1750 rpm range, so the speeds will be as accurate as the pulley effective diameters are. Evidently, that is "not very".