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Clare Snyder Clare Snyder is offline
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Default Single Phase Pulse

On Tue, 2 Feb 2021 13:40:07 -0700, Bob La Londe

On 2/2/2021 1:18 PM, Jim Wilkins wrote:
"Bob La Londe"* wrote in message ...
My bigger import lathe is not bad.* I can dial stuff in by hand to about
3 tenths.* The problem is under power the indicator needle turns into a
blur about 1.5-2 thousandths wide.* For 99% of what I do that is fine,
but that other 1% is growing.* Is the only answer to install a 3 phase
motor?* I'm not completely against it, but its a bit of a job to move
the lathe, swap the motor, and reconfigure the controls.* Not something
I can do in an afternoon.


Can you disconnect the motor from the drive train? If you can, and the
needle still vibrates, the motor may be unbalanced.

Been busy at the computer on design work, but my next thought was to try
a "coast" test first. Spin it up to speed, and then shut it off to see
if the vibration persists when costing. If it vibrates when coasting
then "something" is out of balance. If it doesn't its probably single
phase motor pulse.

I was surprised to find Surplus center sells a 3HP 3 phase 4 pole motor
pretty reasonably. Its a Marathon, but it is rated as continuous duty.
Now whether or not that would drop onto the current mount I don't
know... Some of those imports seem to have odd ball motor frames. I
can certainly make anything I need, but I am not sure I want to spend
several days int he shop without my big lathe. I hate doing anything
but the simplest light work on the smaller lathes anymore.

Put a big torsional ramper - or even just a flywheel on the motor or
the primary drive