Help with motor starting problem (single phase)

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showmedata

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Hi all,

The 1960s Rockwell 21-100 mill I recently acquired has - I believe - a single phase motor but is missing the name plate. It came wired as single phase and worked when tested.

It has a Furnas reversing switch (momentary push-button switches) and Furnas reversing contactor.

I went through the electrical box and replaced a number of wires that were corroded, cleaned up connections, and improved the mounting of the transformer. After that, the motor will not start reliably. Testing with a multimeter told me the start capacitor was bad, so I got a new one. that did not help it.

If I manually help the motor start turning, it will usually pick up and run normally (clockwise, anyway - CCW seems to be a problem). That is a dodgy proposition, though, trying to nudge the pulley along inside the housing .

So, question #1: the motor won't start itself. Any suggestions?

Question #2: the contactor latches solidly and quietly about 20% of the time - the other times is buzzes either a little or a lot. I've checked the switch circuit voltage (24VAC) and it seems to be fine, not dropping significantly when activated.. Is that a symptom of the contactor coils going bad?

Attached are some photos. Appreciate any help you may have to offer.

Thanks,
Ray
motor side.jpeg
switch.jpeg
wiring.jpeg
 
Could be the centrifugal starting switch contacts need dressing, also the contacts on the contactor may be dirty or corroded and need attention.
 
benmychree said:
Could be the centrifugal starting switch contacts need dressing, also the contacts on the contactor may be dirty or corroded and need attention.
Click to expand...
I neglected to mention that I cleaned all the contacts in the contactor (light sanding). I guess I'll have to open up the motor to inspect the centrifugal switch.
Thanks.
 
mattthemuppet2 said:
Did it start reliably before you started work on it?
Click to expand...
Sadly, I don't know. I was so eager to clean up the filth and rust I just dug into it without much testing. Plus, the previous owner had made the power cord out of Romex, so I didn't have a ton of faith in the electrics...
 
showmedata said:
I neglected to mention that I cleaned all the contacts in the contactor (light sanding). I guess I'll have to open up the motor to inspect the centrifugal switch.
Thanks.
Click to expand...
Inspect, remove, clean, test, and reinstall the centrifugal switch. Make sure the springs are there and the moving parts key into the right places. Unless it's rusted, a cleaning should take care of things, assuming everything else (connections/contacts, switch, so forth) are good.

If the motor isn't racing to run up, the centrifugal switch is probably stuck in run.
 
Also a good time to check out your motor bearings and regrease/replace if needed.
Do you have a multi-meter you can check your voltages and continuity?
 
Glad to hear it!
Bearings still in good shape then?
 
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