Where is the capacitor? Should there be one?

[Cahark]

I picked up an old black and decker heavy duty 1/3hp bench grinder the other day. I’m guessing that it was made in the 1940s or 1950’s. It runs ok but I knew it could use a new cord, bearings, and a coat of paint. This brings us to today.

When I removed the cover from the bottom of the base, I was surprised to not find a capacitor. There was a bracket for one on the sheet metal access panel, but the capacitor itself looked to be bypassed and missing. The grinder seemed to start fine, but I can’t help but belive that there should be one here.

-Does anyone have any insight here?
-Anyone willing to remove their base access panel to see what’s on theirs?
-What is the proper size capacitor?
-How would I connect it with 3 leads coming off the motor?
-Is there supposed to be a capacitor at all?!

Thanks in advance,
Cahark

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[ttpete]

It's probably a split-phase motor. They don't need a capacitor to start, but they won't start under load.

 

[mikebaker1129]

That wiring needs some attention.
That looks like it will make you a great grinder,when you get it fixed up!

 

[Cahark]

It's probably a split-phase motor. They don't need a capacitor to start, but they won't start under load.

That’s possible, but don’t split phase motors have capacitors? I don’t know enough about the subject.


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[Cahark]

That wiring needs some attention.
That looks like it will make you a great grinder,when you get it fixed up!

I plan to heat shrink all of the leads off the motor, new switch, and make sure there’s a good ground. Thanks for the encouragement, I’m excited to use it.


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[DenisG]

TWO leads go into the motor - one is hot and the other is neutral. You can connect it directly to a power cord to try it out, but the hot wire should have the switch breaking that connection. The ground wire from the power cord should be connected to the base for safety.
No capacitor is used on this one. The motor is a squirrel cage motor and the bench grinder is a "Special 6":
https://www.garagejournal.com/forum/showthread.php?t=336177
http://vintagemachinery.org/photoindex/detail.aspx?id=14268

 

[nelstomlinson]

Does it start without a capacitor? Yes? Then you don't need a capacitor.

Edited to add: if it wouldn't start without a cap, you could spin it by hand before you close the switch, and you'd still be OK without the cap.

 

[Cahark]

Does it start without a capacitor? Yes? Then you don't need a capacitor.

Edited to add: if it wouldn't start without a cap, you could spin it by hand before you close the switch, and you'd still be OK without the cap.

If i understand correctly there are three types of capacitors. Start, run, and start run. I think some need one, both, or a combined capacitor. I have started motors by giving them a spin To diagnose a start cap, but never a run cap.


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[Cahark]

TWO leads go into the motor - one is hot and the other is neutral. You can connect it directly to a power cord to try it out, but the hot wire should have the switch breaking that connection. The ground wire from the power cord should be connected to the base for safety.
No capacitor is used on this one. The motor is a squirrel cage motor and the bench grinder is a "Special 6":
https://www.garagejournal.com/forum/showthread.php?t=336177
http://vintagemachinery.org/photoindex/detail.aspx?id=14268

This motor has 3 leads to the stator. Not two. I was able to verify when everything was torn down. Does that change things?


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[DenisG]

This motor has 3 leads to the stator. Not two. I was able to verify when everything was torn down. Does that change things?


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Then I don't know. Mine has two.

 

[nelstomlinson]

If i understand correctly there are three types of capacitors. Start, run, and start run.

You might be right. My rotating machines class was in 1984, and it wasn't a strong point. I don't remember anything but the start cap, but after so long, I might not remember what I forgot.

If it starts and runs as is, I'd use it as is.

 

[bpjr]

If it runs I wouldn't worry about it. I checked my boat lift motor by taking the cap out of the circuit. It ran fine wired directly without a load. It needed a start cap just to get it spinning under load.

 

[JJ99SS]

Flux?

Had to do it...

 

[Fcvapor05]

If it runs don't 'fix' it.

If it needed a capacitor and didn't have one, it 100% would not start.