Variable Speed DC Motor or 3Ph. AC motor

I recently picked up a BP Mill, built in 1957 I believe - Serial number starts with BR33. The motor is shot or so I believe. It is a MF pancake like motor. I tried to run it with a static phase converter and all it did was hummm and Between two of the windings (I forget which two legs of the 9) I have zero resistance. I am installing a RPC for my lathe, varible speed Clausing 20" drill press and maybe my BP Mill.

I have two choices on hand as I picked up several motors at an auction. I have a 2hp 3ph 1725 RPM Baldor motor with 7/8" shaft, C face or a 1 hp Baldor DC motor 1750 RPM, C face, 7/8" shaft with a KB variable speed controller, no heat sink or reversing switch.

I am a hobby machinist at best.

My question to the group is which motor would you install and why? go easy on me, my first post and novice machinist

Axgold said:

which motor would you install and why?

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Neither.

Bee Pee motors are closely integrated with the overall machine as to coupling to the rest of the drivetrain. More work than it may be worth to do an integration of the 2 HP 3-P motor and changes to the starter and such it would ALSO need (ELSE a VFD..) . Also too much power = shorter life of other parts, few of them free. And then there is the extra mass to deal with.

For the Dee Cee motor, you have the same mechanical integration needs, plus it can easily be heavier than a 3-P motor of even twice the HP, especially if wound for 90/180 VDC the KB serves up.

It also might need a different KB drive than the open, chassis-mount you have. It should be 4Q 'regenerative' so as to handle braking and reversing all in one box, need no contactors - preferably a NEMA-4 or 'washdown' resistant box at that.

Probably best to have the low-profile motor already on the mill rewound, avoiding need of control changes, then just run with your RPC plan.

Else find a proper match as replacement for the existing motor - same reasoning.

The other motors?

DC? Do you need a grinder, belt sander, buffer or such? Have a care. The brushes are usually exposed to potentially flammable, even explosively so, metal fines, wood dust, or errant solvents.

Would the 2 HP 3-P do yah as light-duty RPC idler? Or as a booster idler for a larger idler?

Trading material, either one? Might want to start right there...

Bill

Agree with above. Have the original BP motor rewound + new bearings. So much simpler and preserves the value if you sell. BTW, don't run machine tools on static convertors. Good way to burn windings, or sometimes not even work with some magnetic starters. If you have to use a static, use it only as the starter for an idler motor, and take the output from the idler to the mill.

Best for your situation would be rewind + rotary convertor whether bought or shop assembled from your surplus motors. Alternately, a VFD has a lot of convenience factor concerning start, run, and speed control with fewer belt changes.

smt

Axgold said:

he motor is shot or so I believe. It is a MF pancake like motor.

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Is the pancaker a 1Hp? Find out what you had on there before making a decision.

Are you using a meter that is able it read low ohms.

Attach pictures of the situation.

You don't say which head model you have. It's probably a J (1 hp), but could be an M (1/2 hp).

Either way, it's usually much easier to have the old motor re-wound and new bearings put in that to make mounts and modify pulleys to fit. Then, get rid of the static converter and get a VFD.
JR

I went to a local rewind shop and they thought it would not be worth it to rewind. I think that they did not want to bother with it. Anyways, it is a Fairbanks-Morse Induction motor; Type QZA; Frame 4570; 1 HP; 3 PH; 1745 RPM motor....if I can find a shop to rewind, about how much should I expect to pay roughly?

Axgold said:

I went to a local rewind shop and they thought it would not be worth it to rewind. I think that they did not want to bother with it. Anyways, it is a Fairbanks-Morse Induction motor; Type QZA; Frame 4570; 1 HP; 3 PH; 1745 RPM motor....if I can find a shop to rewind, about how much should I expect to pay roughly?
View attachment 189724

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No less than $200, I'd guess. Start looking for another ORIGINAL Bee Pee motor, used-but-running, same mounting and fit-up to the drivetrain. New bearings, you can DIY cheaply enough.

DIY rewinds I cannot recommend, though I've had it done in third-world venues in a manner comically slow and amazingly primitive, yet 100% effective. They've no other choice, y'see.

"Plan B" a lighter 1 HP 3-P motor - Bee Pee OEM also if you can find one - that fits the shaft & mount, but is taller.

Neither of your present 'strays' gets promoted to a good fit just because the OEM one has failed.

Bill