RPC Idler question

[682bear]

If I was looking for a 7.5 hp 3 phase motor to use as an RPC idler, would the RPM rating on the motor have any bearing on what motor to use?

For example, I'm seeing motors that are 1150 RPM all the way up to almost 3600 RPM... Is one better than the other?

Thanks- Bear

 

[JimDawson]

No difference at all. The most common would be to use a 4 pole motor (1725 RPM), rather than a 6 pole (1150 RPM) or 2 pole (3450 RPM)

 

[682bear]

No difference at all. The most common would be to use a 4 pole motor (1725 RPM), rather than a 6 pole (1150 RPM) or 2 pole (3450 RPM)

Ok, thanks, Jim, thats what I needed to know!

-Bear

 

[cathead]

The older four or six pole motors have more iron in them are much better suited for building an RPC.
I have built a few over the years and the newer 3450 RPM motors would not be my choice. While they
will work, the constant whine from these motors is a major disadvantage. I would much rather have a
slow running RPC in my shop purring away quietly under the bench.

 

[682bear]

I'm guessing this would be good for a RPC?





I'm probably going to go look at it if I can schedule an acceptable time with the seller.

-Bear

 

[JimDawson]

Looks like a great candidate for a RPC.

 

[Plum Creek]

I was just about to thread the same question. How about this older Westinghouse 15?
I can't read the label and haven't been able to go take a look at it.

 

[682bear]

I went and picked the motor up this morning...



I guess if it runs, it's worth $100...?

The seller has over a hundred motors he wants to sell, from 1 hp to 20hp... and I think he said he had a 70 hp also.

-Bear

 

[Plum Creek]

I would love to find one of those here in Texas at that price!

 

[Joeman77]

I think the lower RPM (570, 1120, 1725) motors are definitely quieter and easier to start than a 3500+ RPM motor & the bearings should last almost forever in a RPC application. If you get an old one I'd give it a good cleaning before anything else, dirt is a motor's worst enemy, traps heat & that's what kills them.
And check the bearings, they're cheap & easy to replace while you've got it out so it's accessible, they'll never go bad at a good time...