3450 ??????

[pineyfolks]

I posted this in the southbend section, but thought it may help me better here. This is the motor off my 9" sb. Am I reading this correct, is this a 3450 rpm motor? Or am I missing something It was wired to run on 110v. Could it have been changed to run a slower rpm? The new motor I bought is 3450 rpm and I had to change pulley size to get my rpm correct.

 

[Ray C]

Bill,

By how much did you need to change the pulley? Is the new motor 120/220 and did you wire it properly? Sometimes a dual voltage motor will have slightly different speeds at the different voltages -especially true with 3 phase motors. For example, I have a 220/440 motor with rated speeds of 1725/1575 at those voltages.

Ray

 

[CluelessNewB]

Could it have been changed to run a slower rpm?

Not very likely. If it really doesn't run at near the RPM on the tag I think a more likely explanation is the end bell and/or tag came from a different motor. How are you measuring the RPM? Optical tachometers are available for less than $20 on Ebay. 60 Cycle motors typically run at 3600, 1800, 1200 or 900 RPM minus some slippage so the actual speeds will be about 6% less. The speed is based on the frequency and the number of poles

RPM = F*120 / NumPoles

Where F = Frequency (60 in the US and Canada)

NumPoles = Number of poles 2, 4, 6, 8 Typically

The number of poles is based on the physical construction of the motor, not easy to change.

If that is really a 440V Single Phase Motor it's a very odd duck! Something I have never seen before. If it really is 440V and you have it hooked up for 110V it might run slow and I would guess it's only running on the starting winding and it's power output will be much less than rated power and the starting cap will not last long at all!

 

[pineyfolks]

The new motor is wired 110v, this is on my 9" sb it's a 12 speed it has a 2" and a 3.5" on the motor and I think a 10" and 11" on the jackshaft that runs 3 cone pulleys to the head. I was using the 3.5" and 10" and it gave me over 1600rpm at the spindle. Switched to 2" and 11" and got 1255rpm in high gear. This puts me in the range of speeds I use so it's ok, I just didn't understand why.

 

[Ray C]

What happens when you run it with the 3.5/10 combo, is it anywhere near 1600 like it used to be?

The new motor is wired 110v, this is on my 9" sb it's a 12 speed it has a 2" and a 3.5" on the motor and I think a 10" and 11" on the jackshaft that runs 3 cone pulleys to the head. I was using the 3.5" and 10" and it gave me over 1600rpm at the spindle. Switched to 2" and 11" and got 1255rpm in high gear. This puts me in the range of speeds I use so it's ok, I just didn't understand why.

 

[pineyfolks]

I measured spindle rpm with an old starrett hand held tach

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I had to switch to the 2-11 to get me to a safe speed for my bearings, I was told 1600 was to fast. It's a 1940's lathe. It never ran 1600

 

[Ray C]

If that is really a 440V Single Phase Motor it's a very odd duck! Something I have never seen before. If it really is 440V and you have it hooked up for 110V it might run slow and I would guess it's only running on the starting winding and it's power output will be much less than rated power and the starting cap will not last long at all!

No, the 220/440 motor I have is 3phase. I was just demonstrating that some motors (not all though) run at slightly different speeds at different voltages. The motor I'm referring to is a new production Easson motor. I've seen similar things on a handful of other motors.

Ray

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If you have a tach, what does it read off the motor shaft?

I measured spindle rpm with an old starrett hand held tach

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I had to switch to the 2-11 to get me to a safe speed for my bearings, I was told 1600 was to fast. It's a 1940's lathe. It never ran 1600

 

[pineyfolks]

I didn't check the new motor it was tagged 3450 for what that's worth. I'll check that tomorrow

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What is the 440 number on the tag everyone is talking about?

 

[UncleRuss]

First-the 440 they are talking about is a totally different motor than what you have. 220/440 3 phase, not 120/240 1 phase. Please disregard as it does not apply to your motor.

Lets think this out Gents. I have never seen a 2 pole motor (3450 rpm) on a lathe application before. I believe the remark by cluelessnewbie about the original motor somehow getting the wrong name tag/endbell is the best probability. We had a guy in school who used to change labels in motor rewind class just to be cute, at least he thought so.

Cluelessnewbie's other remarks seem right on track also. The calculations for motor speeds are the same I learned so you most probably need a 4 pole motor (1750 rpm) for this application.

I am a bit lost as to why this motor was changed in the first place. If it still runs, plug it in, put the tach on it and check the actual, original speed.

The odd rpm noted in Ray C's reply at 1580 rpm I believe refers to a 4 pole motor operating at 50 cycles. The speeds at the given pole ratios by cluelessnewbie are right on for 60 cycle operation. The applied voltage has nothing to do with speed.

I usually only see 3600 rpm motors on such applications as buffers, surface grinders, pedestal grinders and so on. What are your thoughts on the application?

 

[pineyfolks]

I changed motors because the wires were falling apart from old age and caught fire while I was using it. So I just ordered a new one using the old one as a guide. I may check into having it rebuilt but I needed to get it running in the meantime. I normally never switched the belt on the motor, I just used the cone pulleys and back gear as you would on a 6 speed. It works fine. I was just at a loss when the motor speeds didn't match. I'm going to check the new motor rpm tomorrow. No way to check the old one, I can hardly rotate the shaft.