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ogre
06-21-2012, 01:19 PM
I have a southbend lathe from 1930's I went completly through,and it has a 1hp,110/220 motor on it. I wired it for the 110v,which was i thought pretty straight forward,and was connected the same as previous owner,(which should not have owned a lathe for his lack of maintenance) but the motor ran fine for 3months until yesterday, it reversed without warning,or changing anything electrical. Ideas?

flathead4
06-21-2012, 02:56 PM
I'm not a motor maven by any means, but could this be caused by a failing start capacitor?

Tom

MaxHeadRoom
06-21-2012, 03:14 PM
What type of motor is it? some small split phase induction motors with just two windings, no start Cap, will sometimes run backwards if as in the case of a fan, the blade happened to be turning, these are often shaded pole synchronous that have a PM rotor.
Generally fractional HP induction fan motors do no have any caps.
Like the older clocks that had a AC shaded pole synchronous clockwork motor, they generally had a kick start mechanism at switch on, when this mechanism weakened, it was not unusual to see a clock going backwards.
Max.

ogre
06-21-2012, 03:48 PM
Thank u guys. Im assuming motor is no good now then,right??

ogre
06-21-2012, 04:01 PM
The motor is a 3/4hp(sorry) The Brown Brockmeyer Co. Says to reverse move brush ring and relock. Fr. RM720AC. Cyc. 60. 1 phase.. 1750rpm

Paul Alciatore
06-21-2012, 04:21 PM
The motor is a 3/4hp(sorry) The Brown Brockmeyer Co. Says to reverse move brush ring and relock. Fr. RM720AC. Cyc. 60. 1 phase.. 1750rpm

One: something electrical DID change, you/we just do not know what at this time.

Two: The motor is not necessarily bad. You need to find out why it changed rotation. Perhaps something has failed. Perhaps a wire or winding has opened or shorted. Perhaps the brush ring that you mention was accidentally moved.

Start checking things. I would start with that brush ring. Move it to one side and test. Then move it to the other side and test again. You do not say if it runs backwards every time or only once. Make several tests to see if it is consistent. Try starting it with the motor SLOWLY rotating both forwards and backwards to see if this is the determining factor. Use your nose before running and after turning it off and see if there is any burning smell. Come back here with some results and we will offer more advise.

bruto
06-21-2012, 06:18 PM
Something similar happened to my Model A, and it was a burned-though wire in the reversing switch. Check all the wires in there carefully.

ogre
06-21-2012, 07:18 PM
I do not have a reverse switch hooked up to it, but obviously the motor has the capability to run reversed, so i was gonna take it apart and c if the "brush ring" could have moved on its own or from vibration. Thank you guys so much. Ill tell what i find tomorro!

mickeyf
06-21-2012, 10:50 PM
There are a couple of designs (generally long considered obsolete) of commutated, wound-rotor AC motors. In some of these the position of the brushes can be rotated around the axis of field.

There are two things effects moving the brushes can have. One is to reverse the direction of the motor. The other is to shift the phase angle of the rotor windings relative to the field windings not to far as to change the direction of rotation, but enough to change the efficiency by quite a bit. You can experimentally find the 'best spot' for the brushes.

It seems pretty far-fetched to me that things got loose and the brush holding ring changed position, but it is possible I suppose.

You might look up "Repulsion-Induction" if you're curious. I'm actually repairing one something like this at the moment.

Carld
06-21-2012, 11:14 PM
I had a motor like that on my Logan lathe. there is a lever under a cover. That lever is locked in place with a screw. Loosen the screw and move the lever and it runs in one direction, move it the other way and it runs in the other direction.

Simply put the lever in the place where it runs the direction you want and lock the screw and put the cover on.

J Tiers
06-21-2012, 11:31 PM
I had a motor like that on my Logan lathe. there is a lever under a cover. That lever is locked in place with a screw. Loosen the screw and move the lever and it runs in one direction, move it the other way and it runs in the other direction.

Simply put the lever in the place where it runs the direction you want and lock the screw and put the cover on.

+1....

BTW, that type can be a nice motor. Some are easily reversible.... yours may be TOO easily reversible :D

ogre
06-22-2012, 09:18 AM
Yes micky,I am surprised shes still alive for me to use,cause this is an old looking motor. I enjoy using the old machines,theres just something i like about them. I have never reversed it so ill try today.

kf1002002
06-22-2012, 11:38 AM
This is a "repusion induction" motor. We had one in our motor lab way back when Iwas in university and I ran across another on a South Bend lathe so old it did not have a serial number. It is not electricaly reversible hence no reversing switch. Reversing is by brush shifting as someone pointed out.

The brushes simply short two sections of the commutator for starting and, as I remember it are mechanically lifted once the motor is turning. I think you would save yourself future problems by buying a modern motor and installing it with a reversing switch

Ken

Carld
06-22-2012, 06:02 PM
It sure was handy but with a screw on chuck I had to be careful how I used it. My son has the lathe now and I told him it can be reversed but to be careful. I can't remember using but two times.

bruto
06-22-2012, 06:27 PM
One of the nice things about a repulsion induction motor is that it simply will not burn out even if it fails to reach operating speed. It will just run as a brush motor forever. Great for very difficult starting loads. I had one on my 3-phase inverter, didn't care if it took a minute to get close enough to speed to switch over. I once did business at a tire store that had one of these motors on a big old compressor. For a dozen or so years, I would go there, and it would be laboring away on its starting winding. It never kicked into running mode, but never failed.

flylo
06-22-2012, 07:57 PM
If you need a new one maybe I could trade & get the old one as I like old odd stuff. Let me know. Thanks!

ogre
06-25-2012, 08:48 PM
Yup,the "ring" inside isnt being held by anything. i could move it easily. Now i have to figure out what was suppose to b holding it so it dorsnt happen again. Thank u guys!!