Brush shifting motor

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zbang

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Some folks have been using this motor on a printing press and in all my old books, I can't find much about them. From what I could get, it's a repulsion motor and that the brushes short across the armature, moving them changes the pole position(?) thus varying the speed. The owner tells me than if you move the lever from one end to the other while it's running, it'll spark something fierce when it reverses.... I wouldn't recommend doing that.

Any pointers to better info? (No photos of the brushes at the moment, I'll be back there later next week and get some.)
BSmotor1.jpg
BSmotor2.jpg
 
zbang said:
Some folks have been using this motor on a printing press and in all my old books, I can't find much about them. From what I could get, it's a repulsion motor and that the brushes short across the armature, moving them changes the pole position(?) thus varying the speed. The owner tells me than if you move the lever from one end to the other while it's running, it'll spark something fierce when it reverses.... I wouldn't recommend doing that.

Any pointers to better info? (No photos of the brushes at the moment, I'll be back there later next week and get some.)
View attachment 22279
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What kind of pointers are you looking for?

Stop the motor first before trying to change it's direction would be my number one pointer. It has sleeve bearings that need oil. Brushes are still available from the web, you'll likely need a caliper to get the dimensions to order them. It has already run longer than the people that built it have lived, with the right care it will keep running.
 
gar said:
See Chapter 18 of "Alternating-Current Machinery", Bailey and Gault, McGraw-Hill, 1951
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Thanks, that's the kind of pointer I was looking for. I don't have Bailey & Gault and neither does the SF public library (they do have Lawrence, 1953; that's worth a check) (none of my various Croft volumes cover these motors much).

Mechanically, it's an old motor- lube the bearings, make sure the brushes fit and the commutator doesn't have any raised mica, etc. And don't reverse under power. Since it's using a flat belt to the press, overloading will not be an issue. Anything else useful to know?
 
zbang said:
Thanks, that's the kind of pointer I was looking for. I don't have Bailey & Gault and neither does the SF public library (they do have Lawrence, 1953; that's worth a check) (none of my various Croft volumes cover these motors much).

Mechanically, it's an old motor- lube the bearings, make sure the brushes fit and the commutator doesn't have any raised mica, etc. And don't reverse under power. Since it's using a flat belt to the press, overloading will not be an issue. Anything else useful to know?
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Nowhere in the nameplate states that it is a REPULSION MOTOR.
It is usually and clearly stated because these motors have different characteristics.


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Therefore, it would be safe to say that it is not a repulsion motor. You could possibly be looking at a series wound induction motor.


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The field winding of a repulsion motor is not connected to the power source.

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You are correct to infer that speed can be changed by positioning the brushes as well as changing the rotation.​
The arcing you mentioned indicates that it is series wound motor. The above speed adjustment principle can be applied to both series wound and repulsion-induction run motors as well as regular series wound-- pure induction motors.

Repulsion motors of this size (3HP) at 110/220 volts AC don't usually generate arc. This is the “beauty” of this type motor.
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(you probably know this already through your venerable Wikipedia arsenal)


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Higher voltages above 1500 volts can cause arcing-- that's why they don't make repulsion motors with this high a voltage.


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The armature (rotor) winding of a repulsion motor terminates and shorted at the “slip disc”. Shorting is done after the motor arrives or close to the rated speed . At this stage the motor would be acting like a regular induction motor.

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This is in addition to the “segmented” commutator that you see in DC motors.
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Tony S said:
Looks like a Schrage motor, my avatar is a drawing of one.

...
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Tony,
No, it's not a Schrage motor, a Schrage motor is variable speed. Here in the US up until maybe the 1920s, it was a type of single phase AC fixed speed motor called a Repulsion / Induction Motor that started as a AC/DC Universal motor and then changed over to AC induction motor (in an extreme nutshell). Earlier versions (like the one in the video below) had a manual lever to pull the brushes off of the commutator, later on they used a centrifugal clutch that did it automatically for you. The only alternative at that time was a Split Phase arrangement but that had low starting torque. But once they came up with Capacitor Starting, the Repulsion / Induction motor went by the wayside, because the Cap Start was far cheaper and far less maintenance.

Great video of the old original version with the lever.
https://www.youtube.com/watch?v=_KdaipeodLo

I too came across one, also on a flat belt drive system in a farm shop building I was helping to restore. It was a 5HP motor and was the size of a modern 50HP motor, using an old A-B NEMA Size 5 motor starter. (For you youngsters out there, at one time a shop building would have one electric motor, connected to a flat leather belt driving a long shaft and/or other belts that wound their way through the shop to other clutch driven machinery).
https://www.youtube.com/watch?v=7qt5tltnvF8
 
I guess the motor on my air compressor is probably one of the last commercially manufactured repulsion-induction motors. It was manufactured by Reliance electric (bought out by Baldor) and I got it from Grainger maybe 40 years ago. Ran great until a few years ago when the "garter" spring on the commutator broke so the shorting ring doesn't retract anymore. Spring is "unobtainium" unless you want to make one. The tension is critical because it determines the speed at which the ring retracts which changes from start to run much like that video. I did find some guy on a woodworker's forum who made a new spring for a similar motor for one of his machines. He happened to have a lathe with a digital speed readout, so he just chucked the armature up and shortened or lengthened with spring he made until he got the speed right.:thumbsup:

-Hal
 
Jraef said:
Tony,
No, it's not a Schrage motor, a Schrage motor is variable speed. Here in the US up until maybe the 1920s, it was a type of single phase AC fixed speed motor called a Repulsion / Induction Motor that started as a AC/DC Universal motor and then changed over to AC induction motor (in an extreme nutshell). Earlier versions (like the one in the video below) had a manual lever to pull the brushes off of the commutator, later on they used a centrifugal clutch that did it automatically for you. The only alternative at that time was a Split Phase arrangement but that had low starting torque. But once they came up with Capacitor Starting, the Repulsion / Induction motor went by the wayside, because the Cap Start was far cheaper and far less maintenance.

Great video of the old original version with the lever.
https://www.youtube.com/watch?v=_KdaipeodLo

I too came across one, also on a flat belt drive system in a farm shop building I was helping to restore. It was a 5HP motor and was the size of a modern 50HP motor, using an old A-B NEMA Size 5 motor starter. (For you youngsters out there, at one time a shop building would have one electric motor, connected to a flat leather belt driving a long shaft and/or other belts that wound their way through the shop to other clutch driven machinery).
https://www.youtube.com/watch?v=7qt5tltnvF8
Click to expand...

The OP mentioned printing presses, brush shifting and variable speed. The stamping ground of Schrage motors.

I’m not going to argue with you JR, we’ve known each other far too long for that. But a photograph of the armature and brushgear would help to settle the matter.

The pictures I posted were of a very badly worn machine removed by a friend of mine in Northern Ireland, replaced by a VSD drive. Despite me getting two museums willing to buy the motor it went for scrap………… :(
 
Tony S said:
The OP mentioned printing presses, brush shifting and variable speed. The stamping ground of Schrage motors.

I’m not going to argue with you JR, we’ve known each other far too long for that. But a photograph of the armature and brushgear would help to settle the matter.

The pictures I posted were of a very badly worn machine removed by a friend of mine in Northern Ireland, replaced by a VSD drive. Despite me getting two museums willing to buy the motor it went for scrap………… :(
Click to expand...
Tony,
You are absolutely right, I totally missed the variable speed aspect of it.
Got my exercise yesterday by jumping to conclusions...
 
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