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Thread: Brush shifting motor

  1. #11
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    Quote Originally Posted by Tony S View Post
    Looks like a Schrage motor, my avatar is a drawing of one.

    ...
    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
    __________________________________________________ ____________________________
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  2. #12
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    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.

    -Hal

  3. #13
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    Quote Originally Posted by Jraef View Post
    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
    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…………
    The reports of my death are greatly exaggerated.

  4. #14
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    190212-0840 EST

    zbang:

    See https://www.brighthubengineering.com...ulsion-motors/
    and various other discussions by the same group.

    I think much cleared presentations could be made, but you still might find useful information.

    .

  5. #15
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    Quote Originally Posted by Tony S View Post
    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,
    You are absolutely right, I totally missed the variable speed aspect of it.
    Got my exercise yesterday by jumping to conclusions...
    __________________________________________________ ____________________________
    Many people are shocked when they discover I am not a good electrician...

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