Tree 325 Servo Bearing Replacement - Tachometer Removal
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  1. #1
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    Default Tree 325 Servo Bearing Replacement - Tachometer Removal

    I have a 1991 Tree Journeyman 325 and purchased a spare servo motor, baldor cc22525, when one popped up on ebay. I want to rebuild this one to be ready to swap into my machine as my Y axis motor is getting slightly noisy.

    I took the spare motor apart down to the bearings. I have the front bearing off with no issue and need to replace the rear bearing, which is captured between the tach rotor. There are no obvious features to extract the tach rotor from the motor shaft, no nuts, jack screw threads and the edge of the tach rotor is buried in the motor bearing housing so I can't get a puller behind the tach rotor hub. I have two questions on this:

    1. How is the tach rotor intended to be removed? The hub looks like its aluminum, is it on a taper or fixed with loctite?

    2. Will the permanent magnets in the tach lose their field strength as a result of removing the magnet ring as a unit from the rotor? I've read that this is possible but don't understand why this might happen. How do user replaceable tachometers like in fadal brushed motors handle this issue?

    Thanks for any advice you may have,
    Mike

    20191020_202031.jpg

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    I have some Electrocraft (now owned by Baldor) motors with tachs like that and they are glued on. If you look at the joint between the shaft and the rotor you may see the adhesive.

    Ed.

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    Thanks Ed,
    Do you have any idea how these may be removed? Heat would likely soften the glue but the required temperature may be risky to other parts nearby.

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    No idea on the proper procedure. I pressed off a tach rotor one time and bent the spokes, the retro fit this motor went on did not need a tach. In a pinch I would replace the shaft end bearing, check the commutator, and drop in new brushes.

    Ed.

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    yes they can be removed with no issues.

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    If anyone is working on one of these motors, I was able to remove the tach rotor.
    After removing the encoder, tach brush pcb and tach magnet ring, I slowly heated the end of the motor shaft with a propane torch while spinning the motor shaft. On for 10-20 seconds then wait for the heat to soak into the shaft. direct the flame away from the tach rotor. I got the shaft to about 300F with no color change on the steel. Eventually the tach can be pulled off by firmly pulling on the brush plates by hand with gloves on. There is a corrugated steel spring between part of the rotor hub.

    I attached pictures below for reference. Also the bearings are RS10 .625 ID x 1.375" OD x .3425 W double sealed. I assume C0 clearance, but have to look more into it. The pulley end seal is a national 471255.

    I will find out if there is any issue with tach magnet field strength when I reassemble it.

    Mike


    20191102_172917.jpg20191102_172927.jpg


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