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  • 2x72 belt grinder

    Good evening, I am in the process of building a 2x72 belt grinder using a treadmill motor. My question, dilemma, i have to turn the 17mm shaft to .625". Do I take the motor apart, how difficult, or place the motor in lathe between centers and tie off the body of the motor. Thanks in advance. John b

  • #2
    No reason not to do it between centers.
    Done it many times.


    -D
    DZER

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    • #3
      they're dead easy to take apart. Usually a couple of nuts to undo at the non-business end, then the whole thing pulls apart. You can also use a steady rest to hold the shaft end bearing to turn down the shaft if a center won't fit for some reason. I vaguely remember doing that to true up a treadmill motor flywheel many moons ago.

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      • #4
        Why does the shaft need to be .625? If you are mounting a pulley bore the pulley to 17mm.
        North Central Arkansas

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        • #5
          Ulav8r and I did. The 17 mm diameter is less than 1" long then there is a 1/2-13 lh thread. The pully is molded nylon impregnated plastic. 2 1/4" long with a set screw in the middle. So I have to make up a bushing to fit the threaded portion and machine it on the motor shaft to mate with the 17mm. Another .045" and I don't have to bore out the pully. John b

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          • #6
            When I was making something I had to true up an adapter I made that fit the shaft of a motor. To true it up I just strapped the motor down to the lathe and ran the motor itself to do the work.

            Andy

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            • #7
              That is a clever idea and you will be absolutely certain of concentricity with the motor bearings. Treadmill motor is variable speed so you can slow it down as needed, since they are often 5000 rpm.

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              • #8
                If that motor is a permanent magnet type, it may lose magnetism when you remove the rotor.

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                • #9
                  I'm not well up on motors, but I've never had any issues taking apart TM motors and putting them back together again. In fact I do it as a matter of course to clean out dust bunnies and cat hair. They can be a bit of a pain to reassemble sometimes as the magnets are so strong it's hard to stop the rotor sticking to one side before getting the bearings and end caps lined up.

                  John - are you making the sleeve threaded to thread onto the existing shaft? Just be aware of which way round you place the motor in your build so that there isn't any risk of having the sleeve unthread. Might be simpler to turn off the threads and make the sleeve a press fit, unless you've already thought of that.

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                  • #10
                    I'd thread on a sleeve, degrease first and use loctite 62x to secure. I will never come off! Don't disassemble - turn between centers and lightly lock the motor body. Pull the bushes first.

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                    • #11
                      Thanks guys. Loctite and remove brushes, i can handle that. John b

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                      • #12
                        If its your standard open-frame treadmill motor, it wont last very long on a belt grinder. Been there, done that, swarf ingress kills them in a few months of use. Cant say id want to put in the work to modify a motor thats going to be dead in short order anyways, i agree that modifying the pulley is the better option

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                        • #13
                          Originally posted by epicfail48 View Post
                          If its your standard open-frame treadmill motor, it wont last very long on a belt grinder. Been there, done that, swarf ingress kills them in a few months of use. Cant say id want to put in the work to modify a motor thats going to be dead in short order anyways, i agree that modifying the pulley is the better option
                          When I built my 2 x 42 I was worried about that. That was more than 10 years ago and it's still going strong. I might use mine a lot less that you do yours - so the OP would have to consider how much his will get used. Also - this might be important - my motor drives the top wheel and is not close to the swarf stream.

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                          • #14
                            Mr. fail, if you had read post #5 you see why I am doing tha alteration on the motor and not the pulley. The motor being the easy way out. I am aware of the openness of the treadmill motor and will try to address that problem. I am a big fan of thee phase tefc motors and vfd. I have two, lathe and drill press. Some times you have t go with what you have.

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                            • #15
                              Originally posted by Bob Engelhardt View Post

                              When I built my 2 x 42 I was worried about that. That was more than 10 years ago and it's still going strong. I might use mine a lot less that you do yours - so the OP would have to consider how much his will get used. Also - this might be important - my motor drives the top wheel and is not close to the swarf stream.

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                              Your design seems pretty well thought out, most 2x72s have the motor down low and in the path of the grinding swarf. I was getting a fair amount of use out of mine, 15-20 hours a week is a good guestimate. Burned out a total of 3 motors in a few months before I caved and put a 2hp TEFC motor on, no problems since.

                              I don't mean to make my argument sound like the only option, just speaking from my personal experience. After the failures I find it a bit harder to trust treadmill motors, they held up a few projects so I'm a little gunshy around them now

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