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Electric motor mystery (to me,anyway)

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  • Electric motor mystery (to me,anyway)

    I'm fixing up an old Walker Turner 1100 drill press with power down feed. The original motor was replaced by a Dayton Vari Disc motor. The motor is wired for 110v. I took it apart to find out why it would run fine, but the speed wouldn't vary. I found the belt was not on right. I put the belt on and tested it and it worked fine. I then decided to see if I could find a new belt and clean up the inside before putting it back on the drill press. I found one, but was having a tough time getting it on - probably, I thought, due to it's being new. I thought maybe if I could put downward pressure on the cover and touch the on switch, it might turn enough to get the belt in place enough that I could get the screws started ( yes, I know it sounds like a stupid plan ).
    Anyway, when I hit the swich, nothing happened. I opened the box on the side of the motor and there was the problem. Two red wire ends(one coming from the switch and one from the inside of the motor) and a wire nut laying separately in the box. So, I screwed the wires back together and hit the switch. It started turning what I thought was the wrong direction, but then after a couple of real slow turns, sort of clunked and changed directions, turning slowly for a few turns before going to speed. I turned it off and tried it a bunch of more times. It almost always starts slow and then takes off. Sometimes it starts in the wrong direction and changes direction like the first time. Sometimes it starts slowly in the wrong direction and then speeds up still going in the wrong direction. Occasionally, it will start fast in the right direction, but usually only when it has already been turning at speed in the right direction. And it will sometimes starts slow in the right direction and then speeds up. There is no pattern to it.
    I cleaned the inside of the housing with carbeurator cleaner before any of this happened, but was careful not to shoot any toward the motor shaft. I cleaned that side with a shop rag wetted with the cleaner. I feel I have somehow done something simple and/or stupid that is right before my eyes, but I'm missing it.
    Any ideas? Sorry for the length. Just wanted to put the whole story out there.


  • #2
    Welcome Matt

    Check the wiring terminals 1 more time


    • #3
      electric motor mystery ( to me, anyway )

      After you posted that, I felt stupid as I had just grabbed the two loose wires and wire nutted them back together without even checking to see if they were tight.
      But, today I redid everything, but it's still not working right.
      This is a sweet system, so I think I might just find a rebuilder and have it fixed and cleaned up, providing it doesn't cost too much.
      I still feel I'm missing something simple.


      • #4
        Is there enough room in the motor box for a starting capacitor? Maybe the red wires were connected to a capacitor that went bad, was removed, but was not replaced. That might explain the slow start and erratic behavior.
        Any products mentioned in my posts have been endorsed by their manufacturer.


        • #5
          It sounds like there is a third wire to the start capacitor that somehow was missed.

          At the end of the project, there is a profound difference between spare parts and extra parts.


          • #6
            Sometimes there are start windings and a switch, rather then a capacitor. The switch works on centrifugel force. When the motor is stopped the contacts are closed and the start windings have power ( if the contacts are working.) After the motor starts and gets up to speed the switch cuts out disconnecting the start windings. This is the click sound you hear on some motors. Usually the switch is bad. The contact points arc when they disconnect and then the switch will eventually go bad. This switch is usually at the oposite end of the armature but not always . Look for something that has springs and contacts on it. You should be able to trace a wire to it also. If it has a switch just replace it. That should give you more torque on startup.


            • #7
              Or some times you have a Centrifugal Switch and a Start Capacitor. Some times the motor leads even say "CAP" for capacitor on them.

              I didn't reply to you saying "Please check your motor terminals 1 more time" as a newbie put down. I currently work as a Instrumentation Tech, have spent most my career as a Control Systems Engineer, and "I recheck" my terminals 2, 3 times when I'm having problems.

              Your problem really sounds like a starting capacitor problem from your description (which I just reread 2-3 times to get it straight) and if you were to post the Make, Model #, Number of Wires (and what they say on them) of the motor we could help you more

              Don't worry - the group will have the answer for you


              • #8
                Electric motor mystery ( to me, anyway )

                "I didn't reply to you saying "Please check your motor terminals 1 more time" as a newbie put down. "

                I didn't take any offense. I used to work on slot machines and got occasional calls from casinos saying a machine wouldn't power up. I would ask them to check to make sure it was plugged in, which would annoy them. Usually I could get them to check and they would either say it was unplugged or wouldn't call back at all.

                I'm going to have to take another look at it. When I saw the two loose red wires, I made the assumption they had to go together, but maybe they don't. There is a capacitor on the outside of the motor.
                I still may have it taken in. The place where I work has alot of motor work done by a local place (big motors) and the head maintenance guy said if he took it in, the guy might work it over nearly free.

                I'm still listening, though.


                • #9
                  Variable speed motor? is it a DC motor with a controller? I could understand (vaugely) that behavor from a DC motor controller board thats gone all wacky.. but no idea why an AC motor would do that. Maybe an intermitant centrifugal starting switch on the motor..
                  Last edited by Black_Moons; 02-25-2010, 05:09 AM.
                  Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


                  • #10
                    Information might have been helpful.....

                    The best I could find out was that the "varidisc" is a sort of reeves drive setup, with variable pulleys. The motor itself would be a standard constant speed type then, most likely a standard induction motor.

                    But there could be some other "electrical stuff" associated with the motor.....

                    Keep eye on ball.
                    Hashim Khan