Replies

1. 
   DJK | Feb 24, 2004 05:36pm | #1

   Bob:

   Baldor single phase motors are notorius for vibrating on shutdown. The centrifical start switch is " kicking in " when the rpms drop. Try a 180 ohm x 10 watt bleed resistor soldered across the capacitor terminals. This is a fix recomended to me by Baldor for the same problem I had with a new Unisaw motor. I was converting a three phase saw to single phase. The new three hp Baldor motor would vibrate so badly on coast down that the Unisaw would move. The replacement motor did the same. The resistor helped but did not totaly eliminate the vibration. I ended up wiring the start capcitor thrue the LVC contactor to open the circuit during shutdown. Either that or use a different brand of motor. I like baldor motors but Not on a Unisaw, prefer an older Marathon.

   Dave

1. 
   triplenet | Feb 24, 2004 06:56pm | #2

   DJK,

   Thanks for the insight on my problem!  This board is the best! Now I need to deal with the issue.

   Bob

2. 
   Steinmetz | Feb 24, 2004 07:47pm | #3

   Bob, check the back of the disc plate .Is it bored for balancing? Should have a few 'Dimples' put there for dynamic balancing. If so, it may not be tuned to static balance Try to put a thin washer (shim) on the shaft's thread ,then tighten the disc. This will shift the 'moment' of imbalance between the motor and disc. (or,maybe a thicker shim?)

    Did you run the motor without the disc?

   Still vibrate? I think you need electronic braking., or a 'Jam' nut on the shaft locked to the disc (Two wrenches) Stein

   With the disc held between two loose centers, give it a spin.

   It should NOT stop at the same location every time (Out of balance), but randomly (Balanced)

   I recall reading,  if you momentarily introduce a full wave rectifier(Diode) into the line at shut off, (Via a relay) it will stop on a dime (And give you the change) Stein

   When shutting down, wait a bit then give it a shot of DC and it will stop before reaching vibration stage.

   
   

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   Edited 2/24/2004 12:00:33 PM ET by steinmetz

   
   

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   Edited 2/24/2004 12:03:20 PM ET by steinmetz

1. 
   triplenet | Feb 25, 2004 05:42pm | #4

   Thanks for your input.  Both of you put me on the right track to fix the problem.  It appears that the disk wobbles enough to create vibration that is engaging the starter at slow speeds.  Both old and new motor work fine wihout the disk on.  Motor shop said the old motor had a slight bend in the shaft, so it appears the machine was dropped or knocked over.

   I called PM and found the disk is $64 and the mounting hub is $116!  I'll try a machine shop next.

   I can use the machine as is, but I like my equipment top notch, so will work this out.

   Again, thanks to both of you for your help!

   Bob

1. 
   mike4244 | Feb 26, 2004 12:11am | #5

   Bob, a machine shop may be able to true up the original disk.If you have a dial indicator you can check the face to see if it is concentric.If it is the hub that may require a new one.

   mike