TS motor vibration

[Troy Turner]

I have an older (early 80's model) Craftsman beltdrive. It has a 1hp motor on it. I noticed a couple months ago that it was developing a pretty bad vibration. Next thing I know, the arbor pulley broke. No problem, replaced the pulley and belt while I was at it. Retensioned the belt, aligned the pulleys and was back in business.

Well, now I notice it vibrating again. It does it in intervals though. Not a constant, but every few seconds, you can see the motor come forward, vibrates, then retensions itself. So far I've:
- Tightened the screw that allows it to piviot when raised and lowered and that helped some. If tightened too much though, can't raise or lower the blade.
- Took the belt off, still vibrated
- Took the pulley on the motor off, still vibrated
- Tightened the heck out of the bolts that hold the motor to the mount

So I'm convinced it's the motor. I don't mind taking it apart, but what am I going to be looking for once I get inside? I want to take it completely off and turn in on on the bench and see if it does it.

Thanks for any inputs....

[John Hart]

I would be concerned about two things...a bent shaft and something that might cause the rotor to be out-of-balance.

When motor manufacturers do their inspections of motor components, they might balance the rotor much the same as a tire store will balance the wheels on your car...only they don't use lead weights to accomplish this. So, you might want to carefully pull the housing apart and look for a little glob of hard stuff that might have dislodged from the rotor and fallen into the stator or the bottom of the housing. You can then closely inspect the rotor for the spot where that glob had fallen off and re-epoxy it in place.

Or...there could be some foreign matter built up on one spot of the rotor causing it to go out of balance...which just requires cleaning.

But the most likely scenario is that the rotor shaft is somehow bent or misaligned. The run-out of the shaft can be inspected on the bench, while the motor is still assembled. Just set a block of wood near the side of the shaft...place a pencil on the block of wood with the pencil lead touching the side of the shaft at its center. Then slowly rotate the shaft to see if the pencil remains in intimate contact for the full rotation.

Run-out problems can be a bent shaft or bearing problems.

[Bill Huber]

I think the first thing I would look at is the bearings in the motor. Is there any side play in the shaft?

Is this an open motor, if so blow it out really good with an air hose and see how that does.

Do you feel any thing with the belt off and just the motor running?

[Tom Hintz]

The fact that the vibration comes and goes could suggest a bad bearing that gets looser at one point when the race turns, then tightens up some when the race gets to another spot. We had this kind of transient vibration often in race cars when bearings wore out or were damaged. It could be good news though if that is all that is wrong. Replacing a bearing is not all that expensive compared to buying a new motor.

[Troy Turner]

Man oh man oh man...Took it apart to look inside...found this!!! Saw dust was mixed with oil I had put in a while back. Cleaned it up real good, put it back together, set it on the bench, turned it on, and it danged near jumped off the bench. Turned it back off and it jumped to the other side. Didn't come up to speed, just jumped into high gear. This time, I held it down, turned it on...and well, you see the capacitor.

[John Hart]

Is that a wasp nest?

[Troy Turner]

Dirt dawber(sp?)...

[John Hart]

Well, that's interesting. I really can't see anything wrong with the capacitor from here...but it really does seem like you have an out-of-balance problem from all the build-up.

For it to immediately come up to full speed on the bench seems normal to me...unless you are describing something else.

I'm just curious if the vibration is gone.

[Troy Turner]

Guess that's something I wasn't expecting...to go from 0 to 100 like that... I'd love to see if the vibration is gone, but I haven't turned it back on since the smoke and fireworks display.

[John Hart]

Oh...so you're saying that the starting cap smoked?

Probably need to pull it out of its housing and clean it up and ensure that the wires are not touching the end of the housing. And check that the wire insulation going through the motor housing isn't compromised in some way.

Watch out for a charge on that capacitor before you handle it. Generally its a good idea to short across the terminals with a screwdriver blade...just to ensure that it is fully discharged. They usually put an insulating pad in that little housing to keep the capacitor seated snugly, keeping the terminals away from the end of the capacitor housing.

[Troy Turner]

I'll give that a whirl. Hopefully it's salvageable..I'll let you know how/if it works.

[Chip Lindley]

Hopefully, Troy, all you did was blow the start capacitor. When the motor was put back together, the start winding switch (slides up and down the motor shaft) may have not been free to move and make/break the start winding contacts. Care must be taken to put everything back the way you found it. As Yogi Berra said, "You can observe a lot just by watchin'!" Good Luck.