Shopsmith Forums

My Mark 5 has worked flawlessly for over 40 years, but just recently when I turned it on the motor made a stalling noise and did not move.
Of course I instantly switched it off. In my inspection and cleaning I also discovered that the speed control is stuck and does not rotate to slow.

Any advice on how to treat these problems would be greatly appreciated.

David

Welcome to the forum. I'll offer my suggestions, and I'm sure more experienced owners will not be far behind with more advice.

When the motor on my 1980 Mark V 500 failing to start has happened to me, it is usually sawdust build up inside the motor at the centrifugal switch that is supposed to disengage once the motor starts spinning. If blowing it with compressed air or dislodging the dust by a cushioned smack to the motor doesn't solve it, you may have to remove the motor and open up the business end for better access to clean out the dust. Depending on the brand of motor, the start mechanism will vary. In this thread is what my GE motor looked like, and other discussion about a humming motor: viewtopic.php?t=23758

Another possibility is a bad start toggle switch.

As a 40 year user, I'm sure you know to never rotate the speed control (to faster or slower) unless the sheaves are moving. When you say the speed control doesn't rotate to slow, was it at some higher speed when you tried to start? Trying to start with the speed control at a very high speed can also give same symptom of motor stalling. Can you put on the sanding disk and while manually rotating the disk (with power cord unplugged) does the speed control turn to a slower speed? I have never had to do much work on my speed control, so that's the extent of my experience there.

If you haven't done so already, remove the belt cover from the left side of the headstock and makes sure the V-belt isn't binding in the split sheaves.

Helpful suggestions from br549 and Ed already. If you try the Sanding Disk mounted on the Quill and turn it with the Mark 5 unplugged, it can tell you if there is binding in the system. If it is difficult to simply turn the belt it could be binding in the pulley sheave or indicate bad bearings. Removing the belt between the Motor and the Idler Shaft and turning the Sanding Disk can determine which was causing the problem. Still hard to turn I would suspect the bearings or turns freely it is the belt binding in the pulley sheaves or the Motor itself. Turn the Motor Shaft to see how well it turns. If okay check to see if the sheave moves freely on the shaft. You will be pulling against the spring to check that. With the belt between the motor and the Idler Shaft Assembly off you can check the speed control to see if it will now move freely. If not check to see if the Idler Shaft pulley sheave need lubrication. Either way on the condition of both the Motor and Idler Shaft Pulley Sheaves, now would be a good time to lubricate them. Through the inspection hole under the Shopsmith Logo Cover on the back of the Headstock inspect the condition of the back of the Speed Control. Is it clean and free of dust and debris or is it clogged up? Figuring out what is the cause is a matter of narrowing it down from the entire system turning to each individual component.

I had a speed control issue that was kind of similar, and these guys helped me. The thread is titled speed control problems. If I knew how to put a link into my post, I would, but I'm a carpenter, not a tech guy.

JoeSark wrote: Sun Dec 01, 2024 7:34 am I had a speed control issue that was kind of similar, and these guys helped me. The thread is titled speed control problems. If I knew how to put a link into my post, I would, but I'm a carpenter, not a tech guy.

That is a good point because it should remind us that there are several moving parts in the mechanical speed control with the potential for binding/freezing. Joe's recent thread: viewtopic.php?p=316904#p316904

- David