Model 510, Loud Noise as Speed is Reduced

[jhyler]

First off, the machine has been sitting idle about 18 months as my workshop was temporarily taken over as living space. This is not the first time it's been used since I got back in the shop, but pretty close.

I was doing some disk sanding at around speed "F", and for a few moments a loud "roar", not really a grinding sound, came out of the headstock. After a few moments it went away. But later on it came back again for a few moments. I turned the machine off, unplugged, and opened up the cowling to see what I could see. All looked well, no odor, belts looked almost new. Turned the shaft by hand, no resistance or any noise. So I took a chance and restarted the motor with no tool attached. What I found was it runs fine at high speeds, but as I begin to slow the motor down, at around G or F the noise will come back and I also saw a spark and I think a little smoke. Immediately sped it back up and shut it down again.

Does this sound familiar? Last thing I should say is that I'm a fairly good woodworker but not a good mechanic. If anyone could point me at a detailed repair procedure that would be great. (Poking around on the forum I've seen some potential repair procedures but they talk about doing things with keys and sheaves. All I know is that keys start cars and sheaves are bunches of wheat. Like I said, I'm not a mechanic. But I can follow instructions if they are sufficiently detailed.)

Thanks!

[JPG]

Sparks???

Look to see if the wiring has somehow gotten too close to moving parts it should NOT be close to.

[jhyler]

It's not electrical.

The source of the spark is from where the speed quadrant is pressing against the end of the shaft. The edge of the end of the shaft looks somewhat burnt. There wasn't much lubrication there so I've gone ahead and re-oiled the sheaves; the lubrication is now improved but I still see some sparks (I don't mean like a grinder, maybe one or two every couple of seconds) and a little smoke afterward running momentarily at g/f speeds. High speeds still seem okay.

Anyone know how to fix this? Thanks!

[jhyler]

More information... I found this photo in another post:

550A0199-A2A9-4D79-B0E8-4DDFB85EFB2C.jpeg (503.5 KiB) Viewed 8914 times

Notice how the shaft has that smaller black button and bearing between the quadrant and the shaft? With a little loop and spring that goes around the speed quadrant? I don't have any of that. My speed quadrant is coming in direct contact with the shaft, and that's where I see the sparking and burning. So there's the problem.

My Shopsmith looks like this:

My Shopsmith.JPG (61.17 KiB) Viewed 8908 times

From Shopsmith's list of common repair parts, it looks like I have to replace the entire control sheave assembly. But I also see Ebay listings for just the bearing, button, and loop. So what I really need to know is, which is more DIY-able? Replacing the entire assembly, or just the button and bearing? What kind of tools would I need, and are there instructions I can look at to see what I'd be getting myself into?

Thanks!

[JPG]

Looking at 'yours', I would say it is not likely you can repair it with those bearings on e-bay.

It is also likely you will need a new quadrant gear(porkchop).

[br549]

JPG may be correct, and it may be unsalvageable, but here are links to two previous threads about how I and redleg did replace just the bearing. If I were to try it again, I really liked the way redleg did it and I would try that method first.

My attempt: https://www.shopsmith.com/ss_forum/main ... 19133.html

redleg's method: https://www.shopsmith.com/ss_forum/main ... 19238.html

[jhyler]

Thanks, everyone. I finally had time to do the disassembly and it turns out JPG was right. The quadrant is ground up enough to warrant replacement, though the rest of the speed control looks good. And after close inspection I have little confidence in what remains of the control sheave shaft, so I plan to replace the sheave assembly rather than attempt repair.

I appreciate all your help.

[JPG]

Thanks, everyone. I finally had time to do the disassembly and it turns out JPG was right. The quadrant is ground up enough to warrant replacement, though the rest of the speed control looks good. And after close inspection I have little confidence in what remains of the control sheave shaft, so I plan to replace the sheave assembly rather than attempt repair.

I appreciate all your help.

If the rest of the speed control is A-OK, the quadrant gear is available. Look closely at the legs that the quadrant gear pivots on. Splayed legs ARE fixable.