Trouble with speed adjustment

[sryoder]

I just replaced the control sheaves on my Mk V 500. I had removed the old ones because I was having trouble dialing the speed down. When I took the headstock apart, I could see that the control sheaves were kind of chewed up. So, I replaced them. Today, I fired the old girl up and things haven't gotten much better. I can go to high speed w/o any trouble but coming back down, at about "I" it starts to get really hard to turn the speed adjustment handle. One time today it spun really, really easily in both directions from Slow to Fast. But only once. I've lubed everything I know to lube. Any ideas?

-Steve

[garys]

Have you checked the condition of the quadrant gear and worm gear? (86 and 87 on page 6 of this PDF.)?
https://www.shopsmith.com/ownersite/pro ... 0_1_14.pdf

If they have enough wear, they will bind up when trying to change speed. If you pull the quadrant assembly from the headstock, you can run the gears through their movement and see how smoothly they are working.

[sryoder]

Have you checked the condition of the quadrant gear and worm gear? (86 and 87 on page 6 of this PDF.)?
https://www.shopsmith.com/ownersite/pro ... 0_1_14.pdf

If they have enough wear, they will bind up when trying to change speed. If you pull the quadrant assembly from the headstock, you can run the gears through their movement and see how smoothly they are working.

I had them out and they looked fine but I'll pull the assembly again today and inspect it closer. Thanks.

[JPG]

Hokay!!!

Have you lubricated/examined the other set of sheaves(the ones on the motor shaft).

Your description matches symptoms that a sticking floating sheave creates.

As the speed control is adjusted towards slow, the control sheave is moved towards the fixed idler sheave thus 'squeezing' the belt and increasing belt tension.

Normal operation would result in the floating sheave moving away from the fixed fan sheave thus restoring normal belt tension. IF the floating sheave is sticking the belt tension would not be decreased and the speed control becomes very difficult to adjust towards slow since the belt is merely being mashed between the control sheave and the idler sheave.

This is the reason the pulleys MUST be rotating when the speed control is adjusted. The problem only occurs when adjusting towards slow. A different failure mode is at play when adjusting towards fast.

[sryoder]

Hokay!!!

Have you lubricated/examined the other set of sheaves(the ones on the motor shaft).

Your description matches symptoms that a sticking floating sheave creates.

I dripped some 3-in-1 oil in the little hole under the spring. And I can slide the outer sheave fairly easily by hand. I'll try that again today and feel for any roughness. There's also a section in the manual about aligning the lower sheaves. I'm pretty sure mine are aligned okay but I'll check that out, too.

-Thanks

[sryoder]

I think I found the problem. I removed the speed changer and cleaned it up. Once I saw what the teeth looked like, I figured that was probably it. The speed changer works smoothly to a point and then it hangs up, even outside the headstock with no load on it. I was going to order just a new quadrant since everything else looks okay. However, every time I order parts piecemeal, I end up needing something that I hadn't ordered. So, I ordered the whole assembly. Hopefully it won't take 6 weeks to get here like it did when I ordered the control sheaves.

Thanks for the help.

quadrant1.jpeg (76.08 KiB) Viewed 10998 times

quadrant2.jpeg (90.33 KiB) Viewed 10998 times

[JPG]

Since you have the speed control 'in hand', some judicious filing of those mangled teeth cam bring it back to operable. By sighting from the side so light shines between the worm gear and the pork chop gear, you can determine where to file away all interferences(one at a time).

Beats waiting 6 weeks (or more).

The porkchop pivot looks tight(A common source of this gear wear is the arms the pivot pin attaches to become spread adding side play of the porkchop to the mix).

[sryoder]

Since you have the speed control 'in hand', some judicious filing of those mangled teeth cam bring it back to operable. By sighting from the side so light shines between the worm gear and the pork chop gear, you can determine where to file away all interferences(one at a time).

Beats waiting 6 weeks (or more).

Might have to give that a try while I'm waiting (semi)patiently. Thanks.

[beeg]

When ya put it all back together. Do a high speed adjustment.

[sryoder]

Roger that. Is that in the manual?