Control Sheave Retaining Loop Repeatedly Comes Off

[brucekissinger]

I picked up an early Shopsmith Mark V a few months ago and used it for a few small projects. I've been very happy with it so far, but stumped by a problem that I've encountered. I've spent about 8 hours so far trying to fix it and haven't been successfull. I'd appreciate any advice. I've tried to hunt thru the forums and I watched the video on replacing the speed changer but still can't figure out what I'm doing wrong.

Background
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When I first got the machine it looked like it hadn't been used for a while. I watched the Shopsmith videos and tried to carefully lube and align the machine. After a little bit of use, my Gilmer belt broke and I replaced it following the factory instructions.

One thing that I noticed was that my speed dial was extremely difficult to turn. Earlier in the week, I got to the point where I couldn't turn it at all. So yesterday I took the speed dial off and carefully cleaned all the gear teeth. I verified that the worm gear on the speed changer was working correctly and smoothly.

Problem
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The problem that I have is when I put the speed changer and the control arm back in the unit and hook the retaining loop over the end of the spring it comes off as I try to change the speed from the Fast to the Slow setting. The actual retaining loop itself comes off the end of the control sheave and then disappears into the bottom of the motor pan. I noticed that the bearing at the end of the control sheave was stiff at first but I lubricated it and now it spins smoothly and easily. I got some pliers and carefully pressed the ends of the retaining loop so that there was as small a gap as possible -- but somehow the loop keeps coming off the end of the control sheave.

I'm guessing that somehow the speed changer control arm and the control sheave are coming out of alignment and putting stress on the retaining loop, but I can't figure out what I'm wrong.

My machine is old enough that it doesn't have an access hole so it's tough for me to see what's going on. Of course in the process of trying to fix the problem I got in a number of little adventures like:

1) Got my hands stuck in the machine while I was trying to remove the retaining loop from the control arm. I was trying to do this without dropping the motor pan and trying to disassemble the machine as little as possible.

2) Decided to drop the motor pan and didn't realize that I pulled a wire off the power switch. Put everything back together and the motor wouldn't start

3) Lost the set screw to the speed changer dial and had to drive to the hardware store to get a new allen screw.

All in all I learned a lot about the machine but didn't get any further to fixing the problem.

[SDSSmith]

There is a rollpin (513734) that goes in the hole in the end of the control sheave. The loop ends then go into the ends of the rollpin. Look in the bottom of the motor pan for the rollpin.

[8iowa]

When the loop keeps coming off this is a sign that the bearing in the upper control sheave is failing. Most often this is caused by a lack of lubrication thru the small hole shown in the manual. this bearing is practically impossible to replace. You will have to replace the control sheave. (515556)

[brucekissinger]

Thanks for the advice.

I had no idea that there was a pin. That makes perfect sense.

I understand the comment about the bearing as well. I'll have to order one. I put a very small amount of oil on the bearing that was originally very stiff and it smoothed right out. But I can see how that would attract sawdust and quickly get dry again.

Bruce

[remo9371]

I have had my model 510 since 1989, and this is the first time I have had the power head apart!

I tried to change speed the other day and I heard a little snap. The Mark V was stuck on slow speed. When I took the unit apart, I was amazed at what little wear and tear it had. When I found that the sheaves were seized, I thought I had a major problem, but a little lubrication worked like a charm. I cleaned and lubed the moving parts and re-assembled the power head. It works like new, now!

My Mark V purchase has paid off for me. I have built kitchen cabinets, cabinets for fish tanks, tables, display boxes for heirlooms, wooden puzzles, wall mounted displays, and I have done some projects for hire. Several times I have seen smoke from the belts, but there was no evidence of burning when I had it apart.

The drive belt still measures 1/2 in. Twenty years of work, and it only needed six drops of oil! I admit the last ten years were not as intense as the first ten.

I have convinced several of my friends of the value of buying American products. Shop Smith re-enforces my view.

[JPG]

DON'T LET ANOTHER 20 YRS PASS BEFORE OILING IT AGAIN. 6 drops / 10 hrs operation is more like it! Now that you have 'done it' ya ain't got no excuse!!!;) The motor/fan sheave is probably 'thirsty' also!:)

[remo9371]

You are absolutely right! The sheaves all move easily now. I had to use a large screwdriver to move them at first, but now I can move the sheaves with my fingers.

I subscribe to the theory "If it ain't broke, don't fix it." Now that I know how easy it is, I am going to lube the sheaves every time I think about it. I don't want too much oil near the belts.

[JPG]

You are absolutely right! The sheaves all move easily now. I had to use a large screwdriver to move them at first, but now I can move the sheaves with my fingers.

I subscribe to the theory "If it ain't broke, don't fix it." Now that I know how easy it is, I am going to lube the sheaves every time I think about it. I don't want too much oil near the belts.

The objective is to prevent it from 'breaking' so ya will not need to 'fix' it!;)

[beeg]

You are absolutely right! The sheaves all move easily now. I had to use a large screwdriver to move them at first, but now I can move the sheaves with my fingers.

DO KNOT let the sheave go when ya move em. It'll slam back into the motor housing and cause other problems.