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I got a used Mark V Greenie with a Gilmer drive about a year ago. It's been working great including using the table saw speed setting, but a couple days ago I tried to use the router, saw some smoke, and now the drive gets stuck at medium/high speeds until I manually work the v-belt loose. (I posted about it in a Gilmer alignment thread but I'm not sure that's really the issue.)

I'd be very grateful for any advice on what's wrong, and/or recommendations for service (especially in the Boston metro area though it sounds like shipping a headstock's not too bad).

Here's a video (issue @ 1:04) of the behavior: works fine at low speed, but as I speed up at some point there are sparks from the idler shaft and/or Gilmer belt. Then when I turn it off, it's very hard to turn by hand, and when I turn it on again the motor just hums and won't turn.
After it gets stuck, the motor shaft still turns freely (except for a slight rubbing between the sheave and the metal behind it), but pulling on the V-belt to turn the rest of the drive chain I can hear a scraping/grinding noise and it's very hard to turn. I can't tell exactly where the scraping noise is coming from. The V-belt is stuck tight in the control sheave. But if I work it loose and get everything moving again then everything spins with minimal effort; I can turn the idler shaft and Gilmer drive with my fingers on the accessory hub, and low speeds work fine again.

Here's an album with more photos/videos, a couple more highlights below.

The v-belt looks a bit worn on one side, but still measures just over 1/2" at the top.
That end of the idler shaft is definitely getting hot, though from reading other discussions that sounds somewhat normal.
Thanks in advance for any suggestions or questions!

Maybe it's possible the idler bearing was moving outward in the bushing and contacting the casting. The photos in your album don't give any sign of that. Not sure how the bearing was retained in that model. Not sure if that's what's happening. You may be exceeding the maximum separation of the upper sheaves so you need to limit the high speed. That might lead to the belt damage you have. Just guessing on this.

Thanks!

I also found this thread describing the belt getting stuck which sounds similar. So I should probably do a high speed adjustment. The problem started when I was up at top speed but now it's happening at less than 50%.

I also oiled the motor sheave (which definitely needed it) but haven't oiled the idler/control sheave, so I should do that.

Does the v-belt look damaged enough to need replacement? That other thread mentioned it getting worn on one side / bent. The wear worries me but it still measures over 1/2" on top so I've been unsure.

While oiling the control sheave, I found the idler and control sheaves had gotten misaligned so they wouldn't close again. Then I noticed I could scoot the idler sheave away from the idlear bearing. It does look like the cog on the idler shaft is very worn at the edge by the bearing and casting. The idler sheave also wobbles a little bit if I push at the edge.

What's supposed to keep the idlear sheave in place, and is there supposed to be a gap between it and the bearing? I see #106 retaining ring and #107 sheave spring in the exploded diagram but am not sure if I have those. This idler assembly listing does seem to have a small gap.

Edit: This video from Jacob A explains it very clearly, looks like the C clip is missing (unless I have a set screw, I'll have to double check). So I just need to decide which pieces to replace and whether to upgrade to poly-V while I'm at it.

Here's mine:

As Ed mentioned

Not sure how the bearing was retained in that model.

Depending on when your Mark 5 Greenie was made there were changes made as to how the Idler Shaft Bearing and the Eccentric Bushing was held in place. The first Mark 5 Greenies only used the Cap Screw, Washer and Nut to hold it in the casting. This became a problem as changing speeds tended to push the Idler Shaft Assembly out of the Headstock Casting. Tightening the Cap Screw, Washer and Nut more to hold it in place resulted in breaking the Headstock Casting. The Engineers at Magna came up with a simple solution adding a pair of Bearing Retainers (P/N A 3274) that can be seen under the Eccentric on left side in the picture of the exploded parts view below. The Bearing Retainers go between the opening in the Headstock Casting and are held in place by the Cap Screw, Washer and Nut. These Bearing Retainers were made available to owners of Mark 5's made prior to them being added to the Headstock.

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The above picture, from the 4th edition of the Owner's Guide of August 1955, also shows the other Idler Shaft Assembly parts (106 & 107) you were wondering about. 106 & 107 are the current parts and may be different than those of a Gilmer Drive of the 1950's Greenie which are A 2877 Retaining Ring and A 3209 Sheave Retaining Spring.

Later a screw and washer were added to the Headstock Casting above the Idler Shaft Assembly. Followed by a screw in the Eccentric. These screws like the Bearing Retainers help keep the Idler Shaft Assembly from being pushed out and in the mounting when changing the speed.

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Above the screw and washer added to the Headstock Casting and below the screw to the Eccentric.
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Maintaining proper lubrication of the Idler Shaft and Motor Shaft Sheaves will help keep the Idler Shaft Assembly from having excessive pressure put on its mounting when changing speeds.

Knowing when your Mark 5 Greenie was made would be helpful. That would be determined from the Serial Number.

Thanks for all the details Russ! (I have the screw in the eccentric, though oddly I don't have a screw in the casting nor a tap for one. Edit to add: Model 510-R, SN 283464.)

I got the idler shaft / control sheave assembly out, and it turned out the retaining clip had been worn almost to nothing, and the Gilmer drive cog had cut open the end of the idler bearing, though amazingly the bearing still sounds and feels pretty smooth. The spring clip was still fine. But it seemed the idler sheave had moved around enough to wear both it and the shaft a bit. I also can't tell if the key never had a tooth on it, or that was worn off.
Luckily I found a replacement idler shaft + control sheave assembly with a Gilmer drive on it on ebay, so that's in the mail (along with a new v belt for good measure). (The actual control sheave and clip seem to be in good condition, so I guess I'll have them spare.)

markf wrote: ↑Mon Aug 12, 2024 10:25 pm (I have the screw in the eccentric, though oddly I don't have a screw in the casting nor a tap for one. Edit to add: Model 510-R, SN 283464.)

I've run into a machine like this before, missing the screw and the hole was unthreaded. It turns out that the factory screw is of the "thread cutting" type. An unthreaded hole means it has never had a screw in it. In my case I threaded the hole using a thread cutting screw from another machine, then put a standard machine screw in it.

IIUC the "510-R" denotes a machine that the factory retrofit to the 510 configuration. Is your machine, other than the headstock, a 510? We don't see a lot of 510s with Gilmer drives. But I presume this marking is on the headstock.

- David

I do have an updated table, I think 510. The "510-R" is just on the end of the headstock case.
New idler shaft and bearing are installed, and everything is running much better. Visually I can see that the idler sheave is staying in the right spot where before it was sliding over against the bearing, which also keeps the Gilmer belt off the side. Of course there are no sparks/smoke and everything runs much quieter too!
And in thermal images, I can see the idler bearing and the area around it are much cooler.