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:: II MK VII = I MK XIV?

JPG

Where in S TN? It's kinda wide like it's northern neighbor.

Rolling in vert NOT recommended!!!

The bag needs an inlet/port/whatever - check the hole in the back cover.

docmirror

He's in Athens, just north of Chattanooga. Yeah, rolling while vert is a bad program. Not gonna try that again.

JPG

Ditto raising to vert with the headstock unlocked.

docmirror

OK, back on refurb of Pollux. I was lucky to find the MVII headstock rebuild thread and am following that along pretty closely. My motor cover and motor are removed, and I have the aux or idler shaft out. My yucky shaft bearings in the eccentric are causing more pain, as I tried to press one off the idler shaft, and the outer hub shattered sending my balls hither and yon. It did hurt! Now, I have to get a mini bearing separator so I can get the inner race off as it's stuck on there real well.

Sadly also the bearing house I ordered my bearings from are on back-order. Raise your had if you are surprised. Yeah, me neither. Found a new supplier of non-Chinese bearings and ordered them today, may be in by Fri when I can start putting it all back together. There was a fair amount of discussion on the MVII rebuild threads. I'm shooting for a non-Chinese 29.5x0.5" I believe the orig belt had a custom end width and custom taper also due to it's use on a Salisbury type drive where edge traction is different than a standard tension V belt. I ordered a pair of belts for it and I'll have to measure to see what I got from the online vendor. Hoping I don't have to return them.

I haven't started fitting the plastic gear channel to Castor yet, as I was caught up with a few other tasks at the hangar. I may take that on later this week. Did do some drilling with Castor and it's doing yeoman work in that respect so I'm quite happy with it's new home in the shop. Also still waiting to clean and lube casters on both machines.

My rental is reno-ed and rented so I can get back on the SS machines now and finish them up. I got a hose kit for the vac and it fits the housing holes perfect. Once I reinforce the housing a bit with some JB Weld, it'll be back in service.

docmirror

I have decided I've found a flaw in the design of the eccentric for the idler shaft. The bearings specified are being controlled laterally by the torque of the nut on the threaded end of the shaft. A ball bearing, or split race set of bearings like used here with the spacer collar is not the right type of bearing for axial pressure to align. It would be better to have the arrangement as is found on all tractor wheel hubs, with an inner and outer tapered roller(Timkin style) where the pressure from the pinch nut is applied to the thrust faces of the tapered bearings. I'm considering changing the type of spacer in between the two bearings from standing off the outer race, to a smaller dia spacer that would maintain distance of the pair of inner races on the outside and inside bearing pair.

Or, alternately I could use both spacers providing that they were the same thickness so there would be no side/axial load on the bearing balls, just torque from the end nut compressing the first inner race, the inner spacer, the second inner race, and finally up against the snap ring adjacent to the tapered sheave. These bearings are designed for radial loads, and they are going to do a fine job of that with the tension from the two belts, but the axial load from the nut torque is designed to deform the bearing race on either the inner or outer or both of each bearing.

If I were a real mech engineer, I would have the eccentric stepped for the tapered outer race, and convert over to tapered Timkin set. I might even thread in a zerk fitting where the set screw goes, and maintain it with grease every 500 hours. For future consideration. It wouldn't take much of a step in the eccentric to make a tapered bearing race work there.

Edit to add; rather than zerk fit the eccentric as it is a somewhat hidden location, it would be better to end drill the shaft to the thread end, then cross drill the shaft inside the bearing pair and have the zerk sitting on the end of the shaft where it could be lubed much easier.

BuckeyeDennis

I don’t know any specifics about the bearings in question, but tapered roller bearings aren’t the only type that are designed for axial thrust loads. You may have angular-contact ball bearings, which are indeed designed for that application. And IIRC, even (non-offset) deep-groove ball bearings can be used for light axial loads. This isn’t the sort of thing that I’d expect Shopsmith engineers to get wrong.

docmirror

Yes, I'm aware of angular thrust bearings. That would be a third choice after tapered Timkin rollers. Based on what I found in my idler shaft, the bearings in there were destroyed mostly due to axial loads imparted by the torque on the end nut. If that type of arrangement were decided on and they use deep groove ball bearings, they should have a very light limit on the retaining nut. Sadly, It appears Shopsmith(Magna) decided that the bearing was 'good enough', or maybe that the idler bearing job was beyond the service level of owners.

JPG

My 'opinion' of the purpose of the nut is to eliminate end play only. I do not think it is intended to apply pressure against the bearings. The inner 'stop' for the bearings is a c-clip. Since the anti-rotation washer is present I think my opinion is verified(the nut is NOT intended to be torqued past taking up the end play.

docmirror

That would be the sensible method. Only a few inch-pounds of torque, and apply the anti-rotation tabs on the captive washer. I'm going to use the old inner race bearing as the shim between bearings to maintain any axial torque on the inner races of the new bearing against the C-clip. This will insure that little or no torque is applied across the bearing races or balls.

My neighbor is a cool old guy. He has a small shop with a press. He said he can get the inner race off no problem. I left it with him, and will bring the bearings over when they arrive. Once I get the idler shaft and eccentric put together I'll start re-assembly with the new bits and belts.

JPG

Is there not a spacer between the two bearings inside the eccentric? IIRC the outer races bear against the spacer.

docmirror

Well, things are not going swimmingly with the rebuild of Pollux. I got the inner race off my intermediate shaft, and the shaft is a mess. Where the two bearings ride, the shaft is ground down about 50-70 thousands in the grooves where the bearings should ride. These bearings have been grinding into the shaft for a long time. The C clip was also missing so one more thing to resolve.

All is not lost however. I have a hard chrome shop in town, and I will get the shaft to them to build back up and grind back to standard 5/8". I had them do one of my aircraft gear strut legs and it came out perfect. I know it can be done, just have to get on the ball and take it down there.

Unless, someone has a spare intermediate shaft for a Mark VII. Hmmmmmm I have no idea if it's the same shaft for a Mark V, but if so, maybe I can find one here online. Hmmmmmm

docmirror

JPG wrote Is there not a spacer between the two bearings inside the eccentric? IIRC the outer races bear against the spacer.

I have the spacer, I'm just concerned about applying axial pressure against the outer race, with no axial pressure applied to the inner race when I assemble on the shaft.

JPG

It ain't the same shaft! :(

BTW I gots a MVII idler shaft with the same issue(bearing wear/shaft od reduction and worse).

Any chance two could get the fix you mentioned?

docmirror

JPG wrote It ain't the same shaft! :(

BTW I gots a MVII idler shaft with the same issue(bearing wear/shaft od reduction and worse).

Any chance two could get the fix you mentioned?

We are in luck. I have a hard chrome plating shop about 20 min from me, and they can build up and surface grind the shaft(s) back to spec. Send me your shaft and we'll double dip. I'm going to try to send you my addr by PM. If it doesn't work I can give you my email.

Anyone else wanna join in just let me know.

It appears from our failure mode my concern about this type of bearing in this application is well founded.Yes, these machines are 60 YO units, and I suppose they've lasted their design life spec, but if it were a Timkin taper roller with shoulder notch inside the eccentric, the bearings would last forever. They could have drilled a hole in the end for a zerk and have it perm lubricated with the addition of two seals. I'm tempted to switch to tapered roller, but that means more machining. Guessing these new non-Chinese bearings will last my lifetime.

docmirror

Hmmm, sent PM but it is sitting in my outbox, with no way for me to send it. I will try a new PM, not sure how this software works.

docmirror

If the hard chrome and grind doesn't work, I'll just get some 5/8" shaft stock and u-make-it. Won't be the same nut profile, but who cares? Any nut will do. The hard job is the keyway. I'm not good a grinding keyways.

rpd

docmirror wrote Hmmm, sent PM but it is sitting in my outbox, with no way for me to send it. I will try a new PM, not sure how this software works.

That is how the PM system works, the sent message sits in your out box until the recipient opens it, :)

redleg

I thought I took a picture of the shaft after turning and threading but can't find it. I cut the shaft off an old motor armature that already had a keyway. I think it was from an old Mark VII motor. I had to turn it down slightly and thread it. I'm still working on the headstock.

It was trashed when I got it so no loss but my time. Going to the bearing shop to see if they have a bearing retaining ring for the upper shaft and tabbed locking washer for the idler shaft.

Edit 3/5/2022: Here is another shaft from some round stock that I threaded 11 threads per inch so I could get another nut locally. The original was 12 threads per inch I believe.

I added a wraparound bolt to hold the idler shaft.

Edit 3/5/2022:

This will be a Mark VII (sort of headstock) with a reversible GE motor from a Mark V and a Mark V speed control.

Edit 3/5/2022: Currently a wooden prototype insert with an aluminum 1/8" thick plate.

Tried pouring an aluminum insert but my green sand was to moist and it didn't turn out.

I left out 1/3 of the hole that would be in the Mark V headstock. The speed control fits fine through the other two. Is this going to be an issue that I'm not seeing?

JPG

rpd wrote
docmirror wrote Hmmm, sent PM but it is sitting in my outbox, with no way for me to send it. I will try a new PM, not sure how this software works.
That is how the PM system works, the sent message sits in your out box until the recipient opens it, :)

Finally got to open the PM(s) - been off line.

Am putting shaft 'in the mail' today.

Thank You for consideration and patience!!!

docmirror

JPG wrote

Finally got to open the PM(s) - been off line.

Am putting shaft 'in the mail' today.

Thank You for consideration and patience!!!

I got your shaft, and don't take it personally, but your shaft is in real bad shape. Not sure if we can save it. If not, I'll be making new. Will let you know next week.

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