Mark VII “Project Machine”

[shipwright]

What a difference a day makes!
Today I realized that the reason the Mk VII was functionally one speed yesterday wasn’t interference with the crappy cam at all. If you look at the last pic I posted you will see that one of the detent bumps is trapped and unable to release and allow the dial to turn. Makes you wonder why the have that much adjustment…. ???

I still thought the pins in the follower were catching on the cam so I removed them and polished the bearing surface of the follower.
I tried it with no pins. (Does anybody know what they are supposed to do? The big spring on the motor shaft returns the control sheave.)
Anyway it worked better, and even better when I ditched the follower all together and tried the Mark 5 button bearing.

I now have very nice control over a truncated range. I have no doubt that shortening the spigot on the Mark 5 control sheave and re-machining the bearing seat will give me full range. Right now I can smoothly go from about 750 to 3900 even with the cam I have. The 3900 end is dictated by the high speed stop pin on the dial. If the control sheave spigot was 1/4” shorter the pulley would open 1/4” further at the same dial position, likely getting me close to 5200 rpm.
There is also room to adjust the high speed stop but that is fine tuning and can be left for later.

The take away is……. You can sub in a Mark 5 (or V) control sheave on a Mark VII, button and all, and have a range of 750rpm to about 4000rpm with no modification at all.
The pics show the cam positions at 750rpm and 3900rpm.

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[shipwright]

It just got even better. You can drive the sleeve out of the sheave without damaging the bearing seat. That means I can cut off the other end and not have to re-machine the bearing seat. I’m not sure I even need to cut it off. I don’t think there is anything to interfere with it if it sticks 1/4” inside the sheave.
Maybe I just have to drive it in 1/4” and I’m done!

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[docmirror]

Day-um! Deal of the century! FYI, you have a Mk VII 'series 3'. There was no official series for the Mk VII but there were running changes along the production. The open ends of the base footing and the non-hinged lower cabinet door indicate a fairly late S/N model. I think the power switch was beefed up in the very end of production. Most all S1 types have the power selector altered or rebuilt somehow.

Missing the vac is also common. The vac components were poorly designed, poorly made, and poorly supported. All plastic with small metal clips to mash it together. Not up to ShopSmith/Magna standards at all. So, plenty of Mk VII are missing the vac components.

Enjoying the work progress.

Edited to correct version or build date.

[shipwright]

docmirror what pics are you looking at? I do have the tie bars on the ends of the feet, the wheel table raising device, and the cam lock table lock. I understood those were later additions.
My power switch is a beefy aftermarket one that works beautifully, however I thought it’s switch lever was unsafe so I made a new one.

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[shipwright]

I’m actually glad I didn’t get the blower assembly. I have no use for it and would have had to take it to the dump.

[JPG]

At full mesh of the sheaves, there is NOT 1/4" space between the two hubs.

I consider the pinned follower to serve the same purpose as the wire loop on the m5. IMHO the pins only become relevant with sluggish response of the floating sheave due to either too fast adjustment of the speed dial or inadequate lubrication of the floating sheave. Main purpose is non-rotation of the inner race of the control sheave bearing.

One concern: If the sleeve can be pressed out, what prevents it slipping when under rotary load?

[shipwright]

I’ll check first with it just driven in and see what rpm I get. If I don’t get what I want I can probably cut the 1/4” from the inside with a Dremel. If not I’ll drive it out and cut it off. I will also have to re-drill the lubrication hole as it will be mostly hidden.

Rotation prevention makes sense but there must be a cleaner way to accomplish it. I’m sticking with this for now until I get an intact cam.
It works great!
As for the last question the main answer involves the term “bigger hammer” but there is always Loctite.

[docmirror]

docmirror what pics are you looking at? I do have the tie bars on the ends of the feet, the wheel table raising device, and the cam lock table lock. I understood those were later additions.

Yeah, I got it backwards, and your's does look like a later. I had to go back and ref one of the pics of my S1 version with smooth finish paint. Your cam log table, framed ends of the legs, and the pebbly finish were later like a 'S3' type. I was thinking the wrong way when I wrote that. I'm going to edit it.

[shipwright]

Don’t edit it. That will make my comment look silly.

[JPG]

Set screw makes more sense.

I agree the MVII cam follower is cludgy. Not sure the pins are a clean solution but it is 'inexpensive'.