Mark VII “Project Machine”

[JPG]

It would have to be the control sheave. In your latest pix it looked like the control sheave did not have the bearing/cam follower in the 'snout'. ??

BTW the sheave is a pulley half.

[shipwright]

Yeah, I’ll pull that shaft and both the round aluminium things today and have a look at them up close and personal. If there is an oversize keyway it will have to be remedied.
In that pic I had the bearing/follower out for inspection.

Just FYI, AFIK referring to the halves as sheaves and the whole as a pulley is a ShopSmith thing. I’m a sailor and in sailing a sheave is pulley. A quick search of the internet agrees with that but I’m on a ShopSmith forum here and will try to adhere to the vernacular in the future.

[JPG]

'Technically a sheave is in a 'block' that contains multiple sheaves that then becomes a pulley. Or a sheave in a frame becomes a pulley. Old timey stuff that has lost precise meaning over time.

Yes sloppy use has diminished the 'difference'.

Re SS, I think a pair of sheaves constituting a pulley makes sense (each sheave is a pulley 'half'). Standard/typical use, I Donno. Depends upon whom is asked.

[shipwright]

Semantics aside, there is good news and bad news.
Good news: I now know exactly what the problem is.
Bad news: The keyway in the control sheave is hooped. Even the key is worn a little. It was so loose that the tips of the vanes are starting to get beaten up.

Q1) I don’t suppose this is a MarkV interchangeable part??
Q2) What are the chances I can make a JB Weld fix?
Q3) What are the chances of pressing the steel liner out of the cast aluminium sheave (and making a new one)?

My instinct is that I might as well try a JB Weld fix because I have nothing to lose.

……and yes, that was where the snap ring went. Thanks!

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[shipwright]

A quick check shows lots of Mark V sheave assemblies on eBay. They look like they may fit if the button bearing (Mk V) and the follower bearing (Mk VII) install the same way. Could I be that lucky?

[shipwright]

So patience is not my middle name. I stripped the idler shaft out of my greenie and discovered that the control sheaves are identical except the Mark V spigot that carries the bearing is 1/4” longer. The shafts are of course not interchangeable but if I got a new assembly I think I could use both sheaves. The spigot might have to be shortened and the recess for the bearing deepened by 1/4” but maybe the speed dial adjustment on the Mark VII will allow the extra 1/4”.
At any rate a Mark V sheave will be a much better starting point than the trashed Mark VII one I have.

[shipwright]

Mark VII shaft and sheave on the left with Mark V control sheave on the right.

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[JPG]

Length differing matches my 'recollection'. I believe the longer M5 control 'sheave' will shift the effective speeds downward and likely will experience an 'interference' at some point when approaching the slow limit(caused by full meshing of the two 'pulley halves').

Saying that based only upon thy stating the 'snout' is longer on the M5 control 'sheave'. When I can I will verify that 1/4" difference.

Accurately machining a M5 'sheave' to MVII dimensions should work.

[shipwright]

I actually installed the Mark 5 (1957) control sheave on the Mark VII this afternoon and it runs both directions beautifully with no rattle whatsoever. There is a bad interference between my fairly crappy repaired cam and my very rough follower so for now it is a one speed machine, but it sure sounds better than the rattling I was hearing before. With the control base rotated to compensate for the longer spigot on the mark 5 sheave the belt is on the fast side of half way so I think I will need to shorten it and re-machine the follower bearing seat. I have ordered a mark V sheave set from eBay so I’ll put this one back on the Mark 5 and mess with the new one when it gets here.
I think you were right about the roll pins in the follower being too long. That seems to be where the bind is.

This is what it looks like at the moment. You can see the adjustment in the base mount through the hole in the case.

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[JPG]

The sloppy keyway really creates the propensity to rattle since it allows the 'vanes' to interfere.

BTW YA the M5 is 1/4" longer.