Shopsmith Mark VII with Mark V speed control

[JPG]

You have indeed started a process.(or whomever you obtained it from).

I now have to go measure a 'spare' M VII headstock as well as the M 5 speed control.

From the pix it appears the speed control needs to be 'further into' the headstock and possibly lower. Unknown at this time is the distance along the idler shaft.

Seeing as that was apparently successful, this deserves a long look.

Thank You for the exposure!!!

[n240sxle91]

Jpg, quick question. I was looking at my speed control and it occurred to me that because my speed control is modified I have no idea if my speeds are correct. Do you think that's an issue, or is it probably pretty close to correct?

Thanks

[everettdavis]

If the pulley sets of the sheave pairs are the same size and the belt is 1/2 inch wide (not worn down) and the motor speed is the same, then adjusting the speed dial indicator as done on a Mark V should be the same speed as on a Mark V.

Do you concur JPG?

Everett

[JPG]

If the pulley sets of the sheave pairs are the same size and the belt is 1/2 inch wide (not worn down) and the motor speed is the same, then adjusting the speed dial indicator as done on a Mark V should be the same speed as on a Mark V.

Do you concur JPG?

Everett

Maybe.

Yes the pulley sheaves have the same geometry.

If the quadrant positions the control sheave the same as the Mark 5/v then 'I think so'.

I am not sure the quadrant gear is resulting in the same positioning. Main reason is that the quadrant gear appears to be positioned a bit away from the idler shaft axis. However the resultant speeds are likely fairly close. It may run tad fast and be prone to belt jam(with worn belt) at 'fast'.

I have not had an opportunity to take some headstock(both MARK 5/V and MARK VII) measurements and compare the resultant porkchop alignment to each idler shaft/control sheave. Will need to jury rig some 'aids'.

[n240sxle91]

I don't plan on using mine at real high speeds, so it's not a huge deal to me, but I thought I'd ask anyway. If you guys need any further pictures to see how mine is put together let me know!

[n240sxle91]

I have learned a lot about my Mark VII over the last several months, and I still have a LOT yet to learn.

With this better understanding of the mechanics of the speed control I am questioning the Mark V speed control conversion that was done to my Mark VII.

I would like to believe that my Mark V speed control isn't to blame for the damage to my control sheave. However, I am concerned that it just might be doing this. Below is a picture of where everything has to be at to run at SLOW (BTW at slow my tachometer says 750RPM). NOW, before you say "you repaired your control sheave wrong!" I want to say that I simply didn't have the clearance to have the copper bend around the bearing without it contacting the quadrant assembly. SO, I repaired it the best I could, knowing that it would only be used to test my system while I wait for parts to come.

20170423_143751.jpg (118.08 KiB) Viewed 9205 times

I don't have a Mark V to compare to, but it seems to me that the quadrant assembly is too close to the control sheave. In fact it looks like they've had contact before. Do you think that the alignment of the Mark V speed control is causing stress by lateral movement on the control sheave? This would explain its wear.

Thoughts?

If it is a problem hopefully it can be overcome. Otherwise I'm going to be hunting for Mark VII speed control parts....<sigh>

[JPG]

That is 'solved' by moving the entire speed control back towards the sheave. I think the removal of material from the headstock to get it in there has precluded going back to a MVII speed control.

Did the PO position the MV speed control 'centered' in the round portion on the casting? If so moving it back will 'look' strange.

Perhaps a coincidence, but the MVII snout is shorter.

Lotta possible gotchas here. I think careful fitting and critique needs to be the order of the day. We are looking at that end without verifying what is going on on the back side(idler sheave/idler shaft). Also relevant is the resultant positioning of the motor belt on BOTH pulleys at the speed extremes.

I am not saying all this to discourage, but rather a word of caution. After all theses are unexplored waters.

BTW it might affect the motor belt 'length'.

[n240sxle91]

I looked closer at the removal of material from the headstock. They only removed two of the three mounting holes for the Mark VII speed control. So, I'm pretty sure I could come up with a fix for the third hole IF I need to go back to the Mark VII style controller.

I believe you're on to something with the Mark VII snout being shorter. That is probably why the quadrant assembly doesn't contact the control sheave in the right position. I think a longer snout would fix everything (or, as you mentioned move the speed control back towards the sheave).

JPG, I don't suppose you want to get in on this 'fun', and look into modifying one of your 'spare' MVIIs? This would be easier to collaborate on if I had someone else with a physical machine in front of them with the same changes.

I'm not really excited about moving the speed control because it looks good where it is. However, having it look good, but not WORK, isn't an option either! lol

I can't think of a good way to make the shaft/snout longer either. However, one idea I had was to make the quadrant assembly 'wider'. This would need testing, but in theory it could have the same effect as moving the whole speed control further back. I believe I could fabricate something relatively easily that would do this.

Here are some more pics that might help get a clearer picture of what everything looks like.

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20170423_170236.jpg (178.34 KiB) Viewed 9191 times

20170423_170642.jpg (199.02 KiB) Viewed 9191 times

Thanks again for the thoughts/ideas!

[n240sxle91]

One more quick thing, I just realized that moving the speed control further back towards the sheave is not possible. It is already very close to making contact with the sheave. Any further in and it could hit as it spins. So, that is not an option.

EDIT:
I thought about widening the quadrant assembly, but that won't work either. The clip won't fit around the assembly if I widen it.

I COULD be over thinking everything, and maybe it works as is. The previous owner may not have oiled often enough, or maybe they did something that damaged the key. Perhaps if I replace the key, and the control sheave, everything will work perfectly.

That being said, in order to TEST that I will need to order those parts (I was going to do that tomorrow morning). If that does not fix it, I will have spent that money on parts I can't use.

I don't normally give up on these things, but my wife is probably getting tired of me spending so much time on it. So, I think I'm going to look into converting back to a Mark VII speed control. I will be more than happy to share as much info as I can with others if they intend to try this conversion. I think with enough brain power this conversion is doable, but I just don't have the time myself.

Thanks to everyone who tried to help (especially JPG). Hopefully someone else will take the reins on this and figure it out!

[JPG]

I agree, it needs to remain centered in the 'circle'.

Remember you have a MV* control sheave with a MVII idler sheave.

I think you need a new key in any event.

A control sheave has a ready market.(you may be able to get one reasonably off e-bay).

Since you are already sleeving the broken control sheave, It may be possible to make the 'snout' longer.

I think the missing data is the difference between the MVII cam and the MV porkchop distance from the control sheave button over the entire speed range. Clouding that is the control sheaves differ(snout length).

I am not sure(yet) how to measure that relative to a common reference(perhaps the idler sheave?).

* BTW we are assuming you have a MV control sheave. How about measuring from the point the snout abuts the sheave and the end of the snout(not the bearing button).

Also the important dimension of the key is it's width, not it's height.