Shopsmith Mark VII with Mark V speed control

[JPG]

Consider the 'lineup' of the sheaves. There are two 'fixed' sheaves(idler and fan). The movable sheaves are the control and the floating. The fixed sheaves face opposite directions.

When the 'setting' is fast, the control sheave aligns with the fixed fan sheave.

When the setting is slow, the floating sheave aligns with the idler sheave.

IIRC the total distance moved by the movable sheaves is 1/2" in opposite directions.<<<<< wrong, it moves 1"

Thus the fixed idler sheave should be 1 1/2" away from aligning with the fan sheave(1/2" belt + 1/2" sheave motion).<<<<<1/2"+1"

A long way to explain the answer - at fast the idler pulley is open about* 1/2" and the motor pulley is open about 1 1/2"(*typically slightly more due to belt not riding all the way out to the rim).


Edited to correct sheave travel and open sheave width<<<<<<<<<

[redleg]

If I understand correctly you want to make the snout longer on the sheave. Would it work to make a longer button on the bearing instead? If you need a longer button fabricated I can do that no cost just need to know what length.

[n240sxle91]

Redleg,
That's awesome! I just might take you up on your offer! However, I need to finalize the length that it needs to be extended before I can move forward with it.

EDIT:
Figured it out. The button rides on the end of the quadrant assembly on my setup. The end of the quadrant assembly has a wider travel arc, so it's causing the control sheave to travel MUCH further than it would if it was in the correct position. This can be fixed by using my previous idea of setting the max speed set screw. I believe this will completely fix the problem. However, it will also make the speed dial useless. I guess that's not that big of deal since I have a tachometer.

Making the extended button still might be a good option as well, but I need to double check that.

Getting closer!

[JPG]

n240sxle91 did you delete a post????

In it you stated the control sheave moves more than 1/2" over it's range. As a result, I checked my memory(it failed).

The 'correct' range is I believe 1".

Please tell me I did not imagine that post!

[n240sxle91]

Yeah, I did mention that, but edited it because it had some questions that I ended up answering myself. I should have left that information.

The total travel my control sheave moves is about 1 3/8". When I lined up the control sheave above the fixed fan sheave it looked to be about 3/4" away from the idler sheave. Assuming it's somewhere between the 3/4" I measured, and the 1" you measured my MV speed control is pulling the control sheave about 1/2-3/4" too far.

When I only allow the control sheave to be pulled out that far it slides back in easily. It's only when I let the control sheave be pulled out too far that it binds up.

[n240sxle91]

I examined how everything works together some more today. Knowing now that the MV speed control is pulling the control sheave out too far I don't believe the 'snout' needs to be extended at all. I think leaving it alone is the best option.

However, I do believe the quadrant assembly might need to be modified slightly for the best fit. It seems to work just fine as is, but I believe it could be causing some lateral pressure on the control sheave. This pressure might, or might not, cause some premature wear on the control sheave. I think a minor change to the quadrant assembly would allow it to push straight onto the control sheave and fix this completely. I haven't done the modification yet, but I should have time this weekend to give it a try. I have a junk quadrant assembly that will be perfect to use as a test piece.


Here is my photoshopped mock up of what I believe needs to be done. This shouldn't be too hard to do. Just hacksaw the tip off, and bend the thin metal guard back.

20170427_132316.jpg (157.92 KiB) Viewed 8500 times

[n240sxle91]

Ok, I did the mod on my junk quadrant assembly. It looks like it helps a lot! The button on the end of the 'snout' lines up much better now. It's not the same as it would be on a MV, but it's better than it was. I think this will be all that is needed to make the conversion possible. I'm very happy with the way it looks/fits now.

20170428_153221.jpg (135.84 KiB) Viewed 8466 times

20170428_153237.jpg (144.14 KiB) Viewed 8466 times

The top one is the modified quadrant, and the bottom one is the stock one. Notice the angle at the end of the quadrant. The modified one doesn't arc as much.

20170428_153501.jpg (190.3 KiB) Viewed 8466 times

[shipwright]

Hi, I’ve read this whole thread and may be interested in following this route with my Mark VII. You can see where I am in this thread
viewtopic.php?t=34179
At this point I have replaced a bad Mk VII control sheave with a Mk V one and am sort of stalled awaiting a printed cam a friend is making me. If I can’t get it to work, and more importantly, if you are still happy with yours I might consider the conversion.
My compliments on your work and thought process!

[JPG]

Shipwright: Can we conclude correctly that he damaged the 'original' M5 control sheave?

Thank You for bringing this back to the forefront.

Wish he had taken a pix of the control sheave/quadrant at slow pre damage. I think interference caused the damage. His quadrant modification eliminated that interference.

Would be advantageous if n240sxle91 would chime in!!!

[shipwright]

JPG, on my Mark VII the damage was on the original Mark VII control sheave. The one I have on now is from my 1957 Mark 5.
If you mean the OP then yes, I think the damaged one was a Mark V sheave that went in at the time of the conversion.

I do hope to get the OP back in the conversation.