Shopsmith Forums

JPG wrote: ↑Sun Feb 06, 2022 8:48 pm The floating sheave travel should be about equal to the belt width. Dusty's drawing shows 9/16" travel.

I posted that not realizing the 5th page existed. Still true!

I'm still debating that point, just not actively. I'd say we are not talking about the same thing, but Dusty's drawing seems unambiguous and my 'fast' distance matched his.

- David

DLB wrote: ↑Sun Feb 06, 2022 10:17 pm

JPG wrote: ↑Sun Feb 06, 2022 8:48 pm The floating sheave travel should be about equal to the belt width. Dusty's drawing shows 9/16" travel.

I posted that not realizing the 5th page existed. Still true!

I'm still debating that point, just not actively. I'd say we are not talking about the same thing, but Dusty's drawing seems unambiguous and my 'fast' distance matched his.

- David

How far the floating sheave travels is a function of nothing more than the face of the sheaves . Assuming the width of the belt remains constant (1/2") throughout the transition from high speed to low speed, the travel distance is determined solely by the slope in the face of the sheave. This sketch (based on my measurements of the sheave) shows that the absolute maximum travel is 43/64". In the real world, the belt does not travel this deep into the sheaves. To do so would cause the belt to be seized by the sheaves.
Unfortunately, all this discussion about the sheaves does little (if anything) to solve the kicking breaker issue. We need more feedback (hopefully some pictures) of what is happening in the shops of the two members with the problem.

Dusty: Did you ignore the slope of the opposing sheave?

I think my earlier statement re belt width sheave travel is off by a factor of two.

43/64 x 2(sheaves) = 86/64 = 1.34"

9/16 x 2 = 1.125

dusty wrote: ↑Mon Feb 07, 2022 7:05 am ...Unfortunately, all this discussion about the sheaves does little (if anything) to solve the kicking breaker issue...

Agreed, and exactly why I said 'not actively.' I didn't think this thread should be cluttered up with that discussion, but thought the information we provide should be as accurate as possible. So I provided a measurement from a Mark V. I think this new drawing is roughly accurate as far as it goes, but it only shows one sheave and the belt. Doesn't the sheave that moves, whether it is control or floating, move exactly twice as far (axially) as the belt? This is the third drawing you've posted in this thread, seems like two of them for the sole purpose of disagreeing with what I said I measured on an actual Mark V.

I made more measurements on my machine based on your last drawing. In 'fast' the inside measurement at the outside edge of the sheaves is roughly 1/2", the width of the belt as you'd expect. At 'slow' the inside measurement is over 1-1/2". The floating sheave moved over 1". The belt did not. Consistent with my previous measurement where I was measuring the compressed length of the spring, using different measurement points. There remains over 2X difference in how far your drawings depict the floating sheave moving and how far I measure it moving. I think we are stuck until someone other than me measures a machine. I agree to disagree.

- David

You guys are both correct. I erred in the way I was thanking about this.

These two sketches (I believe) are more correct showing that the sheaves move about 1 1/8" during the transition from high to low speed.
Motor is not shown and Motor Shaft is abbreviated in this image.

Lest any misinterpret the last two illustrations, I have to mention that the position of the movable sheaves coincides with the position of the fixed sheave on the opposing pulley at the extreme positions(fast/slow).

i.e the floating sheave aligns with the idler sheave at slow speed, and the fan sheave aligns with the control sheave at fast speed.

I apologize for not responding to the people who made suggestions about my problem
I have been away
I find when I move the upper Sheaves with the dial while turning the sanding disk the belt gets stuck when the Upper Sheaves squeeze together.
its like it wont ride up with the Sheaves.
I just ordered a new Kevlar Belt on Ebay awaiting delivery
will post if its the belt.
could it be the Sheaves? I have taken them off and cleaned them
Again thank you all

JACOBEIS wrote: ↑Thu Feb 10, 2022 12:49 pm I apologize for not responding to the people who made suggestions about my problem
I have been away
I find when I move the upper Sheaves with the dial while turning the sanding disk the belt gets stuck when the Upper Sheaves squeeze together.
its like it wont ride up with the Sheaves.
I just ordered a new Kevlar Belt on Ebay awaiting delivery
will post if its the belt.
could it be the Sheaves? I have taken them off and cleaned them
Again thank you all

If you look at Dusty's detailed drawings of the sheaves both pairs have a portion near the shaft that does not form a "V." It is theoretically possible for the belt to get into that portion and it tends to get pinched. I've only experienced this once, on the Idler. It was 100% my fault, I was not using an OEM belt and my high speed stop was probably out of adjustment. It would only occur at or near the fastest speed setting.

There is a lot of information about motor belts in the forum. Summary: the mechanical speed control system is designed for one size belt and is sensitive to belt size, both length and width are critical. There is one known remaining source for correctly sized OEM belts, the OEM. Most belts being sold for SS will work to some extent, maybe nothing worse than a small error between calculated and actual speed. My first choice is the Shopsmith brand belt. My second choice would be the metric belt that Jacob Anderson used to sell, though he is now retired it is a standard belt. IIRC it reduces the range of speeds a bit, but is more stout. I can't comment about the belt you bought but size is more important than material. It would be a good idea to perform high speed adjustments after you install it.

- David

thanks
awaiting belt

I be suspicious the floating sheave is not sufficiently lubricated. It opening the motor pulley is where slack comes from to allow the idler pulley to move the belt 'out'.