Shopsmith Forums

JPG wrote: Thu Sep 30, 2021 9:10 pm That 710 rpm? Looks very reasonable. How about dial calibration? How about other end(fast)?

I don't dare test the rpm at high speed with the Starrett mechanical rpm meter. I read online it was never really intended to go much above 2000 rpm. To be honest, I have never run this machine at full high. I don't rout or shape on it (yet). So I don't care all that much about high speed.

What do you mean by "that 710 rpm? looks very reasonable." If you are referring to that last pic it corresponds to 825 rpm. That last pic was with the washer removed.

[edit] reread your comment, no, that pic is not 710 rpm.

[edit again] thinking about it, it appears that squeezing the idler pulleys together from one side (eccentric side) doesn't have the same affect as squeezing them together from the speed cam side, interesting. Perhaps that means it is more about the affect it creates on the motor sheaves? Perhaps having the washer in there is forcing the motor sheaves to actually close a bit more, increasing the pulley size, reducing ratio?

Mike -

An unintended effect of the washer is the slight misalignment of the pulleys. This would increase the 'pull' of the belt on the motor pulley and cause it to open slightly further thus lowering the resultant rpm.

The intended effect is to close the idler pulley. That creates the difference of the cam position for a given rpm.

Might be conjecture, but it 'adds' up.

Can the idler sheave (on a MarkVII) be moved back and forth laterallyon the idler shaft (with respect to the eccentric??? On my Mark 5/Vs, the idler sheave is locked (laterally) between two sping washers.

dusty wrote: Fri Oct 01, 2021 7:41 am Can the idler sheave (on a MarkVII) be moved back and forth laterallyon the idler shaft (with respect to the eccentric??? On my Mark 5/Vs, the idler sheave is locked (laterally) between two sping washers.

Yes, it can float or slide. It stops when it touches the snap ring next to the eccentric inner bearing on one side, and the speed cam sheave on the other which is stopped by the speed cam itself.
Mike

JPG wrote: Fri Oct 01, 2021 6:18 am An unintended effect of the washer is the slight misalignment of the pulleys. This would increase the 'pull' of the belt on the motor pulley and cause it to open slightly further thus lowering the resultant rpm.

The intended effect is to close the idler pulley. That creates the difference of the cam position for a given rpm.

Might be conjecture, but it 'adds' up.

You have to be amazed at the precision and how such a slight adjustment of 0.15 inches can be dramatic. Impressive.

miken wrote: Fri Oct 01, 2021 8:52 am

JPG wrote: Fri Oct 01, 2021 6:18 am An unintended effect of the washer is the slight misalignment of the pulleys. This would increase the 'pull' of the belt on the motor pulley and cause it to open slightly further thus lowering the resultant rpm.

The intended effect is to close the idler pulley. That creates the difference of the cam position for a given rpm.

Might be conjecture, but it 'adds' up.

You have to be amazed at the precision and how such a slight adjustment of 0.15 inches can be dramatic. Impressive.

Yes, and it illustrates the "criticalness" of the belt dimensions.

JPG wrote: Fri Oct 01, 2021 2:06 pm

miken wrote: Fri Oct 01, 2021 8:52 am

JPG wrote: Fri Oct 01, 2021 6:18 am An unintended effect of the washer is the slight misalignment of the pulleys. This would increase the 'pull' of the belt on the motor pulley and cause it to open slightly further thus lowering the resultant rpm.

The intended effect is to close the idler pulley. That creates the difference of the cam position for a given rpm.

Might be conjecture, but it 'adds' up.

You have to be amazed at the precision and how such a slight adjustment of 0.15 inches can be dramatic. Impressive.

Yes, and it illustrates the "criticalness" of the belt dimensions.

Really? Are the pulleys and belt the same size as a Mark V?

I'd be real interested in hearing from others about how these dimensions compare to other machines.

PS: This drawing is specific to a Mark V and NOT necessarily applicable to a Mark VII

dusty wrote: Fri Oct 01, 2021 3:26 pm I'd be real interested in hearing from others about how these dimensions compare to other machines.

I can grab a few dimensions for you, my headstock is apart. I am pretty sure the center to center on mine is 9 1/8", but I read in another post where JPG measured 9 3/8", so I will remeasure.

Mike -

miken wrote: Fri Oct 01, 2021 3:54 pm

dusty wrote: Fri Oct 01, 2021 3:26 pm I'd be real interested in hearing from others about how these dimensions compare to other machines.

I can grab a few dimensions for you, my headstock is apart. I am pretty sure the center to center on mine is 9 1/8", but I read in another post where JPG measured 9 3/8", so I will remeasure.

Mike -

Do you also have a Mark 5/V. The Mark VII may very well be different.

Confusion between models is the very reason that I wish this forum was more strategically divided.