Shopsmith Forums

JPG wrote:

jsburger wrote:

JPG wrote:The floating sheave acquired the step at the bottom at the same time.


The early SC did not have that step, and 'bottoming out' was all the way to the shaft.

That was not a good thing so the step(stop) was added and the 6,7,8 removed from the scale.

I am curious if the speed chart in the '1-8' manual agrees with the later '1-5' manual and if the speed range was greater.

That was my initial thought also. However, after looking at both manuals I am not sure that is true. The picture above looks like it has a 1-8 plate. The (Illustrated Parts Breakout ) IPB page from that manual clearly shows the center sheave with the flanges. The second manual does also.

The manual with the crank on the right and what looks like a 1-8 plate has a speed chart. Curiously the other manual with the crank on the left (1-5 plate???) has no speed chart.

I wonder if the 1-8 plate was an error caught early on. Assuming the sheaves and the belts are the same on both versions you can't go past 5. At 5 one belt is riding at the top and the other one is all but bottomed out.

I am gonna crawl out on a limb and 'guess' the manual with the 1-8 plate was created after the step was added, but the pix with the plate did not make it into the manual at that time.

I really would like to know what speeds were 'published' with the original SC. The range had to be greater.

As for the belt positions at the 1-5 settings being maxed out, that is reasonable with the step limiting the travel. Without the step, the belt travel is greater. The travel of both belts is greater.

I assume from your comment that the speed chart in the '1-8' manual does not list speeds for 6,7,8?

I still think the 1-8 plate was a design error and discovered early on and changed. How many of those plates has any one seen? I think I remember seeing one on eBay years ago.

I do totally agree with you that the early manual that appears to have a 1-8 plate but a stepped pulley is the result of the manual not getting updated properly. Of course no normal person would notice anyway.

As far as the belt bottoming out on the shaft I don't see a problem. I talked to Skip one time about it and he said the SC's without the flange show wear to the shaft caused by the belt bottoming out and allowing the floating sheave to rotate on the shaft. I said how can that be? The entire assembly turns in unison. The fixed sheaves and the shaft are one, the belt rides on the fixed sheave and the floating sheave causing the floating sheave to rotate in unison with the rest of the assembly. I think the wear was caused by not a large enough bearing surface between the floating sheave and the shaft. When you are at either extreme of the range one or the other belt is putting side pressure on the outer edge of the floating sheave. Adding the flanges gave added support and eliminated the wear. But, adding the flange causes the belt at minimum diameter riding on the flange to put pressure on the sheave into the shaft at the same time the belt at maximum diameter is doing the same thing in the same direction. Hmm... Maybe they changed material at the same time.

As far as the flange limiting travel, that is true. However, the flange is only 1/16" thick. See the pictures. When set on 0 the belt is maxed out at the outer edge of the sheave. When you go to 3, the equivalent of going from 5 to 8, the belt moves 1/2" on the sheave. The limiting factor is the minor diameter and removing that 1/16" will not allow a 3 increment travel on the scale. Plus you are already maxed out at the major diameter.

Yes the speed chart in what appears to be the 1-8 manual with the crank on the head stock side is only 1-5. The other manual with the crank on the left has no mention of speed other than high and low belt settings. No mention of actual RPM's.

JSB = " I said how can that be? The entire assembly turns in unison."

Normally, yes. But that assumes the belt does NOT touch the shaft.

The floating sheave has freedom to slide on the shaft(the pulley shaft, not the shaft the pulley rides on).

The floating sheave is also free to rotate on the shaft since it is not keyed.

So what can cause that?

Consider what happens as the control knob is adjusted until one of the belts bottoms out against the shaft. At that point all is still rotating together.

Adjust the control further and since the belt is bottomed out, that causes increased belt tension(decreased slack) as the inner shaft is moved further.

Now the other belt is experiencing reduced tension. The floating sheave is no longer moving laterally, but the entire assembly is causing decreased tension on it.

The bottomed out belt having increased tension is driving it's outer flange and the shaft but it will decrease the driving force to the floating sheave since it will move away from the belt due to decreased tension from the other belt.

Eventually the other belt will begin to slip. The outer flanges are still rotating at the same rpm. The floating sheave will begin to rotate at a slower rpm due to the other belt slipping. The floating sheave not having any load will tend to 'follow' the slipping belt rpm.

Thus the floating sheave is now creating wear on the shaft.

The 6,7,8 indexes remains a mystery unless we consider the possibility of allowing the belt to ride above the od of the pulleys.(or maybe a larger pulley????).

It is hard to believe anyone would run the SC like that long enough to damage it. It is also hard to believe that anyone would crank on it hard enough to break the ear off but we all know that has happened many times. So, I guess anything is possible.

Yes, 6,7&8 are a mystery. I am still betting on a design error that got corrected early on by replacing the plate before many got in the field.

jsburger wrote:It is hard to believe anyone would run the SC like that long enough to damage it. It is also hard to believe that anyone would crank on it hard enough to break the ear off but we all know that has happened many times. So, I guess anything is possible.

Yes, 6,7&8 are a mystery. I am still betting on a design error that got corrected early on by replacing the plate before many got in the field.

I ain't bettin aginst that!