Please explain the relationship between the button bearing and the vanes (slope of).
Is it ever recommended that the belt ride proud of the sheave?
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Please explain the relationship between the button bearing and the vanes (slope of).
I would think not. But at the same time, there is nothing to prevent it at the SLOW end. If the geometry of the belt, sheaves, and eccentric work out that way it may ride slightly proud unless the operator limits it. Completely different on the FAST end of course, since we set a stop to prevent it. I tried a few combinations and they all ran slightly proud at slow.
Because of the dimensions of the sheaves (upper) they can go only so far closed. When they his the hard stop, the sheaves are 1/2" apart at the perimeter. With a belt that is 1/2" wide riding in that sheaveI I would think that the belt would stop there.DLB wrote: ↑Sat Sep 10, 2022 5:17 pmI would think not. But at the same time, there is nothing to prevent it at the SLOW end. If the geometry of the belt, sheaves, and eccentric work out that way it may ride slightly proud unless the operator limits it. Completely different on the FAST end of course, since we set a stop to prevent it. I tried a few combinations and they all ran slightly proud at slow.
As someone pointed out earlier, it is probably not the original intent of the design to fully compress the spring at SLOW either. And it probably IS the intent of the design to be able to run at or under 700 RPM.
- David
Consider what is controlling speed. The porkchop that bears against the button bearing that is a distance from the sloping vanes. That distance will affect the resultant speed.
That makes sense. Sample of one, that 1/2" on the sheaves is pretty precise though and 1/2" on the belt is worn out. Belts I'm using are all 1/2" plus. I don't have a new SS belt to measure, but my belts are wide enough to ride slightly proud in a 1/2" Vee. Presumably a new SS belt would ride even higher than the ones I'm using if the rest of the geometry allows the Idler sheaves to close all the way.dusty wrote: ↑Sat Sep 10, 2022 5:42 pmBecause of the dimensions of the sheaves (upper) they can go only so far closed. When they his the hard stop, the sheaves are 1/2" apart at the perimeter. With a belt that is 1/2" wide riding in that sheaveI I would think that the belt would stop there.DLB wrote: ↑Sat Sep 10, 2022 5:17 pmI would think not. But at the same time, there is nothing to prevent it at the SLOW end. If the geometry of the belt, sheaves, and eccentric work out that way it may ride slightly proud unless the operator limits it. Completely different on the FAST end of course, since we set a stop to prevent it. I tried a few combinations and they all ran slightly proud at slow.
As someone pointed out earlier, it is probably not the original intent of the design to fully compress the spring at SLOW either. And it probably IS the intent of the design to be able to run at or under 700 RPM.
- David
It is my belief that if the high speed stop is adjusted with the belt riding within the perimeter of the sheave it will not ride proud at either high or low speed. Remember that the belt moves in equal but opposite directions on the sheaves; if you make a speed adjustment that moves the belt 1/4" on the floating sheave it will simultaneously move 1/4" in the opposite direction on the idler sheave. With a belt of the proper length it is mathematically impossible to get the belt proud.DLB wrote: ↑Sun Sep 11, 2022 9:25 amThat makes sense. Sample of one, that 1/2" on the sheaves is pretty precise though and 1/2" on the belt is worn out. Belts I'm using are all 1/2" plus. I don't have a new SS belt to measure, but my belts are wide enough to ride slightly proud in a 1/2" Vee. Presumably a new SS belt would ride even higher than the ones I'm using if the rest of the geometry allows the Idler sheaves to close all the way.dusty wrote: ↑Sat Sep 10, 2022 5:42 pmBecause of the dimensions of the sheaves (upper) they can go only so far closed. When they his the hard stop, the sheaves are 1/2" apart at the perimeter. With a belt that is 1/2" wide riding in that sheaveI I would think that the belt would stop there.DLB wrote: ↑Sat Sep 10, 2022 5:17 pm I would think not. But at the same time, there is nothing to prevent it at the SLOW end. If the geometry of the belt, sheaves, and eccentric work out that way it may ride slightly proud unless the operator limits it. Completely different on the FAST end of course, since we set a stop to prevent it. I tried a few combinations and they all ran slightly proud at slow.
As someone pointed out earlier, it is probably not the original intent of the design to fully compress the spring at SLOW either. And it probably IS the intent of the design to be able to run at or under 700 RPM.
- David
- David
dusty wrote: ↑Sun Sep 11, 2022 3:32 pmIt is my belief that if the high speed stop is adjusted with the belt riding within the perimeter of the sheave it will not ride proud at either high or low speed. Remember that the belt moves in equal but opposite directions on the sheaves; if you make a speed adjustment that moves the belt 1/4" on the floating sheave it will simultaneously move 1/4" in the opposite direction on the idler sheave. With a belt of the proper length it is mathematically impossible to get the belt proud.DLB wrote: ↑Sun Sep 11, 2022 9:25 amThat makes sense. Sample of one, that 1/2" on the sheaves is pretty precise though and 1/2" on the belt is worn out. Belts I'm using are all 1/2" plus. I don't have a new SS belt to measure, but my belts are wide enough to ride slightly proud in a 1/2" Vee. Presumably a new SS belt would ride even higher than the ones I'm using if the rest of the geometry allows the Idler sheaves to close all the way.
- David
I do not have unmounted fan and floating sheaves to play with but I do have a couple sets of the other sheaves. With these on the bench, mounted on an idler shaft, it becomes obvious that the sheaves were designed "with hard stops" that limit the sheaves from going closed any further than 1/2" measured at the perimeter of the sheave.
I normally adjust the high speed stop so the belt is an estimated 1/8" to 1/16" inside the perimeter of the motor sheaves. But the stop only does one thing: limits pork chop travel in the high speed direction. The only thing the high speed stop setscrew is doing at low speed is providing an axle for the idler gear for the indicator ring.dusty wrote: ↑Sun Sep 11, 2022 3:32 pm ...It is my belief that if the high speed stop is adjusted with the belt riding within the perimeter of the sheave it will not ride proud at either high or low speed. Remember that the belt moves in equal but opposite directions on the sheaves; if you make a speed adjustment that moves the belt 1/4" on the floating sheave it will simultaneously move 1/4" in the opposite direction on the idler sheave. With a belt of the proper length it is mathematically impossible to get the belt proud.
No matter the width of the belt, if you run the speed control up until the belt is near the perimeter of the sheave but not above it and then set the high speed stop, the belt should never ride higher than that.DLB wrote: ↑Mon Sep 12, 2022 10:20 amI normally adjust the high speed stop so the belt is an estimated 1/8" to 1/16" inside the perimeter of the motor sheaves. But the stop only does one thing: limits pork chop travel in the high speed direction. The only thing the high speed stop setscrew is doing at low speed is providing an axle for the idler gear for the indicator ring.dusty wrote: ↑Sun Sep 11, 2022 3:32 pm ...It is my belief that if the high speed stop is adjusted with the belt riding within the perimeter of the sheave it will not ride proud at either high or low speed. Remember that the belt moves in equal but opposite directions on the sheaves; if you make a speed adjustment that moves the belt 1/4" on the floating sheave it will simultaneously move 1/4" in the opposite direction on the idler sheave. With a belt of the proper length it is mathematically impossible to get the belt proud.
It still seems to me that a belt wider than 1/2" which includes new SS belts, will ride slightly proud if the sheaves fully close. And that is what I've observed. Is your idea of a 'proper length' belt one that prevents the Idler sheaves fully closing at the stop? The only other stop I see in the system is full compression of the motor shaft spring. I though there was general consensus that full compression of the spring is not a particularly good stop. While I agree a slightly shorter belt would prevent the belt from running proud, it would do so by fully compressing the motor shaft spring and therefore preventing the Control Sheave from full range of travel and closing to that 1/2" gap. IMO the low speed mechanical limit is always going to be either full compression of the spring or full closing of the Idler sheaves. Unlike high speed, there is no other limiter to the travel. IMO it follows that the ideal belt length will allow full closing of the Idler sheaves with almost full compression of the motor spring and therefore will run proud at the stop.
I'm not suggesting it is a good idea to run the belt proud. What I said is that there is nothing in the design as currently implemented to prevent it. Perhaps with original belts there was, I suspect this is the case. (Narrower belts.) It is a simple matter for the user that is concerned about it to observe the belt position at the slow stop and to choose not to use the slow stop if warranted. I ran mine to the stops during this thread to support discussion of how slow the machine will go, I seldom run the machine at the slow stop, but if you want to know the slowest achievable speed you kind of have to.
- David