Mark V Speed Control

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dusty
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Re: Mark V Speed Control

Post by dusty »

DLB wrote: Tue Sep 13, 2022 9:38 am
dusty wrote: Mon Sep 12, 2022 12:42 pm 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.

I agree that it should never ride higher than that in the motor sheaves. But where you set that limit at high speed has no bearing on the low speed limit or how high the belt will ride in the Idler sheaves.

Having set the high speed stop, if you adjust to low speed the belt should ride in about the same position on the idler sheave. I say that with the understanding that if using a non-standard belt - all bets are off.

I don't agree. The belt position at the low speed stop depends on which stop you hit. And does not depend in any way on the high speed stop. If you hit the limit on how close the Idler sheaves can come together and your belt is wider than the gap at the perimeter, it will run slightly proud. I think there is general agreement that full closure of the Idler sheaves, and not full compression of the motor spring, is the intended low speed stop of the design. Also consensus that new SS belts run a bit wider than 1/2" though perhaps not consensus on how much wider. Interpreting your words more loosely, when you say 'adjust to low speed' you may not mean to the limit and when you say 'about the same position' you may consider 1/8" difference to be as expected.

This illustrates what I believe the belts do as one moves from one extreme to the other.

I think you illustration is basically correct, but I suspect your model creates a 'same but opposite' symmetry between low and high speed that does not exist in the actual hardware. Full closure of the Idler sheaves Vs full closure of the motor sheaves seems symmetric. But we adjust the high speed stop to prevent full closure of the motor sheaves (indirectly) creating asymmetry at the stops/limits. The slower you set the high speed stop, the greater the asymmetry.
It remains my opinion that while it may not be desirable for the belt to run proud, there is nothing in the hardware to prevent it. I have two systems and tried a third belt that all support this conclusion. All belts were SS belts a bit wider than 1/2".

- David
You are absolutely correct. There is nothing in the system that "prevents" it from doing so. But - if the belt is installed correctly and the high speed stop set according to the procedure it will no longer run proud.
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JPG
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Re: Mark V Speed Control

Post by JPG »

SYMMETRY exists.

The sheave geometry is identical.

IF the sheaves are allowed to traverse full range the belt/sheaves move in equal but opposite direction.

However the introduction of the high speed stop creates an off set in the range of motion.

So it is possible that the belt will ride higher on the idler pulley(at SLOW) since the stop is provided by full closure of the idler pulley(at SLOW) which is further closed than that of the motor pulley(at FAST) since the high speed stop prevents the motor pulley from full closure(at FAST).
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dusty
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Re: Mark V Speed Control

Post by dusty »

JPG wrote: Wed Sep 28, 2022 11:05 am SYMMETRY exists.

The sheave geometry is identical.

IF the sheaves are allowed to traverse full range the belt/sheaves move in equal but opposite direction.

However the introduction of the high speed stop creates an off set in the range of motion.

So it is possible that the belt will ride higher on the idler pulley(at SLOW) since the stop is provided by full closure of the idler pulley(at SLOW) which is further closed than that of the motor pulley(at FAST) since the high speed stop prevents the motor pulley from full closure(at FAST).
You will have to explain this to me. If the belt is set at or within the perimeter of the sheave at high speed (and the high speed stop set there) when you move to low speed the belt will be repositioned at or very near to the same position. I don't see how it can be any different (except by using a different size belt or not setting high speed stop).

In addition - the sheaves are designed such that they can not go closed any further than 1/2" at the outer perimeter..

Another truth to keep in mind:

If the belt is allowed to track proud at either extreme the opposing sheave will be tracking small and if allowed to get too deep into the sheave it will seize. This will never happen if if setup is done properly. Proper setup will result in the smaller sheave to have approximately 1 1/2" radius. Smaller will bring about unintended consequence.
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Re: Mark V Speed Control

Post by JPG »

With a given length belt, the range of tracking will be similar on both pulleys.

Without the high speed stop, the fully closed position of the pulleys(at opposite ends of the range) determines the limits.

When the high speed stop is included the belt positioning is short of that fully closed motor pulley position.

The high speed stop prevents two things. 1) interference of the control sheave and the speed control legs 2) allowing the belt to drop too far into the pulley and becoming jammed.

This introduces an offset to the belt positioning range. Fully closed idler pulley is still in effect(limits open position of the motor pulley)

Although the full range of both pulleys is symmetrical, the inclusion of the high speed stop introduces an offset that likely results in asymmetrical speed range. In addition I do not believe the speed range is linear vs sheave positioning (indicator dial rotation).

Belt length affects all of this.(as does center of rotation distance between the pulleys).
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HopefulSSer
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Re: Mark V Speed Control

Post by HopefulSSer »

I just upgraded my greenie with a 1.125 motor complete with sheaves. As a result I had to adjust my high speed stop. I don't know what the difference is between the sheaves or spring on my old 3/4 hp setup vs the new 1 1/8 hp setup but there is one. Since there is no low speed stop, I can now dial the low speed down beyond "slow" on the dial down to "fast", which is where the mechanism runs out of by travel. So this confirms the offset you're discussing. The belt is proud about 1/8" on the idler pulley at this point. I figure I'll just not crank it down that far
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dusty
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Re: Mark V Speed Control

Post by dusty »

JPG wrote: Wed Sep 28, 2022 11:05 am SYMMETRY exists.

The sheave geometry is identical.

IF the sheaves are allowed to traverse full range the belt/sheaves move in equal but opposite direction.

However the introduction of the high speed stop creates an off set in the range of motion.

So it is possible that the belt will ride higher on the idler pulley(at SLOW) since the stop is provided by full closure of the idler pulley(at SLOW) which is further closed than that of the motor pulley(at FAST) since the high speed stop prevents the motor pulley from full closure(at FAST).
Agreed! Depending on how the stop is employed. This is a critical statement in this discussion. The high speed stop can introduce an offset in belt position and this offset has an effect at the other end of the spectrum. But, if set according to procedure, that offset is minimal (about 1/16"- 3/32") and disaster is avoided.

I set it with the belt "flush" with the floating (motor) sheave.

I treat the high speed stop as though it is disaster prevention. It is there if needed but I never approach that end of the spectrum so it is never engaged.
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Re: Mark V Speed Control

Post by dusty »

JPG wrote: Thu Sep 29, 2022 7:53 pm With a given length belt, the range of tracking will be similar on both pulleys.

Without the high speed stop, the fully closed position of the pulleys(at opposite ends of the range) determines the limits.
Understanding that the sheaves are themselves self limiting. They make physical contact with one another when the pulleys are 1/2" apart.

When the high speed stop is included the belt positioning is short of that fully closed motor pulley position.

The high speed stop prevents two things. 1) interference of the control sheave and the speed control legs 2) allowing the belt to drop too far into the pulley and becoming jammed.

This introduces an offset to the belt positioning range. Fully closed idler pulley is still in effect(limits open position of the motor pulley)
If not already restricted by the spring closure.

Although the full range of both pulleys is symmetrical, the inclusion of the high speed stop introduces an offset that likely results in asymmetrical speed range. In addition I do not believe the speed range is linear vs sheave positioning (indicator dial rotation).

Belt length affects all of this.(as does center of rotation distance between the pulleys).
My comments in RED.
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Re: Mark V Speed Control

Post by DLB »

dusty wrote: Fri Sep 30, 2022 7:37 am I set it with the belt "flush" with the floating (motor) sheave.
This statement changes things quite a bit. Elsewhere, you've referred to set 'properly' which I interpreted as meaning per the manual or sawdust session. The manual I'm looking at says to set it at 5200 RPM (if using a tach, I suppose) or until the drive belt is 1/8" to 1/16" below the outside diameter... Same as the sawdust session IIRC. I agree with how you set it, but it's not per the manual. It is likely much faster than 5200 RPM, as well. Then it is purely coincidence that the slow speed belt position is also approximately flush, which it would be no matter where you set the high speed stop.

I used to set my high speed stop ~1/8" below the outside diameter because I didn't have a tach. So I set the stop=Fast (on the indicator dial) = 1/8" below... With a tach, I set the high speed stop faster for ease of maintenance (the only time I use the stop) and set the indicator dial for the best result in the useful speed range, which for me is from slowest achievable to ~3500 RPM. Best result, meaning closest fit to the speed chart independent of load.

- David
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Re: Mark V Speed Control

Post by DLB »

HopefulSSer wrote: Thu Sep 29, 2022 10:15 pm I just upgraded my greenie with a 1.125 motor complete with sheaves. As a result I had to adjust my high speed stop. I don't know what the difference is between the sheaves or spring on my old 3/4 hp setup vs the new 1 1/8 hp setup but there is one. Since there is no low speed stop, I can now dial the low speed down beyond "slow" on the dial down to "fast", which is where the mechanism runs out of by travel. So this confirms the offset you're discussing. The belt is proud about 1/8" on the idler pulley at this point. I figure I'll just not crank it down that far
I like your solution, don't crank it down that far. Your Greenie could be different than other machines we are talking about because it might have different belt dimensions, as SS has changed the belt more than once. Or it could be that the Gilmer gives you a different rotation of the eccentric, changing the distance between centers of the shafts compared to a typical Poly-V with typical tension. (Mine run close to 9:00 in eccentric rotation terms.)

Motor springs were definitely different between Greenie and now. Unknown, to me, how many iterations. My Greenie spring is a round wire spring and all 1-1/8 HP motors I've seen have had a flat wire spring. Also different spring cap and, IIRC, different shaft lengths. Maybe all those changes offset, or not.

- David
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Re: Mark V Speed Control

Post by HopefulSSer »

Just for fun I measured mine just now using a phone-based tach (accuracy unknown). I appear to be getting about 750 up to about 5200.
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