Mark V Speed Control

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DLB
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Re: Mark V Speed Control

Post by DLB »

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
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JPG
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Re: Mark V Speed Control

Post by JPG »

I agree. The "model" assumes equal movement from 1:1 ratio positions and that assures equal belt travel in/out on both pulleys. However that is unlikely when the high speed stop is set. This introduces an offset in the range of belt motion in/out. (more possible travel in/out at the opposite extreme) That introduces a non-linearity in the speeds attained.(greater rpm range going up vs going down)

Consider the range that results from near saw/joint (1:1 ratio). 700 - 3600 - 5200 >>=>> 1:5 - 1:1 - 1:1.4 ABCDEFGHIJKLMNOPQ - R - STUV.

Non-linearity exists even without that offset. Also consider the button bearing slides on the porkchop thus altering the effective length of the "lever" pressing against the control sheave.(more non-linearity again)

I have misplaced my speed chart(with alpha/rpm), but I believe R is close to the 1:1 position.
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dusty
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Re: Mark V Speed Control

Post by dusty »

OKAY...I give.

But do you agree that if the high speed stop is set with the belt riding somewhere inside the perimeter of the fan sheave that it will return to somewhere very, very near that same position each time you hit the high speed stop?

Do you also agree that the belts move on the sheaves in equal but opposite directions when the speed setting is changed?

And, lastly, do you agree that at any given setting of the speed control 12" of the belt length (whatever it is) will be riding in contact with the sheaves.

PS: Do we all agree that when the idler speed equals the motor speed the two sets of sheaves are very, very near equal in diameter.

Why is there a high speed stop?
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DLB
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Re: Mark V Speed Control

Post by DLB »

dusty wrote: Tue Sep 13, 2022 1:27 pm OKAY...I give.

But do you agree that if the high speed stop is set with the belt riding somewhere inside the perimeter of the fan sheave that it will return to somewhere very, very near that same position each time you hit the high speed stop?

Yes

Do you also agree that the belts move on the sheaves in equal but opposite directions when the speed setting is changed?

Yes

And, lastly, do you agree that at any given setting of the speed control 12" of the belt length (whatever it is) will be riding in contact with the sheaves.

No. But I have not done a detailed study. Instead I used an on-line pulley calculator (https://www.blocklayer.com/pulley-belteng) that appears to confirm. I'm expecting more discussion on this one.

PS: Do we all agree that when the idler speed equals the motor speed the two sets of sheaves are very, very near equal in diameter.

I do. Exactly equal, IMO, if the speeds are measured.

Why is there a high speed stop?

IMO, to prevent clobber between the floating sheave and the non-moving parts of the speed control. (The legs with the 'hinge' pin IIRC.) But, machines I've used at high speed, especially Greenie, developed a fair amount of noise and vibration at speed that was unappealing.
My opinions, of course.

- David
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dusty
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Re: Mark V Speed Control

Post by dusty »

The online calculator that you reference works well; provides accurate results within the limits that are imposed. To calculate shaft speeds in the Mark requires far more accuracy that can be achieved with with this calculator.

The one that I reference earlier in this thread requires at a minimum 5 decimal places to get good results.
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Re: Mark V Speed Control

Post by JPG »

dusty wrote: Tue Sep 13, 2022 1:27 pm OKAY...I give.

But do you agree that if the high speed stop is set with the belt riding somewhere inside the perimeter of the fan sheave that it will return to somewhere very, very near that same position each time you hit the high speed stop? YES

Do you also agree that the belts move on the sheaves in equal but opposite directions when the speed setting is changed? OPPOSITE - YES EQUAL - I DO NOT THINK SO. AS THE CONTROL SHEAVE MOVES, THE AMOUNT OF BELT WRAP WILL DECREASE ON THE EXPANDING PULLEY, BUT WILL INCREASE ON THE CLOSING PULLEY.

And, lastly, do you agree that at any given setting of the speed control 12" of the belt length (whatever it is) will be riding in contact with the sheaves.
I DONNO


PS: Do we all agree that when the idler speed equals the motor speed the two sets of sheaves are very, very near equal in diameter. YES

Why is there a high speed stop? TO PREVENT THE CONTROL SHEAVE FROM INTERFERING WITH THE SPEED CONTROL PARTS(YA THE LEG DLB REFERRED TO)
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Goldie(Bought New SN 377425)/4" jointer/6" beltsander/12" planer/stripsander/bandsaw/powerstation /Scroll saw/Jig saw /Craftsman 10" ras/Craftsman 6" thicknessplaner/ Dayton10"tablesaw(restoredfromneighborstrashpile)/ Mark VII restoration in 'progress'/ 10
E[/size](SN E3779) restoration in progress, a 510 on the back burner and a growing pile of items to be eventually returned to useful life. - aka Red Grange
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dusty
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Re: Mark V Speed Control

Post by dusty »

So the stop prevents the Control Sheave from pressing hard against the arm of the porkchop. Stops it dead upon contact with the stop screw. Really has nothing to do with speed adjustment except to stop it (going too far).
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DLB
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Re: Mark V Speed Control

Post by DLB »

dusty wrote: Tue Sep 13, 2022 4:35 pm The online calculator that you reference works well; provides accurate results within the limits that are imposed. To calculate shaft speeds in the Mark requires far more accuracy that can be achieved with with this calculator.

The one that I reference earlier in this thread requires at a minimum 5 decimal places to get good results.
To clarify, I did not use the calculator for speed calculations. I used it to confirm a hypothesis: In a case with a larger and smaller diameter pulleys, neither contact areas is half of the circumference. The larger pulley has a contact area exceeding 180 degrees. The smaller pulley has a contact area less than 180 degrees. In linear terms, for the question you asked, the large pulley contact exceeds half of the circumference while the small pulley contact is less than half of the circumference. And, finally, the two do not cancel. Therefore the total contact area does not remain constant. (The only part that is hypothetical is that the two do not cancel, my plane geometry is rusty and not well maintained. ;) )
dusty wrote: Tue Sep 13, 2022 10:36 pm So the stop prevents the Control Sheave from pressing hard against the arm of the porkchop. Stops it dead upon contact with the stop screw. Really has nothing to do with speed adjustment except to stop it (going too far).
It's the arms on the Control Bracket (89) where they form the stationary hinge point that the porkchop swings on. And nothing to do with pressure, prevents the 'back side' of the spinning sheave from ANY CONTACT with the stationary bracket. Correct, nothing to do with speed adjustment except to stop/limit it. And of course, those of us that set the indicator dial according to the high speed adjustment procedure set indicated FAST and the stop both equal to the speed that correlates with the belt position we chose.

- David
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dusty
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Re: Mark V Speed Control

Post by dusty »

DLB wrote: Wed Sep 14, 2022 9:48 am
dusty wrote: Tue Sep 13, 2022 4:35 pm The online calculator that you reference works well; provides accurate results within the limits that are imposed. To calculate shaft speeds in the Mark requires far more accuracy that can be achieved with with this calculator.

The one that I reference earlier in this thread requires at a minimum 5 decimal places to get good results.
To clarify, I did not use the calculator for speed calculations. I used it to confirm a hypothesis: In a case with a larger and smaller diameter pulleys, neither contact areas is half of the circumference. The larger pulley has a contact area exceeding 180 degrees. The smaller pulley has a contact area less than 180 degrees. In linear terms, for the question you asked, the large pulley contact exceeds half of the circumference while the small pulley contact is less than half of the circumference. And, finally, the two do not cancel. Therefore the total contact area does not remain constant. (The only part that is hypothetical is that the two do not cancel, my plane geometry is rusty and not well maintained. ;) )
dusty wrote: Tue Sep 13, 2022 10:36 pm So the stop prevents the Control Sheave from pressing hard against the arm of the porkchop. Stops it dead upon contact with the stop screw. Really has nothing to do with speed adjustment except to stop it (going too far).
It's the arms on the Control Bracket (89) where they form the stationary hinge point that the porkchop swings on. And nothing to do with pressure, prevents the 'back side' of the spinning sheave from ANY CONTACT with the stationary bracket. Correct, nothing to do with speed adjustment except to stop/limit it. And of course, those of us that set the indicator dial according to the high speed adjustment procedure set indicated FAST and the stop both equal to the speed that correlates with the belt position we chose.

- David
I agree with you 100%. What is true though is that the length of the belt produces the overall limit. If the belt is 27" long that entire 27" is distributed around the perimeter of the sheaves and across the gap between the sheaves (where there is "no contact between the belt and sheaves". At whatever diameter one has set the control sheave, the diameter of the motor sheave will expand as far as the overall belt length will allow. All 27" will be distributed around the sheaves and in the separation area between the sheaves.

In that regard I do disagree with you. They do cancel one another. The total contact area does not remain the same but does remain nearly the same while the balance is distributed in the transition area between the sheaves. The total sum of the belt perimeter remains the same.

I do believe that the intent of the design engineers was for that belt length to be 27" long. The numbers would indicate just a tiny bit longer that 27". The belt that came with my 1st Mark measures 27". I believe that this has changed as a direct result of standardization in the manufacturing arena but is not an issue because of how the SS sheaves operate. Thus the differences between speed dial settings and actual speed.
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JPG
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Re: Mark V Speed Control

Post by JPG »

I dare say belt width available has likely altered. The original SS belt was a non standard size wider than 1/2" and less than 5/8". Recent belts are metric in reality(slightly narrower than 1/2" or 5/8").

The belt width will affect speed range attained with the narrower belt by shifting the range upward.

I have no idea where 27" comes from unless a 26.5" belt pitch diameter.(or stretched)
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Goldie(Bought New SN 377425)/4" jointer/6" beltsander/12" planer/stripsander/bandsaw/powerstation /Scroll saw/Jig saw /Craftsman 10" ras/Craftsman 6" thicknessplaner/ Dayton10"tablesaw(restoredfromneighborstrashpile)/ Mark VII restoration in 'progress'/ 10
E[/size](SN E3779) restoration in progress, a 510 on the back burner and a growing pile of items to be eventually returned to useful life. - aka Red Grange
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