Request Help with Speed Control Issues

[JPG]

Let us proceed one step at a time.

When the speed control stops at "D"/"C"/whatever, what is the open/close condition of the idler pulley?(we have already determined the motor pulley is fully opened(grounded)

A pix like previously posted(new pix for conciseness). IIRC the previous pix showed the belt nowhere near the outer edge of the idler pulley. That would indicate the control sheave is NOT adjusting far enough. (Idler pulley not closing enough.) Question is why?

Is the idler shaft insufficiently 'forward' into the headstock?

Is the fixed idler sheave installed too far back on the idler shaft?????

[shopsmithpaul]

I thought I would put my 2 cents in here since I am rebuilding a headstock at this time and happened to look at the post. Just curious about a measurement on th motor sheaves. What is the measurement between the 2 motor sheaves at the out edge of the sheaves when the movable sheave is against the nut on the motor shaft with spring compressed. Mine measures 1-5/8 innches. This should tell you if they ate opening enough. Just trying to cover everything.

[shopsmithpaul]

Meant to say outer edge of the sheaves.

[oddie]

Responding to shopsmithpaul’s question, this is the measurement for the distance between the outer edges of the motor sheaves when the stub is grounded against the nut.

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The next pics are taken with the speed controller at “D” and using the OEM belt. The first is of the idler/control sheaves. The second is of the motor sheaves. The third shows the end of the idler shaft and the eccentric bushing. The fourth one shows the the poly belt part of the idler shaft.

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My thought is that the control sheaves aren’t opening enough because the motor sheaves have no where to go because they’re grounded.

With the belt off and the idler sheave disconnected from the quadrant, the sheave moves very easily and can bury itself into the control sheave.

BTW, what does IIRC stand for?

[JPG]

If I Recall Correctly.

Refresh my poor memory.

You are installing poly-v parts into an "A" headstock?

You added the screw and washer to position the eccentric/bearing flush with the headstock bore?

Do you still have the bearing retaining clips(A headstock).

I do still believe the grounded fan sheave is a result, not the cause.

I do have an "A" headstock populated with poly-v stuff. It works normally.(so there is hope )

[JPG]

OK so my memory is not serving me well.

You are dealing with a "B" headstock with a mixture of new, "B" and "A" shafts.pulleys etc..

I have a suggestion(again!). Your pix of the motor pulley at 'fast' shows the belt riding outside the periphery of the pulley. That ain't right!

At fast, the belt should be riding about 1/8" inside the periphedry.

So, set the speed control so the belt rides inside the pulley .

Adjust the high speed top.

Position the indicator ring to fast.

Reinstall the knob etc. and check the range towards slow.

I have not thought all this completely through, but, the belt position on the motor pulley being beyond the pulley rim is wrong in any event.

[shopsmithpaul]

I just checked my functional machine and looking at it compaired to many of your photos and the one showing the measurement on the bottom sheave. It appears to me that your bottom sheave does not open far enough. It appears that your bottom sheave is about 5/16 of an inch short of the 1-5/8 inches I measured. I also measured th spring and had 1-1/2 inches on slow and 2-1/2 inches long on fast. So one inch of travel. I do agree you should set your high speed stop so the belt is just below the outer rim if the motor pulley and then see where the slow end goes to.

[JPG]

Some 'general' info on the movable sheaves.

Both typically travel through a range of about 1" from slow to fast. That travel is in opposite direction. i.e. motor pulley opens as idler pulley closes and vice versa.

At the extreme ends of the movable sheave travel, the rim will align with the fixed rim of the fixed sheave on the other pulley.(control sheave aligns to the fan sheave at fast and floating sheave aligns to the idler sheave at slow).

The total range of motion of the floating sheave is about 1 1/4"(measured). I have to assume the control sheave range is essentially the same.

At his point in considering Oddie's problem, I think the high speed stop is incorrect and it is set with the motor pulley closed too far(belt riding too high). This places the control sheave too far open and the speed is too fast. I am surprised the belt is not dropping too far into the idler pulley and getting jammed. However IF the idler sheave is positioned too far 'into' the headstock, the belt will not get jammed. That will also affect the available range of movement of the control sheave towards slow.

It may be that the idler shaft is positioned too far into the headstock(bearing too far into the eccentric).

This condition(at fast) affects the speed range as the control sheave is closed(moved towards slow).

Much of this is counter intuitive so I think Oddie may have more than a single cause.

Oddie I think at this point you should again set the high speed limit with the belt riding just inside the rim of the motor pulley and the original high speed stop screw using the oem belt. Then take a look at the pulleys both at fast and at the slow limit(assuming it still stops prematurely(D?).

[oddie]

I’m doing this using the OEM belt. Please recall this belt is undersized.

First, I took this pic of the motor spring at “D”. We’ll use this later.

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Then I reset the speed by running the speed up ‘til a tachometer showed 5200 rpm. I set the high speed stop and turned the speed dial so “Fast” was under the arrow. These are the states of the sheaves at this point.

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With this setup there are only a very few threads holding the nut on the high speed stop. Not sure if this is best situation.

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I then slowed the machine to the lowest speed and the dial stopped at “H” not at “D”. These are pics of the motor spring and the states of the sheaves at “H”. Tach reads 1588 rpm.

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This last pic shows the spacing of the idler bearing, the eccentric bushing, and the headstock.

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[JPG]

We seem to be chasing our tail!

Let us concentrate on one pulley at a time. Static measurements.

Motor belt off motor pulley. Pulley fully closed.

Width across outside of rim (S/B about 3/4").

Distance from fan housing on motor to outer edge of floating sheave (s/b about 1").

Distance across outside of rim with the pulley manually pulled open max (s/b about 2").Make that 1 3/4"

Now the idler pulley with motor belt off.

At fast(hs stop)* the distance across outside of rim of idler pulley. (??)

At slow(I assume it will go there with the motor belt off) the distance across outside of rim of idler pullet (??)

Yes this is getting quite tedious, but we need to get a better understanding of what is actually taking place.

* I would set the HS stop screw flush with the top of the locknut for a rough setting.