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I'm rebuilding a Mark V 500 headstock following Jacob Anderson's video. I'm down to the part where I'm about to turn on the motor and make sure everything runs smoothly. Jacob A. hand turns the spindle assembly while he turns down the speed control from the fastest to a slower drum speed.
Whenever I do that, the idler shaft starts to poke out from the eccentric bearing. I was careful not to over-tighten the poly V belt.
It seems hard to turn the spindle assembly. It's not the motor shaft that is binding up.

I can't figure what I'm doing wrong. Any ideas?

Jeff

coldje wrote: ↑Mon Oct 25, 2021 8:12 pm I'm rebuilding a Mark V 500 headstock following Jacob Anderson's video. I'm down to the part where I'm about to turn on the motor and make sure everything runs smoothly. Jacob A. hand turns the spindle assembly while he turns down the speed control from the fastest to a slower drum speed.
Whenever I do that, the idler shaft starts to poke out from the eccentric bearing. I was careful not to over-tighten the poly V belt.
It seems hard to turn the spindle assembly. It's not the motor shaft that is binding up.

There are several possibilities, or maybe uncertainties. And there have been several configurations of the relevant parts over the years.

Simplest is the clamping force that retains the eccentric bushing and Idler bearing. But don't overtighten it, the casting can break. A common rule of thumb is enough force to fully flatten the split washer, and no more.

Decreasing speed puts some outward pressure on the Idler parts, and the idea is to keep everything except the control sheave in place. On most Marks, there is a screw and washer that go into the headstock casting just above the eccentric bushing. Its purpose is to keep the bushing in place. On newer Marks, or those that have had the eccentric bushing (not necessarily the bearing) replaced with the split eccentric, there is a second screw that goes into the eccentric that similarly keeps the bearing from going too far outboard. The split eccentric is mandatory with the new Idler from Shopsmith, identifiable by two separate bearings rather than the one long 'water pump' bearing. Some owners use a larger OD washer on the first screw to limit the travel of both the eccentric and bearing. I presume you don't have both screws based on your symptoms, but please describe what you have.

Before reassembly, did the Control Sheave slide easily and smoothly on the Idler shaft? Have you lubricated it?

You said the spindle is also hard to turn. A possible cause for both symptoms is the belt is binding between the sheaves on the Idler shaft. You should be changing speed very slowly while turning the spindle by hand because it is spinning much slower than normal. You could also have a problem with the belt or one of the sheaves. Or, the floating sheave on the motor shaft may not be moving, compressing the spring. The floating sheave should also move very smoothly and easily once you overcome the spring tension.

If none of this helps, consider posting some pictures. My best guess is something is preventing either the Control Sheave or Floating Sheave from sliding on its shaft.

- David

DLB wrote: ↑Tue Oct 26, 2021 12:06 am

coldje wrote: ↑Mon Oct 25, 2021 8:12 pm I'm rebuilding a Mark V 500 headstock following Jacob Anderson's video. I'm down to the part where I'm about to turn on the motor and make sure everything runs smoothly. Jacob A. hand turns the spindle assembly while he turns down the speed control from the fastest to a slower drum speed.
Whenever I do that, the idler shaft starts to poke out from the eccentric bearing. I was careful not to over-tighten the poly V belt.
It seems hard to turn the spindle assembly. It's not the motor shaft that is binding up.

There are several possibilities, or maybe uncertainties. And there have been several configurations of the relevant parts over the years.
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.
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You said the spindle is also hard to turn. A possible cause for both symptoms is the belt is binding between the sheaves on the Idler shaft. You should be changing speed very slowly while turning the spindle by hand because it is spinning much slower than normal. You could also have a problem with the belt or one of the sheaves. Or, the floating sheave on the motor shaft may not be moving, compressing the spring. The floating sheave should also move very smoothly and easily once you overcome the spring tension.
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- David

Excellent analysis on minimal data, David; all great suggestions. I believe another possible cause for the belt to be binding in the idler sheaves is the mis-adjustment of the high speed setting. I know mine was chewing up the belt due to being pinched between the sheaves as I tried to decrease the speed. If the high speed setting is too high the sheaves will get too wide and the belt drops down too far where it gets caught on the bottom of the vanes. If the belt gets hung up on the vanes it makes the spindle is harder to turn, and you can hear and feel the belt grinding as it tries to work its way up out of the bottom of the sheaves.

Photo below shows the vanes on the inside of the idler sheaves, and you can see how they will bind and chew up the belt if it gets below the bottom of those vanes.

. .

Pictures ALWAYS help!




IF they are of a meaningful subject to the problem.

Below is a picture to help with David's description of a possible problem with the eccentric and Idler Shaft Assembly. Also consider Marc's concern about pinching the belt.

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In the picture above the location of where screws go are indicated. None of the screws, washers or the nut are shown in the picture. The picture above has the Idler Bearing and Eccentric pushed out but they will be flush with the casting against the screws when properly aligned as shown in the picture below. The picture below shows the screws, washers and nut in place. It is these hardware parts that hold the Idler Shaft Assembly in place in correct alignment while the sheave is moved in and out on the Idler Shaft. Do note there has been variances over the years as to what hardware has been included there to hold the Idler Shaft Assembly in place. Most older headstocks with the water pump bearing without the split eccentric have a set screw through the eccentric to hold it onto that bearing. Early Greenie Headstocks had other parts to hold the assembly in place.

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Lastly as JPG said pictures really help.

Thank you to all who responded. It really helps. Pictures here. The good news is that I looked inside the case real good to make sure there was nothing loose or broken. Everything looks ok. I did oil the idler shaft before assembly and slid the second sheave back and forth several times to make sure it moved easily. I'm still having to turn the spindle assembly at the front and back with both hands. It sure seems like it should turn much more easily than that. With everything so tight, I'm afraid to plug it in and turn it on. I've adjusted the eccentric bearing until the poly v has 1/8" deflection.

First thing I noticed is the poly-v belt is NOT on the drive sleeve pulley correctly. It is two(?) grooves too far to the 'rear'. The pulley has 13 grooves. The belt has 9 ribs. Center it.

JPG wrote: ↑Tue Oct 26, 2021 8:03 pm First thing I noticed is the poly-v belt is NOT on the drive sleeve pulley correctly. It is two(?) grooves too far to the 'rear'. The pulley has 13 grooves. The belt has 9 ribs. Center it.

Will centering the poly-v belt keep the idler shaft and bearing from pushing out of the eccentric? If the idler pushes out, and the poly-v was centered, would the side pressure on the belt shift it to the left?

left/right??? it???

A belt too far to the rear on the drive sleeve pulley will tend to force the idler pulley to the rear. Only the idler pulley is sorta free to shift.

I am unsure of why the idler shaft is sorta free to shift taking the pulley along fer the ride.

JPG wrote: ↑Wed Oct 27, 2021 7:48 am left/right??? it???

A belt too far to the rear on the drive sleeve pulley will tend to force the idler pulley to the rear. Only the idler pulley is sorta free to shift.

I am unsure of why the idler shaft is sorta free to shift taking the pulley along fer the ride.

I’m sorry, I knew that left/right might be problematic terminology, but I have seen some of you use it here in the forums, and I assumed the default way of looking at the ShopSmith from the front was an understood perspective. “It” refers to the belt. I was asking if side pressure from the idler shaft drift would cause the poly-v belt to shift left two grooves? I would expect the outer race of the idler bearing(s) to be held in place by both the eccentric and a set screw (of which the type of set screw would be dependent on the model of idler bearing(s).