Still Trying to Fully Understand

[algale]

schedule a cleaning and lubrication session and then check the poly-v. Fifteen minutes to avoid a lot of frustration.

I'm probably due. Thanks for the advice.

[dusty]

schedule a cleaning and lubrication session and then check the poly-v. Fifteen minutes to avoid a lot of frustration.

I'm probably due. Thanks for the advice.

If you don't have a problem - DON'T FIX IT.

[JPG]

schedule a cleaning and lubrication session and then check the poly-v. Fifteen minutes to avoid a lot of frustration.

I'm probably due. Thanks for the advice.

If you don't have a problem - DON'T FIX IT.

The goal is prevention!!

[dusty]

The effect on shaft positioning is mostly vertical with some sideways positioning as well. The extreme vertical positions are 6 and 12 o'clock of the slot and 9 and 3 o'clock for the horizontal positioning.

The Mark 5/V uses the vertical movement to control Poly-v or Gilmer belt tension. The horizontal positioning is a byproduct and not intentional.

The Power Pro uses both, but is essentially a tension equalizer between the two poly-v belts.

I have to see in order to understand so I created these sketches to show (me) how the eccentric adjustment effects belt tension. The area of the circle that is "outside" the square box is where the poly-v belt moves to as the eccentric is adjusted. I have shown 6, 10 and 12 o'clock positions. The 12 o'clock position represents maximum tension on the poly-v. You can take it from there. That is a downward movement of the drive shaft of 5/32" as the eccentric is turned. I had problems envisioning this for awhile until I realized that the physical position of the eccentric is held constant and the shaft moves as the bearing runs around the inside of the eccentric.

It seems to me that if the eccentric is at "high noon" you are far over due for replacing the poly-v.

Minimum Tension

Eccentric at 6 o'clock (minimum tension).png (51.02 KiB) Viewed 9614 times

Eccentric at 7 o'clock.png (44.6 KiB) Viewed 9614 times

Eccentric at 10 o'clock.png (54.89 KiB) Viewed 9614 times

Maximum Tension

Eccentric at 12 o'clock.png (56.34 KiB) Viewed 9614 times

The area of the circle that is outside of the square (left and right) represents lateral movement of the drive shaft.

The cross in the center represents the axis of rotation of the eccentric.

Remember: _ The other shaft and pulley (drive shaft) is above the eccentric.

[JPG]

Yep!

A detail that creeps in to the thought process is the "X" is the shaft center. Tain't so!!!!!

[c2h6o]

The eccentric on my PP upgrade is stuck--unable to adjust as per normal procedure. Wondering if there are any suggestions on how I might address this? Lubrication, slight tap with a hammer, or ???

[DLB]

The eccentric on my PP upgrade is stuck--unable to adjust as per normal procedure. Wondering if there are any suggestions on how I might address this? Lubrication, slight tap with a hammer, or ???

On the PowerPro if both belts are tight it is very difficult to turn the eccentric. Either direction you turn it is tightening one of the belts. It is completely different from a conventional headstock where the eccentric is only used to adjust the upper belt. To confirm that it is actually stuck I would remove the lower belt, then see if it will turn toward six o'clock to loosen the upper. If genuinely stuck I might try penetrating oil and possibly tap it with a mallet, but once I got it out I would go back to clean and dry.

Normal adjustment of the eccentric consists of two parts. When the motor belt is not in place, the eccentric is used just to tighten the upper belt, same as conventional. Once the motor belt is installed, the eccentric is used to 'balance' the belt tension for minimum bearing noise. It won't move very far when balancing, and the tighter you installed the belts the more force it will take and the less it will move. The manual does not provide any guidance on how tight the belts should be, I go with slightly tighter than conventional due to greater torque availability.

- David

[edma194]

The eccentric on my PP upgrade is stuck--unable to adjust as per normal procedure. Wondering if there are any suggestions on how I might address this? Lubrication, slight tap with a hammer, or ???

Make sure the casting isn't clamped down too tight on the eccentric if you have that old style. You can also adjust the belt tension and alignment somewhat with the motor mounting blocks. I think if the belt isn't aligned well you are putting extra lateral pressure on the shaft that could keep the eccentric from turning.

[c2h6o]

Thank you. This is an excellent answer--can't tell you how much this as helped me.

[c2h6o]

Excellent answer--thank you