replacing lower Mark 5 belt with common automotive belt

[billmayo]

Another factor is that the center line of both sets of pulley is only even with each other at around half speed. As you go to SLOW or FAST the center lines move away from each other putting a nice deflection angle on the belt running on the pulleys. I believe this is close to 2" or more of center line misalignment at either end of the speed range. I have forgotten these measurements now but always aligned the two sets of pulleys when each set of pulleys are 1/2 open.

[JPG]

Another factor is that the center line of both sets of pulley is only even with each other at around half speed. As you go to SLOW or FAST the center lines move away from each other putting a nice deflection angle on the belt running on the pulleys. I believe this is close to 2" or more of center line misalignment at either end of the speed range. I have forgotten these measurements now but always aligned the two sets of pulleys when each set of pulleys are 1/2 open.

Gotta disagree with the master guru this time.

The 'fixed' sheave on the idler shaft is on the back(towards the belt cover).

The 'fixed' sheave(fan) on the motor shaft is on the other 'side'(towards the motor).

As the control sheave closes the idler pulley, the belt does indeed shift towards the rear(towards the belt cover).

The floating sheave, as it opens the motor pulley, moves in the same direction(again towards the belt cover).

Thus the belt shifts the same amount on both pulleys and the belt does not become skewed.

The inverse occurs when the control sheave opens the idler pulley.

If the belt is skewed, it is so all the time regardless of the control sheave position.

[dusty]

The effective size of the pulley is not the inner or outer diameter but a point in between called the pitch. see link below
V-Belt Transmission Notes and Design

Thank you for this link. The data has been enlightening.

The pitch diameter, as implied in the linked article, will be somewhat less than the measured length of the outside surface of the belt. The unanswered question is whether the marketed dimension (26.5" in the case of the Shopsmith belt) is the surface dimension or the dimension measured at the pitch.

[beeg]

Well my unused one measured 17/32". I measured the length to be 26 3/8's.

[dusty]

I believe that the nominal dimensions of a typical commercial 26.5" x 1/2" belt will work quite satisfactorily as a motor drive belt in the Mark V. The quality of the belt must be good (no lumps and bumps). Typical manufacturing deviations should not matter.

My statement applies only to what I said - "in a Mark V". I have no experience with either a 10 series or a Mark VII.

[JPG]

I believe that the nominal dimensions of a typical commercial 26.5" x 1/2" belt will work quite satisfactorily as a motor drive belt in the Mark V. The quality of the belt must be good (no lumps and bumps). Typical manufacturing deviations should not matter.

My statement applies only to what I said - "in a Mark V". I have no experience with either a 10 series or a Mark VII.

You have a source for a 26.5" belt? A 1/2" belt will provide a slightly faster speed range.

[dusty]

I am going to open a new thread even though my comments are going to be closely related to those in this thread.

Subject: Replacing the Drive Belt with one from Bandsaw-Tire-Warehouse.

[dusty]

Not everyone does the high speed adjust exactly the same. Here is a link to a thread where Nick provided some guidance to resolve a much earlier issue of mine.

http://www.shopsmith.com/ss_forum/viewt ... just#p1321