Pulley with bulge or crown or dome for belt tracking

I am looking for design information regarding belt pulleys that have a bulge, crown or dome built into the working face in order to design an effective belt/pulley system for an electroplating application.

Here is what I found via Google University so far...interesting! The third one looks quite good but CONTRADICTS the second one regarding using 2 crowned pulleys...why? Any ideas?

Three hyperlinks below: Please read these before re-posting them.

How crowned pulleys keep a flat belt tracking

Flat belt tracking on pulleys.

Belt Tracking

Of particular interest is that I read on another website that having one crowned and one flat pulley is fine, but having 2 crowned pulleys on one belt invites trouble.

Any comments or information your deep pools of experience could offer would be greatly appreciated.

BTW, I spent a few minutes searching this forum and found nothing...but that's not to say there is nothing here!
Thanks in advance from Niagara Falls, NY!!

pulley crowns

Belt Tracking
Flat belt tracking on pulleys.

My Dumore has two crowned pulleys so I would say two crowned pulleys is ok. A lot of it depends upon the belt material and belt width to pulley width ratio.
One of the woven flat belts I had ordered needed a specified crown of 1.5% to 3% on both pulleys based upon diameter. Overall i would say the belt manufacturer sets the standards for the crowns, if needed.

Anybody done anything with concave pulleys? Might be interesting to hear the results and might possibly shed some light on what convex crowns do.

Another interesting thing about flat belts and crowned pulleys, is that the belt must necessarily have one linear surface speed. However, a crowned pulley has a multitude of surface speeds, with the lowest speed at the small diameters and highest speed at the center. So the most torque is being transmitted at the center, which probably distorts the force pattern into something like a wake from a boat. This pulls the center fiber of the belt ahead of the edges. There is probably some sort of vector diagram that one could draw of the force directions on the belt fiber. There would likely be two opposing vectors pointed from the outside edges towards the center, and they would be pointing slightly ahead of the pulley axis. So then if that were the case, you've got real force there doing the work of keeping the belt on center.

Also look up trapezoidal crowned pulleys Habasit web site had specs, don't know if still available.

Neil: I guess when you wrote, "Please read these before re-posting them," you did about as much as you could.

Sometimes, rumors get started by people who do not ask enough questions,
before they become experts. While it may(?) be possible to run a flat belt, on only one crowned pulley, it is also possible to run the belt on two crowned.
Look at any South Bend lathe, with a flat belt drive. When my brother, and I,
had a Case steam traction engine, and seperator, both pulleys were crowned. If the pulleys, are not aligned properly, it will take more tension, to keep the belt on, when a load is applied.
It is recommended, with timing belts, that only one pulley, on a belt, have flanges.
Regards,
Bob

I will just point out that Dumore grinders come with a set of five crowned pulleys. The speed change chart mixes the pulleys, so any of the five may be the driver or driven pulley. There is no way the Dumore could have one flat and one crowned pulley unless they provided a second set of five flat pulleys. The system does work, partly because the motor and spindle are precisely parallel.

I have one running machine with four flat belts. It uses a countershaft with shift forks that move the three leather belts sideways on wide flat pulleys. This system of shift forks could not work with crowned driving pulleys on the jackshaft.

Larry

Pulley with a bulge or crown for belt tracking..

With out getting tooooo technical, the flat belt will always track to the tight side. Having said that, the flat belt will will climb to the top of the crown and start down the other side until it realizes the tight side is at the middle of the pulley.
(Precision alignment), They really don't have to be aligned as precise and you would think.....
Regards Walt..

If the pulleys are not aligned precisely, the belt will run on the pulleys but not in the middle of either pulley..
Don't ask how I found that out. It could happen if you don't get the grinder (Dumore) together properly..... Maybe....