I'm turning up an aluminium pulley for a PMR Generator.
For a pulley for a flat belt, how much camber is needed on the pulley for the flat belt to center itself?
Tough question Jim!
There are a whole host of variables involved here that I doubt you'd want or need to go into, but they include the diameter and width of the pulley, the type of belting material and its width and thickness, plus the span between the pulleys, plus the crown or lack there of for the other pulley, and no doubt speed and power factor in as well.
There is also the form of the crown, whether it is a smooth curve, a simple ridge with flat lead in angles, or a flat across the top with just the edges forming tapered angles.
My feeling is that if you crown it just enough so that you can actually see the crown, that will likely be about right .... say about .015-.020 per inch, and if that doesn't do it, add a bit more.
Thanks Daniel, its been a frustrating experience so far with trying to get the PMR belting track right on pulleys and not continuously jumping off.
I'm not overly enthused about the superglue joint that I did either, I think I may have overlapped it too much as there is a distinct 'thud' each time it goes round a pulley.
I've toyed with the idea of doing a butt join and using some soft braided fishing line (like Firewire etc) to join the belt like the old school method of joining leather belting.
I've toyed with the idea of doing a butt join and using some soft braided fishing line (like Firewire etc) to join the belt like the old school method of joining leather belting.
I did this when belting my Case to a burr mill, but instead of a butt, I angled the ends with a razor blade so when pieced together it was overlapped and flat, then I just ran it through a sewing machine.
Is it possible to run the belt crossed, most old timers claim they run best that way, some even doubled twisted them so as not to reverse direction.
Is it possible to run the belt crossed, most old timers claim they run best that way, some even doubled twisted them so as not to reverse direction.
A half twist will also keep it from going side to side while not changing direction. This helps reduce slap and reduces wear as the pulleys are making contact on both sides of the belt.
Jim, I have made a few flat belts & have been to a few leather shops that join leather belts, they have a tool that is adjustable & can strip half of the thickness away , I just do that to both sides, I have also used my 1" belt sander to thin the belt to about half thickness, then I join with "Barge" all purpose cement (suggested by the leather shop) also make sure your belt is "set" dead straight, using a long ruler as this will obviously effect alignment, compress with a clamp (block of wood works well with wax paper above & below the joint) & let set for 24 hrs, & as Daniel has said re; camber "just enough so that you can actually see the crown" is all that is needed on the camber.
Thanks Daniel, its been a frustrating experience so far with trying to get the PMR belting track right on pulleys and not continuously jumping off.
Jim, you might want to just contact PMR with your problem and info - they're pretty nice about helping out.
Thanks one and all for all the advice, very much appreciate everyone's post.
Jim, I am getting late into this about making belts. I was out of town
and did not have the photos I needed. I have run a PMR with an S50
with no trouble in this way. When I make belts for Edison cylinder
phonographs. This how I made them and it has worked well for me
when running the PMR.
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I cut the ends on an angle and overlap a 1/2”. Then thinned the top of one
end of the belt. Then thinned the bottom of the other end sow that they are
now the same thickness.
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Hope this is some help as it has worked for me.
Thank you very much Carl, very much appreciated!
That's an interesting looking tool Frank.
