Non-parallel pulleys? - Ford Mustang Forum
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post #1 of 4 (permalink) Old 05-29-2012 Thread Starter
Boy Howdy's Avatar
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Non-parallel pulleys?

I found these non-parallel pulleys online. I'm pretty sure they are designed for low output situations, but I was wondering if they could stand up to the stresses of a performance engine. I don't think they would be able to stand the stresses because of the twists of the belt. I think it would wear quickly and snap. But that is just my humble opinion because I have very limited knowledge on this subject (but I know you guys are knowledgeable). So just imagine these non-parallel pulleys with modern belts and modern everything in an engine capable of 8000ish? rpm.

1. Would they survive?
2. If so, have there been any application of them?

Thank you.

Im having trouble posting an image, so google "non-parallel pulleys" in images and there should pop-up a black and white drawing that says "harry's old engines." I don't who harry is lol, and I wish I could be of more use in providing an image.

Thanks again.

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post #2 of 4 (permalink) Old 05-30-2012
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I think that this is the image that you are referring to.

These are for low rpm situations. The twists of the belt cause it to heat up, and centrifugal force at high speed causes the belt to jump off the pulleys.

There is also friction of the belt rubbing against the pulley sides which adds more heat and wear. See the second image of figure 18 at point "D". The portion of the belt at the rear of the lower pulley leaves at an angle, with lots of rubbing and friction.

I used to own a 1957 International tractor that had the old style pulley power take off at the back of the machine, mounted on an extension of the transmission shaft, so it was was on a vertical plane perpendicular to the center line of the tractor. I ran a Woods belly mount mower deck on that tractor that had three rotating blades, all operated by horizontal pulleys. The center blade had a three-stack pulley. Two "idler" pulleys were mounted on the tractor, below the power take-off at odd angles. The single V belt was about 18' long, and traveled from the power pulley, over the left idler, to the bottom of the center stack, to the right blade, across the middle center stack, around the left blade, the top of the center stack, the right idler, then back to the power pulley. The belt lasted maybe four seasons for me, or about 100 hours.

Older cars used multiple V belts, usually three, in three different vertical planes. The crankcase pulley was a multi-stack. The accessories had to be lined up perfectly to avoid excessive belt friction, and brackets were adjustable for that as well as to tension the belts. Larger V belts developed more internal friction since they bend then unbend about their depth with every rotation around a pulley. As they wore and stretched the accessories had to be readjusted to keep tension on the belts, and the belts had to be elastic to allow this. Belts lasted maybe 50k miles, about 1500 hours.

Modern serpentine belts reduce friction due to reduced depth. The multiple V shape means that they can be as wide as needed for the intended power transfer. Idler pulleys configure the belt in a path to serve multiple accessories, so normally a single pulley can serve them all. A tensioner pulley allows the belt to be made from relatively inelastic materials that last 150k miles or more, about 6000 hours.

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post #3 of 4 (permalink) Old 05-30-2012 Thread Starter
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Thanks Yadkin for the information. And yes, that was the exact image I was talking about.

2011 3.7L 6sp Performance Package, Ext. Black, Bone Stock with the exception of an oil change.
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post #4 of 4 (permalink) Old 05-30-2012
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I saw something like these on a Corvair that ended up driving a cooling fan, When I asked the guy he said it was something you had to keep your eye on as they came off/broke regularly.

Howdy, curiosity only or do you have an idea???? I'm gonna guess down force fan.....

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