RE the fan belt puzzler

Mechaniker

The puzzler got me thinking about flat fan belts. They are used today where ever ultra high speed and low friction are required. (They are the blades in bandsaws, for example.)

Ever wonder about the contour of the pulley face, and what keeps the flat belt centered on the pulley?

For the curious, the answer is here.

BTW, the story Click & Clack described actually occurred in WWII. The name of the German soldier who came up with the idea, and whose name is forever associated with the technique for reducing fan belt wear, was Obergefreiter Moe B. Usse. He was later stripped of his awards after caught carrying gasoline in a Klein bottle (which he bought at M. C. Escher und Söhne).

the same mountainbike

Low friction? Friction is GOOD when using belts. Perhaps you meant high flexibility (low internal friction)?

Mechaniker

I meant high efficiency, i.e., little to no loss in power conduction. V-belts have higher internal friction (they are thicker and stiffer).

the same mountainbike

Internal friction. That's what I figured you meant. It didn't come out clear.

EllyEllis

"" Ever wonder about the contour of the pulley face, and what keeps the flat belt centered on the pulley?""
Honestly, I never have wondered!!

Mechaniker

Some of us are more curious than others.

the same mountainbike

I wonder about it, and looked it up, many years ago. So far back I don't even remember.

I have an enquiring mind.................

EllyEllis

Monkeys are curious too. JUST KIDDING!!!!!

MBStever

Give me a break: Moe B. Usse? Hummm...Mobius?

wavyonwheels

I am hoping Ober made it past the front lines before they discovered a twist in the belt would make it wear faster.

nickpang

There's no way the mobius strip answer would work. The belt would not rotate around leaving the twist in one spot between pulleys, but the tiwst would rotate with the belt and go over the pulleys, doing nothing to extend the life of the belt. Now if something could be engineered in to keep the twist point constant with relationship to the rest of the motor..... But that's not a 10 minute fix.

MBStever

A flat belt in 1936?

Mechaniker

nickpang — "There's no way the mobius strip answer would work. The belt would not rotate around leaving the twist in one spot between pulleys, but the tiwst would rotate with the belt and go over the pulleys"

And you know this how? Gut feel?

Twisted belts were often used on old farm equipment, either for reversing direction, to reduce effects of wind whip, or to increase friction.I have seen this at antique farm equipment shows. Google tractor thresher twisted belt for some YouTube videos.

One fellow in Maine had a 6 hp gasoline engine attached by a flat belt to a table saw. (Apparently it was a short belt.) While applying belt dressing to the inside surface, a dangerous job, he wondered if he could turn the belt into a Mobius strip and apply belt dressing only to the upper surface. It is easy to do this by removing the belt lacing pin and giving the belt a half-turn before reinserting the pin..

Read his story here

Either that guy is lying, or the twist does not "walk around" even a short belt as you claim.

Charlie RT

What about the fact you are now turning the accessory backwards in the case of a water pump this would be boooogus

GeorgeSanJose

The accessory gets turned backwards with a Mobius twist in the belt? I don't think this is the case. Maybe a misunderstanding about the nature of the Mobius half-twist. The Mobius half-twist is in the belt itself, it's not giving a regular (non-Mobius) belt a twisted (figure 8) belt-path. With the figure 8 belt path, the accessory would indeed get turned backwards. But not with a Mobius half-twist in the belt itself. Google "Mobius Strip".

Barkydog

The mobious twist was all i could come up with,

Royroyroy

I proposed a figure 8 solution and can't understand why it wouldn't work. I just verified it with 2 pencils and a flat rubber band. The belt would Be contacted on both sides and the pulleys are driven in the same direction. Can someone explain why they couldn't manufacture the belt without making it a möbius and just twist it ?

Royroyroy

I should correct the last post. It was NOT a figure 8 that I proposed. Of course that would reverse the rotation of the pulleys. It was simply a half-twist of a straight belt, leaving one side in contact with the, say, top pulley, with the other side in contact with the bottom pulley. Any comments?

hybrid314

@nickpang, the twist might move slightly over time but could never get beyond either of the pulleys so it would be a stable system. The odds are it would remain halfway between both pulleys since that is the position of least torsion and resistance.

@Mechaniker's link mentions putting the twist on the slack side of the pulleys instead of the tension side, which makes sense. Either way, the twist could not move to the other side.

the same mountainbike

Gentlemen, Ladies, see the attached.
http://en.wikipedia.org/wiki/File:AHW_Kammgarnspinnerei_Pfaffendorf_Leipzig_um_1925.jpg

This was the norm intextile mills for a generation or more....much more. They were flat leather belts.

sloking

The solution to the German fan belt problem is wrong.

First, assume that a belt wears thin until it fails. Let"s take for an example a belt which fails at 100 hours when it has worn to 50% of its original thickness. The belt is formed as a moebius loop and a point on one side is marked "A". After it has run 100 hours the point marked "A" will be found to have worn down only 25%. Unfortunately, the belt now has only one side "A" so the "other" side of point "A" will have worn down 25% also. The belt, worn 50% total, will fail.