h a l f b a k e r yContrary to popular belief
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A shaft for driving a wheel or axle, in a car or as an alternative to the bicycle chain, is usually heavy and expensive.
The following is an idea to make it much cheaper and still can bear the same tension.
Take a thin hollow shaft of some rigid plastic, or perhaps hollow metal rod. Wind it tightly
with high tension bearing "thread". (In Top roping, you can find threading that can carry many tons). Glue the wiring flexibly together so that it doesn't lose its shape. Through the hollow of the shaft, a strong rope holds the two sides of the shaft to the connectors keeping the shaft's length straight. But the connectors are also attached to the ends of the winding thread, so that the winding takes almost all of the torque and transfers it, through the windings to the other side, without deforming the shaft length.
In order for this to work for a shaft possibly turning the other way, you would need another winding in the other direction, attached as well to end connectors.
(?) Tyre coupling
http://www.esbi.info/vf.html
Industrial version of the hose coupling you're talking aboot [Custardguts, Aug 24 2009]
[link]
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So you trade off a little weight in the shaft for a much greater weight of the frame that must resist the tension of the rope? |
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Using a hollow tube of, say, carbon fibre composite to save weight is not in itself a bad idea. |
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The driveshafts and half shafts of cars actually have the capability to "wind up" under extreme torque, and subsequently recover without damage. This acts as a useful buffering mechanism. A stiffer shaft might have weight advantages but would not necessarily have desirable mechanical properties - it might in fact be too stiff. |
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Composites of this type have the disadvantage that there is no graceful or partial failure; they simply fail catastrophically, whereas a metal component might deform permanently but not actually fail. |
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// ....carbon fiber..... // |
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Ah yes, that would be the incorrect (American) spelling .... quite amazing, 250 million humans who can't spell or pronounce "Aluminium" ..... |
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My favourite is the way they say "Noocular", when they mean Nuclear. This is what happens when the colonies become isolated and in-breeding takes over. As for that carbon fiber... never could trust carbon with the truth... too fond of the old dioxide. |
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// we have the older meaning of freedom here // |
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Oh yes ... the sort that says that people are not actually "Citizens" but "subjects of the Crown" ..... |
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//people are not actually "Citizens" but "subjects of the
Crown" // |
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We is? Let me just check my paperwork.... |
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And behold, a pedant is born! |
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Fiber, color, aluminum etc. are entirely sensible and logical spellings, but are not used everywhere (we Aussies tend to use the British spellings vis. fibre, colour, aluminium). It's probably not useful for either side to claim to be the only correct one, however. |
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I've used hydraulic hose as a flexible
shaft/flexible coupling. The hose consists of steel
windings, of both-handedness, woven together
into a braid, and encapsulated in rubber. Even a
'one-wire' hose can handle impressive torque and
significant misalignment. The easiest way, is to
cross-drill through each shaft, fit the hose over,
and drive a nail through the hose and shaft. Ain't
pretty but works great.. just remember to tuck in
that nail, and mind the bits of wire braid showing
on the cut ends of hose.. they sharp! |
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Often wondered if a scaled-up version would be
suitable as a CVJ (constant-velocity joint) for cars.
I think the internal friction of the rubber
encapsulant would be excessive. |
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The Triumph Vitesse has a rubber "doughnut" between the half-shaft and the hub to forn the CV joint, and they seem to function well. |
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See linky. Called a tyre coupling, used all over the place when you're too lazy to get alignment correct. |
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I've seen a (I think it was...250mm) tyre coupling run for about 9 months continuous on a 12-10 Warman tailings pump running at 350kW with fully 10mm radial misalignment and a few mill out on the faces. (tip for young players - laser alignment tools are only as good as the "dumb end" operating them. Training, training, training). |
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So yes, they work and they're great. Strength is very much inversely proportional to length, so your long flexible "shaft" is going to be a tricky one. |
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//aluminum etc. are entirely sensible and logical spellings//
I shall be putting sodum chloride on my chips at lunchtime. |
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I'm sure we've done aluminium vs. aluminum before on the bakery, and found that they both have perfectly respectable raisons d'etre, and neither is a corruption or perversion of the other... I'm too lazy to find the link, though. |
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"Aaach, you don't get the HalfBakers you used to these days..... lay young sods ..... wne I was a boy we had to work hard ......" |
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//This is what happens when the colonies become isolated and in-breeding takes over.// |
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Funny that, coming as judged from a smallish rainy island where powdered wigs for lawyers are the norm, good teeth are hard to find, and half the northern end run around without proper britches. |
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As per the idea, I'm thinking fiberglass isn't that expensive. |
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//powdered wigs for lawyers are the norm//
I saw my solicitor only last week, and I'm perfectly sure she's never worn a powdered wig in her life.
You're perhaps thinking of barristers? |
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I'm not sure about having three separate parts like this; they may tend to move relative to each other creating friction and wear, and there may be more chance of one part's failing, with total failure the result. For example, as the wound thread takes up tension produced by torque, it will apply forces that tend to collapse (radially) and shorten the lightweight tube; if the tube does not withstand those forces the entire assembly will collapse. |
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I've often thought about simply using a rope as a driveshaft in high-vibration or shudder applications. |
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I've used car fuel line for the same purpose, much like [iron_horse]'s hydraulic line (but less heavy duty). |
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Better be high-tensile-strength rope under some serious tension, or it'll get all knotted up like those little rubber band powered planes do as they're overwound. |
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Thanks to [pashute] and [iron_horse}, I now have a cheap and simple universal joint for my many insane inventions. [+] |
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