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Klassische Schraubkranzfreiläufe (Quelltext anzeigen)
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(→Demontage des Schraubkranzfeilaufs: Bild ergänzt) |
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[[Shimano]] [[Hyperglide]] Schraubkränze hatten nur Ritzel mit Keilzähnen. Die Ritzel wurden von einem [[Konterring]] gehalten. Dies ist das gleiche System, wie es später bei den modernen Hyperglide [[Kassette]]n zum Einsatz kam. | [[Shimano]] [[Hyperglide]] Schraubkränze hatten nur Ritzel mit Keilzähnen. Die Ritzel wurden von einem [[Konterring]] gehalten. Dies ist das gleiche System, wie es später bei den modernen Hyperglide [[Kassette]]n zum Einsatz kam. | ||
Most multi-speed freewheels have replaceable, interchangeable sprockets. It used to be a common bike-shop service to assemble custom freewheels with any desired combination of sprocket sizes. Unfortunately, with the general decline in freewheels, replacement sprockets are no longer as readily available as they once were. They do show up on eBay, and it is also possible to restore an older, worn sprocket with some judicious grinding. | |||
Sprockets of older freewheels had taller teeth than are usual today. When a sprocket and chain wore together, they would form a hook shape at the back side of each sprocket tooth. A new, replacement chain's shorter links would fall into the hollow behind the hook of one tooth, ride up over the next tooth, and jump forward when that tooth came around to the top. | |||
It is possible to extend the life of a hooked sprocket by grinding off the hooks with a Dremel tool or disk sander. The hardened metal surface has already worn off, so the revived sprocket will wear faster than a new one. Newer sprockets must usually simply be replaced, as the teeth are not tall enough to allow of restoration: see our article on sprocket and chain wear. | |||
To remove sprockets from a freewheel for replacement or restoration, you normally use two chain whips: one to unscrew the sprocket, the other to prevent the freewheel from rotating backwards. This is easiest with the freewheel installed on the wheel. Or you can use a special freewheel vise in place of the second chain whip. Remove the freewheel from the wheel to use the freewheel vise. | |||
. freewheel_visesm.JPG | |||
Freewheel vise. The photo is for illustration only. The freewheel vise must be clamped in a bench vise in use and when separating two sprockets of nearly the same size, place the smaller one underneath, for less interference with the chain whip. | |||
Older European freewheels mostly used all threaded sprockets. Usually the two largest would have left threading, and would have to be removed/replaced at the wide end of the freewheel. Because of the low gearing provided by the larger sprockets, they would usually be screwed on very, very tight, and could require a considerable amount of effort to unscrew. The smaller sprockets would screw on from the outside, using normal right threading. If you don't have a chain whip, or if you are trying to remove a particularly stubborn threaded sprocket, you can substitute a short length of chain held in a vise | |||
chain-vise | |||
A length of chain and a bench vise also can clamp a sprocket | |||
In practice, you usually did not have to remove all of the sprockets at the same time, because you needed a sprocket to hold the freewheel in place while you unscrewed the one you wanted to remove. There were special vises that gripped the threads to let you take off the last sprocket, but I never found the need to use one. Another way to remove all of the sprockets is to tighten the two largest ones against each other, loosen the remaining smaller sprocket and then unscrew the largest sprockets from each other. British Cyclo freewheels were different -- all the sprockets screwed on from the left except the smallest -- and quickest wearing -- one! This sprocket was integral with the freewheel body and could not be removed. Mechanics who didn't know this have broken teeth off this sprocket trying to remove it. But that's ancient history and you will probably never see a British Cyclo freewheel! | |||
Newer freewheels use splined sprockets: you need only unscrew one or two outer sprockets, and then the others slip off. Shimano Hyperglide freewheels use all splined sprockets, with a threaded lockring similar to the system used on Hyperglide cassette hubs. | |||
Keep track of the spacers between the sprockets, to maintain correct sprocket spacing when you reassemble the freewheel. When reassembling the sprockets to the freewheel body, grease the threads to prevent corrosion and make removal easier the next time. | |||
Many sprockets are asymmetrical. The high side of the teeth of SunTour sprockets faces to the right. The ramps for chain pickup on newer sprockets also face to the right. If installed backwards, these sprockets will shift very poorly. Some older sprockets are symmetrical, so you can extend their life by turning them over. | |||
== Die Geschichte des Freilaufs == | == Die Geschichte des Freilaufs == | ||
