Freewheel
device that selectively disengages the driveshaft to allow faster rotation
A freewheel or overrunning clutch is a device in a transmission that disengages the driveshaft from the driven shaft when the driven shaft rotates faster than the driveshaft. An overdrive is sometimes mistakenly called a freewheel, but is otherwise unrelated.
The condition of a driven shaft spinning faster than its driveshaft exists in most chain-driven bicycles when the rider stops pedaling. In a specialized fixed-gear bicycle (that lacks a freewheel) the rear wheel drives the pedals around.
Some automobile transmissions include freewheel mechanisms for reasons ranging from fuel efficiency and noise reduction to preventing damage that some engines incur when driven by the wheels.
Mechanics
The simplest freewheel device consists of two saw-toothed, spring-loaded discs pressing against each other axially with the toothed sides together, like a ratchet but with the usual stationary part also rotating. Rotating in one direction, the saw teeth of the drive disc lock with the teeth of the driven disc, making it rotate at the same speed. If the drive disc slows down or stops rotating, the teeth of the driven disc slip over the drive disc teeth and continue rotating, producing a characteristic clicking sound proportionate to the speed difference of the driven gear relative to that of the (slower) driving gear.
A more sophisticated and rugged design has spring-loaded steel rollers inside a driven cylinder. Rotating in one direction, the rollers lock with the cylinder making it rotate in unison.
Begin with the source’s own compact description: “Freewheel” is device that selectively disengages the driveshaft to allow faster rotation. The dossier treats that line as a proposition to test through Freewheel, device and selectively, not as a finished interpretation.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Sep 15, 2026. The linked authority identifier is Q1293233. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Freewheel” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.