Why doesn't this counter spin with the trailer wheel? Hubodometer ? #truck #hubodometer #howitworks

A hubodometer is a mileage counter bolted to the hub of a trailer wheel. A trailer has no engine and no dashboard, and different trucks pull it from one job to the next. Fleets read its miles from this counter to schedule service and to work out lease charges.
The trailer's axle doesn't turn: the hub and the wheel rotate on bearings around it. The counter's case is bolted to the hub cap, so it turns with the wheel. Inside, a heavy weight hangs on bearings from a shaft that turns with the case. Gravity keeps the weight at the bottom. The dial and the number wheels are mounted on it, so they stay upright while the case turns around them. A worm gear on the shaft drives gears on the hanging frame, and these advance the numbers. An 11R22.5 tire, a common trailer size, makes about 493 turns per mile (about 306 per kilometer), so each counter is made for a tire size. The weight sits on springs, which keeps it from being flung around with the case when the wheel hits a bump or a pothole. A mechanical hubodometer counts every turn in both directions, so backing up adds miles too.
The animation simplifies the parts and draws the gears larger so they can be seen. Gear trains differ from one maker to another.
Sources: US patent 2,638,274, "Hub odometer" (Engler Instrument Co., 1953); US patent 4,430,561, "Hubodometer" (Standard Car Truck Co., 1984); Timken hubodometer product sheet; Stemco Mechanical Hubodometer page; BFGoodrich DR444 data sheet (revs per mile).
#truck #hubodometer #howitworks

Category : Trailers in English

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