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Old 16-12-07, 22:55
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Bob Moseley (RIP) Bob Moseley (RIP) is offline
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Join Date: Feb 2003
Location: Adelaide, South Australia
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Default Speedometer Head

Hi Tony - I'm afraid I disagree with you regarding your interpretation of a speedo head and that all speedos being the same speed. Below is a definition of a speedometer that contains the words speedometer head.

The mechanical analog speedometer is driven by a cable housed in a casing and connected to a gear at the transmission. This gear is designed for the particular vehicle model, considering the vehicle's tire size and rear axle ratio. In most cases, the speedometer is designed to convert 1001 revolutions of the drive cable into registering 1 mi on the odometer, which records distance traveled by the vehicle. The speed-indicating portion of the speedometer operates on the magnetic principle. In the speedometer head, the drive cable attaches to a revolving permanent magnet that rotates at the same speed as the cable. Floating on bearings between the upper frame and the revolving permanent magnet is a nonmagnetic movable speed cup. The magnet revolves within the speed cup, producing a rotating magnetic field. The magnetic field is constant, and the amount of speed cup movement is at all times in proportion to the speed of the magnet rotation. A pointer, attached to the speed cup spindle, indicates the speed on the speedometer dial.

I've also posted the image of the rear of a 2pdr speedometer showing the number 5 that the manual states is on the speedometers specificall designed for the 2pdr. If all speedos are the same why bother with the number 5 and the explanation in the manual.

Bob
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