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Post by c64 on Nov 15, 2017 21:58:54 GMT
The strangest speedometer setup I ever saw was on a 1993 Chevy Corvair. The cable wasn't connected to the transmission but came through the driver's side front wheel axle and the inner spiral part went through a small square hole in the hub cap.  Actually, this is more precise. The driven wheels have a slight wheel slip all the time while there is load on the transmission. Precision speedometers used by taxis and police chase cars (at least in some EU countries) measure distances (and speed) on a non-driven wheel, nowadays either using the ABS sensor or using a camera pointing to the ground. The camera works just like an optical mouse which contains a small camera with low resolution but high FPS. Early optic mice used 48x48 pixels @400fps. Farming tractors used to have no odometer. They used a "motometer" which measures the engine RPM and you need to convert the engine RPM to the speed all by yourself. Fast farming tractors had a scale to avoid speeding. Here is an old Motometer which also counts the hours required to maintain the service intervals.  |
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Post by GTCGreg on Nov 16, 2017 2:01:17 GMT
When I use to fly, the flying club had planes that had an hour meter built into the engine tachometer. If the engine was running at cruise speed (something like 3400RPM) the tach hour meter would be correct. If the engine was running slower, the hour meter would be slow. They also had a Hobbs time meter that ran off a crystal oscillator and that was always correct. The good thing is that the club would charge by the tach hour, not the Hobbs meter. If you were using the plane for something like shooting touch and go landings, you could get about an hour and twenty minuets of actual flight time, but you were only charged for an hour.
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Post by the light works on Nov 16, 2017 3:44:14 GMT
my dad's first backhoe had the combination tach like that. the later two had a regular speedometer.
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Post by c64 on Nov 29, 2017 19:07:36 GMT
When I use to fly, the flying club had planes that had an hour meter built into the engine tachometer. If the engine was running at cruise speed (something like 3400RPM) the tach hour meter would be correct. If the engine was running slower, the hour meter would be slow. They also had a Hobbs time meter that ran off a crystal oscillator and that was always correct. The good thing is that the club would charge by the tach hour, not the Hobbs meter. If you were using the plane for something like shooting touch and go landings, you could get about an hour and twenty minuets of actual flight time, but you were only charged for an hour. Same on the old farming or construction machinery. In the picture, it says "1650 UPM = 1h" (UPM: Umdrehungen Pro Minute = RPM). This is the engine RPM required for the standard PTO RPM to drive trailing machinery or generate power using an external generator. It is also the "sweet spot" for plowing or traveling. The more stress on the engine, the higher the reading. Sounds fair. Modern motormeters are digital and contain a quartz clock so you can't tell if the machine was idling or working "that much". |
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