Motometer continued as the instrument supplier for the motorcycle side of BMW and a new large binnacle with speedometer on the left, tachometer on the right and a liquid crystal display quartz clock in the middle.
Left click on the illustrations to enlarge them....
so calibration figures for the speedometer are....
49.7cycles/second (hertz) = 60kph
66 cps(hertz) =80kph
82.1 cps(hertz) =100kph
97.9cps(hertz) =120kph
113.4cps(hertz) =140kph
128.7cps(hertz) =160kph
The rear wheel had a metal disc with "teeth" on it that a hall effect pickup in the final drive was set near and detected the passing of the sheet metal "teeth"...the speedometer then displayed this as kph or mph and drove an odometer by a form of servo motor.
The instrument binnacle suffered from mild corrosion on internal terminals such that the signal would be lost and the speedometer stop working.
A frustrating instrument at best....
The LCD display on the clock and the gearchange indicator would, with time and vibration, segment to a black blob appearing visually and masking any reading.
Once Motometer stopped the supply of parts in the early 1990's it became almost impossible to repair....
5 comments:
You, good sir, are a legend! I have spent more than I care to admit on replacement 2nd hand bits for my k100 instrument cluster, over the last 5 years.. Now I have the specs and pinouts to simply replace the whole thing with a nice big LCD display and a small microcontroller, next time it plays up!
Excellent resource! Do you know what voltage the signal is going into the speedo? I'm trying to match the BMW sender to an acewell speedo.
Cheers, Dave
Dave,
Regrettably I can't remember what the sender voltage was, assuming I measure it.
My notes, well what I've left of them, show no figure....
Kindest regards,
Dennis.
According to: http://www.ibmwr.org/ktech/speedo-repair2.shtml it's a 6v square wave.
HTH
Sorry folks, let me clarify.
After passing through the amplifier in the speedo unit it's a 0 to +6V square half wave feeding the speedo head.
The speed pickup coil signal is roughly 1V p-p, as raw input to the whole speedo unit.
I can't claim any of the credit for this, see ref http://www.ibmwr.org/ktech/speedo.gif
So all kudos and huge thanks to Jack Hawley in Urbana, IL for all this.
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