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Discussion Starter · #1 ·
Hey, not sure where to put this quesion, but does anyone know the aprox rpm speed of the speedometer cable?
 

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Detritus Maximus
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I think, by definition, it depends on how fast you are going....
 
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This depends on a number of things but can be calculated for any speed by factoring in all of the variables including tire circumference, differential gear ratio and the gear ratio of the speedometer drive gear and the speedometer driven gear (essentially the ratio of driven gear to one turn of the gearbox output shaft). One calculates the number of revolutions of the output shaft of the transmission at a given speed, then translating this against the drive/driven ratio you determine the cable RPMs.

A crude benchmark can be determined if you know the RPM output of your electric drill -- hook up the speedometer cable to the drill and spin it and see what MPH the speedometer registers.
 

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Discussion Starter · #4 ·
That was a pretty good idea, think I will try that. Then I can use a rpm laser gadget to measure the drill.

Need to know the range to buy the correct motor.
 

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1970 Opel Gt - Purchased July 1972 - Chartreuse - restored - 3000 miles as of 02-16, 2021 -
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Easy way to check your speedometer is using GPS I use the WAZE app and mine is right on. Also, if I am not mistaken your RPM's on a 1.9 engine should be around 1/2 of the speedometer that is 30 RPM = 60 miles per hours - since I am now driving a 2.0 it does not line up exactly like it use to. Not sure that should make a difference or if it really does but that was my experience. That is a 4 speed transmission....
but the WAZE app gives you the exact miles per hour....so that really takes the guess work out of it....
 

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Your Noble Friend ;-)
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That was a pretty good idea, think I will try that. Then I can use a rpm laser gadget to measure the drill.

Need to know the range to buy the correct motor.
What do you actually wanna do?

Dieter
 
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Discussion Starter · #7 ·
What do you actually wanna do?

Dieter
I want to use my original instrument with a different gearbox with no out, so I'm thinking using a motor to drive the cable.

The Speedometer is not linear, so it does 30km/h with 200 cable rpm, at 70km/h it's at 700, at 137,5km/h it's 1510 crpm.
 
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