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speedo gearbox ratio

bodlan

Well Known and Active Forum Website User
VOC Member
Does anyone know the final ratio of the speedo gearbox? The chap servicing the speedo off my Comet needs to know this in order to check the calibration of the speedo.
One revolution of the front wheel produces something like 2 and a bit??? revolutions of the cable. Both Richardson and Stevens tell me the ratio is 1.5:1 between the drive gear and pinion but the worm/wheel must give it a bit more. Anyone know the exact figure?

thanks

Dave
 

clevtrev

Well Known and Active Forum Website User
VOC Member
Does anyone know the final ratio of the speedo gearbox? The chap servicing the speedo off my Comet needs to know this in order to check the calibration of the speedo.
One revolution of the front wheel produces something like 2 and a bit??? revolutions of the cable. Both Richardson and Stevens tell me the ratio is 1.5:1 between the drive gear and pinion but the worm/wheel must give it a bit more. Anyone know the exact figure?

thanks

Dave
With 12 teeth on one pinion, and 8 on the other, you can work it out.:)
 

Paul Ennis

Well Known and Active Forum Website User
VOC Member
The speedo drive ring has 41 teeth and the pinion has 13 teeth, so the ratio into the gearbox is 1:3.154..........then the gearbox has 1.5:1

So wheel rotations/mile x 3.154 divided by 1.5 will give you revs/mile into your speedo.

Paul.
 
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