• Welcome to the website of the Vincent H.R.D. Owners Club.

    Should you have any questions relating to the Vincent H.R.D. Owners Club, or Vincent H.R.D. motorcycles in general, please contact Graham Smith, Hon. Editor and Webmaster by calling 07977 001 025 or please CLICK HERE.

    You are unrecognised, and therefore, only have VERY restricted access to the many features of this website.

    If you have previously registered to use this forum, you should log in now. CLICK HERE.

    If you have never registered to use this website before, please CLICK HERE.

PR: Proprietary Items Speedos to rev counters


vibrac

Well Known and Active Website User
VOC Member
How similar are mechanical speedometers and rev counters? apart from the dial face how complex is the change for a specialist and has any nonspecialist here done it?
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
How similar are mechanical speedometers and rev counters? apart from the dial face how complex is the change for a specialist and has any nonspecialist here done it?
Simplistically I assume that chronometric speedos and rev-counters convert revolutions of the cable drive to a "pulsed" movement that outputs to a graduated movement of the needle. I think later instruments use magnetic force to drag the needle round. You would have to make sure that the gearing suited the amount of movement at the needle and make up your dial marking by checking against maybe another rev-counter. Only guessing, an expert might tell us something different.
 

TouringComet

Well Known and Active Website User
VOC Member
VOC Forum Administrator
They both count revolutions per unit of time, so I suspect they would be very similar. Converting revolutions to distance is simply factored into the gearing internal to the device, dependent on tyre diameter of course.
 

ClassicBiker

Well Known and Active Website User
VOC Member
Simplistically I assume that chronometric speedos and rev-counters convert revolutions of the cable drive to a "pulsed" movement that outputs to a graduated movement of the needle. I think later instruments use magnetic force to drag the needle round. You would have to make sure that the gearing suited the amount of movement at the needle and make up your dial marking by checking against maybe another rev-counter. Only guessing, an expert might tell us something different.
I would have to agree with you Ed. What I have read on Smiths speedometers is the numbers on the face indicate the model and the number of rotations of the cable per mile. Which I take is for there for the odometers but it would stand to reason that if the number is say 1000 and I cover a mile in one minute the cable turned 1000 rpm. So if the cable is spinning a 1000 rpm the needle will move to the 60 MPH mark. So if I know the ratio of my speedometer drive I know how many RPM the cable is doing for a given speed. A tachometer that is driven from a gearbox on the end of a camshaft is running at 1/4 engine speed times the gearbox ratio. If that gearbox ratio is 1:1 for argument then the cable is turning at 250 RPM for an indicated 1000 RPM of engine speed. So if you were to hook it to a cable turning at 1000 RPM is would indicate 4000 RPM.
Steven
 

Latest Forum Threads

Top