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Smith's Electronic Speedo


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#1 Kap'n Krunch

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Posted 25 June 2020 - 04:49 AM

Hello all,

 

I have tried the forum search tool but not getting anywhere so reaching out to the technical wizards on the forum for this query.

 

For my current project, the two speedos rolling around in the bottom of the spares box were trashed and unusable so I upgraded to a Smith's 200kph electronic unit.  The installation instructions are fairly cavalier when it comes to calibration and setup so wondered if any one had some input data they had used for their own setup.

 

To calibrate, there are 2 options. 1/ you can drive an exact distance and the unit will sense how many pulses it received, or 2/ you can input tyre revolutions per mile and then count the number of spindle rotations that occur while pushing the car 6 tyre rotations (presumably in gear) and then you can calculate the pulses-per-unit for the speedo to use.

 

Counting spindle rotations on a Mini is not humanly possible considering it's location, whilst pushing the car exactly 6 tyre rotations - unless I set up some sort of video recording of the speedo housing.

 

I have reached out to Caerbont Instruments technical department but they weren't able to help.

 

Does any one know a way to calculate spindle rotations?  I am running a standard A+ gearbox with 3.44 final drive and a green 16-tooth speedo spindle.  Additionally, I'm running 165/70R10 wheels that make 1057 revolutions per mile.

 

Any help would be appreciated.  Thanks



#2 Moke Spider

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Posted 25 June 2020 - 05:40 AM

Hi and welcome to the forum.

 

I run Smiths Electronic Speedos and have now for many years, though the ones I run are based on their generic 100 mm type, though, I am pretty sure the calibration numbers would be similar, however as I set mine for kph I'll offer up 2 starting points for you to try.

 

If you enter the Manual Programing Mode try first up 3100 if that's way off, try 5000. These won't be spot on but should well get you well in the ball park. If you have a straight stretch of road and a GPS where you can do some test runs, we can fine tune these numbers from here.



#3 unburntfuelinthemorning

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Posted 25 June 2020 - 07:28 AM

I had to count the number of speedo cable revolutions before sending my non-electronic unit for calibration. 

 

I found it straight forward to do by marking one of the front tyres to count tyre revolutions, standing next to the tyre and moving the vehicle in order to rotate the wheel six times.  I had the speedo cable disconnected from the speedo and the end of the cable in the engine bay with a cardboard arrow attached to the inner cable and the whole thing positioned where it could easily be observed.


Edited by unburntfuelinthemorning, 25 June 2020 - 07:29 AM.


#4 Kap'n Krunch

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Posted 25 June 2020 - 08:25 AM

Thank you both for the input.

 

As this rebuild never started with an engine in the car, I wasn't able to employ the "Unburnt" method before swapping to electronic - great idea, though and obviously works.

 

Spider, that was just the sort of info I was after, many thanks.  Just as a follow up, although my speedo is KMH, the odometer defaults to miles on the little screen.  I couldn't find a mention of changing it to KM's in the setup sheet - did you have to do this or do you know how?



#5 Moke Spider

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Posted 25 June 2020 - 08:45 AM

Glad the numbers maybe of some help.

 

Just as a follow up, although my speedo is KMH, the odometer defaults to miles on the little screen.  I couldn't find a mention of changing it to KM's in the setup sheet - did you have to do this or do you know how?

 

Short answer here is no, I'm sorry.






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