Indian-made motorcycle speedo and tacho

[Tony Griffiths]

Hi all, I have an anticlockwise 2:1 chronometric tachometer and a matching speedo ("Smiths" on the faces, but made in India nonetheless) and I'm intending to used them in my Special. Has anyone else done this? -- particularly the speedo. Speedos are a black art for me, I literally have no idea about ratios or anything, whether or not there is a fixed ratio for speedos. How does one match up a speedo swap otherwise?

Also, does anyone offer a tacho drive conversion from under the distributer?

Well, I've never done it myself, but the builder of my Ulster Replica did. He cleverly used a pair of decent-looking speedometers from a Ford 10, leaving one as a speedometer and making the other into a rev counter. To get them working correctly, he built onto the back of each a train of Meccano gears—having first calculated the effect of all those ratios built into the transmission system and, I suppose, the speedometer itself. I believe the calculations ran to a sheet or two of A4. He also converted the bottom of the distributor housing to take the rev counter drive using the speedometer cable from a Land Rover. Tony Betts used to do a conversion kit: www.7ca.co.uk/
If you can get hold of a copy of "A Guide to Building Reproduction Austin Ulsters" by Chris Gould, there's a section by Vinc Leek devoted to the problem you have including discovering the TPM - the turns per mile - of the drive cable. Another tip in the book is to contact your local Tachograph agent; they can supply small gearboxes for fitting to the drive cable to get the ratio correct. This company can convert your instruments and can also provide suitable parts to do the job yourself: https://www.speedograph-richfield.com/  Also, see this older "Friends" post: https://www.austinsevenfriends.co.uk/old...7&cmd=show
and this one on revcounter drives: https://www.austinsevenfriends.co.uk/for...r#pid96357