So with the project at a virtual standstill right now I have got to enjoy one of my other favorite past times. With camera in hand and some image fiddling on the computer I have been playing at being artsy with bike bits. Here are the results...
Nine years ago I moved from London to Seattle, WA and once I settled down and figured that I would be here for a while it was time to find a cool ride to keep me busy and out of the pub. I settled on a 1942 BSA M20 - an old English army bike on which I could relive all of my Steve Mcqueen fantasies of exciting chases and jumping barbed wire fences.
After much searching I found the bike I was looking for, rough but complete, and after two years banging away in the tool shed I emerged proud as punch and ready to take on the streets. I took my motorcycle test and I was soon racing around trying to escape from prisoner of war camps. Now anyone that has ridden one of these old BSA's will know that you are not going to be able to escape from anyone, and the thought of getting airbourne to flee the country, well, it just isn't going to happen.
Four years later, and I started to realise that 60 mph is a bit of a crap top speed, and suspension might make rides over 2 hours a little easier on the back and arse. So I started hunting for a new project. I came accross a 1956 Norton Dominator Featherbed frame complete with Roadholder forks and decided a Triton was going to be the next project. I soon found a 1958 Triumph T110 650cc motor and a Norton Gearbox (thanks to our friend Ebay) and the major components were there. Atleast that is what I thought.
This blog is an attempt to catalogue my struggles of putting this bike together. Be patient, it might take some time....
Gearbox ratios are for a standard four speed AMC gearbox.
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Smiths Chronometric Speedo Fitment
The calculation for determining the speedo series number is 1680 x A/B, where A is the number of turns of the speedo cable for six turns of the rear wheel; B is the radius of the rear tire in inches; 1680 is a constant.
Find the drive ratio as described in my post above. Let's say it's 2:1. Let's also say the tire radius is 13.1 inches. The calculation then is 1680 x 6 revs x 2(drive ratio) divided by 13.1 inches equals 1538.9. This number is within 10% of 1600, so in this case a 1600 series speedometer head is required. (A 15 to 12 drive will alter the number to 962, in which case a 1000 series speedo is required.)
This gets you to within 10% which is the adjustment range of a Smiths unit. The final tweaking can be done internally by a specialist. Or the unit might be spot-on, as is.