Thanks guys for all your motorcycling memories, you have all had more machines than me it would seem. My best bike was a pre unit 650 Triumph Trophy much modified with a BSA Goldstar front end. Bob Joyner cams, SW valve springs, 10.5:1 pistons etc. also running twin Wal Philips so called fuel injectors. After much playing with gearing it would just hit the ton in third and about 115 in top, I used it a bit in amateur sprinting, best time ¼ mile standing start was just under 15 sec.
This was also my road bike and to be honest I have no right to be here but it was the best fun ever. I sold it after putting in the third crankshaft, over revving by not having a rev counter (and oh yes getting married).
Just had a few beers with a friend I met on my first day at school who had moved to South Island, He and his partner have come North to look after his mum so good to catch up. A 1928 Triumph 247cc motorcycle has emerged from a shed and now there is a need to cut some change gears to cut the correct threads needed for items such as a front axle, foot pedal mounts etc.
Why did I feel the need to go metrickery? If I had an Imperial lathe none of the threads I deal with regularly would be a problem.
Olderdan, I have an inkling that I may be exploring making taps any tips?
We know that some metric threads can be cut with inch leadscrew but from my searching it would seem that the reverse is not that straight forward, especially
26 TPI. Maybe some of the more mathematically minded on HMT might help (I can think of a few).
To be honest I would probably buy them at the prices these days, they seem a lot cheaper than when I made mine.
In the UK I buy from Tracy Tools and they ship world wide.
By the way will the bike look something like this.
Good luck with it.
The magic ratio relating metric and inferial is 1.27. (The prime factors of 254 are 2 and 127). While a 127 tooth gear is doable, it's generally very unwieldy for the averge banjo. Approximations are in order.
Using my GEARFIND program, the simplest two gear approximation is:
47:37 = 1.27027... with an error on the order of 0.02%
If willing to go to a four gear set...
30:23 - 37:38 = 1.27002... with an error on the order of 0.002%
Using gears with larger numbers of teeth can produce better approximations but I've searched for small tooth count sets to keep them of reasonable diameter. You're free to download the program and explore it more fully if desired.
Home Shop Freeware
Paul Jones (09-23-2017)
I reversed the controls. That is; the throttle stop and cable were put on the air valve as was the ratio adjustment. So instead of 3 adjustments each time there was only 1. It made them so much easier to set up. In Australian racing at that time we could use any fuel and I made some WP clones with larger fuel valve spindle to take the larger holes needed for alcohol.
Click on pix for full size versions.
Here is a pic of the WP "injector" for those unfamiliar with it.
On the left is the original crazy linkage, on the right is my simple but very effective modifications.
Pit work 1960s style, adjusting my WP clone.
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