Tuesday, July 7, 2009

Some technical stuff with vintage 3-speed bicycles

G'day All!

I have not been active much over the past few weeks with my cycling. I had a nasty bought of Influenza recently, and I am in fact still recovering from it. However, I've been crunching some numbers and working out what modifications to make on my bicycles. For the purposes of keeping everything simple, I round the final number of gear inches to the nearest whole number.

My "Malvern Star - Skidstar" (Standard straight-framed version, not the distinctive curved-tube GT version) has received the 27" wheels that were previously in the "Universe". The gearing set-up has been a 46-tooth chain-ring with an 18-tooth sprocket. This gave gearing of 52"/69"/92". Rather high, and uncomfortable, unless you are riding in dead-flat country. A larger 20-tooth sprocket will reduce the gearing to 47"/62"/83". This gives a much more acceptable range of gears, even if it does curtail my top speed somewhat. I find that a gear of about 48" is good for climbing moderate hills.

The "Universe" is currently running as a single-speed bicycle with a 44-tooth chain-ring and an 18-tooth sprocket. This gives a gear of about 68" or 69". I have a Sturmey-Archer AW 3-speed hub which I intend to lace into the 28" rims when the opportunity arises (my first foray into wheel-building!) The use of a 20-tooth sprocket will give a slightly-lower gearing of 46"/62"/82" .

With any luck, both bicycles will be complete in time for the 2nd Annual Canberra Vintage bicycle ride in September. This does create a few problems for me. Assuming that both bicycles are ready, I would need:

1.) A way of getting them to Canberra (Free bicycle carriage only goes as far as Goulburn, and after that there are basically zero bicycle facilities on trains).

2.) A friend willing to be the caretaker and rider of the second bicycle. (thoughts turn to Michael, who is a good sport, and would dress up appropriately for the occasion).