31 May 2011

So here’s one for you – can you guess what this is for? Something I couldn’t find a good solution to, so I had some of these made. No? Well it is an adapter to allow a 74mm BCD chainring to fit onto a Shimano cassette body. Not something needed very often, but for a recumbent mid-drive (as on my tandem), it fills a gap where I have not been able to find individual sprockets big enough that aren’t designed for shifting (which means derailing, not what is wanted with the final drive ring!). It will also enable easy fine tuning of the gear ratios by simply bolting a different chainring on.

In other news, this is my prototype folding-road-concept. I wanted to take my folding mountain bike design, but apply it to a lightweight road bike for racing away from home (without paying airline fees). Compared to the mtb this has an additional pivot at the base of the seatstays to allow the rear triangle to fold flat, and so the rear triangle doesn’t need to be removed to pack the bike. As you can see, it looks like I will get it in the case with the fork and stem still in place, I’ll have to see if this works out once I have to fit the wheels in too. I got the bike cabled tonight (pictures to follow!), and a short first ride showed it to feel just like a bike should, more testing to come. With clincher wheels and not too much effort on the parts it is under 15lbs; with a bit more effort and my very light climbing wheels it should just nudge under 12lbs. Which is good as the inspiration for building this is that I have just booked to go back to the UK in October to race in the National Hillclimb championships! It will be interesting to see how I fare after five years away; back in 2005 I was fourth, so hopefully I can still make the top ten.