|
In 2002 I had some good races with Hachi, despite a few drivetrain problems. But then in September, when I was just testing the addition of a chain keeper to the final drive, the frame snapped! That's the nature of trying to build a lightweight machine; the failure was at the headtube area - when I designed the frame I had debated about whether to include a gusset here or not.... turns out I should have! So over the winter I had the anodising stripped, the crack welded up, gussets added, the frame re-anodised, and then I was able to put it all back together. The rebuilt version has more lumbar support on the seat, a neck rest and SRM cranks fitted - hopefully I can now get some empirical data on its performance.   ...
I had thought about making a tailfairing for Hachi, but last year was too involved with Mango, and I never really got motivated over the winter. But some friendly taunting by a certain Razz-Fazz riding German on the BROL message board prompted me to get on with knocking something together, so in the last couple of weeks I've built a fibrelam skeletoned foam tailfairing, just in time to test it at the first BHPC event of the year at Manchester velodrome. Basically it consists of several sections cut from fibrelam, with widths appropriate for my hips, body, shoulders etc, built into a rigid frame that slides onto the bike via two dropout mounted brackets, being secured with two bolts to the seat (I wanted it to be easily removable for transport and storage). The top section is done similarly, but in foam, and the whole lot was then wrapped with camping mat type foam. The top section is designed to match up to my helmet.  Mounting brackets attach to the rack mounts that George handily left on the dropouts when he built the rear triangle.  Checking how well the foam structure matches up to my helmet - the neck rest was a necessary addition to ensure my head is always in the same place!  How the skeleton shapes up from the front.  Yes it could be a lot lighter - but I wanted something done quickly, and that I could change relatively easily if necessary. Hence big sections and mostly bolted construction. If the results show that it is worthwhile, then I will probably build a carbon one later. 
Onto adding the foam. It was tricky trying to keep it smooth; there are a couple of kinks at the front, but the sides follow the profile of the skeleton pretty well. It nests on to the helmet nicely. Should be good enough to prove the theory anyway.   ...  
And so onto Manchester. I did the 30 minute plus three laps race on Hachi with the new tailfairing on. My average speed was 33.15mph, with average power of 275W. My knees were hitting the handlebars a bit, due to the thicker foam on the seat I think - I will move the bars up a little to compensate. My upright bike fitness translates well to Hachi - the positions are similar, just Hachi is rotated back by ninety degrees or so. But I haven't done any speed work at all so far this year, so later in the season, and with a bit of recumbent conditioning, I should be looking at over 300W for an hour. After racing the Mango for the same time it was back onto Hachi, this time without the tail, to get some comparative data. Over 15 minutes plus three laps I averaged 30.15mph and 240W. So not as easy to do the comparison as if the powers were the same, but with a bit of use of the analytic cycling website, I was able to conclude that the tailfairing is worth 1.5mph, or 35W. Not as great as I hoped, but not bad as a first attempt. I think I need to get a better fit between my body and the start of the fairing, and then when the shape is finalized it will probably be worth making a carbon one. We'll see how the time goes!  |