Tuesday, March 29, 2011

The frame is done!

Another stellar session at the shop (and another late night!). The frame is done bar the cleaning of dried goop and the sanding and filling of holes. All that remains is to construct the extended steerer tube and hang the components! It's hard to believe that in just over two months we have gone from an 8'x4' sheet of birch ply to a complex structural form that has, by & large, come together much as we envisioned. It speaks to the huge potential of computer aided design and CNC technology (I'll take credit for that) but more importantly to Jeff's awe-inspiring craftsmanship (he is, after all, the skilled one in this collaboration). This really hit home to me when Jeff perfectly trimmed the side panels to the head tube block entirely by eye using one of those cool Japanese saws. He then went on to essentially free form the head tube cap in space armed only with a bevel gauge, a pencil and the band saw. I will gloss over the fact the we totally muffed the first attempt by forgetting to drill the hole for the head tube first (duh!) .

The evening started with Jeff demonstrating the strength of the frame by standing on it. I would say it deflected by less than a quarter inch over the entire length. Jeff then nearly gave me a heart attack by jumping up and down on the frame! The frame flexed but didn't crack and I drew another breath. We found ourselves in the odd position of having a cargo bike frame that was very light, extremely strong but flexible as a noodle. And oddly the flex was all in the cargo bed. When we had originally conceived the design our concern, as far as rigidity, was all about the rear end, this being the area where all the energy transfer from the rider to the rear wheel was concentrated and not the cargo bed which we figured would be bombproof. The reality has been the exact opposite; stiff rear end, noodly cargo bed. So the decision was made to add panels to the underside of the cargo bed to fully enclose the struts and lock down the form. This has radically changed the visual of the bike. The cargo bed is now transformed into a stealthy slab which I rather like. "This things going to be amphibious!", chortled Jeff and it's true, it is developing a decidedly aquatic look. We are really hoping this will eliminate the warping of the frame but we do have one more option should we still fall short; fiber glassing the deck but we shall wait and see what transpires when the glue drys......

Next session.....lots of scraping, sanding and then adding parts. Exhausted but stoked we are.

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