Thursday, April 30, 2009

Frame Class, Continued




Frame completely assembled. Brazed on chainstays, seatstays, rear caliper brake bridge, and top tube brake cable stops. All that remains is cutting down head tube and seat tube, reaming and facing head tube, reaming seat tube, chasing and facing bottom bracket, and cutting the fork crown. And filing all those ugly blobs!

Today was a milestone for me, as I did my final brazes unsupervised. Of course, I also set my shoe on fire, but that's another story...

4 comments:

poser said...

so give us the skinny - do you feel confident that you could actually make serviceable frames with this class? or do you think a serious frame builder should have some time working/apprenticing with an experienced frame builder for a period of time before he/she is ready to produce frames for the general public? what would you say the necessary tools would be for someone who wants to do this? is it cost prohibitive to set up a hobby shop for frame building? or would plunking down the necessary change for the tools to have a decent shop only be justified by a business?

very curious to see where you go with this...

Nic Pottier said...

What I want to know is when can we get together to build a tall bike!!??

Anonymous said...

I have a bunch of questions too Ted. When building a custom frame will you take many measurements of the rider? I ask because every body is different. Two people of the same height/weight could have vastly different inseams, torso length, arm lengths, etc. In fact people with the same length leg may have differences in the length from hip joint to knee joint and from knee joint to ankle joint. Are these measurements manifested in the design of the frame or is frame design still somewhat of a one-size-fits-all? Also how does this relate to the cranks? Are there many different sized cranks? Seems like different bodies would need different lengthed cranks for a perfectly suited pedal radius. I'd love to have a tailor-made frame some day. I imagine it would feel very different than any bike I have ridden so far. Have a great time Ted. Bob

Ted Diamond said...

Hey, Bob -- yes, getting detailed measurements, as well as understanding how the rider intends to use the bike, is definitely a part of the custom frame-building experience. For this class, since I was building for myself, and I really wanted to focus on the building itself, I just took measurements from an existing frame. So, ironically, I still have not had a custom frame built just for me.

In the class, we did go over frame fit "systems" for deriving optimum dimensions from body measurements and rider interviews: top tube length, seat tube length, bottom bracket drop, head tube and seat tube angle, wheelbase, and fork rake and trail.

Once the frame is built, other factors can influence the fit of the bike: stem reach, handlebar dimensions, saddle height, forward-aft saddle placement, and crank arm length.

Crank arm length is somewhat limited by the need to maintain pedal clearance when cornering (Although some kinds of frames, like cyclo-cross frames, have a higher bottom bracket, and can accommodate longer cranks with ample clearane). You can generally get cranks arms measuring 165mm to 175mm (and even up to 180mm). For my body size, and my preference for turning higher gears, I prefer 175mm arms.