a question for framebuilder-y types.

i'm interested in learning to poke frames at some point. (in the near future if i'm so lucky.)

i figure it's more cost effective to destroy old beater frames than it is to potetially waste new columbus/other spendy tubesets for fooling around and learning.

how difficult would it be to unbraze and rebraze tubes on a lugged frame?

http://www.ollierkkila.com/Site/?page_id=4&album=11&gallery...

a transformation similar to that would be what i intended to do.

i'd want to rip apart an old lugged 4130 schwinn (since they're so cheap/plentiful), replace the seat and chainstays with shorter ones, change to a completely silly looking 1 1/8" integrated headtube with a steeper angle, and if it would be beneficial, wrap the chainstays, bottom bracket shell and downtube in carbon fiber for added stiffness where i need it similar to an old ridley gladius carbon-wrapped aluminum frameset.

for a bit of background, i've been a mechanic for the better part of a decade, i've been doing armchair auto chassis/engine/suspension engineering (simulations) for over a decade, and bike engineering for a good few years as well, so i'm not super green when it comes to forces and knowing the shapes and angles and lengths i'd be after in many cases. i also have access to a jig and a means to cut tube ends, and if not, i could likely just build one and find a machine shop for the tube cutting.

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Permalink Reply by S on January 2, 2013 at 4:18pm

Unless the carbon fiber stuff is superficial, you'll need a mold and a pressurized oven to get carbon fiber and resin to cure and form something that provides structural support.  I suppose if you talk to Ruckus or someone similar, they can do it for you but it'd probably be expensive.  Even more so if you want carbon fiber wraps on the BB shell and anything that isn't just a tube.

Permalink Reply by zerofivenein on January 2, 2013 at 4:34pm

oh, i'd want to do it myself, since it would be practice for when i got around to building my own frames.

i'd likely go for room-temperature cure stuff initially which would likely result in less stiffness for a given weight, but would be doable in a garage without an autoclave. similarly to http://forum.slowtwitch.com/gforum.cgi?post=3708103;


the carbon would likely be used structurally to build up/thicken the outside diameter of the steel tubes/bb area vertically, and probably be applied in a manner similarly to that used when building a bamboo/carbon-lug bike if i'm lazy, or a foam-core monocoque if i'm feeling adventurous.

Permalink Reply by Doug Haynes on January 2, 2013 at 6:51pm

Not true.

You can lay up carbon with vacuum bags and heating elements; how do you think they repair carbon structures on aircraft?  It ain't easy to find an over to fit an airplane...

S said:

Unless the carbon fiber stuff is superficial, you'll need a mold and a pressurized oven to get carbon fiber and resin to cure and form something that provides structural support.  I suppose if you talk to Ruckus or someone similar, they can do it for you but it'd probably be expensive.  Even more so if you want carbon fiber wraps on the BB shell and anything that isn't just a tube.

Permalink Reply by djm on January 2, 2013 at 7:09pm

notoriousDUG said:

how do you think they repair carbon structures on aircraft?  It ain't easy to find an over to fit an airplane...

...they do have large autoclaves for building them, though.

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