On Aug 9, 6:52*am, stryped wrote:
I dabble in metalworking for fun. I also run marathons and some triathlons. Been thinking it would be neat to be able to say I built a bike and used it in the triathlon. I have a road bike but not a triathlon bike.

As far as frame, I am limited becasue I dont have a tig welder. I do however have a mig, oxy torch/weld set and arc welder.

I am guessing my choices are aluminum tubing or chrome moly steel.

I can mig weld the tubing with argon and aluminum wire but not sure if this is ideal. I have read you can braze it.

I have read conflicting advice as to whehter it is recommended to mig 4130 or not. (The same for brazing it).

Weight is an issue. I want it to be light but at the same time be strong enough to do a half or full ironman. 56 miles/112 miles.

I appreciate it!

Any heat at all will change properties on aluminum alloys, post-
welding heat-treat may be necessary to get strength back.

Brazing or welding 4130 shouldn't be a problem, the aircraft frame
guys have been doing it for decades. Oxy-acetylene in the early days,
just needs the right filler rod. Lug fittings were the old-timey
method of making a bike, you can make your own from short lengths of
chrome-moly that will make a slip fit on your frame tubing. Get a
book on home-built aircraft, they'll show you some jigs and such that
should be easy enough to put together from plywood.

How about a bamboo bike? Local outfit makes them, gets big bucks,
too. The secret is in the joints. google it up.

Stan