Thursday, October 23, 2008

further construction

fitting some legs


Erik said...

How is welding stainless compared to 4130?

D n L said...

i only braze (for now) so i cant speak on welding stainless.

but as for brazing stainless, it is different to say the least. i have been using mostly nickel silver to join SS tubes, sometimes 50N silver. bronze brazing doesnt work for stainless. to get the nickel silver to flow one has to get the stainless really hot, but without burning the flux and overheating the tubes. another difference is that SS tubing is really soft, which makes cold setting (when necessary) difficult. the 4130 is much more rigid, and generally easier to work with.

some would say that using nickel silver to join stainless tubes is incorrect, but i feel that with the loads carried on a bike rack the joints are more than strong enough. i have also done a bunch of destructive testing and none of the joints have failed. furthermore, it is technically improper to brass braze 4130, it interferes with the grain structure of the metal, or something like that. BUT, for bike applications it is a-ok. just dont go building a personal aircraft out of fillet brazed 4130!

bill said...

very nice work! how did you achieve those nice bends and what size and gauge of tube (4130) did you use? thanx

D n L said...

for the bends i use 2 hand benders. i have a nice large rigid bender for 3/8 tubing that will do a 180deg bend, and a cheapo autoparts store small bender for 3/8, 5/16, and 1/4" tubing. that one can only bend up to 90deg.
this is the same one you can get at an auto parts store, for less $$.

mostly i use a mix of 3/8 for main tubes and 5/16 for the rest. wall thickness is usually .035, with .028 used for certain applications.