I’ve picked up a little lay knowledge over the years, I’ve found the ally used in bike frames is quite hard and not very ductile while the filler rod used for welding it seams to be softer and more ductile, probably because it needs to melt at a lower temperature than the ally it’s joining.
any stress
left in a frame tube is likely to be transferred from the ridged tube into the more ductile weld making it a potential week point.
I’d say that if the frame is
bent so it stays at the required size after bending, it is no longer under stress.
Alternatively, if a frame is only pulled apart long enough to get the wheel in ( without the wheel it returns to the original size ) while the wheel is in place the frame will still be under some stress.
On a recently project I cut my chain stays in order to make them about 4inches longer, In order to do this I needed to bend the seat stays a fare bit.
Working with bolts, blocks of wood, a crowbar and lots of huffing and puffing the frame tubes didn’t want to bend and I felt my efforts were being transferred to the weld. I stopped before I did any damage.
knowing a little of the properties of ally, I got my blowtorch out and heated the frame where I wanted it to bend, with very little effort I bent it to the desired position and once cool all the original rigidity returned.
(I also had to bend the chain stays a few degrees as well)
I machined two pieces of ally to fit the gap I’d created and took it to a local welding company, job done (well not quite as I needed it powder coated)
Ive probably only done 200 miles on it so far but I’ve every confidence it will hold together, I’m even considering an E conversion
