The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Frame => Topic started by: Rich on 16.05. 2021 11:39
-
Having put a sidecar on my A10 I had lean out on the front tyre but not on the back, which is telling me it's twisted the wrong way, checking my spare on the bench that seems to be twisted as well , W hat is the procedure for straightening I only have a 12 ton press as far as I can see there is no way it will do the job as I can't clamp the arm down, so is this a job for a specialist?
-
As you identify, not easy without a large press, as you need to clamp it down. There will no doubt be ways one could improvise, such as jamming the front end in something solid and easing the forks with a crowbar or something but hard to give advice in such a scenario.
-
also difficult to actually see how much its twisted as the castings on the lugs are not the same, so I am going to turn some spacers for both the bush end (no bushes fitted) and the spindle ends and put some rods through to actually get a measurement I did think heat around the bush end gusset to make it easier to move, but worried that I may compromise the steel.
what does the panel think?
-
also difficult to actually see how much its twisted as the castings on the lugs are not the same, so I am going to turn some spacers for both the bush end (no bushes fitted) and the spindle ends and put some rods through to actually get a measurement I did think heat around the bush end gusset to make it easier to move, but worried that I may compromise the steel.
what does the panel think?
In my experience if you can work out how something got bent eg where the force (s) were applied you will have a fair chance of it returning to it’s original shape by “reversing” the same force.
In the case of the swing arm the chances are the force on the wheel end was applied by the wheel and bent it, so a “dummy axle” , preferably bolted in like the wheel axle, could be used to twist it back. The swing arm bearing end was obviously held by the swing arm bearings and shaft.
I would not be surprised if you could make up some brackets to bolt the bearing end to a heavy bench, and put some bar (fairly long) through the spindle end and just use brute force to twist it back to shape. You may need to make up something “fork” shaped for twisting the spindle end if the dummy axle is not strong enough and bends. I guess you are just bending it a few mm?
The issue with applying heat is that you are not “reversing” the force and you will get a local bend, not a bend spread over the length of the bent tube.