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An appeal for help from the STW metal workers:
Bumped the caravan into the house the other day and it's torn off a piece of the trim/awning bead and bent it. The bead is extruded aluminium, dunno what kind particularly but it's relatively malleable since I bent a little bit before to help get the awning in and also it's bent this far without snapping. My intention was to cut off the offending bit, flatten it out and glue it back on.
Now - I don't want to snap it whilst trying to bend it back, so what's the best approach? Bending it by hand or beating it? I saw some chap on telly beating alu sheet and he annealed it first with a blowtorch... wonering if this is going to help? He showed how to use washing up liquid to get the right temp.
If it's 7000 series then you want shampoo (organic) to work out the temp.
IS there a 7 stamped on the back?
I doubt it!
I guess I will try annealing it. I'll try different levels of heat until it gets nice and bendy.
I don't think you'll need to heat treat it. If it's already been bent to shape as part or manufacture then it's soft enough to keep working. It won't have been re-treated to harden it after fabrication in this application. I know copper needs to keep being re-annealed as it will harden as you work it, but I don't think that's the case with alu, if the alu is soft it'll stay soft unless you use heat to tell it otherwise. It can be very soft, quite often clay-mation models have an alu armature inside them.
I use black marker pen for annealing, when it starts to disappear, you are there, but be quick...
Cool.. thanks.. I guess if it's soft to start with there's less risk of it snapping. It's obviously been extruded and then bent to the curve of the caravan, and I suppose that was probably done cold.
I'm thinking of putting it on a block of wood and hammering it flat from the reverse side of the bend.
Of course, some aluminiums age-harden... 😀
I wish my caravan had age hardened...
Something tells me it's not a stress-bearing part?
No, it's just trim. I suppose you could fit an awning into it but it's on the opposite side to the door so that'd be a bit weird 🙂
Aluminium does work harden. If you need to anneal cover soap then heat until it turns brown/ black
Or use the marker pen. Be careful heating up as it melts at a low temp. It may not need annealing be gentle when bending back
Right, finally got around to doing this. Took 6 months to get the garage to a state where I could work in it 🙂
Removed the trim, it's pretty tough and very hard to bend. I'm going to try annealing it. I wonder if there's a way to re-temper it afterwards to get a bit of strength back, using simple garage tools? Again, not a load bearing part but it'd be nice if it was back the way it had been originally...
What could possibly go wrong? 😉
What could possibly go wrong?
Over enthusiastic annealing
[img] http://t3.gstatic.com/images?q=tbn:ANd9GcRCizy3kYA_pa9Tdq4mplXBcIP_E31EwDkVe36d2m56mjs6IqcH_SiYiGCC [/img]
what Kempy said
Well I tried. You have to heat it up a lot, good minute or so with a blowtorch, and it does become malleable. However the bit was too badly damaged to fix.. gonna need some more. Now, where to find a wrecked caravan, other than the one in my drive? 🙂