How to straighten cast ali

[Hooli]

After friday afternoon's entertainment of a dick in a volvo trying to ram me into a lorry as I filtered past I now need to repair the pillion peg hanger. It got caught under the volvo's arch & has bent down so the peg is at about 45 degrees.

Anyone know how to do it? I think you heat it (till red?) quench, hammer & repeat. Doing a small bit at a time because it case hardens & will shatter.

[doggydog33]

I'm not sure Aluminium goes red like steel. I seem to remember rubbing a bar of soap on and heating until the soap turned brown.

Reagards, DD

[Hooli]

Ta, I had a feeling it didn't too. Hence asking before I tried it.

Just got a price on a replacement, £75+vat 2nd hand. FFS it's a peg hanger not the whole frame!

[southgate]

+1 for replace. It'll just snap if you try to repair.

[Mort]

I wouldn't heat, quench hammer... that will snap it. Chances are it will snap but heat and bending might work. What have you got to lose.

Watch this too : https://www.youtube.com/watch?v=8-aNNYo24RU

Edited by Mort on Monday 6th July 13:33

[southgate]

Mort said:

I wouldn't heat, quench hammer... that will snap it. Chances are it will snap but heat and bending might work. What have you got to loose.

Your pillion?

[bass gt3]

Problem is the hanger will be of a very low quality aluminium alloy which is cast and with a very low malleability . So typically once it's bent, it won't return to shape regardless of how or what process you employ. Having stretched in the bending, the alloy is now weakened and can't be manipulated back. It'll fracture and snap if you try to reshape it either during the process or worse, later when it's subjected to stress like when it's taking someone's weight.
You'll need to be replacing it sadly...

[Hooli]

Bugger arse n bks then.

I might try it for the hell of it anyway then pay out for a new one.

[bass gt3]

Hooli said:

Bugger arse n bks then.

I might try it for the hell of it anyway then pay out for a new one.

Try to manipulate it in a 10 tonne press if you can get to one. heat it in the oven and give it a small amount of pressure until it cools.
Heat and repeat.
Are there lateral stress lines at the point of the bend? like little hair line cracks running across the outer surface of the bend? Or raised material like a fold on the inside of the bend?
There is also the soot method for heating cast aluminium where you coat it with soot from a dirty acetylene flame, then heat with a clean flame until the soot starts to burn off. Then bend. But it depends very much on the alloy in question. I'm betting it's a low grade alloy with a very granular property which won't bend back.
Also remember that in being bent, it has been work hardened, so it's structure at the bend will have changed..

Edited by bass gt3 on Monday 6th July 14:31

[steve954]

Bend it without heat! Heating it up will make it snap! I've learnt this the hard way, it bent down without heat it will bend up.

[Wedg1e]

bass gt3 said:

I'm betting it's a low grade alloy with a very granular property which won't bend back.
Also remember that in being bent, it has been work hardened, so it's structure at the bend will have changed..

Aye. It might go back to something approaching shape but I wouldn't want to use it as a load-bearing component.

I work in NDT; would you like it x-rayed, MPI'd or dye pen'ed? Although I suspect we could write the report without even seeing the part

[anonymous-user]

I'm in the process of building a 1988 caterham so last week I vidiod a program on how they fitted the body, to bend the aluminium they coated it in soap and then heated it until the soap turned brown, then bent it.

But when ever I've damaged a foot peg ebay.

[MKnight702]

I would recommend heat, lots of it.

Heat the ali until it is nice and runny, then pour into a mould. Pretty much the only solution without breaking the peg. However, what have you got to lose trying? As the engineering adage says "if it sticks, force it, if it breaks, replace it!"

[DuraAce]

Wedg1e said:

Aye. It might go back to something approaching shape but I wouldn't want to use it as a load-bearing component.

I work in NDT; would you like it x-rayed, MPI'd or dye pen'ed? Although I suspect we could write the report without even seeing the part

MPI wouldn't be much use on an Alloy would it?!

Agreed about not using it again though. Even if you could put it back into shape you'll regret it if it snaps whilst cornering etc

Buy a new one.

[Hooli]

Topic over girls.

I've discovered that foot pegs hangers are listed on ebay as footrests. Found one for £20, which is reasonable so I ordered it.

PS. I like the idea about heating until runny & pouring in a mould, I'll have a spare to shape the sand with now...

[bass gt3]

Hooli said:

Topic over girls.

I've discovered that foot pegs hangers are listed on ebay as footrests. Found one for £20, which is reasonable so I ordered it.

PS. I like the idea about heating until runny & pouring in a mould, I'll have a spare to shape the sand with now...

Well there's no fun in that!

[Hooli]

I know, I'll just throw the bent one in a box & revisit this in a few years - by then we should have finished the house & workshop so I can destroy it in peace.

[evil len]

southgate said:

Mort said:

I wouldn't heat, quench hammer... that will snap it. Chances are it will snap but heat and bending might work. What have you got to loose.

Your pillion?

[Hooli]

evil len said:

southgate said:

Mort said:

I wouldn't heat, quench hammer... that will snap it. Chances are it will snap but heat and bending might work. What have you got to loose.

Your pillion?

I missed that, well worth a

My luggage would be closer, I hardly ever have a pillion but the pannier racks attach to the pillion pegs when fitted.

[Wedg1e]

DuraAce said:

MPI wouldn't be much use on an Alloy would it?!

Well spotted
Given the circumstances, neither x-ray nor DPI would tell you much you couldn't see with the naked eye either!