How to straighten cast ali

[dingocooke]

Hooli said:

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.

Hooli,

You need to anneal it first, rub old fashioned soap on the hanger where it's bent, heat up with blowlamp until the soap goes black, then let it cool.
Now you can straighten it.
Once its straight, anneal it again, same way, that way if you bang it again, it wont snap.
I can do it for you gratis if you pop it in post to me; drop me a message
Steve

Ah edit, you did the ebay thing, well offer stands anyway!!

Edited by dingocooke on Tuesday 7th July 15:07

[13aines]

steve954 said:

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.

This didn't work for me when straightening a cast aluminium brake pedal last year - it just broke. I should know better, having studied a materials engineering module at university, but I was desperate to fix it quickly and didn't even have a blowtorch to hand.

Replacement from Triumph begrudgingly purchased for £67, ouch... rare as hens teeth in used condition sadly.

[dingocooke]

13aines said:

steve954 said:

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.

This didn't work for me when straightening a cast aluminium brake pedal last year - it just broke. I should know better, having studied a materials engineering module at university, but I was desperate to fix it quickly and didn't even have a blowtorch to hand.

Replacement from Triumph begrudgingly purchased for £67, ouch... rare as hens teeth in used condition sadly.

Yup; when you bend it, you work harden the material, so it has to be annealed, once you have bent it straight (sic), you have work hardened it (again!), so you have to anneal it, (again!) That way, if you ever bend it (again!) you can straighten it (again!).

[Hooli]

dingocooke said:

Yup; when you bend it, you work harden the material, so it has to be annealed, once you have bent it straight (sic), you have work hardened it (again!), so you have to anneal it, (again!) That way, if you ever bend it (again!) you can straighten it (again!).

That makes sense, thanks.

Like I said, I might try anyway to find out how for future reference.

[13aines]

dingocooke said:

13aines said:

steve954 said:

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.

This didn't work for me when straightening a cast aluminium brake pedal last year - it just broke. I should know better, having studied a materials engineering module at university, but I was desperate to fix it quickly and didn't even have a blowtorch to hand.

Replacement from Triumph begrudgingly purchased for £67, ouch... rare as hens teeth in used condition sadly.

Yup; when you bend it, you work harden the material, so it has to be annealed, once you have bent it straight (sic), you have work hardened it (again!), so you have to anneal it, (again!) That way, if you ever bend it (again!) you can straighten it (again!).

That makes sense, so yes - I should have heated it, bent it, and then heated it again to restore ductility. What a plum - shouldn't have been so hasty!

[dingocooke]

You don't even need a blowtorch, you can anneal most bike parts on a normal gas ring on your cooker; always ask you wife first though...NOT!!!

[Wedg1e]

So have you snapped it yet?

[Hooli]

Well I've fitted the replacement....

We don't & won't have a gas cooker, so I will need a blowtorch for when I try straightening it. Don't hold your breath though, bit busy at the mo.

[Wedg1e]

Hooli said:

Well I've fitted the replacement....

We don't & won't have a gas cooker, so I will need a blowtorch for when I try straightening it. Don't hold your breath though, bit busy at the mo.

Wat's wrong with a gas cooker? Much better than bloody electric. The only thing better than a gas cooker is a twin-burner petrol stove, when you're camping