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March 19, 2019, 20:45:00 PM

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Author Topic: Straightening aluminium retract leg  (Read 644 times)

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Offline StevieM

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Straightening aluminium retract leg
« on: March 06, 2019, 14:05:41 PM »
Folks,

I am wondering if anyone has any advice on safely straightening out a cnc-machined retract leg.
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I have no idea of the alloy type used, but there is no sign of any visible surface cracks from the abuse it has had.
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Please comment if you can.
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Many thanks, Steve


Offline itsme

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Re: Straightening aluminium retract leg
« Reply #1 on: March 06, 2019, 14:18:07 PM »
blowtorch and gently bend back?

Offline StevieM

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Re: Straightening aluminium retract leg
« Reply #2 on: March 06, 2019, 14:45:22 PM »
Tks for you reply.
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I was going to try that, using the technique of covering it with soot from a candle, then heating with torch 'til the soot disappears to ensure I reach the correct temperature to allow it to be straightened.
I am just not sure if it will remain too soft for subsequent use.
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Rgds, Steve


Offline itsme

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Re: Straightening aluminium retract leg
« Reply #3 on: March 06, 2019, 15:28:41 PM »
I know aluminium hardens back up, not sure about whatever alloy it is.

Offline PDR

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Re: Straightening aluminium retract leg
« Reply #4 on: March 06, 2019, 16:13:05 PM »
You need to be very careful about how much heat you use with aluminium alloys. Ideally you want to take a hardness reading before you heat it so that you know how much you need to reharden it (but I'm guessing you don't have a rockewell tester to hand!). It would work-harden slightly when you rebent it, and then if it's a dural-ish alloy (one with some copper and pinch of manganese to taste) it would age-harden, but that's problematic without a means of testing it.

If it's an all-machined-from-plate item I would guess it's propbably 2014 or similar. You can anneal 2014 by heating to about 410degC for an hour (for a small part) in an oven and then switching it off and letting it cool with the oven for a couple of hours before taking it out to air-cool. In that form you should be able to bend it straight again, but try to do it in one bend rather than bending it too far and trying to bend it back (which will harden it and start a crack).

You will then need to re-harden it. You could do this by heat treating - flame-heat to 500degC and then water-quench, and then to get a useful temper you'll need to oven-heat it to ~150degC for (say) 30 mins and then air-cool. If it is indeed 2014 that should get you to about a T6 temper which is what I'd expect for this kind of thing.

Alternatively you could strain-harden it using vibration. Anneal the part as above, bend it to shape and then bolt a weight where the axle would be (or onto the axle). Then clamp the top of the part to something that vibrates (like a washing machine on spin-cycle) and the weight will shake around - this action will work-harden the alloy very effectively. This is how the old club-20 super-silencers worked. When they were brand-new they were freshly annealed by the welding process, so you could bolt it to the engine and be pretty aggressive in bending the header to fit it tightling inside the cowl. But as soon as you ran the engine the vibration would shake the whole thing, and it would fully harden the header in about a minute of running, "fixing" the fit of the pipe. After that any attempt to rebend it would just crack it...

HTH,

PDR
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Offline paulinfrance

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Re: Straightening aluminium retract leg
« Reply #5 on: March 06, 2019, 16:19:13 PM »
Order a new one before starting, or just make a new one,,,  :''
Mode 2 THE only way to fly

Offline StevieM

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Re: Straightening aluminium retract leg
« Reply #6 on: March 06, 2019, 19:57:02 PM »
My domestic oven has max 250C.
I do have IR thermometer though.
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I'll give it  a go.

Many thanks for your responses, very much appreciated.

Rgds, Steve

Offline StevieM

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Re: Straightening aluminium retract leg
« Reply #7 on: March 07, 2019, 16:24:53 PM »
My only reliable method to gauge temperature was to use the soot method.
Seemed to take forever for the soot to clear, but bent back nicely in vice.
Cannot see any cracks.
PDR...really appreciate your detailed response, but I will test like this, hoping it will naturally strengthen over time, and monitor closely.
Thanks again, Steve
« Last Edit: March 07, 2019, 16:26:14 PM by StevieM »

Offline itsme

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Re: Straightening aluminium retract leg
« Reply #8 on: March 07, 2019, 17:03:19 PM »
looks a good job!


Offline PDR

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Re: Straightening aluminium retract leg
« Reply #9 on: March 07, 2019, 22:14:34 PM »
PDR...really appreciate your detailed response, but I will test like this, hoping it will naturally strengthen over time, and monitor closely.

Try the vibration-hardening option - it can be very effective for something like this

PDR
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Offline itsme

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Re: Straightening aluminium retract leg
« Reply #10 on: March 08, 2019, 08:21:06 AM »
Try the vibration-hardening option - it can be very effective for something like this

PDR
ask the missus if she has anything that could help with that..... :''

Offline Martyn Griffin

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Re: Straightening aluminium retract leg
« Reply #11 on: March 08, 2019, 14:31:49 PM »
ask the missus if she has anything that could help with that..... :''
Washing Machine on spin?

Offline StevieM

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Re: Straightening aluminium retract leg
« Reply #12 on: March 08, 2019, 20:06:09 PM »
ask the missus if she has anything that could help with that..... :''

I just showed her this comment....this went over her head for split second, then saw the funny side!!


 

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