PiccoLino

Because of the tendency of my Extra 230's landing gear to easily bend, I decided to have a small soldering work inside the 45 degree corner of both aluminium legs.
The work looked like well done since I just meant to add some thickness to the corners only.
So that I mounted the gear and went to fly, but soon I realized that the gear had become much weaker than before.
I mean that the metal is now so ductile that I can bend it with my hands.
Then I made a search and I found out that aluminium can be annealed by heating it at around 600 F and cooling it down slowly. By this metallurgical process alluminium can be softened to fit some manufacturing needs.
Since I have found too little about this subject, my question is:
Is annealing a reversible process? If yes, how can I get the alumimuim strength back?

Stickbuilder

Yes, you can, but you would need to know what aluminum you have. Different alloys have different hardness ratings, and I'm not a metalurgist, however there are some who do come to the forum.

Bill, AMa 4720
WACO Brotherhood #1

MinnFlyer

My Feedback: (4)

I know enough about aluminum to know that it is a much more complicated process than steel.

If I were you, I would just buy a new set. Maybe get composite or carbon fiber next time

scratchonly

I have read in this forum that you can restore temper in some alum by heating in a 350 degree oven for 6-8 hours. Maybe someone can correct/verify this. Easy to try tho.

bbbair

Let's go directly to 'PLAN C'.

Buy some music wire and make a new set of landing gears.

HOWEVER; this time build in a spring action (only 1-2 turns) this will prevent the everpresent problem of bending the gear back.

j.duncker

My Feedback: (2)

Carbon fibre replacement is the way to go. Lighter stronger and more resilient.

Hey it's only money!

But this will work as well. Add a piano wire anti spreading device. The U bolt needs to go though the ply uc mount.

PiccoLino

Ok, let's assume that restoring temper in aluminium is impossible, but why should I replace it with a carbon fiber one?
Actually I have neglected to mention that my plane stays in the over 20 pounds category and so far I haven't seen planes this size with carbon fiber landing gear on, have you?
I think that I will give a try to what scratchonly says (350 degree @ 6-8 hours), on the other hand I have nothing to lose because the gear strength cannot get any weaker than the present.
Just one more question: are those 350 degree Celsius or Fahrenheit?
Thanks.

MinnFlyer

My Feedback: (4)

I've seen a 40# plane with CF gear

PiccoLino

Well, I get no doubt that CF can be used for very heavy duty stuff. I have seen F1 race car suspensions made by CF.
Let's put it down in this way: I can find CF gear for up to 10# planes and I am not willing to search throughout the rest of the world for it, as I can go to my friend's workshop again and get a couple of alum stripes bent in a couple of hours at longest.

scratchonly

Farhenheit.

rclement

My Feedback: (1)

I had some problems with some soft aluminum gear due to the temper of it (or lack of it) from the factory. I was told by a professional heat treat man that heating it at 350 degrees F (176 C) for 6-8 hrs. would bring it to T6 condition. You could try that.

PiccoLino

Thanks a lot Rob, this is the answer I wa looking for.
Cheers,
Franco

scratchonly

Be sure to let us know how it works out.

rclement

My Feedback: (1)

Siete benvenuti. Buona fortuna con il vostro progetto. You're welcome. Good luck with your project.

jeff1127

You should check the data sheet available on line for the specific alloy you are working with.
Incorrect treatment could have adverse effects on the material. If you had 6061 t6 alloy and performed welds on it then it would certainly be weaker without heat treating but heat treating is a very involved process and the temperatures used are beyond what we as modelers usually have available.

jeff1127

Following is the process listed for aging (hardening) for 7075 alloy. I was incorrect in the above post. The annealing process uses much higher temperatures than the aging process so it is possible.

Aging Precipitation strengthening (aging) is done at 250 F for 24 hours and air cooled for T 6. The T 73 temper requires heating to 225 F for 8 hours followed by 24 hours at 325 F and air cooling.