Today's Message Index:
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1. 12:46 AM - Re: Metallurgy and undercarriage legs (tennant)
2. 01:30 AM - Re: Metallurgy and undercarriage legs (clivesutton)
Message 1
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| Subject: | Re: Metallurgy and undercarriage legs |
Hi Jonathan,
Without knowing the material and the heat treatment condition it is difficult to
give any advice.
The important property for a spring leg is the yield strength, as stresses above
this Level will bend the leg permanently.
Assuming that the legs are quenched and tempered to increase the yield strength
(probably SAE4130 as they are made in the US), any extreme heating of the metal
will reduce it again so that the next "not so hard" landing will bend the legs
again.
I remember some years ago that the nose wheel legs of the RANS were regularly bent
here in Germany, and we did an Analysis on one and changed the material to
something slightly stronger, but not so that the structure would be damaged instead
of bending on a hard landing.
Sorry I cannot help any more, but I would suggest that a set of new legs is probably
the way to go.
Best regards
Barry
--------
Barry Tennant
D-EHBT
At EDLM - Germany
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=479804#479804
Message 2
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| Subject: | Re: Metallurgy and undercarriage legs |
Hi Jonathan,
My two-pennarth is that there really may only be a handful of experts in the whole
World who could give a fully informed answer to your question. Phase diagrams,
microalloy additions, stress intensity factors - it's another world . .
.
However, general steel industry knowledge tells me that as per many spring steel
grades, susceptibility to fatigue-cracking is made worse by the introduction
of surface blemishes induced by e.g. corrosion, dents/local impacts and even
factory surface hardening treatments like carburisation. So the risk of creating
surface stress-cracks during a local bend repair for the typical grades used
(AISI 6150 et al), is high.
But your S6 friend may find the following EAA article more informative and authoritative
and save themselves a lot of grief . . .
https://www.eaa.org/en/eaa/aviation-communities-and-interests/homebuilt-aircraft-and-homebuilt-aircraft-kits/resources/building-articles/landing-gear-wheels-and-brakes/spring-steel-landing-gears
Quoting here from a paragraph within it:-
"You may as well face it, rebending and heat treating a spring steel gear leg in
your own work shop, with a single welding torch, is not practical. You simply
cannot get enough uniform heat on it, over a wide enough area, to allow you
to bend the metal without inducing stress cracks. Countless builders have tried
to anneal and straighten, or rebend, the gear legs themselves but only a few
have succeeded while many have thoroughly botched the job"
I hope useful
regards,
clive.
--------
Live as if you were to die tomorrow. Learn as if you were to live forever. Mahatma
Gandhi
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=479805#479805
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