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Ernest,
I am not so sure. If this would be the case, OEM's would use it....
Not being a specialist, I am guessing:
stainless is less flexible, more brittle, harder to weld than 4130
There may not be any stainless with similar properties as 4130....
For the relative ease to preserve a 4130 inside I would never bother with stainless.
If you are inot makeing your own frame, it is little extra work to drill/chamfer holes into all interconnecting positions. Use plug screws/bolts to rinse the interior with linseed-oil or SP-400 or whatever strikes your fancy for rust-protection. You also can install a valve and pressurize with Nitrogen or Helium - that way you control wether you have holes.
No holes, no more oxygene than the tubes held before closing - no ox, no rust :))
A relative crude example:
For some "tests" to mount a A/C compressor on a Lyc.-540, we bent up a bracket from stainless (quality unknown), like the one used for the alternator, but taller.
It broke within 5 hrs "operating time". Same bracket made from some non-stainless highstrength steel never expired.....
Thomas
----- Original Message ----- From: "Ernest Christley" <echristley@nc.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Wednesday, February 28, 2007 9:38 AM
Subject: [FlyRotary] Re: engine mount 4130 vs 304 SS
Russell Duffy wrote:
Greetings,
As I ponder my choices for mounting the single rotor engine, I noticed something that surprised me. 304 stainless is cheaper than 4130 steel. One thing that's always bothered me about steel tube type construction is the concern for rusting inside the tubes, so stainless is appealing. There must be a catch here. Is there a good reason I should use 4130 instead of 304? Either will likely be sized much larger than needed, since I don't have the means to do any proper analysis of the strength. Thanks,
Rusty (Autoflight drive supposed to be shipping next week)
Something Richard Sohn told me, and I soon after found to be VERY true. The HAZ of stainless weldment will rust almost as easily as mild steel if not properly treated. It must either be buffed to the original shine, passivated/pickled, or painted. Since you won't have access to the inside of the tube, going stainless may not get you much.
I've often thought of a tube and fabric fuselage made of stainless would make a lot of sense. Most tube airframes are heavily overbuilt just from a materials availability point of view. That is, one size tube is just barely under the stress limit, so there is no choice but to choose the next larger size which give you an extra 50% margin. Any increase in weight from needing to use larger tubes would be offset by the work and weight saved from not needing to paint it. If there was a way around treating the HAZ zone, it could be a winner of an idea.
-- ,|"|"|, Ernest Christley |
----===<{{(oQo)}}>===---- Dyke Delta Builder |
o| d |o http://ernest.isa-geek.org |
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