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Ernest,
I agree, once you stop air-exchange on the inside it cannot rust a lot for lack of oxygene.
Question: "Rust Wars" - did you never prime or "SP-400" the frame while assembling?
I know primer is just that, primer for paint and should not be considered protection, but it is better than nothing?
Wiping with WD-40 helps, but comes fairly fast unless stuck with dust. Also when you need to weld you have to clean extra well not have any of the oils of WD-40 inthe weld area.
Also just plainly painting the frame any cheap paint is good, sand/grind/blast where you need to work and when all is finishes do the one time for all blast/clean/etch/prime/paint/polish/IDKW ......
Thomas
"..not pulling your hair, just looking for arguments - I am still in the plannig fase, so any and all mistakes you guys ever made and are willing to tell, I hopefully will avoid! Thanx"
----- Original Message ----- From: "Ernest Christley" <echristley@nc.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Wednesday, February 28, 2007 10:56 AM
Subject: [FlyRotary] Re: engine mount 4130 vs 304 SS
Russell Duffy wrote:
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.
Hi Ernest,
I can't say I've ever heard of, or thought about this problem. I know that the weld will carbonize (I think that's the correct term) if air is allowed to contact the weld before it cools a certain amount, and shielding gas can be used inside the tube. Would this prevent the rusting you're talking about?
I don't know. I've just tried to clean up the welds I've made 8*). Richard, can you jump in here?
Lynn, it's actually not very hard to weld stainless. If I can do it with my Harbor Freight torch, anyone can handle it. You just use a fairly rich flame. The test welds I ran broke just like my 4130 welds, right next to the weldment.
Thomas, I don't see the benefit of stainless being the protection of the inside of the tube. The benefit would be not having to treat the OUTside. Having sandblasted and painted a Dyke Delta airframe after fighting the Rust Wars* for several years while I was putting it together, I would sacrifice a few things not to suffer that pain again. I wouldn't substitute any old tube into an existing design, even though in a typical tube fuselage the tube diameter and wall thickness are chosen for many reasons other than absolute strength (construction practicality, buckling resistance, inventory simplification, etc). A switch to stainless would require a clean sheet design, but I think it could possibly be easier to build and lighter when all is said and done.
*Rust Wars -- you're absolutely forbidden to sweat while welding a 4130 frame, not matter how hot it is outside. If sweat touches the airframe, it must be cleaned immediately with a damp rag followed by some sort of oil. Each place you fail to treat in such a manner will start turning reddish brown by the next day. I used to walk around regularly with a scotchbright pad and a can of WD40.
-- ,|"|"|, Ernest Christley |
----===<{{(oQo)}}>===---- Dyke Delta Builder |
o| d |o http://ernest.isa-geek.org |
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