Mailing List flyrotary@lancaironline.net Message #35795
From: Dale Rogers <dale.r@cox.net>
Subject: Re: [FlyRotary] Re: engine mount 4130 vs 304 SS
Date: Wed, 28 Feb 2007 10:09:19 -0700
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Russell Duffy wrote:
Message
The 4130 can be gas welded. It will last longer than you will, if it is dry inside when welded.
 
It is stronger than stainless in the same section.
 
You can wash the inside with Linseed oil and weld the hole shut when finished. Then it will outlast all of us. You can use scrap 4130 from aircraft salvage.
 
You can fix it anywhere there is a gas torch. Not just a TIG set. Rare at little airports.
 
Check the Dillsburg aeroplane co. In Dillsburg Pa. for best new prices. 
 
 
Thanks for the comments Lynn.   I only have TIG to weld with, and the gyro won't be traveling unless it's on a trailer, so weldability isn't an issue.  I did figure that 4130 was stronger, but don't know if it's enough to matter, particularly since I'll be probably using 2-3 times the size I really need.   Fortunately, the quantity I need is so small that I won't be shopping around for price.  I'll just order from McMaster Carr, and have it next day via UPS ground.  Gotta love the way that works :-)
 
Cheers,
Rusty
Rusty,

   The main strength difference between 4130 and SS304 (aka 30304)
is that 4130 can be heat-treated, 304 cannot.  Then again, 4130
used in airframe constrution is almost always in "normal" state,
so the UTS values aren't terribly far apart: ~75K psi for 304 and
~100K psi for 4130.

   Yield strength is a different matter.  304 is ~29K psi vs 50K
psi for 304.  If 29K is enough to do the job, then there are a
lot of good reasons to use SS.

   If you are going to do a lot of drilling on 304 (or 316, which
is nearly the same, except slightly better salt corrosion
resistance) get some M42 (cobalt) bits.  304 is hard on tooling.
(Go ahead, ask me how I know ...)

Dale R.
COZY MkIV #1254



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