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Actually Inconel is probably best. I'll grant you
that 304 will work (if you go heavy enough) and that its cheaper. Taken to
an extreme you could follow Mazda's example and use cast iron.
As an example a 1 3/4" x .065" 304 U bend from
Burns is about $50 it weighs 2.34#. The same (more or less) bend from Kevin's
source is clearly a bargain at about $20. Or you could go with Burns 321 with
.032" wall for about $50, same price as their heavier 304. The 321 piece
weighs1.28#. That's just one example chosen at random - others may show more or
less difference in price.
I guess the bottom line is that you are either
going to pay extra $ or extra #. I'd guess going with 321 over 304 might have
cost me an extra $200. And I probably saved at least 5 pounds in exhaust
system weight. The weight saved is actually significantly greater because I'd
have ended up adding tail weight to offset the added nose weight.
Ya pays yer money and takes yer choice. But to me
this was a no brainer and I'd go with 321 again if I were doing it
today.
Oh, and I'll dispute the claim that Burns gets
there bends from the source Kevin cited. I went to Burns shop when I bought all
of my bends and I saw their mandrel bender in action.
Mike
----- Original Message -----
Sent: Friday, November 13, 2009 4:01
PM
Subject: [FlyRotary] Re: renesis stock
exhaust flange
Jeff/ Mike,
Yep 321 is the best. A neighbour worked at
an airport exhaust shop, they used 321SS exclusively, however they made
their own bends out of flat - I guess there's a trick to it. When I enquired
about a price, their base price is $1,000.00 - a bit expensive I thought. So I
decided that I could go up a bit in thickness and go to what ever bends were
available i.e. 316, 304.
I guess it's down to the individual -Ed's had no
problem with the thicker ( other) SS
I know which way I'm going - the cost effective
way.
George ( down under)
I thought that the
recommended material for rotary engine exhaust parts was 321
stainless. Is 304 OK to use? I thought the temp rating for 321
was higher (like 1500F)?
Please correct me
if I have incorrect info.
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of kevin lane
Sent: Friday, November 13, 2009
11:31
To: Rotary motors in aircraft
Subject: [FlyRotary] renesis stock
exhaust flange
I didn't come across
this fact in the archives and thought I'd pass it on. the stock
exhaust flanges appear to be made from powdered metal. when you
attempt to weld to them the base metal breaks off very easily. I was
going to modify the stock exhaust, then was talked into a new header, using
the original flanges. it's only money. better to break on the
workbench, no? I ordered a new 304 flange from ed klepis today.
BTW, Columbia River Mandrel Bending supplies Burns with parts and costs 1/3
to 1/2 the price, plus sells schedule 10 tubing & elbows [.090
wall] as well. they have been good to deal with. http://www.mandrel-bends.com/catalog/contact-us.html
kevin
interesting to watch
mandrel bending. they pull this "chain" of brass doughnuts thru the
tube while bending
it.
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