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Find an old Continental powered VariEze. Short stub (maybe 2 ") welded to the flange with 'eyelets' also welded to the flange. Straight exhaust stacks (ID slightly larger than the stub OD) had 'eyelets' welded several inches down from the engine end. Stacks slide over stubs, butt against flange & are held on with springs. (A loop of heavy safety wire through the spring would probably be a good idea.)
The story I was told was that Rutan came up with this after several VE's had welded stacks break off & go through the prop. I heard this story about 15 years ago; things may have changed a lot since then.
Charlie
Ben Baltrusaitis wrote:
Al,
That strobe is a great idea!
I'm going to do that. I appreciate all the knowledge you share.
I'd like to see a pic of your slip fit exhaust. It seems to me I could use a heavy piece of header pipe that goes all the way into the muffler and a smaller walled piece for the slip fit with maybe a three inch overlap.
How do you stop the gases from leaking past the slip fit?
Thanks!
Ben
Acroduster Too (still building)
20B
----- Original Message -----
From: al p wick <mailto:alwick@juno.com>
To: Rotary motors in aircraft <mailto:flyrotary@lancaironline.net>
Sent: 07/26/2006 5:56 PM
Subject: [FlyRotary] Re: Inconel
I have a lot of experience with failure analysis. Used to do it
with GM, Ford, other warranty returns. One of my favorite
experiences was solving a million $ warranty issue on a tubing
product. Although I'm not expert in this area, I'd sure encourage
considering other factors, other solutions.
In particular I'd encourage use of strobe lamp. Take cowl off,
fire up engine, use strobe. (yes, it's dangerous with prop on) You
will suddenly have appreciation for the forces involved. You
should be able to predict failure points with this test. Tack
together the broken one to see what I mean.
The exhaust will turn into a sine shape at certain rpm. You will
see huge amount of movement on the busted one. Make a new design,
compare movement to predict how long it will last. A very minor
design change can greatly improve how much movement occurs.
I'm not sure this is applicable to you guys, but my exhaust design
has slip fit of two pipes instead of welding. It works phenomenal.
I've had conversation with other guys who welded instead and had
failures. Same exact application. So my exhaust floats in relation
to the header. I just attach a small bracket to the floating
portion to prevent if from blowing off. Truthfully, I never
expected it to work, but it has quite well. I might have pic if
verbal description not adequate.
-al wick
Artificial intelligence in cockpit, Cozy IV powered by stock
Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland, Oregon
Prop construct, Subaru install, Risk assessment, Glass panel
design info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
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