Ed,

Are the pipes supported anywhere = but at the flange?

Joe = Hull

Cozy Mk-IV N31CZ (65 hrs - Rotary = 13B NA)

Redmond (Seattle), Washington

From: = Rotary motors in aircraft = [mailto:flyrotary@lancaironline.net] On Behalf Of Ed = Anderson
Sent: Thursday, July 27, = 2006 5:34 AM
To: Rotary motors in aircraft
Subject: ***SPAM*** = [FlyRotary] Re: Exhaust pipes

Just for another reference point, I have two 2" = dia 0.11" thick stainless Steel (304) pipes as my headers. Each = header is approx 18" long and make one 90 deg turn before exiting out the = bottom of the cowl. I now have over 400 hours running time on these headers. They were welded by an aerospace welder who used to = weld turbine blades - need I say a great job? Since the two = pipes are not attached to the same point anywhere, any heat related = expansion stress is at a minimum.

I do use "ball joints" between the headers = and the muffler tubes.

Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com http:/= /members.cox.net/rogersda/rotary/configs.htm#N494BW

----- Original Message ----- =

From: Al = Gietzen

To: Rotary motors in aircraft

Sent: = Thursday, July 27, 2006 12:47 AM

Subject: = [FlyRotary] Re: Exhaust pipes

From the pictures of his exhaust system, it appears that the pipes were supporting the muffler can. My understanding, is that the entire = exhaust will glow red, and the metal will soften (as in almost melt) at high = power settings.

The melting point of inconel is = over 2500F. Things will start to glow at about 1000F if the light = isn’t too bright. It is still quite strong at our exhaust temps. = It is worth noting that one of the features of expanding the gas into the = large tube is that the temperature drops (Charle’s Law of expanding gases); = the temp of the large tube is somewhat below the temp in the header (how much = lower depends on too many factors that I don’t know) and depends on backpressure and engine rpm.

Al W. brings up a good point. I = had been primarily considering thermal stress, but stress due to vibration from = the engine (aside from exhaust pulses) could be a major factor. = Some high frequency resonance with engine vibration could do a job on = the welds where joe’s broke; or a resonance with the unsupported exit = pipe?

I guess I’ll learn some = more as I accumulate some hours on my plane. Now a real challenge is coming = up with some kind of damping support . . . .

Al = G.