Mailing List flyrotary@lancaironline.net Message #14903
From: kevin lane <n3773@comcast.net>
Subject: exhaust port shape
Date: Thu, 6 Jan 2005 10:08:42 -0800
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
I decided to have my exhaust flanges recut to better match the ports.  Originally I simply had a 2" dia hole.  How important is it to match the shape of the ports, which is a collection of radiuses, straight sides, fillets and even a sort of non-tangential "fillet".  It appears that a 1 7/8" OD tube could be hammered to match this shape if I had it cut in the flange.  A 2" OD tube left round also looks like it would cover the port, but would leave edges where the straight edges of the port would dump into a round pipe.  These areas are very small.  My welder says that he routinely hammers exhaust pipes into "square" shapes, that the ports usually aren't round anyways.  He can stretch the pipe to a bigger dia., although I don't think that is a great idea, despite my using 1/16" wall 321 s/s.  I realize that I don't want the exhaust gas to collide with a smaller exhaust pipe shape, but what about a larger size?  Is it OK to spill into a slightly larger size?  Am I worrying too much about a small detail, or is this worth the time and effort?
Kevin Lane  Portland, OR
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