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Hadn't really thought about it, Bob. But, I would say they need to be make out of SS (304, 316 or 321), would need at least a 30-45 deg angle to the cone and be a min of 0.090 thick. The diameter would depend on the size of tube being used. I would think not smaller than around 2 1/2 - 3". They would need some perforations punched in the metal before making them into cones. The idea is to break up the shock wave but not seriously hinder the flow of gas. This is the design that you see on the market for exhaust inserts. See this URL
http://www.secureperformanceorder.com/dynatechstore/getproduct.cfm?CategoryID=30&ClassID=278&SubclassID=1309&ProductID=2476
(Note: need to past both halves of URL address into your browser's address window).
From what I think I understood in reading about exhausts, my idea was to have a series of cones in a tube such that the would form a series of expansion chambers. The cone would force the exhaust gas against the sides of the tube (area between cone and tube), then expand into a chamber between a pair of cones and then again have the gas forced against the outside (to the tube wall) by a cone and then into another expansion chamber. Supposedly this contraction/expansion is good for reducing the shock wave.
I do know that after several experiments that 1/8" thick stainless steel just won't stand up to the shock wave of a turbo block (without exhaust splitters) for any period of time if oriented perpendicular to the shock wave.
Ed
----- Original Message ----- From: "Bob Perkinson" <bobperk@bellsouth.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Tuesday, May 02, 2006 7:26 AM
Subject: [FlyRotary] Re: new hangar
Ed,
What would be the dimensions of the cones if someone were to make them?
Bob Perkinson
Hendersonville, TN.
RV9 N658RP Reserved
If nothing changes
Nothing changes
Sounds like the right formula, George - will wait for your project's outcome
before I try cones. Yes, I did find some cone inserts at $60.00 USD each.
I would need 4 for my two tubes - hummm makes one tube sound better all the
time.
Ed
Just the shells, TJ, the 1/8" thick SS washers are history. I have
concluded that no reasonable thickness of metal will stand up to the
exhaust
pulse for long if it is perpendicular to the shock wave. I believe that
if
I could shape them into cones where by the shock wave would hit the side
of
the cone at an oblique angle would probably survive - now all I have to
do
is find some {:>).
Ed
Ed,
There plenty of SS cones available in 1.6mm, I'm using them in my exhaust
which is a joint venture design with Bill Jepson - the idea is to redirect
the shock waves but not restrict the exhaust, as you have alluded to.
George ( down under)
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