|
|
Al: Are there pictures of your exhaust available?
2. What thicknesses of Inconel did you use, and were did you buy the materials?
3. If I may ask, what was the cost of an Inconel tangential muffler?
Knowing how heavy the RB flange is, I am amazed that your whole muffler system is only 12 pounds!
Phil
Subject:
RE: [FlyRotary] Exhaust Manifold material
From:
"Al Gietzen" <ALVentures@cox.net>
Date:
Sun, 6 Dec 2009 07:58:28 -0800
Phil;
I know youre asking Ed, but hope you dont mind another opinion.
Both 304 and 321 SS are subject to inter-granular stress corrosion at the temps were talking about. 321 is a better choice and will last longer, and could be lighter by some reduction of thicknesses.
Yes, making it thicker will make the 304 last longer by lowering stress, but it is still subject to limited life, and at the thicknesses you suggest, my estimate is your system will be rather massive at close to 30 lbs.
I dont know the details of his design, But Dave Atkins had a SS tangential man/muff that basically crumbled to pieces within a couple hundred hours.
Id also suggest a larger diameter for the tangential muffler; like 5+. This allows for more expansion which lowers both temp and pulse strengths. Flat ends would definitely be a failure point. Reinforcing with a central tube would be a big help, but I would still make them conical, or concave inward.
I know that inconel kicks up the cost a fair amount, but it gets you away from the stress corrosion issue and allows a system of about 1/3 the weight of what your considering. When you consider the overall time, effort, cost, risk, and weight, I still think inconel comes out on top. My inconel tangential muffler weighs in at about 12#; including the rather massive RB exhaust flange. The 321 secondary muffler and exit pipe add another 3 ½#. It has now been running for 170 hours; and as far as I can tell, is about as sound as when it started.
Al
|
|