Al Gietzen wrote:

Subject: [FlyRotary] Re: Stainless Steel 13B Exhaust Flange?

 

How about 1/8" SS and then weld on the cut-off tiangles as stiffeners from bolt holes to exhaust hole?

If I'm not mistaken, Tracy said he made some flanges out of 1/8" steel (don't recall if it was stainless), and I guess they worked.  Seems like he felt that was pretty minimal though.  I don't think I'd hesitate to use 3/16".  Personally, I'd probably rather use stiffer material, than go to the trouble of welding the stiffeners on.  

 

Rusty;

 

It’s not the stiffness of the flange we’re after;

Actually it is. Those studs are quite a distance apart! It may be different on the Renesis (or maybe Bruce added new studs to Tracy's engine).

I'm using 1/8" SS flanges and am getting some blowby. The preferred welding method (least stress) is to put the weld on the engine side of the flange. Actually I extended my headers past the flange into the exhaust holes. Alas, the edges of the 0.035 SS tubing is wearing down after 500 plus hours, probably contributing to the blowby.
But stiffening the flanges from studs to near the tubing would ensure higher clamping force of flange to gasket/engine around the tubing.

Finn

it’s strengthening of the pipe to flange joint.  It’s an area of lots of thermal stresses; and the flange to pipe weld is likely the most common failure point, especially if there is not flexibility for stress relief downstream on the pipes.  Of course the geometry and the welding of the stiffeners is a bit critical as well.