While I was visiting with Bob Barrows (to pick up my engine), we started talking about the exhaust system. He told me that after about 1000 hours, the pipes on Proto 1 had started cracking at the point where the mounting flange meets the pipe. The fix was to weld on some reinforcement pieces as shown below.
Here is the piece of 3/16" wide steel, cut to a triangular shape about 5/8"
long to fit the mounting flange and pipe:
After welding the reinforcement piece looks like this:
The reinforcement pieces were positioned where the most stress will be, at
the front of the curve and at the inside of the curve. They were then
welded to the mounting flange and to the pipe as shown here:
After everything was welded, the face of the mounting flange, where it mates
with the engine cylinder head, was faced off using a flat file until I had
a smooth level mating surface.
There is still plenty of weld area to hold the pipe to the mounting
flange.
With the right side completed, it was time to start on the left side. There is more room on the left side because the cylinders on that side are offset aft, away from the nose bowl. Even though there was more room and clearance on the left side, I still manufactured the exhaust to tuck in closely with the bottom of the engine for maximum clearance from the bottom cowl.
Here is the left side fitted and tack welded:
Again, the two exhaust pipes run parallel to the boot cowl tunnel.
This side's exhaust pipes were then final welded at the mounting flanges,
splices and reinforcement pieces:
