Saturday we ran #2 under load for 45 minutes from 600 rpm up to 2700 rpm. The exhaust got a little hot.
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Jerry Gilmartin
TOP BOSS
Posted on: May 31, 2015 - 7:10pm
Hey Randy,
Sounds like you figured out the problems with the dyno from last time. In looking at those cherry red exhaust pipes, it reminded me of when we suffered the same exact problems with those exhaust pipes getting so hot. To fix the problem, we had a total of 6 of those water cooled exhaust pipes custom made -2 to fit each engine. I have read several examples (from the wartime diary of RON13) of Higgins Boats "blowing out an exhaust stack" and having to replace them because a steam bubble formed inside the cooling passages and prevented water flow, which in turn melted the internal copper exhaust pipe. I can see how this might happen when the melting point of copper is not too far from the temperature of those flames coming out of the exhaust manifold during operation. I also found the startup procedure makes sure to check the cooling water inside the stacks is primed before operation and also drained after shutting them down to prevent the formation of steam bubbles inside the pipes. I wonder just how hot that pipe got? Pretty cool picture I must admit.
Good luck on the rest of your tests!
Jerry Gilmartin
PT658 Crewman
Portland OR
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Gerry we used a laser thermometer it was around 1100 degrees at the elbow. We still have to find a bigger dyno with this we can only pull 1000 hp. So we are running them up and checking for leaks and braking them in. I have a lead on one around 80 miles away. We are trying to make a deal so we can get the hp and torque curve to make the wheels.
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Jerry Gilmartin
TOP BOSS
Posted on: Jun 1, 2015 - 10:33am
OK, so I just looked it up and copper melts at 1981 F so I guess it was the steam bubble formation that caused the historic failures or the rubber outer hose melting and not the copper.
Anyway I am glad you guys have a lead on getting that other dyno. Thanks for the updates and photos! Jerry
Jerry Gilmartin
PT658 Crewman
Portland OR
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Engine 2 hit 1325+ 2850 ft lb of torque. but still only building 14.6 inm on the boost, it should be 46.inm We are going to check the spacing between the
fan and the housing we feel the gasket stock was to thick and we are lousing pressure in the gap.
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