Hi flashsteamers,
New failure mode!!!!@~###
Yesterday and today at the Guildford Steam Rally, Vital Byte was put through its paces, but only for about 10-15 minutes.
Yesterday V.B. experienced a heavy clunking sound after about 10 minutes of near silent running. The sound seem to come from the prop shaft rather than the engine, but finally the power train seized and the boat was hauled out of the water.
I removed the cylinder covers and, although one piston needed tightening slightly, there was no apparent engine problem. I then found the prop shaft shear pin had fallen out after over a years service. I replaced then pin but found that the shaft seized at certain positions, but, if I lent on the stern, it would free up. I concluded that the very hot sun ( it was 31degC!) had caused the hull to warp during it's open air display.
Today I ensured that the shaft would turn whilst it was on diasplay and everything was ok. Then after several hours it was time for a pool demo and again after about 10 minutes of perfect running the shaft seized again!
What a puzzle.
Suspecting the pool water temperature, I put my max/min thermometer (its amazing what useful junk one carries) in the pool and recorded 27degC! The only thing I could think of was that I have some reiinforcing aluminium strip under the stern that was expanding and causing the hull to "hog", thus causing mis-alignment of the engine to prop shaft coupling. Normally, I run V.B. in the local lake where the temperature is quite low thus avoiding this problem.
Solution: open up the gap on the dog-tooth coupling to increase its tolerance.
There was another chap there with a tug powered by a D10 engine and his loc-tighted prop became loose on the prop shaft - whether this was to do with water temperature, I don't know.
Ian.