Since the successful hydraulic and steam test we did on "Achilles" a few weeks back, I've been spending the odd hour here and there messing about with her. I've been convinced for a long while that the piston rings needed looking at, mainly due to the engine feeling a little weaker than it used to. In a haze of inexperience and laziness, I didn't change the rings when we re-bushed the engine several years ago, neither did I do it when we repainted it a few years after. The pistons have largely remained untouched throughout my ownership of the engine, with efforts concentrated on other repairs and replacements. However, the time had now come and some new rings could do her no harm. Therefore, after half an hour with the spanners and the screwdrivers, the pistons were out. Needless to say, they didn't owe anyone anything...
The O-Rings had quite a pronounced flat on them, so much so that they were actually slightly smaller than the piston heads themselves. (The resistance when in the cylinder was minimal at best). Having measured up the bores and the ring grooves, some new O-Rings were ordered from Kennions and arrived a few days later. Ken always maintained that he completed the loco in 1986 and, to my best knowledge, these rings must have been in since then. A change every 36 years is fairly cost effective...
I read up a lot about piston rings of various types and found a lot of debate about giving the ring room to roll. The piston grooves on "Achilles" were enough to allow some side roll and, with so many years behind her on the same rings, it was easier to change the cheap O-Rings more often (if necessary) than go through the hassle of machining out the grooves. Here we see an old ring against a new one...
Bores cleaned and re-oiled, the freshly oiled new piston rings were trial fitted...
The fit of the new piston rings was, as you can guess, far superior to the old ones and I do feel that the engine will have far less issues with back pressure now that the rings have been replaced. With the pistons refitted with their new rings on, the next job was to reconnect them to their crossheads. I then had to spend time removing the old spent gasket gel from each cylinder front face before making new paper gaskets. Both cylinder covers were thoroughly cleaned prior to refitting...
"Achilles" is seen here with the RH cylinder rebuilt...
And a few days later with the LH cylinder rebuilt and cover shining...
A snap shot of both refitted cylinder covers looking nice under the front end...
It was then a case of refitting the other cosmetic bits like the running boards and of course the all important mechanical lubricator. Even just pushing the engine along the bench now creates a pronounced beat at the chimney so I'm hoping that the new rings will be a success. Only a test run will tell of course...
Myself and Norfolks own dawn chorus denier 'Eddie the Late' are hoping to attend the CMES track with our two engines on April 2nd, weather permitting of course. Lets see how we go! Everything is crossed. Cheers all, Sam...
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