Bluebell Railway Villa Team
The cylinders after removal from the frames and separation of the two sides On the left of the picture is the left cylinder, standing on its front end with the lower side towards the camera. The large flange on its right is where it joins to the right cylinder block, and the smaller flange on the left is where it fixes to the engine's frames. The slide bars fix to the square lugs on the cylinder rear, with the two long studs used for the gland which seals the piston rod. The three holes visible on the bottom are for the drain taps, one for each end of the cylinder and one for the steam chest. The right cylinder is standing on its rear end, with the steam chest facing the camera, showing the flange where it bolts to the left block, and the valve ports.
When Fenchurch's repair started we had no reason to suspect that there was any particular problem with the cylinders, other than that several of the old engines with inside cylinders have suffered corrosion from the top of the casting downwards, caused by condensation in the smokebox mixing with the ash to make an acid solution which leached through cracks in the concrete floor to attack the cylinder casting itself. Stepney, Birch Grove, and 1178 have all suffered from this, the two smaller engines each having holed through into one of the cylinder barrels; this was repaired with a metal filler, and in Stepney's case enabled it to run for nearly 10 years.
The first problem with Fenchurch's cylinders was found whilst preparing to remove the boiler from the frames, during removal of the some of the concrete which forms the floor of the smokebox, in order to get at the bolts holding the smokebox to the frames. The powered hammer used broke through the exhaust manifold a few inches below the blastpipe, where the casting had corroded down to zero thickness of metal. After the boiler had been removed, the rest of the concrete was removed from the cylinders, showing that there were three serious problems.
The hole in the exhaust manifold showed up that the whole of the manifold on the right side casting was very thin. A patch had been added, obviously quite some time ago, to enable the stud for the the blastpipe to be anchored. The way in which this was done suggests that it had been a poor casting when first made, and the present problem is due to the manifold wall having been too thin. We have no record of the date of these cylinders, but as they are of the 14in type with condensing equipment they may have been fitted at the time of its conversion to class A1X in 1913. [The picture shows looking down onto the top of the right side casting, and towards the left side. The top of the picture is the division between the two castings, with the exhaust manifold immediately below; the blastpipe bolts onto the flange around the manifold (and its partner). The patch is seen below the flange and still carrying the blastpipe fixing stud, with the hole to its left.]
The second problem is with the flange where the main steam pipe fixes to the cylinders, at the rear of the left casting. The edges of the square flange have corroded away so much that there is inadequate metal remaining to anchor the studs which hold the pipe on. In the picture you can see that one stud has completely fallen out, and the other three could not be relied upon to apply the force required. It appears that this has also been repaired at some time in the past, with an extra flange fixed on above the actual casting. The light-coloured bit sticking out in the front of the picture is a connection for an oil feed pipe which is now redundant (the oil from the hydrostatic lubricator in the cab is fed into the front steam chest cover).
The third problem became known when the top of the right casting was cleaned of concrete and rust down to solid metal. With no steam pipe connection, the right casting has a large part of the barrel wall exposed to the concrete. In the centre of this part the barrel wall was found to be only 3/16in thick; originally it was 1 1/4in.
The cylinders were removed from the frames and split apart. It is possible to repair all three faults, but it was decided that making a new set of cylinders would be the most satisfactory repair. This decision was influenced by the poor condition of Stepney's cylinders, and the fact that the other five potentially working Terriers are all in or heading for the same sort of condition.
Our master pattern-maker Brian Wilkie, fresh from his triumph with the new wheels, was prevailed upon to undertake the making of a pattern for casting the new cylinders. This is an altogether different proposition - a much more complex casting. The two sides are different, with few interchangable parts.
Several major parts of the pattern assembly have been made. Click here for details.
Brian and his assistant Roy Stirling have been working on the pattern for past two years, and have made considerable progress. [More about this will appear here when I've taken some pics.]
Repairing the old cylinders
When the decision to make new cylinders was taken, it was in the knowledge that on the old ones the barrels and valve faces were in very good condition, and this would therefore be wasted. Recently, a re-evaluation of the job has brought the conclusion that, whilst new Terrier cylinders will be required at a not very distant date, in Fenchurch's case it would be much quicker to rerpair the old ones. So, the current plan is that the making of the casting patterns for new cylinders will go ahead, and meanwhile the old cylinders will be examined by our full-time machinist Ray Bellingham with a view to replacing the top parts of the casting with a fabricated section where the main steam pipe and the blastpipe bolt on.
Anyone got a spanner that fits this ?
Whilst removing the bolts holding the cylinders into the frames, one of the nuts (the one hardest to reach) proved difficult to turn with a spanner. After undoing it with a hammer and chisel it became obvious why. One can conjure up images of workshop jokes involving new apprentices. The bolt for this nut passed too close to a web in the casting, so a full-size nut would not fit.
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