Now do I make the other side the same? I bored out the second cylinder and of course there in the centre was another pit. I've managed to get rid of most of it but now the cylinder is a little over size, so do I go back and bore the first cylinder to the same dimension? Probably. Having honed the bore to a nice finish, the pit that remains is quite small and shouldn't affect the running. The actual finish isn't as good as I'd like as the boring cutter seems to have dragged what looks like coarse carbon grains as it cut, leaving streaks. The photo shows half way through the honing and what remains of the pits. As a friend said, don't worry, the pits will hold the oil!
When I've fabricated some cylinders in the past, I've used a lump of continuous cast cast iron, which is really lovely stuff to work; never a pit to be seen. While I was at the suppliers, I thought I'd get the crosshead castings, but when I saw them I changed my mind. They looked as if they had been squashed sideways and by the time all the corrections had been made, there would not be enough wall thickness left, even assuming there were no more pits.
The last job was to turn and fit the slide valve extension to the steam
chest. I suppose this was meant to be cast iron to match the block, but I didn't have
anything suitable, so I used a piece of phos bronze which was in the cuminandy drawer. Once permanently
fitted, it will have an 'O' ring clamped between; I reamed out the valve rod hole.
I've fitted
the blocks temporarily with the cover plate off so that at a later stage I can get the valve
timing accurately. In the meanwhile I shall be hunting for suitable piston rings before I start
to make the pistons. This is because I might have a problem with size since I've had to bore oversize
and I may have to re-bore if I can't get the size I want or of course, make my own! The other pictures
show the crosshead slide bar and a rather ornate supporting bracket, which is as original. To get the
shape of this and a matching one for the other side, I drew it out on CAD and printed it full size. I
cut it out and stuck it to a suitable piece of steel and cut them out.
Getting the slide bar support in the right place was a question of positioning it between the two wheels and this governed the length of the bar. When I looked at it, it was obvious that the shape would have to be adapted to stop the conrod from fouling. This is where CAD came in again and I was able to go through all positions to make sure of clearance. It meant cutting the end at an angle so that there was enough reach to the bracket. Even then, I made up a card replica and ran it through on the model!
The drawing states that the slide valve be made of gunmetal, but since it is probably another casting, I've changed it to cast iron. This will be perfectly OK against the steel plate. The cast iron is cut from a piece of the continuous cast cast iron, which has a perfect surface.
This page represents a month's work; it doesn't look much but there is a lot of work in making one cylinder
block and its bits.