Part three by Jason Ballamy

The cylinder top cover started as a disc sawn off a length of 80mm dia cast iron bar, held in the outside jaws, and the internal spigot formed.

It was then reversed in the chuck and held by the spigot while the top profile was machined. I copied the shape in the photos, the curve was done free-hand and then fine tuned with a file.

Then over to the mill and the centre was located.

The PCD function on the DRO was used to place the stud holes around the edge and the ones for the gland studs. I found on another engine that if I doubled up the fixings from the smaller version then they seemed too big. So on this engine I went by what looked right rather than just double the size of everything.

The photo of the full size suggests there is a recess in the top of the piston rod packing gland to catch oil from the drip feed oiler so this was added rather than a plain gland as per Anthony Mount’s drawings. I like to make the studs and fixings as I go along.

The prototype has a large air pump that would have blown cold air through a condenser, this can be made as a working pump or a dummy, mine is a dummy at the moment but may add some internals at a later date.

I was in two minds whether to machine the pump body from a solid lump of 40mm cast iron block or fabricate, as this will be a heavy engine when done I opted for fabrication as it will be a bit lighter. A rummage around failed to find a suitable bit of 3/16" plate for the base flange so a few offcuts were welded together and then machined to give the required 2.5" square followed buy boring out for the tube with a boring head.

While the boring head was set to the correct dia I used it to flycut the end of a 3/4" bar to form a boss for the air pipe.

The top flange was cut from 1/4" plate and a stepped hole bored in the lathe, then holding by this hole the outside was turned round but left a little oversize.

The tube that goes between the two flanges was made from some that was a bit too big in diameter so I worked out what needed to be cut from the circumference and cut out the waste. Here you can see the parts ready to be soldered together.

And after silver soldering.

After sitting in the pickle and a quick scrub, the assembly was put back on the lathe and the top flange turned true to the base and to final size of 2.5" dia x 7/32" thick.

A bit more cleaning had it looking like this after which I added JB weld to all the internal corners to get that filleted cast look and left it overnight to harden.

While the JB Weld was going off I made the top cover, very similar to the cylinder cover but as the curved top which is not shown on AM's drawings runs right down to the flat bolting surface it was not ideal to use a file to refine the shape without marking the flat face. Solution was to hold a bit of bar in the tool post to act as a rest and then hand turn the curve, this posed photo will give an idea of how I did it with a woodturning scraper.

Finally, the JB Weld could be smoothed off and a bit of primer added. Then it was machine the gland and screw it all together.

See part one here     See part two here    Part three here    Part four here   Part five here     Part six here      Part seven here     Part eight    Part nine   Part 10     Part 11   Part 12   Part 13    Part 14    Part 15   Part 16