Part ten - cylinder liners - by Ramon Wilson

Liners came out of a piece of very free cutting leaded steel. The bores were finished before the ODs to keep the wall thickness as much as possible to prevent distortion. Once done - to measurement using tele gauges (no plug gauge) the ODs were quickly roughed from each end to 1.0mm over size. One end (which will be the lower) was faced at the same time as doing the bores. The pic is of roughing the OD - not facing the other, top, end.

A quick skim over a previously used expanding mandrel
And the ODs could be brought to finished size and the other end faced square to the bore
The transfer passages were easily put in to a fixed stop and the porting carried out by plunging - 3mm followed by 4mm to finish.
The passages proved a bit narrow as initially drawn so were widened using a ball ended cutter.
Finished ready for lapping ....
..... and a trial fit to check the transfer passages. They are not particularly large but there is not a lot of material to play with however it's felt they will be more than adequate for the kind of performance anticipated.
The lapping will come last after the pistons are made and as the 'cast' will get left to last too, the comp screws seemed like a good idea to be done next.

Very different to the usual 'tommy bar in a hole' practice these require a shaped blade as the lever. The profile was copied onto a piece of card and cut out then transferred to the material - steel for the bead version and a brass one for a bit of bling. The levers were silver soldered into bosses first.

Then the boss blind bored before transferring to the rotary table to mill the outer diameter and the sides of the blade.
This may look a bit precarious and indeed it was. Though the steel one was successfully machined the brass one was tweaked well out of shape as the cutter passed the outer edge. Despite being rather bent and defaced a couple of taps with a pair of small hammers soon had it back in line but, by the time the burrs were filed out, the shape had changed a mite. Though it looks okay I decided to wait until it’s in the cylinder head to see how it looks before deciding whether to make another. The 9/32 x 32 threaded parts would be bonded in and pinned later.
Having got the threaded portions made and fitted and screwed them in place it wasn't the brass one that looked too small but the steel one that turned out a mite too large. A bit of reworking of the shape and both were okay.

The inlet 'regulators' were turned from brass and steel respectively - these had an 8mm slot run up the back and were expanded slightly using a tapered mandrel (dot punch) in the tailstock. This has given a nice tight fit but allowing smooth rotary motion.

The tank filler parts were also completed.

In the past the rotors  have been turned on the end of a block of Tufnol, the profile and any lightening cavities milled in then the rotor itself parted off. I tried something different this time, in parting off two discs a mil thicker than the thickness required. These were then faced and bored to a running fit on the bearing before reversing and facing to finished thickness.

A stub of ali had a stepped washer turned and parted off before turning a register for the rotor and drilling and tapping. With the chuck on the rotary table the inlet cavity was quickly milled. First off was the drive pin location - the rotor reference point.

After the drive pin hole the leading and trailing edges of the timing 'pocket' are accurately milled to ensure the timing is as called for.
Then remove the waste by rotary milling taking care not to run into the previous milled edges.
Finished parts.
Tentative assembly of one of the bottom ends.

part one    part two   part three   part four  part five   part six   part seven   part eight

part nine  part ten   part eleven   part twelve