Part 13 by Jason Ballamy

Pistons and plumbing

Next on the list is the piston and rod, this has a marine type end so first machine some steel and bronze.

These were then machined up in the same way as the other rod ends so I won't detail them again.
I like to use aluminium for my pistons to keep the reciprocating weight down which helps with a smoother running engine at low revs so a lump of 2" stock was machined down to 1 7/8".
The groove was put in and the diameter left 10thou or so oversize before parting off and a recess cut for the lock nut.
The rod was then screwed into the piston and used to hold it by while the it was skimmed down to finished size and thats it about done.
The Steam enters the valve chest by a tightly bent flanged elbow. These cannot easily be bent and carving from solid takes a while so one method that I have adopted in the past is to use a standard compression plumbing elbow, in this case 12mm.
Throw away the nuts and olives and Loctite one end onto a suitably sized piece of rod. Turn off the external thread from the mandrel end and saw the other off before milling flush.
Then turn up a couple of suitable flanges with spigots to locate them into the modified elbow.
Then silver solder the bits together.
After a quick clean up the elbow can be held in the mill and a light skim taken off the face of the flanges to ensure they are at right angles.
While set up true, the bolt holes are easily drilled letting the DRO work out the positions.
While the PCD settings were in the DRO I also bashed out the exhaust pipework, here it is along with the elbow in the foreground.