< Superheater >
The William original drawings suggest a horizontally divided smokebox for easy piping work. But a divided tube losts its roundness and also it doesn't look neat. So I left the idea and instead designed smokebox, superheater, steam pipes and cylinders as simple as possible.
See the pictures. The tubes have no bend except for the superheater inlet tubes. The steam pipes are straight forward to the cylinders. Procedure for assembly is as follows. First, the steam pipes are inserted from inside of the smokebox, and screwed deeply into the cylinders, next the superheater assembly is mounted onto the boiler tubeplate, then the steam pipes are screwed back into the elbows and fixed with locknuts in each end.
The superheater assembly is consist of a brass wet-header, copper tubes, stainless steel return bends and brass elbows. I introduce how to make them.
The inlet tubes were bent with the UNIVERSAL METAL BENDER, although we don't need such a tough tool to bend annealed copper tubes.
Copper is satisfactory for the return bend but the stainless steel extends its life. After drilling two parallel holes and a cross hole, the block was filed down to a thin skin.
For the return bend, the brass soldering is better than the silver soldering. The melting point of each material is approx.
Silver solder : 650 deg.C
Brass : 900 deg.C
Copper : 1100 deg.C
Stainless steel : 1400 deg.C
I employed 1mm brass wire as a solder, winding it around the tubes. Applying flux freely, the whole job was heated up quickly to a bright red. Once you succeeded a brass soldering, you may feel silver soldering much easy job !
The remainders are assembled with silver soldering. Before soldering the elbows, I assembled whole job tentatively, positioned the elbows and fixed them with lock screws which would be cut off after soldering.
The exhaust pipes from the cylinders are connected to the 'tee' at the center. It looks difficult to assemble, however the differential pitch threads make the job easier. The exhaust pipes have totally 4 threads (M10). The pitch of them are, from left to right, 1.0, 0.75, 1.0, 0.75mm. The pipes are screwed deeply into the cylinders, then screwed back into the tee at a time. Expected phase difference can be eliminated with the differential pitch, moreover, with a revolution of each pipe, the left pipe push the tee 0.25mm while the right pipe pull the tee 0.25mm. It means you can adjust the position of the tee with the screws. After the adjustment, each pipe is secured by the lock nuts.
The blast nozzle is due to the original drawings except additional lock nut to adjust its height. The height was determined regarding Martin Evans' '1:3 and 1:6 method'. Note, a tiny blower nozzle is slightly tilt toward the chimney.
The copper tube for the blower was bent following the CAD drawings, before cutting to a desired length.
The original drawings suggest the snifting valve mounted on the side of the smokebox. However, to simplify the piping, I moved it to the top of the smokebox, screwed directly into the wet header. In this position, the valve works 'normally open' instead of 'normally close'. The valve seat is formed at the lower end of the top cap. To prevent the ball falling down, a brass pin is added, crossing the valve body and silver soldered.
Spectacle of the smokebox piping without the smokebox and the saddle.