< Boiler Fittings >
I started boiler assembly with a firehole door. The door itself is a laser-cut
stainless steel disk. The hinges are made with the same manner of the smokebox
door hinges. The lock bar is laser-cut and bended. In order to let the
bar rotate freely, the center bolt is lightly screwed in the door and locked
at the back with a nut.
You need screw holes on the backhead to fix the firehole door. I hate hand drill, so I set up a drilling machine as the photo shows. Incidentally the backhead is being lined with copper plates around the firehole, so as to ensure enough screw depth.
The door hinge bush is made of brass rectangle bar, while the lock bar hook is bended from a steel band plate. They are screwed onto the backhead with suitable sealant.
The photo shows Rectorseal, heat-resistant epoxy putty that I employed to seal the smokebox. It achieves strength of metal in 20 minutes after mixture.
Seams of smokebox plates as front, back, side and bottom plates are sealed. When disassembly, the bottom plate can be removed together with the smokebox.
As circular form of the boiler barrel is incorrect, there is gap between the barrel and the smokebox back ring. So I packed the putty between them. It means the ring is permanently fixed around the barrel, but the boiler can be removed together with the ring.
To strengthen the fixing, I added five screws between the ring and the barrel.
Most of the fitting parts are OS products. I made only a steam dome and a regulator by myself. The steam dome is at the top of the firebox and has two safety valves. It's also treated as a steam turret for instruments. I made it from a gunmetal casting. At first, all of the faces are finished.
The top face has two M14 holes for safety valves and a M12 hole for water plug. A M7 nipple for pressure gauge is silver-soldered on it. The side face has three M7 holes for blower valve, whistle valve and injector valve.
The water plug is to pour water into the boiler before steaming. It is made of two brass parts and has a rounded pocket for O-ring.
The regulator is screw type as same as "William". Regulator bush on the backhead has 20mm I.D. So I would use 20mm round bar for the regulator body. But I was making a mistake of boiler designing. Crown stay of the firebox is in the way of the regulator body! Therefore I reluctantly used 16mm round bar for the body.
The photo shows disassembled regulator. The valve and the stem are made from stainless steel bars and connected together with a taper pin. The handle has rectangle hole to fit to rectangle part of the stem, as same as the smokebox door dart.
The boiler and the steam dome are painted black. And then all of the fitting parts are fixed on the boiler. Safety valves, water gauges, check valves and other valves are OS products. Most of OS fitting parts adopt M7x0.75 thread. If you utilize them for your boiler, you need a tap of this size.
Steam from the regulator is led to the both cylinders through a wet header and copper tubes. The wet header is made of brass round bar. I used an O-ring for sealing.
The photo is front view of the smokebox with the boiler. Note the copper tubes are arranged not to hide the screw holes.