Hi, Recently I have made a replacement hard soldered copper boiler for a model Mamod locomotive. The original Mamod boiler is brass with a Plexiglas viewing window for the water level. If the boiler is allowed to run dry the Plexiglas melts and sometimes the soft solder that holds the boiler's end cap also melts. The new boiler is a simple pot boiler with two take off's one for a filler valve the other an attachment for a safety valve and regulator. The coper tube used at 1.7 mm thick is about twice as thick as necessary for a boiler operating at 25 psi but the tube was available and cheap. The boiler was tested to 100 psi for another possible application for a higher working pressure without having to fit a longitudinal stay. There was no significant defection of the end covers so the boiler should be OK for up to a 50 psi working pressure. A 22 mm stop end has been used as a steam dome/filler valve cover. I hope the photographs explain the construction techniques used, if not please ask. Regards Tony.