This is another example of the excellent work of Phil Gravett AKA Philcraft. It was designed to fit into a small launch type boat hull. To quote Phil - "This engine unit was originally designed to go in a 15" open launch designed by Richard White of ship and boat international, but be able to slip into any suitable hull instantly." I would say that a "suitable hull" could be one a lot smaller than 15". The overall length of the engine is only 5 1/2", and that includes the drive pin on the flywheel! I don't know how many were made originally but there were a couple left over with problems, which Phil left lying around for some time until he fixed them up. He sold the last one to me at a substantial discount - many thanks Phil :-)
The boiler has a butane gas burner. The gas is held in a nice brass tank with what looks like a standard Ronson filler valve, which doubles as a control valve when screwed into place. The burner end is fitted with a ceramic diffuser.
The boiler is a simple vertical type with a single flue. It has wood clading and a polished brass top plate. The top houses a spherical steam dome and a safety valve identical to those on the Jenny Wren and Lilliput engines. Either the dome or SV can be unscrewed to fill the boiler.
Steam is fed through a stainless steel coil type superheater under the boiler to the engine. The engine consists of a pair of Jenny Wren cylinders mounted in V twin configuration at 90 degrees. The cylinders are only single acting so the engine is not self starting. The pistons are 3mm diameter with a stroke of about 4mm. The crank shaft is terminated with a flywheel 16mm diameter by 13mm thick. This is fitted with a pin to engage with a propeler shaft.