I am doing some shop work for a friend on an engine that he wants to get running. I got my hands on the engine two days ago. It is a German WWII torpedo engine model G7a. Very interesting design. It is called a "wet heater" design. It uses an external combustion chamber that burns Decalin mixed with compressed air and then at the bottom of the combustor just as the hot gasses are leaving water is injected to produce superheated steam. The steam and exhaust gas is then fed into what is essentially a 2 stroke 4 cyl radial engine. Each cylinder of the radial has 1 conventional valve for bringing the steam into the cylinder and then the cylinder is ported at the very bottom of the stroke so that the steam exits through the case and out the hollow tail shaft that drives two counter rotating propellers. It's a small package, all mechanical (no electrics at all) and from what I have read produces 350 HP at around 1800 RPM when set to the highest (of 3) power settings. So far I have just bore scoped it and after seeing all looked good I put some low pressure shop air into the combustor and it turns right over! Pretty cool for something that has been sitting since somewhere around the early 40's. It's an amazing piece of engineering and manufacturing.
As I disassemble it I plan to get lots of pics and measurements. I think this design would be a really interesting and fun 1/4 scale model engine build. I have a set of engineering drawings for it, all in German of course. I have found some good translations though. I hope this would be of interest to some of the builders here...
[ame]http://www.youtube.com/watch?v=Ax6nOVwgpQ0[/ame]
As I disassemble it I plan to get lots of pics and measurements. I think this design would be a really interesting and fun 1/4 scale model engine build. I have a set of engineering drawings for it, all in German of course. I have found some good translations though. I hope this would be of interest to some of the builders here...
[ame]http://www.youtube.com/watch?v=Ax6nOVwgpQ0[/ame]
