Jensen 55 Twin engine model Steam EngineOur #55 Twin engine series is the result of an ambitious design and engineering project undertaken by Mr. Jensen in 1948. The complicated slide valve timing was solved, providing a power stroke every 1 4 turn of the flywheel, thus making the #55 self starting with a very high RPM. Our Large Capacity Solid Brass Boiler Exclusive Hotwatt 110V. Immersion Heater Massive Cast Iron Engine Base and Axle Journals Heavy Cast Iron Flywheel with PTO "V" grooves