“Rasant MK III” Diesel Radial Model Airplane Engine

Although radial in appearance, this “Rasant MKIII” Diesel engine operates like an inline engine. Instead of a master rod with its articulating rods in the same plane, the three cylinders are staggered from front to back. Therefore, the crankshaft is linear, similar to that used in an inline engine. The engine was built by Ron Valentine of Germany in 2004. The journals on the crank are spaced to match the cylinders at 120 degrees apart so all of the cylinders fire at the same time. It burns a special form of diesel fuel (less viscous) that produces combustion when heat and pressure is applied. The piston and cylinder are lapped together to within a tolerance of several millionths of an inch, eliminating the need for piston rings. The fuel provides a liquid seal in the cylinder and as the piston compresses the fuel-air mixture into the combustion chamber, it is ignited by heating through compression. Diesel engines require no form of mechanical or electrical ignition but can be difficult to start on cool days. This engine is just 2.5″-long, 3″-wide, and 2″-high.