Diesel Radial Engine Designed For 1 HP Per Pound Of Weight!

04.01.05 Special Edition: Radical Radial Engines Incorporated is in the final stages of design of a new 6 cylinder radial engine that is specifically optimized for the light sport aircraft market. The engine uses several modern technologies to achieve 1 horsepower per pound of fully equipped ready to run total engine package weight.

The engine is a 2 stroke, multi-port fuel injection turbo-normalized diesel with 22:1 compression ratio. High pressure fuel injection is electronically controlled with injectors located in the transfer tubes between the lower stepped piston charging chamber and the combustion chamber. (The two stroke oil injectors can also be located in the transfer tubes. The engine initially will use premixed oil in the fuel at a ratio of 190:1.) The compression ratio is high enough that no glow plugs are needed for cold starts to -60 degrees Fahrenheit. The engine operates with no throttle, so there is no restriction in the intake system to reduce induction efficiency. Power is selected by the pilot through an electronic signal provided by a potentiometer, but it is controlled by the electronic fuel injection system. The turbo-normalizing maintains sea level rated power to 15000 feet.

Due to the three lobed cams that drive the pistons each piston fires three times for each revolution, for a total of 18 power pulses per output shaft rotation. The engine incorporates stepped pistons that directly charge the cylinders via transfer porting to the adjacent cylinder. The stepped piston charging allows use of a standard dry sump lubrication system to lubricate the standard bearings for the drive shafts, and the cam rollers and gearing that drives the counter rotating 3 lobe cams. A minimal amount of 2 stroke oil (190:1) is still required to lubricate the upper piston ring, but it is drastically less then that need for standard 2 stroke engines (50:1).

The engine uses one piece cylinder/head units cast from high silicon content hypereutectic aluminum which has excellent strength and high temperature characteristics. These cylinder/heads are cast using lost foam methods to near net shape, require minimal machining. The 3 block components are CNC machined from aluminum billet and plate. The hypereutectic aluminum pistons and the cylinder bores are ceramic coated to minimize heat transfer and reduce wear. The internal drive cam roller and gear components are hardened and ground 4140 steal.
 
The cams allow refined control of piston motion compared to the fixed sinusoidal motion generated by a crank shaft. This allows for very quick compression to maximum pressure, long dwell at top dead center for fast, efficient, clean burning of a very lean mixture and maximum torque generation with a large moment arm through the power stroke.

Radical Radial Inc. plans to complete design and manufacturing of the prototype engine by August 2005. The engines fuel injection system will then be tuned using dynamometer runs to optimize performance. Endurance testing will take place on a test stand prior to placing the engine on a test aircraft mid 2006. The long term schedule estimates production of engines starting mid 2007.

FMI: www.radicalradial.com