Revolutionary model aircraft engine ends up in a spin

Wear life difficulties were being experienced with a revolutionary design of model aircraft engine on which Apek Design & Developments and RCV had collaborated.

Whilst the internal components of the engine are entirely conventional, it is the particular arrangement of these and the streamlined shape of the engine, which measures only 102mm in length, that has singled out the RCV60 four-stroke engine as the most significant development in model aero-engines for over 20 years.

The rotating cylinder is suspended on two bearings which allow it to rotate around the piston; a cylinder bevel gear around the base of the cylinder meshes with a smaller crank bevel gear on the crank, with a gear ratio of 2:1; and as the piston reciprocates and the crank turns, the cylinder rotates around the piston at half engine speed.

The rotary valve is formed by drilling a port in the side of the rotating cylinder and then surrounding the cylinder with a ‘timing ring’. Incorporated into this ring is the inlet port, glow plug and exhaust port arranged radially around it, thereby effectively combining the rotary cylinder with the rotary valve in a single component.

The propeller is bolted to the top of the rotating cylinder rather than the crankshaft, which gives the design its main operational advantages.

It was found, however, that the wear life of the gears in the prototype models was only 10min.

Following consultation with surface heat treatment specialists, Flame Hardeners, a heat treatment programme, using the spin hardening process, was designed and an initial test run of the process increased wear life to 3hr. Further development and re-design of the process has now produced improvements, resulting in almost indefinite wear life.

Flame Hardeners. Tel: 0114 276 8167