Designed by Frank Ellis and manufactured in England by Aerol Engineering of Liverpool. Frank was influenced by the Arden's design a fact that is quite evident when one compares these engines. The Elfin originals are no longer available. There have been many replicas available over the years as it is believed to be the most popular choice for replicators. Some notables are: produced by Dunham Engineering in the UK, Gordon Burford in Australia, Targos in the UK, CS in China,. RJL and Hobby House in the USA.
This engine was produced with either a beam or firewall mounting systems. It incorporated an updraft carburetor, cylinder liner is hardened steel with the 4 traditional Elfin internal transfer grooves, the lapped iron piston is extensively milled out on the inside to lighten, with a very shallow conical crown, which matches a similar profile on the counter piston. Gudgeon pin is 3.5mm dia, blind drilled 2mm ID from the front to save weight, and retained by a wire circlip. The connecting rod is a massive for this size of engine with ball ends and the crankshaft runs in a bushing type journal bearing.
Displacement 2.49 cubic centimeters
Practical Speed 9,000 RPM (10 x 4 propeller)
The short output shaft requires undue complications when finding a suitable propeller to fit on the shaft.
The unscrewing cylinder is another problem; it has a tendency to unscrew when making compression adjustments.
On the positive side the engine is noted for it's reliability and high power to weight ratio.
Click the play button below to view a short video featuring the starting and running of a replica by CS of this interesting little engine running again after a major repair.
Special thanks to YouTube Channel valic000and engine collector R.M. Rojo.