The Elfin 50 of 0.54 cc (.033 cuin.) displacement was introduced to the British market in January 1952. It was the smallest-displacement engine ever manufactured by Aerol Engineering of Liverpool, England, makers of the Aerol Gremlin and Hurricane 2 cc models as well as the famous Elfin 1.49, 1.8 and 2.49 model diesels. The Elfin 50 was designer Frank Ellis's favourite among his various designs. It owed much to the Arden radial mount engines from America, of which Frank Ellis was a great admirer. The engine performed at a very high level indeed by contemporary standards for an engine of its displacement. 

The downfall of the Elfin 50, and indeed of the whole Elfin range, was the fact that it was manufactured using worn-out surplus machine tooling which had given its best to the war effort. This resulted in serious problems with the maintenance of acceptable fits and tolerances. It proved impossible to manufacture the little Elfin 50 to a consistently acceptable standard using this equipment, resulting in the engine's speedy withdrawal from the market after only a few hundred had been sold. In consequence, it is the rarest Elfin model of them all these days. 

The full rather sad story of the Elfin 50 may be read elsewhere on this web-site.