Introduced in mid 1958, the FROG 150 R diesel of 1.5 cc displacement was a development of the earlier FROG 150 model which had first appeared in June 1951. The amendments to the design of the FROG 150 which resulted in the 150 R were primarily developed by Gordon Cornell, who was assisting FROG designer George Fletcher at the time before moving over to E.D. in late 1958.
The FROG 150 R was a timely reponse on the part of its manufacturers, International Model Aircraft (IMA), to the simultaneous appearance of the competing Allen-Mercury (A-M) 15. Both engines set new standards for consumer-grade lightweight sports diesels of 1.5 cc displacement in Britain. The FROG 150 R was found on test to develop some 0.152 BHP @ 14,500 RPM, an excellent performance for an inexpensive lightweight plain-bearing 1.5 cc diesel of its day. It proved to be deservedly popular among Britsh and Commonwealth model fliers, remaining in production for some eight years, latterly by Davies-Charlton (D-C) Ltd. as the FROG 150 Mk. III. At least 30,000 examples appear to have been produced over the years.
A detailed article covering the history of the FROG 1.5 cc models from start to finish (including the 150R) may be found elsewhere on this website.