Soon after the successful launch of his famous ETA 29 racing glow-plug motor in February 1949, designer Ken Bedford embarked upon a development program for a .19 cuin. (3.27 cc) glow-plug companion to the 29 in the ETA range of model engines manufactured by ETA Instruments Ltd. of Watford in Hertfordshire, England. While engaged upon the .19 design exercise, Ken also developed a preliminary design for an even smaller .15 cuin. (2.47 cc) model arranged along the same lines as the .19.
The reduced displacement was achieved by under-stroking the 19 rather than taking the more usual approach of under-boring the larger engine. In fact, apart from the bore, everything about the 15 was downsized, including the castings.
The ETA 19 duly made its market debut in May 1950 after a lengthy development period. At the same time, a few prototypes of the 15 variant were also constructed, although these never led to the release of a commercial version of that unit. The reason for this was apparently the prototypes' failure to perform up to the standards for which Ken Bedford was aiming.
Thanks to the efforts of Miles Patience and a number of his colleagues, at least five examples of the ETA .15 prototype remain in existence today. A full review and test of one of these units may be found elsewhere on this website.