This unique powerplant – the Jetex motor – provided the motive power for a highly innovative advance in modelcraft.
On this page we give an overview of the working principle of Jetex propulsion.
On other pages in this section (see menu on the right), we give details of the full range of Jetex motors, other contemporary Jetex-type motors, and the fuels that powered them all.
How the Jetex motor works
Safety clip spring
Threaded hole for attachment bolt
Solid fuel charge
The burning of the solid fuel charge (5), once ignited by the wick (8), generates a large quantity of gas in the combustion chamber (7). This is forced out of the jet orifice (9) at great speed, producing (by Newton's third law of motion) a reaction which drives the motor in the opposite direction.
The springs (1) are intended to hold the end cap (12) tightly seated on the asbestos washer (11) so as to seal the combustion chamber (7). They are seated on the spring plate (3) and act through the clips (4) to provide a safety release mechanism in the event of the orifice becoming clogged.
The gauze disc (6) serves to hold the coiled wick tightly against the fuel charge, while the back plate (10) protects the washer.
Illustration sources: - Cutaway drawing adapted from Jetex 200 instruction sheet, Wilmot Mansour and Co. Ltd., 1948 Information sources: - "Jetex!" by Kenneth Brothwell, SAM 35 Yearbook #3, Dec. 1984 (Bill Henderson) - "Engine Analysis No. 15 (New Series)" by Ron Warring, Aeromodeller Nov. 1953, Jan. 1954 (Bill Henderson) - Additional personal knowledge from Bruce Ogden and Bill Henderson