Category:Jetex rocket motors

Toy Brands and Manufacturers
Jetex rocket motors
1948 -

1956: Jetex and Wimco ready-to-run models [image info]

The Jetex rocket motors were designed for model aircraft, but were sometimes also fitted to model cars and other toy and model vehicles.

Characteristics

The popularity of the Jetex system in the 1950s was due to how well the system had been thought out. The propellant (guanidine nitrate) was comparatively slow-burn, with a comparatively cool exhaust and a decent burn time, which meant that a model aircraft didn't have to deal with severe stresses or have to have extravagant fireproofing, and the reusable shell could be made of aluminium or aluminium alloy with a lower melting point. The casing design included a sprung safety release valve so that the rocket wasn't prone to exploding if something went wrong, and the fuelling process involved placing a spiral coil of fuse against the pellet's flat face, held in place by metal gauze, producing a guaranteed consistent burn and removing another possible cause of unreliability. The metal gauze sheet was a fixed distance from the exhaust, which meant that there was a guaranteed length of fuse "tail" between the gauze and the lighting-point, and a minimum time delay between lighting the fuse and the fuel igniting – unless the use rammed a lit object inside the actual engine, it was pretty much impossible to accidentally light the fuel directly.

The manufacturers also made of point of mentioning that the guanidine nitrate propellant was supplied to them by ICI (who seem to have been a co-patenter), eliminating the worry of small-batch production producing variations in performance.

Overall, the Jetex system was easy to use, reliable, and comparatively safe, and its predictability meant that makers were confident about making model vehicles (even cars!) that could be sold as "Jetex-compatible" – knowing that the behaviour of the customer's unit would be pretty much the same the same as that of their test model.

1952 article excerpt:

The tiny aluminium motor burns pellets of solid fuel. So the fuel won't go up all at once like a firecracker, it is especially treated to burn quite slowly. The Jetex unit holds a single pellet of fuel, which takes about ten to twelve seconds to burn. Sounds like a short time, but this is a fast plane and will get high in the air with this length of power run. The Jetex motor comes packed with complete instructions for use, so we won;t go into it here. But READ the instructions before you try a power flight.
— , Howard G McEntre, , A Jet-Propelled Delta Plane, , Boy's Life, , September 1957

1967 promotional text:

How Jetex motors work

Solid Fuel Charge (4) is ignited by the Plastic Igniter Wick (2), the coiled end of which is held against the face of the charge by a Gauze Disc (3) The gas is compressed in the main case (8) and forces its way out through the jet at supersonic speed, producing thrust. The end cap (5) is held by spring (9), and acts as a safety valve. If the jet were to clog, the gas escapes via the end cap.

Cars

Aircraft

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Boats

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Patent

The Jetex concept seem to have been patented in 1950 (submitted in March 1948) by an A. C. Hutchinson, M. Wilson, and ICI Ltd., patent number GB645897.