GB642689A - Improvements relating to reaction motors suitable for the jet propulsion of model aircraft or the like - Google Patents

Abstract

642,689. Rocket motors. WILMOT, MANSOUR, & CO., Ltd., WILMOT, C. M., and MANSOUR, J. N. Nov. 11, 1947, No. 30022. [Class 9 (ii)] A reaction motor for propelling model aircraft comprises a casing for a gas-generating charge in which a spring-pressed member containing one or more jet orifices is movable relatively to the casing to allow the combustion gases to escape past it if abnormal pressure builds up in the casing. The motor 3 comprises a cylindrical casing 5 of aluminium closed at the front end 6 and enclosing a solid gas-generating charge 7 with an igniting wick 8 led through a wire gauze disc 9 and a jet member 11 in a removable end cap 10. The end cap comprises an outer plate 12 separated from a backing plate 13 by an annular asbestos washer 14 and held together by the jet member which is screwed into a boss 15 on the outer plate. Wire rods 16 bent into an annular groove 18 in the plate 12 hold the cap in position. These rods pass through holes in a front plate 20 fitting over a boss 21 projecting from the end 6. The rods carry anchorage members 22 against which abut springs 25. The boss 21 has a threaded bore to receive the end of a bolt in a model aircraft. To insert a charge the end cap 10 is removed by applying pressure to the anchorage members. When the charge is ignited combustion gases escape through the jet member. Should the pressure become excessive the end cap moves rearwardly against the action of the springs to allow the gases to escape between the cap and the casing. To prevent overheating of the surface of the charge the casing wall is thickened towards the rear or provided with fins. A model aircraft, vehicle or vessel may be provided with a metal clip in which the motor is placed so that two of the anchorage members 22 enter a channel in the clip and the boss 15 drops into a slot in an upturned lug. Alternatively a lug secured to the boss 21 may enter a slot in the body of the craft, or again the motor may be simply inserted in a socket. Air passages for cooling purposes are left between the wall of the socket and the motor. In a modification, the nozzle or jet member has a cup-like extension and is held in position within an extension of the casing by a spring which yields to allow the nozzle to move outwardly under excess pressure.