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Jetex Engines |
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In the late 1940s, I was a member of the Epsom and District Model Aircraft Club; and around twelve years old.
At about that time a new type of engine appeared, a solid fuel rocket motor named 'Jetex'.
The motor comprised a tubular shell with a sprung loaded end cap with venturi. The fuel was a solid cartridge lit by a length of fuse which ignited the end of the cartridge; this then burned at a controlled rate giving off enough gas to give a few ounces of thrust, with a burn time of between 30 secs and 1½ mins. Some 'whiz' soon found that by taking the fuse along a groove made in the cartridge it was possible to ignite both ends of the cartridge at the same time, which although halving burn time, doubled the thrust !
Record Attempt
A rash of aircraft designs appeared for the new engines. and the Club decided to attempt to break the Indoor Tethered Flight World speed record.
A room in our headquarters (local Scout Club) was set aside and a tripod pole and wire tethers were set up. A rocket powered tailless design was chosen, with a wingspan of about 5".
All members (about 25) crouched around the walls of the room, and trial flights began.
Very soon there was a thick fog of burnt fuel in the smoke filled room.
Flight after flight with small changes in trim were made and soon the model was just a blur in flight.
An official timing session was set up and the speed record achieved!
Next was an attempt at the Indoor Tethered 'Floatplane' record. Someone in the club made a tinplate radial water tank about 12" wide by 6 ft long.
One evening during trimming flights with all members in the room, the wire tether (control line wire) failed and the model crashed into one of the walls removing a large chunk of plaster, fortunately managing to miss all members surrounding the flightpath - white faces all round!
All subsequent flights and record attempts were made with only the model operator and timing marshal present, and they had the protection of an upturned heavy topped folding table!
During the war, having seen Vl flying bombs passing overhead, making a sort of burp-burp-burp-ing sound, (if the engine stopped find somewhere to hide quick) my brother and I tried to make a pulse jet engine. The engine had a rose petal valve at the end of the combustion chamber, made from steel shim. Sadly, the best we ever achieved from this was a few coughs and bangs, and a sheet of flame from the rear pipe!. We didn't have a good enough grasp of the principles involved to make further progress.
A couple of Canadian friends, (twin brothers) decided to build a rocket powered model of Campbell's record breaking speed boat. It was very quick riding on its sponsons but was prone to capsizing on encountering the least wave formation.
Hmm!
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