The following two pieces are by Dave Bramwell, designer and constructor of the engines I photographed at the recent Harrogate exhibition. The first is an extract from a letter he wrote in reply to my request for more information. The second piece is something he sent to Mike Crisp, an model engine builder and repairer, who subsequently wrote a piece for Model Engineer Magazine.
Extract from Dave's letter to myself:-
.."I have two or three stationary gas engines, all running on butane and, just to be different, all six are six strokes, to help keep the speed down. When I finished the silly aero engine I sent photos to Mike Crisp who made up an excellent page in M.E. using his words to explain the list of ideas I sent him, such as twin glows for extra power, ditto for polished crankcase [even if it was on the outside], downthrust on the crankshaft to control the aircraft's attitude, or make it suitable for control line. He called it the "ENIGMA".
After I finished the V six with its 4 valve heads and distributor / coil ignition, I felt I had to get a bit more complication, so after having a break by doing a couple of hot air engines, I have made a start on the twin row radial but actually the complication doesn't really beat the V6 being just two 7 cylinder engines back to back. It will be a bit bigger than usual, being 22x20mm but added up should total about 100cc. All my engines are spark ignition [except when I'm taking the Mickey] so it will have two distributors and contact breakers. Looks like at least a 2 year project with the multiplicity of bits to make.
Anyway Ken, thanks for writing and I feel honoured that such well known chaps from USA and Australia approve of my endeavours"
The piece that follows is I think the piece that appeared [ghost written by Mike Crisp] in the Model Engineer:
A quest for improved efficiency.
Some years ago I made a stationary steam engine with a bent boiler using a large copper plumber's elbow both for inspiration and materials. It was featured in Model Engineer 4 June 1993 raising both interest and concern for my sanity in about equal measure.
Moving from steam to the more modern world of internal combustion, I have now developed the aero engine shown in the photographs. The suggestion to adopt the use of bubbly chocolate bars for fuel was dismissed as foolish.
Important design features and innovations include an interesting valve arrangement, the single overhead valve gives the high revs. required for high speed flying with a side valve also being incorporated to provide high torque for power. Further power improvement derives from the adoption of twin glow plugs. In this modern age, the quest for improved efficiency must remain paramount in the designer's mind, both for economic and environmental reasons. Note the highly polished crankcase, etc. Everyone knows that polished engine parts improve efficiency. Automatic lubrication of the cams, situated on either side of the bronze gear, was another serious consideration.
Safe flying is of course something which we should never forget. To aid this, a special universal joint using low angle bevel gears is employed on the crankshaft. The resulting l0deg. of side thrust ensures that the aircraft flies in circles and doesn't get lost. Similarly, l0 deg. of down thrust prevents the aircraft from climbing out of sight. The unusual four stroke practice of a ram air carburettor does have penalty of dangerous throttle controls, although the safety measures noted above should allay most fears. During testing the engine has successfully run at speeds of up to 5,500rpm. Due to the shock protection system installed between the engine and bulkhead no problems are expected in flight.
City of Sunderland MES