Gregory Perkins
Well-Known Member
I can think of 5 or 6 other ground shaking UL engine designs over the last 45 years but one stands out and that was the engine designed by Colin Chapman of Lotus for Burt Rutan and Eipper. The Lotus company had orders for 3,500 of the motors when Colin died and the subsequent management decided they did not want to be in the airplane business. They sold the design to a UAV
drone company ahead of its time I think. The truely "unique" part of this design was that they attached the propeller to a beefed up valve camshaft that ran half the speed of the engine. Brilliantly, they saved a lot of weight compared to any engine with a
PSRU unit and how can you make a lot of power for the weight if you do not run the engine at hi revs. Imagine this engine today
with electronic fuel injection, ignition and maybe turbocharger. I keep thinking there is no UL market for engines like this but actually the drone market could be bigger than the UL market ever could be. I dont know where the sweet spot is as far as HP requirements
of drones. I dont know if they ever had a four cylinder prototype but it was supposed to be 50 hp for not much more than 50 pounds. I am not familiar with "backpack" paramotor engines but does 25hp at 33 pounds sound competitive? They expected 500 hour TBO at a high duty cycle. I photographed this engine 25 years ago in a motorcycle museum in Birmingham, Alabama in their LOTUS section. Incidentially, this late stage development engine had a torsional dampner built in to the camshaft direct drive
drone company ahead of its time I think. The truely "unique" part of this design was that they attached the propeller to a beefed up valve camshaft that ran half the speed of the engine. Brilliantly, they saved a lot of weight compared to any engine with a
PSRU unit and how can you make a lot of power for the weight if you do not run the engine at hi revs. Imagine this engine today
with electronic fuel injection, ignition and maybe turbocharger. I keep thinking there is no UL market for engines like this but actually the drone market could be bigger than the UL market ever could be. I dont know where the sweet spot is as far as HP requirements
of drones. I dont know if they ever had a four cylinder prototype but it was supposed to be 50 hp for not much more than 50 pounds. I am not familiar with "backpack" paramotor engines but does 25hp at 33 pounds sound competitive? They expected 500 hour TBO at a high duty cycle. I photographed this engine 25 years ago in a motorcycle museum in Birmingham, Alabama in their LOTUS section. Incidentially, this late stage development engine had a torsional dampner built in to the camshaft direct drive
