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HAL-9000 · 03-07-2005, 08:58 PM

Yeah, heat cycle like a gasoline engine or something like that. Something like a 50cc Honda two-cycle for dirtbikes, or even better, those motors they put on "pocketbikes."

Two of those, you would be in business I think. And since you can get the whole bikes for about $500 a pop, the motors can't be more. You would need to find a prop and then apply appropriate gearing to get the prop rotational speed to match the motor's most efficient RPM for cruise. You would want that for as much endurance as possible. The prop's "exhaust velocity;" the speed of the air the prop pushes out, should be as close as possible to the cruise speed of your airframe for maximum efficiency at you desired cruise speed.

Once you know what the cruise speed you want is, you can figure how much thrust you need to push the airframe at cruise, and then you can go from there to pick the prop's size, pitch angle, and RPM to move enough air at that speed. Convert that power to watts and then find some motors that can do that. However, the motors/props combo max power needs to be about 40-50% above the cruise value for effective takeoff performance.

03-07-2005, 08:58 PM	#10
HAL-9000 Cooling Savant Join Date: May 2004 Location: San Diego, CA Posts: 202	Yeah, heat cycle like a gasoline engine or something like that. Something like a 50cc Honda two-cycle for dirtbikes, or even better, those motors they put on "pocketbikes." Two of those, you would be in business I think. And since you can get the whole bikes for about $500 a pop, the motors can't be more. You would need to find a prop and then apply appropriate gearing to get the prop rotational speed to match the motor's most efficient RPM for cruise. You would want that for as much endurance as possible. The prop's "exhaust velocity;" the speed of the air the prop pushes out, should be as close as possible to the cruise speed of your airframe for maximum efficiency at you desired cruise speed. Once you know what the cruise speed you want is, you can figure how much thrust you need to push the airframe at cruise, and then you can go from there to pick the prop's size, pitch angle, and RPM to move enough air at that speed. Convert that power to watts and then find some motors that can do that. However, the motors/props combo max power needs to be about 40-50% above the cruise value for effective takeoff performance.