bodex
Member
A mate and I managed to acquire two old moyes tempest last year. Although they fly well for what they are We wanted to see if it could be converted to electric in the hope of getting a self launch from it.
Originally the idea was going to mount the motor behind the fuselage under the boom, but ground clearance was a problem. Then we thought nose mounting, ground clearance again...even with a dolly launch idea.
we then thought about a boom mounted pusher prop. Mccready used one on his human powered glider and the concept has been used before. The idea was to have the reduction pulley mounted on the tail boom using a roller bearing, the carbon prop blades then bolt to the pulley which is driven from the drive shaft below.
A few ideas and cad drawings later we had a concept and we had our machinist friend James make the parts, after removing the boom and mounting the bushing and bearing (2 day job) it was ready to connect to the engine. The power was going to come from a 150cc twin gas engine, we mounted a starter gear, clutch, and starter motor. Everything was looking good until we tried to start the motor, to much compression, so we tried auto decompression valves, still no luck.
We were stuck for ideas and I was getting frustrated with the gas engine. I had a pletenburg predator 37 brushless outrunner from my electric trike lying around and I decided to try that instead. So I removed the gas engine and 10 minutes later it was ready for a test run.
The reduction on the prop was based around the gas engine 7500rpm to give 2600 at the prop. To get this from the pletenburg required around 65v, so I decided on a 18s lipo pack. I ordered 8x 8s 5800mah packs from hobbyking and wired them to a bms in a 16s4p config to give me 23.2Ah of usefulness. The pack came out at 7kg and charges and balances through a inbuilt bms.
To control the power I used a alien power systems 450a speed controller. A linear pot running through a servo tester provides the signal. A HV contactor provides a safeguard between the battery and controller, two switches on the throttle quadrant control everything in the aircraft. A vincon battery monitor provides data on power used, current draw, voltage, time to go etc.
after installing it all we did a cofg check, originally they were really nose heavy, after installing the system cofg was around 32% Mac.
initial flight test was a aero tow, stall test was benign, power was added and a climb of 200fpm resulted, however full power wasnt available so the actual climb rate is still unknown (after landing I realized I programmed the speed controller to 18s instead of 16s so it was powering down thinking I had exhausted the battery)
more test flying to be conducted this weekend!
Originally the idea was going to mount the motor behind the fuselage under the boom, but ground clearance was a problem. Then we thought nose mounting, ground clearance again...even with a dolly launch idea.
we then thought about a boom mounted pusher prop. Mccready used one on his human powered glider and the concept has been used before. The idea was to have the reduction pulley mounted on the tail boom using a roller bearing, the carbon prop blades then bolt to the pulley which is driven from the drive shaft below.
A few ideas and cad drawings later we had a concept and we had our machinist friend James make the parts, after removing the boom and mounting the bushing and bearing (2 day job) it was ready to connect to the engine. The power was going to come from a 150cc twin gas engine, we mounted a starter gear, clutch, and starter motor. Everything was looking good until we tried to start the motor, to much compression, so we tried auto decompression valves, still no luck.
We were stuck for ideas and I was getting frustrated with the gas engine. I had a pletenburg predator 37 brushless outrunner from my electric trike lying around and I decided to try that instead. So I removed the gas engine and 10 minutes later it was ready for a test run.
The reduction on the prop was based around the gas engine 7500rpm to give 2600 at the prop. To get this from the pletenburg required around 65v, so I decided on a 18s lipo pack. I ordered 8x 8s 5800mah packs from hobbyking and wired them to a bms in a 16s4p config to give me 23.2Ah of usefulness. The pack came out at 7kg and charges and balances through a inbuilt bms.
To control the power I used a alien power systems 450a speed controller. A linear pot running through a servo tester provides the signal. A HV contactor provides a safeguard between the battery and controller, two switches on the throttle quadrant control everything in the aircraft. A vincon battery monitor provides data on power used, current draw, voltage, time to go etc.
after installing it all we did a cofg check, originally they were really nose heavy, after installing the system cofg was around 32% Mac.
initial flight test was a aero tow, stall test was benign, power was added and a climb of 200fpm resulted, however full power wasnt available so the actual climb rate is still unknown (after landing I realized I programmed the speed controller to 18s instead of 16s so it was powering down thinking I had exhausted the battery)
more test flying to be conducted this weekend!
