Tower Hobbies Edge 540
Tower Hobbies Edge 540 prior to conversion

Last year I put together a Tower Hobbies Edge 540 with an NGH GT9 Pro 9cc two-stroke engine. It was a lot of fun, and I probably put in 50-75 flights on it. Unfortunately after I tried using a larger 13″ prop, it flew great for a couple flights, and then I’ve had a hard time getting the engine running right again. It was fun to experiment with this small gasoline engine, but I figured I’d rather just make the airplane. Electric rc airplane have many advantage over fuel, especially if you don’t want to tinker with an engine.

New Equipment

To convert the airplane to electric, I purchased a GForce G32 Brushless Motor, a 60 amp ESC, and a 4s 3300mah battery. My first propeller to fly I chose a master airscrew 12×6 wooden propeller. The motor should draw around 500-700 watts depending on the propeller. The airplane gross airplane weight will be roughly 5.5 pounds. The general rule of thumb is that you should be drawing around 100 watts peak per pound for general sport flying, so this power setup seemed appropriate. It won’t be enough power for 3d flight, but I would pick a lighter frame if that was my goal.

Electric Motor vs 9cc Engine
Electric Motor vs 9cc Engine

 Conversion Process

The conversion process is fairly straight forward. Remove all the engine components (engine, ignition module, remote kill switch, fuel tank) and replace the components with the electric components (motor, esc, battery). The only tricky part for mounting the motor is I no longer had the electric motor mount that came with the airplane. It’s important to have this motor mount to position the motor further away from the firewall. This gets the motor so it comes out of the cowling, but it also pushes the center of gravity forward on the airplane, since we’ll be losing significant nose weight with the conversion. So I 3d printed a motor mount out of PETG plastic. PETG is very strong, and does well outside as it heats up.

Edge 540 Motor Mount
Edge 540 Motor Mount
The inside of the cowling is a mess from the gas engine.

Flight

I decided to fly the new conversion on 4/10/2021 at the Utah Valley Aeromodelers club field. It was 50 degrees with 5 knot winds. When the airplane was a gasoline airplane, it was slightly nose heavy. After the conversion the center of gravity moved back, and now the airplane was close to being tail heavy, but it was still within the CG range recommended by the manual. It’s able to spin a 12×6 propeller at 8900 RPM and draws around 500 watts. It successfully flew the airplane. I wish it did have more power to it, so in the future I may try a 13×4 or 13×6 propeller to push the motor closer to it’s operating limits. I do have space and weight to spare for a bigger battery, which I may need to support the higher amp draws with a larger propeller. I got distracted during the landing talking to a fellow club member, so it was a bit bouncy. Overall I’m very happy that I get to continue flying this phenomenal airplane, but am kind of glad to not have to deal with the gasoline engine anymore.


0 Comments

Leave a Reply

%d bloggers like this: