Custom Remote-Controlled Electric Lawnmower Lets You Pilot it Across Grass

Simply put, using a remote-controlled electric lawnmower is similar to operating a toy car to cut your grass. Maker Max took an existing Metabo push lawnmower, removed the internals, and basically started from scratch.

The first thing he did was remove the handle, controls, and wheels and replace the entire push mechanism with a far more powerful one. He used two high-torque motors from an electric wheelchair to power the rear wheels. These motors are ideal for the job for a couple of reasons: they pack a punch but don’t need to travel very fast, and they have a long shaft, allowing him to bolt them directly to the wheels without the need for any extra gear or bearings.

He then added a couple of wheelbarrow wheels on the back to give it some substantial traction on outdoor terrain. He also chose air-filled tires, which allow him to alter the pressure to fit the job at hand. Out front, he replaced the fixed wheels with casters, allowing him to drive the lawnmower in tight circles without ripping up the lawn with foolish skid steering. Initially, the casters were a little unstable, but he replaced them with forklift-style wheels on strong axles that are rock solid. To keep all the parts together, he utilized a combination of welding and custom brackets/spreaders to keep the front wheels in the proper position and out of the way of the mower deck.

Height adjustment was essential, therefore he reinforced the original linkage arms with flat bars, threaded rods, and aluminum profiles to make them more durable. He replaced the original height adjustment mechanism with a 20v linear actuator that he can operate from a distance, and after he’s set the height, it locks in place. He also used rivnuts to make it easier to add and remove bits, as well as disassemble and reassemble it as needed.

A custom steel frame keeps everything together, and the motors are attached to a solid plate to ensure they’re in the correct location. He added some cross bracing for extra strength, and the entire thing is modular, allowing him to disassemble it if necessary. Finally, he painted it black to give it a clean look, and the mowing deck and basket remained in place, so it looks and performs like a regular lawnmower, cutting the grass and gathering up leaves and clippings as it went.

The electronics are all stashed away behind a sleek-looking 3D printed shell that makes a statement at the top. He’s going to use an Arduino Mega as the main brain, converting signals from a normal RC receiver into a language that the drive motors can understand. The BTS7960 motor controllers handle PWM signals, gradually jerking the motors up so that the entire system does not lurch around like a maniac. To keep it running longer, the batteries are wired in parallel and the power is scaled down by a voltage regulator. A relay board is used to control the actuator and other functions, and an indicator light and an emergency stop switch are kept in place by magnets on the top of the casing.

Max’s biggest headache was figuring out how to make a single joystick control the differential steering, coming up with acceleration curves that would get the mower to start and stop smoothly, and ensuring there were failsafes in place so that if the signal went out, the thing just stopped dead in its tracks. That was all handled by the code, which is available online for anyone who wants to follow in Max’s footsteps.
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