Want a robot that carries your cooler, umbrella, and towels across soft sand while you walk empty-handed? Here's the parts pile you'd gather first: an e-bike cargo rack for the frame, two 350-watt geared DC motors, a pair of 12V sealed lead-acid batteries, wide balloon tires, an ESP32, and a fistful of bicycle chain and sprockets. That's the shopping list behind John Boss's beach-hauling cart, and none of it is exotic.
What Boss actually built
Living near Lake Michigan, Boss got tired of dragging gear across sand that turns every trip into leg day. He bolted a 3/4-inch plywood deck onto the cargo rack, then raised the drivetrain on wooden standoffs so the batteries and motors could tuck underneath. Each rear wheel gets its own motor, driven through standard bicycle chains and sprockets. Because the two motors run independently, the cart steers like a tank: spin them in opposite directions and it pivots in place. The fat, low-pressure balloon tires float over sand instead of digging in.
The electronics that make it drive
The two batteries wire in series for a 24-volt system. A DC-DC buck converter drops that to 5 volts for an ESP32, which spins up its own Wi-Fi access point and serves a web page. Pull it up on your phone and you get an on-screen joystick for one-handed driving, plus a toggle for the LED headlights, no app install needed. Time-of-flight distance sensors on the front bumper watch for obstacles and cut the motors if someone steps in front. A heavy-duty relay carries the big motor current instead of running it through the dashboard switch, and an inline fuse guards the whole system. Boss also chased down a grounding fault that kept the motor controllers from responding, a classic gotcha worth checking your common ground for first if your own build acts dead.
Worth a weekend?
The skid-steer trick and the ESP32 web-joystick pattern port straight to smaller robots, so this is a solid template even if you never touch a beach. Start with a cheap ESP32 dev board and two geared motors on a breadboard, get the web joystick talking, then scale up the frame. Full build notes and photos are on the Hackster writeup. Grab an ESP32 and a motor driver at circuit.rocks and you can prototype the control side this weekend.
Originally published on blog.circuit.rocks.
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