Radio Controlled Watermelon

Created on: 17 December 2012

Updated on: 3 January 2013

A radio controlled watermelon built out of parts taken from a radio controlled aeroplane (RC airplane) and a hollowed out watermelon.

The video below shows the RC melon being tested in a small pool. Steering the melon using the remote control requires some learning before the melon can be controlled properly.

A skeg under the melon in the middle and another at the back were necessary to increase the overall stability and also improve control of the melon.

Can't see the video? View on YouTube →

Unfortunately the watermelon tipped over shortly after filming it, burning out the electronics.

The Parts

The RC watermelon is built from a hollowed out watermelon and the parts from a kit RC airplane shown here:

hollowed out watermelon

Hollowed Out Watermelon

RC aeroplane, airplane

RC Airplane Kit / RC Aeroplane Kit

The Electronics and Parts

Motor and Propeller

The watermelon is propelled by the air propeller from the RC airplane. The direction of thrust of the brushless motor was reversed by swapping two of the three wires of the motor – any two of the three wires can be swapped to reverse the direction of the motor; any two of the three wires can be swapped again so that the motor rotates in the original direction.

Radio control parts and transmitter

Radio Control Parts and Transmitter

Direction Control

The propeller is mounted on a threaded rod that rotates in a wooden base block. The threaded rod is rotated about the base block by a RC servo which points the propeller in a different direction enabling the melon to be steered.

RC motor, threaded rod and base block

RC Motor, Threaded Rod and Base Block

Two fixed rudders were needed to gain proper control of the melon. Without the rudders, it is not possible to steer the melon – the melon just skids around without proper control when there are no rudders.

Watermelon with rudders

Watermelon with Rudders

The rudders are shown detached in the above photo. The rudder to the left was attached in the middle of the melon and the rudder shown on the right was attached at the rear of the melon. Both were attached using sticky putty (Blu-Tack). The rudders were cut out of the lid of a plastic ice-cream container.

The Radio Controlled Parts

The radio controller handset sends signals to the receiver which then controls the speed of rotation of the propeller and the RC servo position.

A speed control unit connected to the receiver provides the correct voltage for controlling the brushless DC motor.

Radio controll electronic parts

Radio Control Electronic Parts

The Assembled Melon

Wood blocks are used for the base of the electronic parts. This photo shows the parts mounted in the melon.

Assembled radio controlled watermelon boat

Assembled Radio Controlled Watermelon Boat

As already mentioned, the RC melon met with an untimely death after tipping over. The water in the electronics managed to destroy the battery and speed controller (which just burned out). Please help us by making a donation to help pay for the damaged parts and to fund new and exciting projects. Any amount will be much appreciated. :)

See below for a video and photos of the burned out electronics.


Burned Out Electronics

The battery and motor speed controller were destroyed, but amazingly enough the receiver and servo survived. The video below shows the burned out electronics, the receiver and server operating from a 5V power supply and the battery that swelled up after the boat tipped over.

Can't see the video? View on YouTube →

RC Motor Speed Controller Photos

The motor speed controller board got so hot that the solder melted and some of the components slid off their PCB pads.

Top View of the RC Motor Speed Controller

Top View of the RC Motor Speed Controller

The bottom of the speed controller board showing the heatsink.

Bottom View of the RC Motor Speed Controller with Heatsink

Bottom View of the RC Motor Speed Controller with Heatsink

The bottom view of the speed controller with the heatsink removed shows the ICs that burned out and emitted smoke after the watermelon boat tipped over.

Bottom View of the RC Motor Speed Controller with Heatsink Removed

Bottom View of the RC Motor Speed Controller with Heatsink Removed

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