A YouTuber has taken Lego engineering underwater by building a 6.5-pound, radio-controlled submarine that uses a range of modified Lego Technic components.
Brick Experiment Channel has spent years developing several versions of the homemade vessel, gradually adding more advanced systems with each redesign. The latest model, called Submarine 5.0, has successfully operated in both a swimming pool and a fast-flowing river.
The submarine weighs about 6.5 pounds and is built around an acrylic hull, while many of the systems responsible for movement and control rely on Lego parts or Lego-based modifications.
One of the biggest upgrades is its ballast system. Earlier versions used a syringe-style piston to draw water into the submarine, but Version 5.0 uses a modified peristaltic pump to fill a 50 ml IV bag with water.
The flexible bag serves as ballast while requiring less space inside the hull. The pump was also adapted using Lego components so it could work with the rest of the submarine's mechanical system.
The extra interior space allowed the creator to install a new pitch-control mechanism. Around 3 pounds of tungsten pellets are mounted on a motorized track, allowing the weight to move forward or backward inside the submarine.
Shifting the weight changes the vessel's center of gravity, tilting its nose upward or downward. When combined with forward propulsion, the system allows the submarine to dive and surface more quickly while giving the operator greater control.
Submarine 5.0 also replaces the Raspberry Pi Zero used in earlier versions with an Arduino Nano ESP32 microcontroller. It works alongside a six-axis gyroscope and accelerometer, a pressure sensor, and a 40 MHz radio receiver to manage proportional controls and underwater communication.
All of the electronics and mechanical systems are packed inside a 250-by-120 mm acrylic tube powered by a 9V Lego battery box.
The creator also addressed a stability problem discovered during earlier tests. Previous submarines had flat fronts that caused them to drift sideways at higher speeds, so Version 5.0 was fitted with a rounded 4.72-inch plastic nose to improve its movement through the water.
After testing the submarine in a swimming pool, Brick Experiment Channel took it into a river. The vessel successfully completed an underwater run at a depth of around 4.9 feet while operating against the current.
The project is another example of creators pushing Lego builds far beyond traditional models, combining custom engineering, electronics and Lego components to create functional machines.