Robot: Beach Buggy

Among other things I do with Legos, I build robots using various kits from the Lego Mindstorms line. I built this robot back in 2003, when I was 17.

This robot was built for travel on the sand and rocks of a beach. It traveled slow, but it did move. I should note that this wasn't a robot, persay - I controlled it using a remote control. However, it did have the capability to be autonomous, if I had equipped with a couple more sensors and a more complex program.

 

I designed the Beach Buggy (BB) for high ground clearance, so it could more easily move over the terrain.For this, I wrapped Lego caterpillar treads around the biggest wheels Lego makes. Surprise surprise, they were a perfect fit. Then, the wheels are connected to an independent suspension system, so they can move up and down when traveling over rocks and such.

 Given the nature of the suspension, I couldn't build a real steering system, so I used skid-steering: the wheels on one side of the BB turned the opposite direction than the wheels on the other side. It was crude, but it worked.

Being that the BB was made to travel on rough terrain, it needed a lot of torque; not only because of the terrain, but the robot itself weighed quite a bit! I only had enough motor ports to use two motors; one for each side of wheels. I geared down the motors to a ratio of 1:75; for each turn of the wheel, the shaft of the motor turned 75 times. This gave a slow moving, but moving, robot.

Field Test

I brought this robot along to the house of a friend who lives across the street - literally - from a beach. I turned it on, ran the program, and set it loose. It performed very well, driving up and over small rocks and twigs on the beach. The motors were also set up high enough that interference from sand and other debris was minimal. I can't remember, but I might have sealed the gears inside housings, too.

That was the first and last time I have built a robot designed for outdoor travel. The world is a big complicated place, especially for a robot. However, if I can get my hands on some of the new Mindstorms NXT sensors, that might change. One day, I may build robots that venture outside once again.