If you’ve ever ridden a two-wheel bicycle, you know that you have to not only pedal to move forward, but also balance in order to stay upright while you move.

Two wheeler robots are difficult to make because they need to balance in addition to carry out commands. The balance is done autonomously, meaning that the robot must be programmed to figure out how to balance itself.

We’re going to skip this complicated step and instead use gravity to balance for us. While this makes the robot a lot smaller, it’s also a lot quicker and easier to build than the model in this image. Are you ready?

A cable car transports people or things in a vehicle that uses a strong cable to pull at a steady speed. Also called aerial lift, aerial tramway, or gondola, these are different from the cable cars associated with San Francisco, which use buried cables to move the car up steep streets.

The world’s longest working cable car is in Sweden and covers 26 miles. Sweden used to operate a 60-mile cable car, but only a 8.2 miles (13.2 km) of it still works today, however this section is the longest passenger cable car in operation currently.

We’re going to make a durable cable car that can travel as long as you have string for it to move along! It’s really a cool and simple project, and you can add cups or berry baskets below to transport cargo. Here’s what you need to do:

The ferryboat was one of the ways folks got from island to island. Usually ferries make quick, short trips from one spot to another, picking up cars, people, or packages and transporting them across the water. In Venice, you’ll hear the ferry also referred to as the “water bus” or “water taxi”.  Ferries that travel longer distances usually transport cars and trucks.

If you live in a waterside city or group of small islands, then the ferry is probably in your daily routine, because they are much cheaper than building complicated bridges or underwater tunnels.

Some ferries don’t have a “front” and “back”, but are double-ended and completely reversible, which allows them to shuttle back and forth across short distances without turning around. You’ll find these ferries in Australia, British Colombia, and Washington state.

There are many different types of ferries, including hovercraft, hydrofoils, and catamaran. Hydrofoils (shown in the image above) have special “wings” attached to the bottom of the boat that actually lift the boat out of the water when the speed increases. The special wing is designed to work in water and generate enough lift to move the massive boat out of the water so only a small part of the wing remains in the water to minimize friction (drag) force on the boat. With less friction, the boat can go even faster!

We’re going to make a simple ferry that works in the pool or bathtub. Don’t forget to add a remote control with extra-long wires!

Catamarans are boats with two or more hulls that are strapped together and move by either wind power (using sails) or engine power. They are one of the first boats humans ever floated in. Catamarans are used when speed and large payloads are needed: their interesting geometric design (their balance is based on geometry, not weight) allows them to glide through the water with lower friction and carry more than single-hulled boats.

We’re going to create two different versions of the catamaran, mainly depending on how many water bottles you have available. Put these in a swimming pool and watch them zoom!
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This robot as a BIG version of the tiny Bristlebot robot. Using an eccentric drive motor, this robot will show you how a cell phone vibrates by using an off-center weight being slung around by a motor. We built these types of robots in all sizes: from tiny toothbrush versions all the way to large commercial-sized sweeper brooms.

This project is just the right size to give you a fun robot that really works. It’s lightweight enough so you don’t have to use large, expensive motors or power supplies and worry about high voltage… so enjoy!

The image here is the 2003 Gibbs Aqauda at full speed in deep water! It looks like it’s just skipping along the surface, doesn’t it?

The Gibbs company uses auto, marine, and propulsion technologies to build water-land vehicles used mostly by the military. But wouldn’t it save time to cut through the traffic on the bridge if you could skim through the water?

One of the main issues with amphibious vehicles is that they are painfully slow – both in the water and on land. (Although the 2003 Aquada gets up to 30 mph in water.)

The other issue is safety – the lift from the bow on a boat is needed to avoid plunging, but on a car you don’t want the front end to lift at high speeds.  Also a boat distributes the load evenly across the hull while a car has  concentrated loads where the suspension is attached to the frame.

The Aquada car uses a 160 hp engine for land and a compact jet that produces 2,000 pounds of thrust. It broke the record for crossing the English Channel by four whole hours (third image below with the orange boat in the background).

And if the car goes fast enough, you can pull a waterskier.

The Gibbs company has also invented the Humdinga, which is for military use, as it has four-wheel drive at can cruise at 40 mph on water, as well as the Quadski, which travels at 50 mph on land or sea.

We’re going to build our own model, though not with a jet engine. We’re going to use a motor, wheels, floats, and wires to build a real working model you can use in the tub tonight. Our model is also going to have a transmission that will enable you to get  two different speeds using very simple materials. Are you ready? Here’s what you need to do:

After you make the Waterbot, you can create a two-motor version that you can steer using a remote control!

This is a fun variation of the Jigglebot that uses markers for legs so it can scrawl you out a masterpiece as it entertains you with its curious dance.
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Building the perfect robot for the right job.

If you’re new to robotics, LEGO makes it easy to build robots.

Even if you think you’ve outgrown LEGOs, take a second look at the inventions below that I’ve created. Many scientists and engineers got their start building with LEGOs! My kids and I share many LEGO sets together, and my absolute favorite is the 1999 Lego Mindstorms set.

We still use it to build and program robots today! But don’t feel limited to this set, as it’s hard to find nowadays. Use this page as a source of inspiration for your own inventions. Although these are images and not videos, do you think you can still figure out how they move?

Tabletop Cleaner

A combination of the Ultimate Builder’s Set and my own creativeness and a differential light sensor (see below under “sensors”), this little guy can stay on a tabletop with right and left edge detectors, rear edge detector, and avoid obstacles with a left and right bump touch sensors, and can track a beam of light or find a light source using Michael Gasperi’s differential light detector.  Using six sensors mulit-plexed into three available input ports on one RCX, a little creative programming, and three motors (one for the brushes, two for the drive) makes for a cool project!

The Claw IV

One of the first things I’ve built from the Mindstorms box: I added pneumatics and a ball, and suddenly I have a 4-axis grabber arm with a pneumatic claw that picks up balls from one location and deposits them to the target every single time! I must add that if it were strictly open-loop program, it would miss after the second or third try, as it never quite comes back to the same spot. This MEGA CLAW uses four sensors, five motors (three for the three-axis movement, one to operate the pneumatics valve, one as a pump to keep the air tank stocked), one RCX, and one Scout (to handle the extra motor ports).  Sensors detect the mechanical limits of the arm.

I initially wanted to make a 5 or 6-axis arm, but decided to wait until I understood how to get these pieces to fit together more efficiently.

Max the Hexapod

I was so intrigued by the idea of a six-legged walker that I went right to the source – Flik by Nick Donaldson and Hexapod by JP Brown and made JP’s posted version of a single RCX Hexapod.  It worked wonderfully!  It took every last LEGO piece I owned to put Max together, as he’s a rather large robot – over 2 feet long, not including the whiskers.

Aft Articulation Point	Forward Articulation Point

Killough Platform

This is a Killough drive system from Macs Robotics Page.  This platform can simultaneously rotate while driving forward.  Think of how an office chair’s wheel base rotates around while you push the chair across the
room.

Same assembly three times make up the structure of this amazing robot platform.

Synchronous Drive Platform

This is a Synchro motor drive system also inspired by Building Robots with LEGO Mindstorms by Mario Ferrari et al.  The coolness behind this system is the robots ability to turn its wheels in place without
turning the platform – hence this robot does not have a “front”, “rear”, “left”, or “right” – it goes in all directions!

Wheel assembly – each wheel is powered and can change orientation.

Top view – note that this robot was built upside-down!!

Tricycle Drive

Yet another Building Robots with LEGO Mindstorms inspired design.  I did not have an RCX free when I built this, so I plugged it into the Scout and made both motors go forward.  What was interesting about this was the vehicle initially went straight, then slowed and turned, then reversed direction in the turn, went backward, and began to turn again.  One motor controls the drive, and the other controls the front wheel’s orientation.  So when someone asks, “Can you build a car to go forward and reverse without reversing the motors?” you can say “Yes!”

Twelve-Legged Robot

This robot was inspired by Building Robots with LEGO Mindstorms by Mario Ferrari et al.  The idea is to make a walker platform stable enough to turn tight corners while line-tracking.  The only improvement I would do next time is to couple the motors (independent motors – one per side – in above photo) so it does not have a gradual turn while it walks!

MIBO

From Jin Sato’s book, The Master’s Technique, we created MIBO, a LEGO version of SONY’s AIBO – a robotic dog that can sit, shake (sort of), and shuffle along the floor.  He barks (more like a beep, really), and is lots of fun!!!  We’re adding non-LEGO parts, such as a wireless camera and sound sensor for further abilities for MIBO.  (Chasing ball and following a whistle?)  We’re really excited about MIBO and thank Jin Sato for all his hard work!

SHRIMP

The SHRIMP is a high-mobility wheeled rover designed by the Autonomous Systems Lab in Lausanne, Switzerland.  This innovative rover is capable of climbing over objects 2.5 times its wheel diameter!

Whiz

Whiz is a “whiz with sensors!” robot geared for a complex game of RoboTag.  This amazing robot is capable of exploring and reacting to its environment!  Whiz is loaded with a differential light sensor to seek and find
light, a sound sensor to detect and react to sharp sounds, a line-detecting sensor mounted on the front for staying on a tabletop or within a black-outlined rink, and it can avoid obstacles by knowing which bumper – front or back – is triggered.

Close-up views of the cool stuff:

Differential Light Sensor

Sound Sensor

Due to port limitations, I’ve plugged in a relay to switch between the sound and differential light sensor.  The following ports are connected:

Front View(Two “eyeballs” are CdS light detectors in the differential light sensor)

Rear View (see the microphone?)

Top View (Blue box on left side is the relay)

Right Profile (Rear -> Front)

Left Profile (Front -> Rear)

Homebrew Sensors & Actuators

These sensors were adapted from Extreme Mindstorms: An Advanced Guide to Lego Mindstorms by Dave Baum, Michael Gasperi, Ralph Hempel and Luis Villa.  Many thanks to all these wonderful inventors for their genius!

This differential light sensor (as described in great detail in Michael Gasperi’s section of the book mentioned above) does a wonderful job of being a “smart sensor”.  What would normally take 2 of your 3 sensor input ports to tell which way a light source is (to the left or right), this one tells you the difference and takes only 1 input port!  You don’t need the full capacity of the LM324N – if you have a 358 handy, use it.  The larger the CdS photocells, the better it reacts.  This sensor is excellent for tracking a light source!!  Currently used on Whiz.

A sound sensor initially seemed like a silly idea – especially when Michael Gasperi pointed out that it turned your expensive LEGO robot into a clapper.  But then, during a game of RoboTag, we realized that it might not be such a bad idea.  It would be handy to have one robot beep and the other listen and search for it.  It worked pretty well for our application, and allowed us to use multiple robots to search for different characteristics (light, sound, touch, temperature…).  Currently used on Whiz.

I just had to know what was inside the expensive little light sensor that comes with the RIS.  I was very excited when I found the schematic online and went to work right away.  I am lucky enough to have a lot of parts on hand, and have noted some standard parts you can use if you don’t have the oddball ones mentioned in the schematic.  Works great!!  (Not currently used on Whiz)

I figured, if the sensor above can see light, why not add in IR capabilities and find out if it can see the difference between white and black?  Take out the phototransistor (the transistor in the schematic without a base) and insert an IR detector.  Add in the LED everyone’s always taking out – but be sure it’s an IR or visible red LED (red LEDs often also emit in the IR range, and you can see if they are on).  If you wrap the detector in electrical tape to shield it from side-lighting from the LED, it works more accurately.  It has a drop 15-20 (out of 100) between black and white, depending on your lighting conditions. Good enough for line-tracking!  (Not currently used on Whiz)

If you’re short on input ports, and you’ve got two touch sensors to wire to only one port, consider this:  wouldn’t it be nice if the RCX read one value for one sensor, and a different value for the second sensor?  To make one sensor read differently than another when both are plugged into the same input, you’ll need to make a special wire for the connection.  Solder in a 22k resistor at the end of one of the wire leads just before it goes onto the electric plate, and your touch sensor will read about 50, whereas your straight connection (using the black wires that came with your RIS set for connecting sensors) will read 100.  When you program, pretend it’s a light sensor reading two different values.  Currently used on Whiz.