We had a fun little project with my friend when we were asked to build a demo board for the visitors of the Robocup Junior Finland 2014. We gathered all the Lego pieces we could find so this was kind of a "what happened if I had all the Legos in the world" project.

The idea was to let the visitors compete in loading freighter ships in the harbour by using the cranes made of Legos. The cranes were controlled through Lego NXT 2.0 bricks and joysticks & other controls based on Lego sensors.

Step 1: The Stuff We Used to Make This Happen

2 x cranes made of Legos

- Large number of Lego technic pieces to build the frames of the cranes, I´m not going to explain the building of the cranes too much in detail as the structure can be seen in the pictures quite easily and I´m not very proud of the final construction. It could have been done a lot better :D

Each crane has 2 x Lego Technic 9V Motors (43362) on their base structure and 2 more up on their hoist sledge. Other 2 motors are from Lego NXT 2.0 series. Also you need 2 x Lego NXT 2.0 bricks for each crane.

2 x spring loaded Lego joysticks for which you need:

- 8 x Lego touch sensors

- 8 x miniature springs of suitable tension

- Some more Lego technic pieces

2 x controllers for the crane hoist & grabber for which you need:

- Another 8 x Lego touch sensors

- Some more Lego technic pieces

2 x miniature freighter ships with funnels installed on top of them

A large basin for the water to resemble the dock

A board to resemble the harbour and its installations

4 x plastic balls to be loaded and containers for them

Step 2: Building the Cranes

The size of the cranes were dictated by the miniature freighter ships we borrowed for this project. The actual building of the cranes started from the engine blocks. The cranes use Lego Technic 9V Motors (43362) to move along on their rails. The length of the motor block is about 22 cm and there are rubber tyres on each end. Everything is built over these blocks. The height of the whole structure is about 60 cm. The cranes have movable hoists running overhead along rails of their own. The hoist sled is motored by similar lego technic 9V motors as the crane itself. The actual hoist is motored by Lego NXT 2.0 engine which lowers and lifts another lego NXT 2.0 engine which controls the grabber. The instructions to build different kinds of Lego grabbers can be found on their own websites.

Step 3: Building the Controls

There are many ways to build controls with Legos but none of the existing examples suited our needs. This is why I invested quite a lot time on this and finally came out with 2 - axis joystick for controlling the crane and its sledge. Left-Right axis controls the crane movement on its rails while Up-Down axis controls the hoist sledge forwards and backwards. After some testing it was obvious that the joystick had to be spring loaded especially if we wanted to drive both the crane and the hoist sledge at the same time. The touch sensors are pressed down all the time by the springs by default. Movement only happens when one or more of the sensors are not pressed down which happens when you tilt the joystick. You need some instant adhesive to make this work properly and I know this is not "Lego parts only" but this was the best solution I could come up. The joystick uses one of the 2 Lego NXT 2.0 bricks on one crane. Mostly because of the amount of the ports. The motors that are controlled by the joystick are Lego Technic 9V Motors (43362)

Another controller has a lever for lowering and lifting the hoist and buttons to open and close the grabber. Again this is based on touch sensors of which 4 is needed for each crane. The lever basically just pushes down one of the touch sensors depending which way the lever is pushed/pulled and that controls the motor which coils/unleashes the cables of the grabber. The buttons are there to control the last motor which opens/closes the grabber. This controller uses the other Lego NXT 2.0 brick.

Step 4: Building the Harbour

For the harbour I borrowed a table which has split plastic pipe on it - perfect for our miniature freighter ships. The harbour "pier" is made of MDF board of 25mm thickness. The total width of the board is 160cm and the lenght was dictated by the slot which we were given for the event - around 2 meters. It could have been fun to have even longer board :/ The water area of the harbour is 60cm wide.

Step 5: The Rails for the Cranes and Paint Job

The rails of the cranes are made of "cogwheel rail" - I do not know the proper word for it in english but it is about 20 cm long plastic piece with teeth on it and on which the teeth of the Lego wheels fits nicely. The rails are milled about 1 cm deep on to the board and glued to stay in place. The cranes did also need additional wooden rods to guide their movement.

The board was painted with primer to help the paint to stick on it before painting it black. The yellow stripes were added to make it look a bit better.

Step 6: Final Product

The idea of the competion was to load 2 plastic balls from their containers to the freighter ships. The competitors were fighting agains clock and each other.

I´m sorry I could not upload videos of the kids playing with these because I don´t know how to blur their faces on the videos, all I can say is that the Lego harbour was pretty popular among the event participants :)