Castorbot

Castorbot is a sturdy but quick bot. Using two large wheels and one castor it's very agile whilst strong bracing ensures it stands up to the rigour of a RoboRugby lab. Pictorial instructions for building castorbot appear below - note that the brick and plate colours are shown merely for purposes of clarity. Pay attention to the difference between grey and black pins and bushings however - remember from the kit page that the black pieces provide friction, whilst the grey ones do not.

Add in some motor supports - these connect with grooves on the side of the LEGO motors.

Add in the next set of motor supports. You can link the two bricks using the black pins in your kit.

We're going to add gearing to allow the motor to drive the wheels with suitable speed and torque. Note the ratio of the gearbox and the gears used - later on you'll see that certain ratios are easier to implement in practice than others. Although you could gear the robot for faster operation, or for unity gearing (no speed/torque change), you may overheat your motor if it cannot supply enough torque to move your robot. If this happens, examine the gearing and allow the motor's protection circuit time to reset, then try again.

We're going to try bracing the brick you just added. Take a 12-length brick, and insert a black pin into each end. Now connect the topmost beam you added to the lowest one. Try the same on the other side - we'll be doing this a lot in RoboRugby.

Note that the red plates shown here are the 2x6 plates with holes - you need the holes in order to mount your castor later.

Try breaking off what you've just built - it's probably quite easy to do. The LEGO bricks can support quite a heavy mass, but they won't necessarily stay together if you've got any appreciable side acting force. We are going to brace the castor holder to ensure that it stays together:

Take two of the seven-length beams, and insert a black pin into the end of each one. Now try to insert it into the holes of the bricks such that the beam goes diagonally from the lowest brick to the tallest one. When you've found the right angle, do the same on the other side. Now try and move the castor holder again and note that it's much more difficult!

At this point it might be a good idea to examine the contents of your motor bag X - you'll find three wires, two short and one long. One end is terminated in a lego electrical brick contact, the other has a small moulded plug to fit your handyboard. Place the brick on the motor's electrical connection. You can lead the wire out any way that seems sensible! Connect each motor to a motor port on the handyboard - make sure you've connected it correctly - ask your demonstrator if you're not sure!

Now let's make a suitable mounting space for the Handyboard. Later on, make sure you always pick up your robot by the Robot chassis, not the handyboard - the robot may fall from under it!

You can try any of the wheels in your kit - the wheels shown here are only an example. The large silver-centred wheels (in two tyre-widths) perform particularly well.

Now all we need is the castor - start with a 48-tooth gear wheel.

Now insert axles as shown - the four and six length axles will provide the castor height required by this design. Experiment and see what meets your needs - later on you will see that your robot will in general perform better if it's level, as well as looking much more pleasing!

Add the wheel - you might find it advantageous to use a bush in the hollow side of the wheel. Make sure that the axle turns freely. If it does not check that you have both bushes and the four-length flat arm (hint: look in your kit description for this!) with axle fittings correctly positioned.

Now your wheel is complete and ready to add to the robot.

Now insert your castor into castorbot's holder, use two bushes to hold it together - one inside the holder, another outside. Make sure your castor turns freely - if it does not check that it's inserted into the hole furthest from the robot. If it still doesn't turn look carefully at both bushes and see that both ends are different - there's your clue! If it still will not turn, ask for help.

Congratulations! You're now the proud owner of Castorbot. It's now time to get Castorbot to explore its new-found surroundings...

Mount the handyboard on the two bricks shown in white on the diagram, display module facing the front and you're ready to go.