Tankbot

Invading armies usually favour tanks with tracks over wheels. Manoeuvreable in almost all ground conditions, they favour power and reliability over speed and agility. Tankbot is a simple sturdy robot, still standing when the going gets tough. It's a great robot to test out your programming and building skills on and can form the basis of a much more powerful bot later on.

Pictorial instructions for building tankbot 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.

We're going to add some low-level bracing to Tankbot. When used together with bricks, right-angle plates make it very easy to keep LEGO structures rigid.

The two beams at the front will be used later on to brace the structure more:

Now add the mount plates to hold your motor.

Two identical plates either side, vertically stacked (shown as black and white) ensure that the motor is at the correct height for mounting.

Now push the motor into the two back plates:

and also add another brick with the motor-mount plates fitted, as shown. Note how the motor sits relative to the bricks. Examine the underside also - you should always plan ahead in your own designs to make sure the motor fits where you're planning to put it!

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.

Start building your gearbox by adding the small eight-tooth wheels to the motor spindle.

Now turn your chassis over - the next step is much easier done from the underside.

Add a 24-tooth gearwheel to engage with the motor spindle gear and another 16-tooth gearwheel which fits the sprocket on the tank tread wheel.

Turning your chassis back around check that both gearboxes spin freely. There should not be much/any difference between the effort required to spin either one by hand.

Now add the tank tread wheel, checking that it engages with the 16-tooth gearwheel you added in the last step.

The front axles are easier - you need to use the bushes to keep the wheels in place, but the 16-tooth wheel can replaced by a bush this time.

Carefully slide on the tank tracks. Turn the wheel whilst gently edging them onto both wheels.

Now add in the handyboard support brick, shown in pink. This will provide a base for our microprocessor board. Make sure once you've done this never to pick up the robot by the handyboard. If you do, the handyboard and robot might separate and the robot will fall away!

Brace the front beams with a 4x12 plate. There are other ways to brace lego - one very secure way is to put beams and bricks vertically into the design clamping them with black pins. Can you find the 'golden ratio' that LEGO uses for doing this? You can try this if you wish - try bracing the motor support bricks to others you add in or to bricks on the chassis.

Add bricks to support your handyboard.

Tankbot's ready for action:

There's a lot still left to do - Tankbot needs to learn how to find its way around. Place the handyboard in position. 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! Switch on and you're ready to go.