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Picaxe Robot

Not sure whether this should be under cars or model engineer, probably under computing but we don't have a section for that. So here it is my first play with a PicAxe controller and a servo based robot.

The first place to start is here: PicAxe.com

Well, actually this wasn′t the first place I started. Firstly I spoke to a friend Dave White who explained the different Picaxe controllers, showed me some code and then proceeded to build me a board and populate it and do some initial basic coding. The board layout is shown below:

As per some of my other models I started the wrong way round, this time with the wheels. Actually this is the correct way as these are the hardest parts to make and so best to get them out of the way first.

These were machined from 3mm thick aluminium sheet and the diameter is too big for my Hobbymat lathe so I had to use a mandrel that bolted to a hole in the centre. The plate was then pulled back against the 3 jaw chuck with the larger outside jaws fitted to maximise the radius of support.

A small groove was machined in the outer rim to give a location for the tyres.


As you can see the back of the wheels are smooth (left hand) and the front has radial grooves machined connecting two of the holes.

The centre of the wheels were drilled 13mm to fit the mandrel and this would then allow a hub to be made to fit the servo.

I bought the servos as continuation rotation ones, saves the messing around and they were only 5 each on ebay.

The servos were mounted back to back on 6mm thick cross-beams.

The holes for the screws were drilled, the screw wound in and then back out and then super glue was placed in the holes and allowed to dry thoroughly. This then gave very secure fixings.


The rear (third) wheel was again machined from 3mm thick aluminium.

A groove was machined around the rim to locate the o-ring to work as a tyre and a 10mm outer diameter ball bearing was made a tight push fit into the centre.


The framework around the servos taking shape.

These brass sash clamps are around 300mm long and are absolutely brilliant.

The horizontal frames at the top were made from U-section wood that I machined using a Unimat 3 with the circular saw attachment - the idea is to make a carrier for the electronics board that will allow it to be slid into place.


A balanced frame. Starting to look interesting. The swivel for the rear wheel was a piece of brass tube and I found a perfectly fitting piece of brass that would rotate freely inside.

I glued the brass tube to the wooden frame. A piece of piano wire was cut and bent to shape to hold the wheel along with a brass hub that was a tight fit into the rear wheel ball bearing.


With the Picaxe board balanced and the batteries strapped to the side of the frame the robot can be powered up to check it functions.

Not sure if this has the initial start to look like steampunk or not? Maybe some more brass.

The next job is to create the buffers and switches for the front end and a carrier for the batteries - maybe something brass??


The bumper at this stage is just a simple wooden beam. The plan is to replace this with a brass beam and to paint the chassis of the robot black.

Underneath are two small micro switches. The beam has some "play" so that it floats between the two switches.

In addition you can see the main power switch, a small metal toggle switch.


You can read the other pages on building the robot here:

Part 1 - Picaxe Robot.

Part 2 - Picaxe Robot Code.

Part 3 - Picaxe Robot - Battery Box and Main Housing.

Part 4 - Picaxe Robot - Wings, seats and lights.

Part 5 - Picaxe Robot - Details.

See also: Car Gallery, Model engineering Gallery.