Starting Again

We're back, for another year. After PiWars 2021 there was no question when I asked John and Charlotte if they wanted to try again. This year's theme of farming is exciting for us as well as Katie's family are farmers, and while their farm uses more traditional human-operated machinery they were well aware of the rise of robots in the industry.

We've got our chassis from last year, and a wealth of inspiration in agricultural machinery to consider.

A four wheeled robot with dragon head next to a toy tractor.
Last year's entry alongside a handy toy tractor.

Last year we started with the electronic design and made a whole bunch of custom boards. This year with the chip shortage in full force I think we'd struggle to do that again, and most of the boards we made last year are in good condition to use again. The motor drive and steering mechanism gave us excellent manoeuvrability and power last year so we're going to stick with the general design. We had to swap to smaller less rugged wheels shortly before the competition due to the steering geometry last year (see the blog post) this time I'm hoping we can re-instate those wheels to give us some more off-road ability for the farm yard tour.

We've sourced some new motors with similar power/size/torque/speed to last year's but with 90-degree drive so we can make the wheel assembly spin closer to its axis, making the steering geometry a little more forgiving when trying to fit those big wheels into the size limit for the competition.

Four metal housed worm-drive gear motors.
New motors to try out

Another thing we learned from last year was that FreeCAD makes for much easier modelling and prototyping than trying to do it all with OpenSCAD or 2D drawings. A drawing of the new chassis is coming together, hopefully with the big wheels, some suspension and front and rear mounts for attachments and/or counter weights like a real tractor.

A 3D CAD render of a section of a 4 wheeled robot.
First wheel design with motor, steering servo and some printed bearing mounts and brackets.