Grove pi on top of mr bit complete shassis

Building Mr Bit’s Chassis

Mostly we’ve been testing out the electronics for Mr Bit and learning about motor control all the time itching to drive Mr Bit too. Without a chassis though we weren’t going to get very far. So last week with some aluminium-rubber laminate board off-cuts from a sign-writer and a number of nuts, bolts and stand-offs, as well as motor brackets we printed, we set about building one. We didn’t really have much of a plan having never designed a robot and we didn’t really know where to start.

We made it up as we went along starting with laying out our components on an A4 piece of paper (the size limit for PiWars), folding the paper, drawing around things, staring into space and frowning with concentration trying to imagine what it could, should and would look like. It got to a point where we just had to make a prototype to get more of a feel of how it would all fit together.

Using jigsaw, files and drill we. Sticking card to the board we were using with spray mount helped as we could draw on the card and then cut or drill where needed. Our prototype ended up a simple elongated rectangle with a hole in it for wires to go through. With this we were able place our components and even test drive using our command line controls we wrote for our motor tests. It was great to have a moving machine at last – even if it looked a bit odd…

After we’d worked out how much space we needed for our components and a configuration of where to place them we took the prototype chassis back to the saw and drill to re-shape it. We made it slightly less elongated and more rounded, creating a lower-deck at the front end for sensors we will attach for the autonomous challenges.

We’re very pleased with the outcome of it. We’ve put switches in the back now to power both the pi and the motor controller. We’ve got wheels for our motors, which are a bit small so we might look at getting some bigger ones or even making some (though I doubt very much we’ll have time or much success). We’ve run our command line motor driver program and it even moves! We are over the moon with it. Moments like this make up for all the frustration of trying to get sensors and programs to work.

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