Monday 10 August 2015

Lets get physical! - Hardware prototyping

Yesterday I started putting together the first hardware prototype of my robot. Starting from a piece of plywood I marked it up and cut it based on the whiteboard scribbling I had done last month, before drilling a couple of holes for mounting the motors on.

To hold the motors in place I'm currently using some plastic piping and butterfly hose clips to squeeze it tight. The pipe is larger than my current motors (32mm vs 25mm) and the idea was to allow easy switching between different sized motors. However it doesn't look like the pipe is gripping the motors sufficiently enough to stop them moving when underway. I'll have to play with this a bit more.. Maybe taking another cut out of the pipe will help (so its in quarters), or I'll just have to switch to a smaller pipe. Its not as if I currently have any larger motors!

Next I tried attaching my large, all terrain wheels, which is where the first problem cropped up.
Whilst the chassis and wheels should, in theory, fit inside the A4 size restriction, in practise they don't. The issue here is the length of the motors plus wheel mounts. For these large wheels to fit they need to be positioned so they are almost touching the chassis itself and, unfortunately, the length of the motors preclude this.

Flipping the wheels so the connector goes inside the tyre might work, but the hubs only connect one way round on this make, so that's not possible. In theory I could offset the wheels or add some sort of 90 degree adaptor to the motor shaft, but that would add extra complexity and more things to go wrong. I always thought it would be a tight squeeze to get the all-terrain wheels on, so like last year I'll just have to drop them and go with something a little smaller. This should mean that I can make the main part of the chassis a little wider, but I'll test my other wheels first before cutting up any more wood!


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