Chassis v1

Despite the lack of activity on this development blog I haven’t been completely idle. On the train whilst commuting to work I’ve been working on the chassis design. The other day I got back the first version and managed to get it mostly assembled to see what works and what doesn’t. It’s not looking too bad. Apart from a couple of missing holes which meant I couldn’t fit the plates that hold the outer end of the wheel axle it mostly fits together OK. Of course I had to do a bit of whittling because I’d designed for 3mm MDF, but the board I used turned out to be 3.3mm (I’ve since bought myself a shiny new pair of digital calipers - like I needed an excuse). Also, I mis-measured the size of the gear on the stepper so the gear wheel that fits on to it doesn’t fit either. I’m using old-school pegs to keep it all together to avoid the use of any more additional components like screws. Apart from the steppers and other electronics, the only components that aren’t laser cut are 7 screws, 4 nuts, 6 washers, 5 elastic bands and a ball-bearing caster wheel (that I’m hoping to eliminate in a future iteration. Still pretty cheap.

Here are a few photos of the assembled chassis. This is an overall view of the chassis:

Here’s a close up of the pen arm:

I’m particularly pleased with this part as it only requires one extra part (a screw) to function. Pressure is maintained through the use of elastic bands (which aren’t fitted to this version) and the pen is also held tight by a couple of elastic bands. It sits into a couple of slots on either side of the chassis to keep it nice and rigid and the hinge is made by sitting a 110° corner against a 90° one and using the angle of the elastic band to hold it in place. You can see how this is raised and lowered using a servo in this next picture:

Here’s a close up of the motor being kept pressured against the wheel:

I’m thinking about thinly spreading some rubbery glue on the outer edge of the main wheel which will both grip the floor surface as well as providing grip against this wheel, alternatively another elastic band stretched around it may work well (or it may just keep coming off).

I’m hoping that the next iteration (which I’ve sent off to Sukkin at skpang.co.uk for laser cutting) will assemble without to omany tweaks and I might actually be able to get the whole thing powered up and moving.