From Prototypes to Pretend-O-Bots

It was a dark and stormy night!
Actually it was the complete opposite, a lovely warm sunny day in July. I was sitting watching the Wimbledon final (go on Andy!) and finally decided to sort out the CAD for the jaw assembly. I'd decided to opt for some sort of CNC cutting, either waterjet, plasma or laser, for getting the jaws cut out of Hardox. I could have tried something by hand but it wouldn't have been as fancy, as neat or as quick. After procrastinating and putting off the CAD work multiple times, I finally forced myself to get it done.

I drew top and bottom jaws similar to the MDF ones so that I could make sure that the mounting holes and pivots were all in the correct places. I realised with the prototype that the jaws were a bit on the small side for a heavyweight, so took this moment in CAD to enlarge them slightly while still retaining the hole geometry. I then decided that the top jaw needing a bit of characterising to make it more visually appealling. I already had the name Coyote by this point, so this was when a conscious decision was made to focus on giving it an animalistic look. Therefore the top jaw would have to resemble some sort of head. This was the first effort:

coyote_partial.jpg

It wasn't too bad and remained like this for a while, but there were a couple of bits I wasn't happy with and it just didn't feel right looks-wise. I then sat down again and refined the design, added more serrated edges, added more obvious 'ears' as well as bracing pieces, and once that was done it felt much better:

coyote_jaw_CAD.jpg

The one part I hadn't factored into the CAD was outrigger arms to support the robot when the bottom jaws lift up. This was due to the way the base chassis attached to the jaw assembly, I wasn't able to work out where they needed to be without actually having the robot in front of me, so they would be made at a later stage.

When it came to cutting, I opted to go down the plasma cutting route. From the above CAD, the various pieces were laid out in a 2D dxf file that the cutting company could feed to their machines. Several monies, a few days and 32kg later, this lovely jigsaw puzzle arrived:

coyote_build (32).jpg

This was the first time I'd gone down this route on such a scale, and it was a weird but fun feeling seeing bits in the flesh that I'd only previously dealt with in computerised form. The size of the parts surprised me too, as the prototype arms were that bit smaller. Lifting each new part out of the box was like being a kid at Christmas again, as illustrated by my expression:

coyote_build (33).jpg

It was at this stage Rachel got involved. We both did a volunteer project in Peru several years ago, building a 2kW wind turbine from scratch for a rural community. She picked up welding really quickly while working on the project, so I let her loose on the jaw assembly:

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I think it took about three days to get the whole lot welded up. I had a week off at this point (lead up to Insomnia) and I remember thinking I wanted to get the robot about 90% by the end of it. Turns out that was way wide of the mark as a possible achievement
But getting the jaw assembly done was a big hurdle out of the way, and allowed the first Pretend-O-Bot to happen which, at this stage, I thought looked cool as hell!

coyote_build (46).jpg

The size of the thing hit home at this point, taking up a lot of my workbench and measuring approx 1.4m tip to tail. Love it!

The next step was to make some small brackets to weld onto the jaw assembly bulkhead so that the actuators could be mounted. Once that was done, it threw up a slight error. Even when you use CAD, you can still make mistakes if you don't check things or use accurate models. The barrel of the bottom actuator was interfering with the base brace of the bottom jaw, preventing it from fully retracting. So after all the time spent fabricating the jaws nicely, I had to go ghetto with an angle grinder to rectify it:

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Live and learn, and it all worked out fine in the end

So with all the Hardox stuck together, it seemed an opportune moment to stick everything we had on the scales:

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Not too shabby at this stage. It still needed armour, the majority of its internals and the chainsaw mechanism, but with 45kg to play with, we were confident about getting it in weight. The main factor now was time, as that last photo was taken at the start of October, and it was looking extremely likely that filming would now be the start of December, leaving just seven weeks of spare time and weekends to get everything done. Full blown nerves weren't setting in yet, but it wouldn't be long....

Seems a good place to stop for now. Next time, relocations, applications and loads-of-other-stuff-ations.