Frantic Finale! (continued)

With the armour finally out of the way, the focus turned to the one last big challenge, one that I had been putting off again and again; making the chainsaw gearbox. I had a plan in mind but the trickiest part would be working out how to connect the chainsaw driver tooth to the gearbox and incorporating the chain bar support, all while making sure everything lined up with regards to bearings, pulleys, belts and shafts. The motor powering it was the same one that was in Drumroll for the drum, so 1100kV and ~2kW. At 6S, the motor would be kicking out 24,420rpm and the target for the chainsaw was 3000rpm (this was taken from the Series 1 house robot intros where Matilda's chainsaw is quoted as 3000rpm. Finding actual realistic chainsaw rpms was difficult as most gave figures in m/s and a long oval bar isn't as easy as a circle for converting those figures). We opted for a 9:1 ratio, putting it just under 3000rpm, so two stages of 3:1 was looking like the most compact way to achieve this. First up was playing around with the pulleys to sort the layout:

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The whole mechanism would be sandwiched between three layers of 10mm aluminium plate. First thing was to get the pulley centres spot on. Devised a simple setup for this:

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I didn't take too many photos of the process since time was tight, so a few drilled holes and some pockets bored out on the mill later, and it was starting to look semi-decent:

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A few more holes, grub screws and fixings later, and voila:

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Another thing I was proud of making from scratch. It wasn't the smoothest mechanism around, but it worked and didn't fall apart, so I'm counting that as a success. With the mechanism complete, attention then turned to mounting it on the robot. This part was no-frills, just a couple of pieces of steel angle bolted to the back with a pivot hole drilled in. A small 50mm stroke actuator conveniently attached to the bottom threaded rod of the gearbox and allowed the chainsaw to move through a decent distance:

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This picture was taken about 10pm two days before we had to pack and travel down to RW. You can see the 'hackle' spikes on the top panel and the angled brackets on the rear corners for attaching the armour to (all of which had rubber in between to try and reduce shocks). The spikes were meant to be more like Dead Metal's but they were a last minute job so had to improvise and simplify. Things still to do at this stage included completely wiring up the insides, devising and fitting some sort of link mount for top and bottom, assembling the whole robot including Loctiting all connections, painting the thing and making locking bars. May not sound like a lot but all very time consuming. There were various other small things still on the to-do list that would have helped in general but that weren't too important and had to be sacrificed as we just couldn't do it all in the time we had. A 10-hour shift at the day job the following day was followed by working from about 8pm til midnight in the workshop, most of which was spent trying to wire it. I took this picture at the start of wiring then became too frantic to document the rest until we got to the warehouse:

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The Thursday involved an early start to go and collect the hire van (a horrible-to-drive Fiat Doblo), getting everything packed up at my flat then heading over to the workshop for some finishing touches. Despite planning to leave by 5pm-ish to head down the road, the finishing touches took from midday til 9pm non-stop (which I didn't realise until I did stop!) followed by a 4-hour drive back home to my own workshop. The only finishing touch I did manage to photograph was a bit of painting on the front jaws:

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We had to be at the warehouse for 8am on Friday, so after just a few hours sleep, and with several things still to do on the robot to pass tech check, I threw a few last things in the van from my workshop and headed to Glasgow. We then spent 15 hours in the warehouse, from half 8 in the morning til half 11 at night, getting Coyote finished. This included completing the wiring, cutting the rest of the HDPE to layer over the metal armour, working out and making locking bars for the front jaws, chainsaw blade and actuator and little cosmetic bits and pieces. Finally, after all that, we had a robot that had passed tech check and was ready to fight......Coyote.

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Thanks for reading if you made it this far. Apologies if the content seems rushed towards the end but it perfectly sums up what it was actually like at the time! I won't go into details of how we got on in the competition as I'll mostly just be repeating what was shown on TV, but upgrades are on the cards after Coyote got well and truly mangled. I'll share the changes in update posts sometime soon. Til then, happy roboteering