Hey everyone,

It's been a while since I've touched my regular RogueTwo Robots build diary as I haven't done much stuff outside of RW since the start of 2016, and it's always been my plan to document the build of Coyote on here so I figure a new thread is the best option.

Coyote was my first scratch-built heavyweight. I've been doing this since 2004 (2001/2 if you count numerous failed builds) and in that time I've never managed to build my own heavyweight. I joined Gary and PP3D for Series 1/8 of Robot Wars and that was a tick off the bucket list, but building my own heavyweight for the show was still the dream. I'm going to detail the whole process as much as I can for those interested in it or looking to do the same. I'll warn you now, it'll be several posts and a lot of them will likely warrant TL;DRs but, well, tough

The Beginning

There were rumours at the end of Series 1 filming that Series 2 was going to be filmed in August/September time. Gary wasn't sure he'd be able to get PP3D ready for then but I was still desperate to be involved in the show so I decided to finally get cracking on my own heavyweight. I'd sold all my previous HW gear about two months before the reboot was announced (typical!) so starting from scratch was the only option.

Since the reboot would be on Series 2, and S2 of the classic era is one of my favourites, I immediately decided I wanted to have a chainsaw. Ineffective weapon? Yep. Massively outdated? Yep. Did I care? Nope! I reasoned that as it was designed to be used with wood, and that HDPE can be worked with wood tools, then it may actually be able to cause some cosmetic damage. So that was the first weapon. I say first because I knew a chainsaw wouldn't be good enough for a primary weapon.

I then bought a pair of actuators off Gary, ones that he had bought with plans to fit into Smidsy but no longer needed. They were compact but powerful and reasonably fast, so I knew I'd find a use for them. I think it was around this time that I also bought the Scot-Bots middleweight/Tanto Jr. off Tony. Making a functional drive system was always one of the biggest hurdles for me building a HW as, more often than not, it requires a lathe and I didn't have one, or easy access to one. So the MW gave my a fully built drive system that I could build a HW around.

coyote_build (4).jpg

I picked up a cheap chainsaw on eBay and plundered the bar, chain and sprocket setup from it. At this stage I wasn't sure whether to use the actuators for a lifter or some sort of grabber, but I knew the chainsaw would be a tail, actuated to move up and down like the original Matilda.

After some deliberation, I decided to use the actuators for a clamp and lift weapon with dual, independently operated jaws, akin to Diesector from Battlebots:

Diesector_SF02.jpg

I reckoned this would be more interesting than a lifter and therefore more likely to be successful when applying for Robot Wars. The Tanto chassis was just a bit neat width wise to fit the actuators and expected gubbins in, so I shortened the bulkheads supporting the wheels and motors and rotated them 90° on the baseplate which gave about 100mm extra width. It may not sound like a lot but it was just what I needed for things to fit.

I also needed some extra height allowance to be able to run inverted as I didn't anticipate the jaws being capable of self-righting, and the original chassis wheels were a bit on the short side, but thankfully the hubs were a perfect fit for the foam wheels we used on PP3D in S1, spares of which I had lying around. So on they went, and I started to feel like this was bordering on HW territory

coyote_build (18).jpg

Next up was to make an MDF prototype for the jaw assembly to work out ideal locations for mounting holes and pivot points. I knew getting the right geometry would be tricky, so the MDF would allow for corrections!
As it turns out, I got it spot on first time. Drawing out the shapes of the jaws took a few goes but once I was happy with them, I cut them out and rigged them up and they seemed to work well.

coyote_build (23).jpg

And a video of them in operation:


Overall I was really pleased with this. I could see that the jaws moved at different speeds depending on whereabouts in the actuator's travel they were at, but I was confident that it could be accounted for and wouldn't cause problems. This was is May last year, so only a couple of months since Series 1 filming and I was happy and surprised at the rate of progress. I knew there would still be a lot to do but that it was achievable. If I remember rightly, by this point talk of S2 filming had been changed to October-ish so it gave several more weeks build time.

That's enough for now. Follow up will be turning the MDF prototype into something battleworthy and more chassis developments.