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Thread: Coyote - The Robot Wars Chronicles

  1. #1
    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 Massively outdated?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.

  2. #2
    Really cool stuff Jamie, good read

  3. #3
    I like this design, reminds me a bit of Pitbull, a very successfull robot from the
    early days of Robot Wars, it's only downfall was the lack of scrimex but it looks
    as if your robot works both ways up so it shoulden't matter.
    Only one question-what make and model are your actuators and where can I
    buy them?.

  4. #4
    Thanks for the kind words guys!

    Colin, I'm afraid I have no info on the actuators beyond the brand being Servomech. I've tried for ages to find replacement ones online with no luck. In hindsight, they're not really tough enough for HW combat as the bodies and mounting points are cast ali, so unless you were to look at machining replacement bodies from proper stock, then going for a stronger alternative is a safer bet.

    I remember Pitbull well. The first year Robots Live did their event at the Air Museum just outside Edinburgh, I went and chatted to a father and son post-show to see how they enjoyed it, and it turned out to be none other than Ivan from the Pitbull team, in the area for a holiday

  5. #5
    Looking forward to the rest

  6. #6
    Redirect Left
    Guest
    Interesting to get a behind the scenes look at these sorts of builds. Hope to see more, not just from Coyotes build, but from other bots too!

  7. #7

  8. #8
    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:

    coyote_build (36).jpg coyote_build (37).jpg coyote_build (38).jpg

    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:

    coyote_build (49).jpg

    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:

    coyote_build (54).jpg

    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.

  9. #9
    Relocation, application and determination

    We pick up this tale as we venture into the dark depths of October in northern Scotland. Cold all round, therefore perfectly acclimatising us for the Robot Wars warehouse!

    I say northern Scotland (for reference, my workshop is in south-west Scotland) because I relocated the robot, several boxes worth of tools and accessories, and all the spare parts and materials to Gary's workshop. Time was marching on and with me moving onto a winter shift timetable at work in Aberdeen, there were barely any weekends I could head down the road to work on the robot. Gary graciously offered me the use of his workshop in the run up to filming, making it a much shorter distance to travel to work on the robot on odd days off here and there. We categorically wouldn't have been able to complete Coyote on time had it not been for this, so I can't thank Gary and Sarah enough for their hospitality during this time!

    So, by this point in proceedings, Series 2 had been confirmed and applications were open! This is the photo of Coyote I included in the application:

    coyote_build (55).jpg

    It's obviously far from completion, so in order to give the production team a rough idea of how it would/should look when finished, I attempted a CAD/MS Paint/Photoshop crossover. Emphasis on the 'attempted'

    coyote_partial_render.jpg

    As I already had a Matilda-esque chainsaw, I decided to try and incorporate some other small house bot elements, so the back was to feature spikes like Dead Metal (representing the hackles of the coyote as it's preparing for a fight) and a small copper exhaust stack reminiscent of Shunt. The copper was to try and help style the machine in a steampunk theme, plus I work with copper in my day job as a gas engineer and wanted to have something that I could tie into the robot from work. Anything that could make our application more appealing.

    On that note, for anyone looking to apply for future series, along with the above pictures I also included a video cut together featuring clips of the robot driving and the jaws working (separate clips as they both weren't working together at this point) as well as explaining in real time what was planned for the robot in terms of armour and looks. We also tried to make the application fun; bombarding them with generic stats in a serious tone will get repetitive for the production team when they've got hundreds of applications to sift through, so keeping it light but informative can help your chances of being noticed.


    With the application in, we needed to get cracking. We wouldn't hear for a couple of weeks whether we'd been accepted or not, but we couldn't hang around twiddling our thumbs until then. The first port of call was to deal with the internal components. Coyote's main chassis is incredibly small, 410mm x 265mm (some featherweights are larger), and we had to fit in two drive motors, a battery, a linear actuator for the chainsaw, various wiring gubbins and no less than six speed controllers! Five brushed (two weapon actuators, two drive motors, one chainsaw actuator) and a brushless (chainsaw spin). Thankfully the majority of the controllers were compact and/or low profile, which reduced the headache slightly.

    The biggest single component after the drive motors was the battery, so installing that first would determine how much and what space we would have for the other components. We opted for a single Optipower UAV lipo pack to power the whole machine; a 22.2V/6S, 8000mAh pack. I made a simple HDPE retainer and the battery fitted perfectly with padding:

    coyote_build (57).jpg

    The motors pictured are just cans from Bosch 400s. The innards were sent off to be rewound for 24V, however it took ages for the job to get done and we ended up having to buy some second hand Bosch 750s further down the line to substitute for them in order to let us test and tweak the drive as necessary. Speaking of the drive, the motors were to be controlled by a pair of Victor 883 controllers. I've long since dispensed with the fans that come with this range of speed controllers as the fan blades always break in battle and become useless. Removing the fans leaves a low profile speed controller, which meant that they fitted perfectly on a plate which doubled up as the battery cover:

    coyote_build (59).jpg

    The space between the motors was earmarked for the chainsaw actuator, so that left the gap on the left hand side free for the brushless ESC and three TZ-85s for the actuators, as well as the radio receivers, any power distribution bars, wires and a possible link location. Thankfully the TZ-85 controllers are easily mounted in any orientation, so I stacked them all side by side next to the brushless ESC and clamped them all down. As a speed controller unit it was solid, but I wanted a bit of give when they were installed in the robot to prevent shock damage, so the plate was located on some M6 threaded rod with springs to allow for bounce:

    coyote_build (60).jpg coyote_build (61).jpg

    Below is the chassis with all the main parts bar the chainsaw actuator in. Very compact as mentioned, but workable. The chassis also needed some beefing up for heavyweight combat, so you can see a couple of pieces of steel angle welded to the base and 8mm aluminium plates cut for the back. This would not be the outer back armour so we could get away with ali. The front of the chassis would also need a steel plate welded on so that the jaw assembly could bolt to the chassis:

    coyote_build (63).jpg

    By this point we'd received confirmation that we had been accepted onto the show and production had been in touch to arrange our VT.

    For those interested in what's involved, for ours we had Joe (camera) and Sam (sound) arrive at about 9.30am. They set about making the workshop suitable for filming, which involved blacking out the windows and door, bringing in various artificial lighting, setting up the camera and deciding what colour filters to use to match the robot (orangy brown for us). They also used a smoke machine for added effect. The day began with them interviewing me, asking about general details, day job, the why and how of the robot and getting some soundbites. They then swapped us around and did some more interviewing, this time with Rachel. Once they were happy with that, they filmed us working on various bits of the robot, shots of welding, grinding, soldering etc, then did our hero shots where we pose with power tools while trying to look intimidating. The last part involved getting clips of the robot working as much as possible. We still had no drive motor internals so we rigged up the jaws to operate and ran them up and down several times while they filmed from different angles. This led to a great shot in the edited VT from the episode where the jaws opened and they overlayed the sound of a dinosaur roar, which looked really cool. We also 'crushed' a spare go-kart wheel that was lying about which again made it into the edit. Sam then needed to get back into Aberdeen to get a train home so everything was wrapped up nicely by about 3.15pm. Several hours spent for a 30 second snippet in the episode but it's good fun to do!


    coyote_build (73).jpg coyote_build (83).jpg coyote_build (86).jpg

    So concludes today's chapter. Tune in next time as things start to get frantic with only three weeks to go!

  10. #10
    You're welcome Jamie!

    Fun fact, our VT was filmed at Laurence's workshop so that it wouldn't look like PP3D and coyote were built in the same workshop when they were

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