Hi All! It’s Rob here, ARC’s captain (somehow) and designer of our heavyweight robot, Big Dave 3. We’ve all been pretty quiet over the last few weeks, due to a bit of a lull in build progress (a whole series of small snowballing problems) and because we haven’t all had much time to all be at the workshop at the same time. BUT! There is now news – we’re all working on Featherweights.

Featherweights, for our non-robot friends, are combat robots that weigh less than 13.6Kg. 30lbs for our friends stateside. Now, as with most combat robotics, smaller doesn’t necessarily mean less powerful… it just means optimising weight where we can and sacrificing certain items… like armour. Or dignity. Chris has already broken into the Featherweight fighting arena by competing with his 10 week build, Catch Me If You Can. Over the last few Extreme Robots events, he’s even started to develop a good-natured rivalry with Extreme Robots veteran, Oddbot, who’s managed to put more than a few dents (and a couple holes) in CMIYC.

As I said, we’re all working on our own Featherweights – Chris is working on another feather (& a toaster!), whereas Ali is working on his Tazbot inspired feather, currently working under the name of ARCTank. I’m very interested in where Ali is going to go with the design, as it’s currently looking awesome but mystifying.

I’m also working on a Featherweight – a little away from the massive kinetic energy weapons that Big Dave 3 and CMIYC – but no less impressive.

Enter Battlebots. 

More specifically, enter Battlebots Season 2’s Chomp. Running at 4500psi, with a massive air powered axe of awesome destruction. There’s a whole series of awesome things about Chomp’s second guise, and it’s something I’m hoping to emulate with my Featherweight, Boing!

Boing! is my attempt at a axebot with some power that isn’t common at featherweight level. I’ve just about completed the design of the custom pneumatic cylinder, allowing me to run at 1000psi of CO2 goodness. (Although High Pressure Air (HPA) is a far better idea for pneumatic, that’s a long blog post for another time). Boing! is completely built around the 3 liter buffer tank provided by Armotech. I’ve used Armotech bottles on and off for the last 7+ years in tournament paintball, and have full confidence in its ability to function whatever the circumstance.

The pneumatic cylinder is where the fun happens. I’ve gone for the John Reid-esque approach of cutting gears into the piston itself, and will be using a Mod2.5 gear to drive the axe head itself. According to my calculations, the pneumatic cylinder itself with deliver just over 3.5 tonnes of force when it completes its full 200mm stroke. I have literally no idea how much power this means for the axe head though. 

The idea behind Boing! is simple – shock and awe. I want this to be a crowd pleaser at Extreme Robots, Robots Live and, with some luck, Robot Wars itself. But, apart from being a crowd pleaser, I want Boing! to deal out some serious damage. I’m going to be learning a lot about dynamic simulations in Autodesk Inventor to make sure that Boing! doesn’t fall over on its first fire.

Now, this is all conjecture at the moment – to bring it all full circle, I’ve run into a couple of problems. Firstly, somewhat obviously to those experienced at the sport, Boing! is currently a little too heavy. The above picture – detailing the chassis plate, buffer tank, feed tanks and pneumatic assembly – comes in at a little under 9Kg. Ideally, this should be in around the 7.5Kg mark. I’m gonna see if I can get away with only one 9Oz CO2 tank, or think about making it all a little smaller – at nearly a meter long, it’s far larger than other Featherweights at the moment.

The second problem isn’t what you’d expect – you’d think it was motors, or wheels, or armour. But no. It’s O Rings!

Dynamic Sealing for 1000psi of CO2 isn’t exactly a normal application for O Rings. So, whilst I get my grooves and glands checked over by some friends, I’m looking at designing the axe head. Any suggestions?


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