Anatomy of a robot: Investigating the chassis of Storm 2

August 24, 2016
Anatomy of a robot: Investigating the chassis of Storm 2

For anyone watching this latest series of Robot Wars, or indeed the previous series of the show through the 90s and early 2000s, you’ll be aware that these robots come in all shapes and sizes. Though perhaps the key talking point, the appearance of the robot and structure from the chassis goes way beyond aesthetics. Storm 2’s shape and size contribute enormously to Team Storm’s success, so let’s take a look at why that is.

When Storm 2 was being designed, the team took a leaf out of the IT cookbook and started with a functional breakdown from the end goal: to win. As it turned out, this was a particularly useful approach (for two reasons). Firstly, it told the team that actually a weapon was surplus to requirements, and secondly, it allowed the team to focus on two key requirements – maintainability and reliability. The logic being that if you’ve broken down in the fight, it doesn’t matter what state the other robot is in, you’ve lost. Also, if you can’t fix the robot to get into the next fight, you’ve lost. Once you have those two as guiding principles the rest follows naturally.

Storm 2’s chassis is mostly made from mild steel, it’s a 25mm square box section with a 3mm wall thickness. Simple, cheap and not very light – although, did you know that the bare chassis of Storm 2 was built to weigh 32Kg? Why 32Kg, you might ask – because that’s the maximum weight of a bag that you can take on a long haul aircraft. That means that we can fly Storm 2 overseas should we want to as hold luggage, with all of the internal parts of the robot just stowed in bags. We did this when we competed in RoboGames in San Francisco – it did get a few strange looks from airline check-in staff!

Onto the chassis everything mounts, we use M8 nuts welded onto the back of the box section with holes drilled through to allow the mounting bolts to hold the armour in position – this is a design that we’re having to review, as it looks like that simply might not be strong enough going forwards. You just can’t fix the armour on with bolts strongly enough. Our current record is 8 x 8mm bolts simply being pulled straight out of the nut from a single impact!

Photon Storm by comparison is a very different design. It uses a monocoque made out of a material called ‘Hardox’. Hardox is a very strong, toughened steel that is usually used for wear-plates on construction equipment, like a JCB for example. On Photon Storm there is an underlying Hardox chassis – like the carbon fibre tub that a Formula 1 car is built around and it varies in thickness from 10mm on the side, to 3mm around the front. On top of that 3mm Hardox base is an additional 6mm of Armox 600. Armox is an incredibly tough material that is very hard to work with and almost impossible to drill – but deals with the high impact the robot receives very well. In fact, the Armox is actually stronger than the welds that hold it in place, so if anything we’d expect the Armox panels to come off whole, ripping the welds apart.

The other common thread between both Storm 2 and Photon Storm is the compact size. The smaller you make a robot, the thicker you can make the armour – as there is less robot to armour. This does have a downside however, in that you find that you have little space for components to go. We’ve often said if we were to make Storm 2 again we would make it 1mm longer, wider and taller, as every time we try to fit something in, it seems that Storm 2 is just 1mm too small! It also means you don’t have large air gaps to protect things – and this is something that for future design we might have to refine. How can we leverage these exotic metals better? Storm 2 was originally conceived in 2001, and Grade 5 Titanium bolted on to a steel box section chassis was absolutely cutting edge. Today, with more and more robots running a monocoque chassis, they’re simply better at handling impact.

You can find out more about Storm 2 and what it takes to be a battle-ready bot in our anatomy of a robot blog series. Look out for our final blog next week and why not check last week’s blog looking at the software used in Storm 2.

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