Battlebots 2015 - Half-Time

We're now half way through the new reboot series of Battlebots and already the series has brought a wave of new fans to the sport. So far I have been impressed but many people have raised questions about rules and strategies. I think it's only right to answer them.

1. Why not make a huge robot with guns or massive, heavy weapons?

Pretty much all robot combat competitions divide the competition into weight classes to keep the competition more even. Each class has a different weight limit (as well as a few other rules in some cases but I won't go into detail here). The weight limit set for this Battlebots competition was 250 pounds, around 113 kilograms. There are a lot of things needed on a robot and each item adds more weight so a decision needs to be made about putting more weight into a big weapon, thick armour or beefy drive motors.

Untethered projectiles (e.g. bullets) are disallowed for safety reasons. If a hammer accidentally goes off in the pits, you better hope your hand isn't underneath it. If a gun goes off, chances are someone will get hit, even if they're on the other side of the pits.

On a similar note, sometimes people expect big humanoid robots. You only have to watch the entries to this year's DARPA Robotics Challenge stumble and collapse to see why this isn't an option. True, they did have humanoid robots on Robot Combat League but these were held up by big metal rods coming out of the floor.

"Sir, you appear to have a big metal rod up your ass."

Source: http://www.post-gazette.com/ae/tv-radio/2013/03/23/Reality-Check-CMU-student-her-partner-fall-in-Robot-Combat/stories/201303230142

2. Why are minibots allowed? What are the rules regarding them?

This is the most common question that I've seen. Minibots are small robots which help a larger, main robot. This setup, with multiple robots fighting as one, is called a clusterbot or multibot. 

The most important thing to bear in mind here is that the robot as a whole (all parts of the cluster - the main bot and the mini bots) still has to meet the weight limit. These limits divide the competition into separate weight classes to keep the competition more even. This year, Battlebots' own ruleset put the weight limit at 250 pounds (~113 kg), which is a unique and slightly odd weight limit that doesn't quite fit into any normal weight class. The closest one is the heavyweight class, quite a common class with a limit of 100 kg, or 220 pounds. I have no idea why they decided to ignore this and invent their own weight class.

What this means is that a robot built specifically for Battlebots' weight limit is too heavy to use elsewhere. As a result, some people have opted to build normal heavyweight-class robots that they can use at other events. This leaves around 30 pounds, or 13 kilos, of spare weight. Might as well make a smaller robot or two to fill that gap. Incidentally, 30 pounds is actually the weight limit for another popular weight class, the featherweight class, so the minibots could be used as standalone robots at other events.

Having many robots which can all attack at the same time might seem like an advantage but that's often not true. Since the robot as a whole (main robot + minibots) still has to fit below the weight limit, each individual unit of the robot has a weight disadvantage. The minibots will weigh a tenth or less than the opponent and there is only so much they can do offensively, which is why they are mainly used as an annoyance to get in the way.

This is the moment when one of Warrior Clan's minibots was eviscerated by Nightmare.
Such a small bot was never going to survive a shot from that massive blade.

Source: https://www.youtube.com/watch?v=3s7V7igh5QQ

Some teams prefer to spread the weight more evenly between robots. Gemini of Robot Wars fame consisted of two flipper-bots each weighing around 50 kilograms. They did reasonably well but it was all too easy for an opponent, weighing twice as much as each individual Gemini bot, to pick a target and beat it.

3. Why was Wrecks so rubbish?

I don't much like this question. The problem is that I actually quite liked Wrecks. Yes, it was slow and it could barely turn, but it was a really unique and interesting design. An antweight robot built by the same team named Gyrobot uses the same system for mobility and it's actually quite good. It even has an honourable mention in the Combat Robot Hall of Fame, a prestigious award indeed.

Gyrobot (foreground), seen here fighting Warpig in 2010, will from now on
be known as Tiny Wrecks

Source: https://www.youtube.com/watch?v=gxmJXRlsksY

Why was Wrecks so much slower to turn? Probably something complicated to do with power-to-weight ratios. Wrecks turns using the momentum of its spinning blade, something called precession. If you scale down a weapon, you basically end up with a bigger power-to-weight ratio (don't ask me to explain why). The antweight version therefore has a more powerful blade for its weight so the momentum is enough to make it turn quite quickly. Scale the antweight up to something 1000 times its size and you don't have as much power, for the weight, to use.

Why even try then? Because it's a unique, interesting design. I'm really glad I got to see a big robot able to turn and move just using the power of its weapon. Besides, watching a big hunk of metal waddle around on those two flat feet was quite funny.

I'm hoping that next year Battlebots will re-instate weight advantage rules. In most competitions, walking robots get double the weight allowance (or 150% weight allowance, depending on who's organising the event). This is because walkers tend to be slower, less agile and more complicated but are still entertaining. Shuffling, driving small legs using cams instead of wheels, only earns a smaller weight advantage, or none at all.

Waddle you crazy robot dino, you

Source: https://www.youtube.com/watch?v=apixM-HXpGY

4. What's happening with the killsaws? Why aren't the hazards being used?

For those who don't know, a hazard is an obstacle or weapon built into the arena, like the killsaws or the screws.

We've already seen plenty of the screws and they look to be more effective than they've ever been! Back in the old series they were little more than decoration but this year we've seen robots picked up with pieces torn off them. Some have said that they are a little too deadly, picking robots up and carrying them off the arena and out of the competition. Perhaps they're right, though others argue this new danger encourages drivers to be a little more careful and strategic. These were underused at first because they used to be quite weak, almost decorative really, but teams are finding them to be more effective and are now making better use of them.

The pulverisers are now controlled by the teams (the coloured circle corresponds to the team), which is an interesting new feature. I'd like to see more of this in the future, since at least an upset caused by a hazard will still be down to the teams, not the producers. Obviously a team isn't going to use a pulveriser on their own robot, so we've been seeing less of these.

We've also seen a little bit from the new hazard, the pinball-style flippers. A similar, far weaker thing was used in the original Robot Wars competitions way back in the mid '90s. The modern flippers are a lot shorter, sturdier and probably more powerful but we haven't seen much of them. Look for the diagonal panels next to the screws and you might catch a glimpse of one flicking a robot away. It has to be said that they don't seem to do much but they ought to stop robots getting caught in the arena corners like they used to.

Now, about everyone's favourite hazard, the killsaws. I'm honestly not sure what's happened there. All I can see is that it appears most of the saws are broken. Some are working, as we've seen, but only some. I can't say whether they'll have been fixed for later episodes but no one from the live audience has said anything encouraging.

Here they are before the event. Shame we've barely seen them.

Source: https://www.facebook.com/battlebots

5. Do flamethrowers actually do anything?

This depends on the flamethrower itself and the opponent. A quick lick of flame is unlikely to do anything. Even a long roasting won't really effect robots' outer armour. The trick is to use a large-enough flame, or aim it right, to get through gaps and reach the opponent's innards. Solder melts, batteries blow, motors overheat. Yes, flame can work if used well.

Getting in close enough for long enough with a flamethrower is the tricky part, so they are usually not too useful. Still, they look great and help win favour with the committee selecting robots for the competition.

6. Can anything beat Tombstone?

Yes. Stinger has beaten Tombstone a number of times at other events while both went under their usual aliases of Sewer Snake and Last Rites respectively. Stinger is designed to take on spinners. It can lose wheels and keep on trucking. The huge, thick wedge is great at deflecting blows whilst 6-wheel-drive provide traction enough to shove robots around the arena. Team Plumb Crazy's usual strategy of using the opponent's weapon against them ("break his fist with my face" as Matt Maxham, team captain, once put it) takes advantage of the force spinners have to take from their own weapons.

Sewer Snake spits flame at a smoking and beaten Last Rites in 2011

Source: https://www.youtube.com/watch?v=DXHnvCNGjqQ

Many think Bronco could do enough as well. The weapon is powerful, the team is experienced. But the same could be said for Last Rites. Flippers are less useful for shoving an opponent around than lifters, too. Still, Bronco looks quite tough (though I don't know what those wheel guards can stand up to) and it may be able to take the punishment. Flipping Tombstone alone may do little but getting Tombstone caught on the screws is a possibility.

Bite Force is often overlooked here but we have seen that it can stand up to spinners. The wedge deflected Warhead's attacks nicely, throwing it into the air. Tombstone's weapon is heavier and spins faster but Biteforce might have a chance. Still, they will be on the defensive and would struggle to win a judges' decision here.

Finally there is ICEwave. This is the big spinner-versus-spinner battle we all want to see. As good a robot as ICEwave is though, I can't see it beating Tombstone. Its spinner is shorter, with less reach, so the main body of ICEwave would be hit before Tombstone's. Tombstone may even be able to reach that petrol motor an that would be catastrophic. Yes, the back of Tombstone is exposed, a problem ICEwave doesn't face, but the former can turn quickly and has a big enough weapon to not be left vulnerable.