Mister Transistor at Robot Wars

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On 23 August 2003 my family team "Zoid" and our Gothically-inspired heavyweight fighting robot "Skorpizoid" took part in a qualifying heat of Robot Wars the 7th War. Unfortunately we did not qualify for the subsequent televised rounds, however we acquitted ourselves well for a first-time entry. I started serious work on a fighting robot in December 2001, although I had been researching the possibility for a couple of years previously. Skorpizoid is in the heavyweight class, for machines that weigh between 80 and 100 Kilograms. Yes, that's 220 pounds weight, a seriously heavy machine to build and drive around. A single person cannot lift it, and if it fell on your foot, it would break your bones. It's about 3 feet long, 3 feet wide and 18 inches high.

The important thing to understand about Robot Wars is that it is a television program, not an engineering competition. Above all the robot must look good on TV. I therefore wanted a machine with a good image. The original concept was really a cross between a scorpion and a stealth fighter: a narrow triangular-section body with an over-arching tail, and a removable weapon arm on each side. In the course of construction this changed: the body section became rectangular and the tail disappeared. This meant a major design flaw was built in: there would be no self-righting mechanism. Many robots have 'flippers' that can upturn another robot, or even throw it several feet in the air, despite the 100 Kg weight. To counter this, you must either be able to run either way up, or have a self-righting mechanism. However, as my goal for Skorpizoid was the modest one of getting onto the program, I was not too worried. I knew that just building a working machine was enough of a challenge for the first year.

I am not a mechanical engineer, so I had to teach myself to arc-weld in order to build it. It is based on a frame of 1-inch square steel tubing with body plates of either 3mm or 1mm steel. I bought some surplus industrial servo motors on eBay and used them to drive the wheels via an industrial sprocket and chain. I had to do a lot of research to understand how standard model radio-control gear is used to drive motors of a kilowatt. I designed and built the power electronics controllers myself, and used an open-source programmable radio-control interface that can be bought on the Web. Skorpizoid uses three 12-volt 17-Ah sealed lead-acid batteries for power.

Skorpizoid weapon Originally I wanted to use a low-voltage high-current electrical discharge weapon, but Robot Wars told me this was not allowed. The most destructive robot weapons on the program are either gas-powered flippers or massive spinning disks. The former are just too dangerous for me: one mistake during construction or testing and you have lost some body parts. But on the other hand I did not want to make a boring clone of Hypnodisc (although there are plenty of teams that have). So I designed a unique device based on rotational storage of energy, but not a disk: instead a massive rotor is attached via a shaft to a pair of cutting blades that are intended to rip into anything they touch. I found a good little engineering firm in West Croydon to build the weapon, as I could not make parts precisely enough myself. This thing has 10 Kg rotating at about 1000 rpm, and any imbalance will shake the machine to pieces. The image on the right shows Skorpizoid and its weapon (with the blades inside a plastic bottle).

By Spring 2003 I had the body built, the electronics half-complete, and the weapon order placed with the engineering firm. I had expected to receive the application forms in March as usual, but nothing happened. Then there was an announcement that the production company of Robot Wars had signed with Channel5 rather than BBC2 for the 7th War, and that filming would probably be in the last week of August, rather than June as normal. Time passed without much progress on Skorpizoid, then the application forms arrived with no further information than filming would be in the last week of August, about the same time as the weapons would be ready. By then it was urgent to book our summer holiday. We eventually arranged to go to Normandy for 11-22 August, which I thought would allow a weekend to finish things after our return. The weapons (I had asked for two to be made) would be ready then, and I could fix them to the body and try them. This was cutting it fine, but I had seen and even tested an incomplete weapon and it looked good, although I was a bit worried about its weight. I had weighed all the parts separately using ordinary bathroom scales, and the total was very close to the limit of 100 Kg. On Saturday 9 August I received confirmation that my entry had been accepted, and that Skorpizoid should come to a qualifying heat event on 23 August at 9:30, in the usual venue of RAF Newton near Nottingham. This was a nightmare: we would be arriving back from Normandy late in the previous evening. However at least we had a chance: we could have been allocated to the other qualifying day of the 22nd. I arranged that the engineering company would deliver the weapons on the afternoon of the 22nd. I would have to attach them that night, load up the car, get a short sleep, and then drive to the event.

On the 11th, while waiting to board the SeaCat, I phoned the engineering company to check that all was OK, and confirmed with Robot Wars that we would be there. Then we went to France: the SeaCat was late in leaving, an ominous sign for the return. Needless to say, I worried quite a lot about things during the holiday. Eventually it came time to return. After driving most of the day, we reached Calais. The SeaCat was even later this time, and we arrived in Purley at about 23:00, to find the weapons sitting in the front porch as promised. I unpacked the car, and went to the garage to drill the mounting holes. Then I loaded everything into the car - the body, the armour, the weapons, the batteries, the R/C transmitter, and a big toolbox. I thought I had everything, so I went to bed at 1 am.

hangar Next morning we got up early, left Purley about 6:15, and drove for three hours to reach RAF Newton on time just before 9:30. Newton is a semi-derelict base that has not had planes there for decades. In recent years it has been the base of the RAF dog-handling unit. It's full of spooky derelict two-story buildings with radioactivity signs on the doors, surrounded by metre-high vegetation. Ideal for a Doctor Who set, if you remember that far back. There are several huge hangars, and one of these is used by Robot Wars. The image on the right shows a view of the hangar from the queue of cars and vans bringing roboteers there.

Once you reach the head of the queue, you drive into the unloading bay, unload the robot onto a trolley, and join a queue to have your team photo taken and your robot weighed. I had to assemble Skorpizoid in the queue, and discovered that I had forgotten the armour plates that cover the wheels. This was not a big problem, as the weapons ensure that other robots cannot get near the wheels. My son Neil pointed out another problem: Skorpizoid did not have sharp-edge protection on the weapon blades. My wife suggested that I cut in half a plastic bottle, which I did, taping one half over each weapon. This was criticised and I was told that I could get away with it once but if I came back for the televised parts I would need something better. The biggest problem occurred on weighing: Skorpizoid was embarassingly 10 Kg overweight. This shows the inaccuracy of bathroom scales. The only option I had was to remove one of the two weapons. As I was doing this, Alan Gribble (ex-captain of team Pussycat) suggested that I just remove the rotor, which I did using his Allen keys, and which took the weight to an acceptable 95 Kgs, but now I had a distinctly unbalanced robot.

Having passed the weight limit, we entered the hangar, where I checked my transmitter into Transmitter Control, because roboteers are not allowed to have any kind of radio-control in the so-called "pits". Its use is dangerous because of possible interference with robots fighting in the arena that is located just through a large curtain. Transmitter Control asked me to change my frequency from the standard channel that came with the set to a less common one: I had been expecting this and had the necessary crystals with me. We were then allocated table 41 in the pits where we installed Skorpizoid on its cradle, which allows the wheels to turn without the robot moving. I also had to sign a contract absolving Robot Wars from any liability etc etc. We then had to await the full 'technical check', an important part of Robot Wars and a critical test to pass. Robot Wars applies very many rules to all aspects of robot construction, mostly intended to ensure safety. There are limits to voltages and gas pressures allowed, requirements for radio-control fail-safe circuits, a large number of possible weapon types are banned, and every weapon must have a clearly-marked immobiliser and sharp-edge protection. The robot must have a 'removable link' that completely de-activates it, and it must have a cradle on which it can sit and be driven without moving. Most new robots have problems with the tech check. As we had expected, we had to wait around a long time for the check, and so we chatted to various other roboteers, in particular team Aggrobot who were next to us. Many people passed by and examined Skorpizoid's weapon with interest, as they had not seen anything else like it. One roboteer told me it was good to see something new, as many of the machines were very similar.

In the meantime fights had started in the Arena. They were 4-way melees in which the winner qualified for the main War, and the producer also could nominate one non-winner to go through, if they liked their appearance. Even fifty feet or more away, the noise from the Arena was frightening: an air-horn would signal the start of a fight, and then there would be some tremendous crashes. My wife and children went round to watch some: there were no house robots or special effects (pit, flame pit, etc), just straight combat watched by the producer and a few other judges. Although we had been told to wear our 'costumes' (in our case, black T-shirts with 'Team Zoid' labels stuck on them) there was no filming, which was a disappointment.

Finally, about lunchtime, George Francis (of Chaos2 fame) came to do the check. He was happy with Skorpizoid, but another problem was revealed during the check: the transmitter battery was flat. (It's not clear to me how the check can use the transmitter while fights are going on: presumably Transmitter Control, whose main function is to ensure that no channel clashes occur, are aware of its use). The flat battery was yet another embarrassing problem that would have been avoided if I had not been so short of time. Team Aggrobot offered to swap batteries with me, but they did not have the same one. Eventually, Transmitter Control put my set on a charger, although not a fast one. After another hour or so, during which we ate our sandwiches, we were called to fight. You have to load the robot, including cradle and all protective devices, off the pit table onto a large trolley that is the same height, which you then wheel to the queue for the Arena. Only at this point do you find who your opposition is. In our case, we were against three spinning disk robots: at least there were no flippers. I could not believe how nervous I felt waiting in the queue: the image shows me there. pits When our turn came, we wheeled the trolley up to the back of the stage, which is the same height. Kim Davies of team Panic Attack was running the pit crew that handle the transfer of robots in and out of the Arena. He helped me manhandle Skorpizoid off the cradle and then roll it into the 'bull pen'. This is the small area under the competitors' gallery. The bull pen has a low back door that is closed after the robots has been rolled in and then you have to reach over this door, remove the weapon safety devices, and then plug in the removable link to activate the robot. Then a shutter is lowered to close off the back of the bull pen. You then look through a small window to the side, the pit crew opens the shutter at the front of the pen, and you drive out into the Arena. Then you climb the stairs to the gallery above and start the fight when the air-horn sounds (no '3-2-1-activate' in the qualifiers). Well, that's the theory. When I tried to drive Skorpizoid out, it turned in a circle and ran into the wall. Kim turned it around and I tried to drive out backwards but nothing happened and I could see the sprocket wheel on one side had come off the motor axle. We closed the front of the pen, de-activated the robot, and lugged it back onto the trolley. Kim said that if I could fix it I could try again later.

Back in the pits I was exhausted. I had known that the grub screws that clamp the sprockets to the motor axles were a weak point. Most high-power motors have keyed axles that cannot slip, but mine do not. I had intended to grind a flat on the axles to alleviate the problem, but had not got round to it. I felt that this was a show-stopper and I suggested to my family that we quit and go home. The children refused to accept this so I fitted the sprocket and chain back on, tightened the grub screws on both sides as hard as I could, and informed Robot Wars that I wanted to try again. I was also worried about the weight imbalance caused by the missing weapon. Because the weapons are outboard of the wheels, they could touch the ground, and so there is a ball transfer unit under each one. However, this requires four points (the two balls and the bottoms of the two wheels) to be aligned correctly, and of course I had not been able to properly check this, as the weapons were only fitted the night before. If this were wrong, one wheel might be too high and this could explain the circular movement in the bull pen. I tried to align the balls with the wheels as best I could, but as the tyres are pneumatic, they might settle under load. Robots MUST be on their cradles in the pits, so I could not be sure that all was correct. We then had another long wait of several hours. My family went and watched a few fights, and I chatted to lots of roboteers, especially after fights. I saw massive damage caused by spinning disks. I saw numerous well-known machines, although the seeded ones were only there for a tech check: they did not need to qualify. At last, about 18:00, we were on again. This was to be the last melee, for machines that had technical problems earlier in the day. There were five of us: Skorpizoid, Metallica, I-Bot-It-A, Tough as Nails and one other that was made of plywood. I fancied trying Skorpizoid's weapon on the plywood if possible, but I was mostly just concerned to get into the Arena.

arena Again we went through the loading process. This time Skorpizoid did drive into the Arena, but I had a lot of trouble getting it to go in a straight line, or even to drive forwards. There was a strong imbalance that caused it to turn sideways. The other robots were having problems too. Finally the fight started. Metallica and Tough as Nails crashed together and became immobile. I-Bot-It-A was attacking the plywood machine erratically. Skorpizoid would only turn in circles, and ran much better backwards than forwards. This battle was not going to be too exciting. After a while only I-Bot-It-A and Skorpizoid were moving so I-Bot-IT-A foolishly decided to attack Skorpizoid. It ran into Skorpizoid's weapon and bounced off, then came around the back and hit the tail. It then went off somewhere else. By then Skorpizoid's batteries seemed to running flat as the weapon was turning slowly, so I turned off the transmitter as the air-horn ended the battle. The image on the right shows the Arena with the Skorpizoid and Metallica.

During unloading I was too busy and hyped up to notice very much, but my children tell me that I-Bot-It-A had a big hole where Skorpizoid's weapon ripped through its body. Nevetheless I-Bot-It-A won the heat as it was the only really mobile robot during the whole bout. My children say that Skorpizoid was second as we were still moving until near the end. However, we did not get invited to the later rounds. Skorpizoid itself had a split weld on its face, and the tail had been forced open by I-Bot-It-A's rather clumsy rotating bar as shown in the image. Later on I thought I could just hammer this back into shape, but 1-inch square section steel tubing is not so easily bent! Skorpizoid's weapon tips had been deformed, and the 1-inch diameter steel axle had bent slightly, so it must have struck with some force. After the fight I had to dismantle Skorpizoid into its components, load the 110 Kgs back into the car and drive for three hours to get home. As I was loading the body I noticed that the drive motors were quite hot. damage

I learned a lot from all this, not least how the whole Robot Wars 'circus' works. Unfortunately it looks like the TV series has come to an end, and combat robotics in the UK, if it continues at all, will be under a different organisation. Secondly a lot of things went wrong that would not have, had I been properly prepared. Next time I must weigh properly and get some driving practice. In reality that's hard as it seems to be the norm to be struggling to finish construction on time. My power electronics worked well, a major achievement. However I want to check the motor controllers anyway. They did not seem to brake the motors when expected. The weapon design is poor. It is too easy to bend the axle, and any significant bend would render it useless because of vibration. I still like the idea of using rotational energy, and I definitely want to have an original weapon construction.

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futurebots whose owner Dan has been serving robotic and electronic technology since 1985. He sells chips, robot parts, and even PC parts.

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