Clusterbots

"A clusterbot is a machine that's made of two or more parts, which gives our opponent not just one problem to deal with, but multiple issues about how you fight something that's in two places at once."

- Alex Botwright explains the logic behind Crackers 'n' Smash

Clusterbots, first introduced in the fourth series of Robot Wars, are a special type of competitor robot which consist of two or more greatly identical robots rather than one. They would enter the arena together as one machine, before separating and fighting as separate robots when the battle began.

Clusterbots were rather uncommon in Robot Wars, with only five having competed in the UK Series to date. These were joint-pioneer and Series 4 Heat-Finalist Gemini, (heavyweight), Black and Blue (heavyweight), Crackers 'n' Smash (heavyweight), Typhoon Twins (middleweight) and Legion (antweight). Another clusterbot, Share + Destroy, was also planned to enter Series 4, but failed to qualify.

Rules
The rules governed for clusterbots state that while there are no limits for the number of robots they can be made out of, the combined weight of each robot must be within the given weight limit for each category (for example, 79.4kg, 100kg or 110kg for heavyweights).

An additional rule for clusterbots states that if 50% of the robot - in terms of weight - is rendered immobile, then the whole robot is deemed immobilised, and therefore eliminated. Since most clusterbots consisted of two parts of equal weight, robots that fought them would often concentrate on defeating one half of the robot as a result of this rule. A key example is Tornado during its Series 4 Heat Final against Gemini, which focused on impaling one half on an arena spike in order to eliminate it. Although consistently applied in the main heavyweight competitions, this rule was not strictly enforced in the lower weight classes, with both Legion and Typhoon Twins continuing to fight even after one half had become immobilised or pitted.

In Series 9, the rule was changed so that 60% of a robot must be defeated for the whole robot to be considered immobile. Competitor robot Crackers 'n' Smash maximised this by having each half of the robot weigh 50kg and 60kg respectively - as neither part of the robot weighs more than 66kg, both halves of the robot would need to become immobilised before Crackers 'n' Smash can be deemed immobile.

A variation of the 50% rule occurred in the second series of Dutch Robot Wars, where roboteers from the Netherlands created and entered a three-part clusterbot called √3. The rule here was that all three parts of the clusterbot had to add up to the weight limit, and the opponent had to immobilise two parts of the clusterbot in order to win (half of 3 was 1½, which rounded up). Therefore, even though Matilda threw one part of √3 out of the arena during its battle against Pika 3, the other two parts still managed to win the battle on a Judges' decision. Had this occurred in Series 4 or earlier, √3 would have been eliminated, as the original rule stated that the entire clusterbot was out if one piece was immobilised regardless of how many robots comprised the clusterbot. Nothing more than a three-part clusterbot was ever seen in any domestic or international series of Robot Wars.

Interestingly, clusterbots were not allowed to fight in melees prior to Series 4 due to radio interference issues.

Minibots
A similar concept to the clusterbot exists in the form of minibots. These involve small robots that competed alongside the main competitor, which were significantly lighter, and were neither required to be attached to the main competitor at the start of the battle nor to feature an active weapon.

Minibots were typically used to distract and disrupt an opponent's movements, interfering with their attacks, but were considerably more fragile than standard clusterbots due to their smaller size. As a result, minibots were largely considered to be sacrificial, and would not usually fight again if they were severely damaged in battle.

The first robot to use a minibot, although the concept was not named as such at the time, was Psycho Chicken in Robot Wars: Extreme Warriors, with its egg-shaped minibot, 'Scramble'. However, the concept would not be explored again until Series 8 of the UK Robot Wars, with two minibots appearing as part of Nuts, and one ('The Hatchling') accompanying Terror Turtle.

Advantages

 * Through comprising of two or more robots, clusterbots are more difficult for opponents to defeat quickly, since they require one or all parts to become immobilised before they can be eliminated.
 * A clusterbot can allow for an effective attack synergy between individual segments; it was not uncommon for all parts of a clusterbot to block and surround opponents when fighting simultaneously. This tactic was regularly demonstrated by Gemini, √3 and Crackers 'n' Smash during their respective appearances.
 * Additionally, if one part of a clusterbot is attacking an opponent, the others can be used to activate arena hazards very quickly. √3 notably demonstrated this tactic in its Dutch Series 2 battle against ODT-Zero, with Elevation pressing the pit and Floor Spinner buttons immediately while the other two thirds attacked ODT-Zero.
 * If one part of a clusterbot is attacked, the other parts can assist it by targeting opponents which initiated the attack. This is best demonstrated in Gemini's All-Stars battle against Razer in Extreme 1, where one half of Gemini lifted and flipped Razer over in a successful attempt to free its twin from the latter's grasp.
 * Depending on their design, minibots could prove especially effective in disrupting an opponent's movements, as their small size can enable them to block or even get underneath them. On two occasions, Nuts' wedge-shaped minibots succeeded in getting themselves underneath Terrorhurtz, preventing the latter from driving properly and attacking the main robot.

Disadvantages
"If both robots take a lot of damage, we don't have just one robot to repair, but two, which could potentially be twice the work."
 * In order to keep within the given weight limits, each segment of a typical clusterbot was required to be significantly smaller and lighter than normal competitors in their respective weight classes. As a result, they were usually more susceptible to getting pushed around, flipped, or seriously damaged by opponents, as the defeats of Gemini, Black and Blue, √3 and Crackers 'n' Smash demonstrated.
 * Minibots were especially susceptible to these issues due to their significantly smaller size and usually lower build quality. Nuts' minibots in particular were both thrown by Behemoth and damaged by Carbide at various points during Series 8, while Scramble (Psycho Chicken) was so severely damaged by Propeller-Head in US Season 2 that it entered its next battle without any form of mobility.
 * Due to them comprising of two or more robots, clusterbots require significantly more time and effort to maintain in between battles than regular competitors, since the team has to repair all parts of the robot at once within the allotted timeframe. Additionally, they require at least two or more drivers, adding to the complexity of operating them in the arena.

- Alex Botwright

List of Clusterbots/Minibots
Robots are listed alphabetically. Clusterbots which are not heavyweight entries are listed with a green background. Minibots are listed with a blue background.