Robot Wars Wiki
Robot Wars Wiki

"A failsafe is an electronic device which detects radio interference, or lack of a signal from the transmitter, it is then able to set a servo to a predetermined position. The servo must be able to then switch off power supply to drive and weapon systems – this can be achieved via micro switches, relays, etc."
— Official definition of a 'failsafe' (Robot Wars Technical Sheet No. 1, 2002)[1]

In Robot Wars and other robot combat competitions, a failsafe is an electrical component which automatically cuts off power to a robot's circuitry systems (e.g. for drive and weapons) when there is a malfunction or the radio signal from its transmitter is lost. The device can either be a separate component or integrated into the circuitry of certain types of receivers or speed controllers.

A common way of demonstrating the failsafe's operation is by switching off the robot's transmitter while the robot itself is activated. If properly set up to return the circuits to a neutral 'off' position, the failsafe should cause the robot to immediately stop moving if it is being driven, not start moving if it is in a stationary position, and to also automatically disable weapons if they are being operated in similar ways.[2]

Failsafes are an essential safety feature for all combat robots and other radio-controlled vehicles, preventing them from losing control if the radio signal is lost and potentially causing injury.


Series 1-3[]

An early mention of 'radio control failsafe systems' was made in the regulations for The Second Wars, which mandated their use on middleweight and heavyweight class competitors.[3] Their importance was also highlighted in official media such as The Constructor's Guide and during auditions. In the former, Team Razer briefly explained the failsafe they used for their own robot, which operated off a microswitch connected to its cam mechanism.

" ...the microswitch shuts the whole system down. It's linked up to the speed controllers and it cuts the supply voltage to them, and stops the machine clearing off under its own steam. As soon as it loses the signal from the transmitter... the machine shuts down completely dead."
— Ian Lewis explains the microswitch used as part of Razer's failsafe

Panda Monium initially applied for Series 2 without a failsafe, but was equipped with one following severe control issues during its audition

Some robots, such as Panda Monium, were nevertheless not fitted with a failsafe by the time of their auditions. One, Disruptor, even competed in the televised show without one or or an on/off switch, another safety feature required under the Series 2 rules.[3]

"The most disturbing fact about Disruptor is that it had no safety circuits and no main on/off switch which meant Disruptor was always live and if you touched the microswitches, well I think you get the idea."
Oliver Steeples, commenting on Disruptor's lack of failsafe or power switch[4]

The risks of not having a failsafe manifested themselves once Panda Monium was placed in the test area for its audition. On its first test, it drove straight into the safety barrier when Team Panda switched off its transmitter under Mat Irvine's prompts. Upon powering up their machine for a second test, Team Panda inadvertently caused Panda Monium to drive off and hit the barrier again without any control inputs from captain Pete Collier.

"Mat Irvine took a look over Panda and discussed the merits of failsafes (which we didn't have). He then gave us a slip so we could check out the transmitter. We moved Panda into the test area and started her up. After a few moves, Mat told us to switch off the transmitter. The result was that Panda turned towards the security barrier and charged at full pelt. I couldn't stop her in time and she hit the barrier at full speed. She pushed it about 1.5 feet backwards and stopped. Chris [Loader] shut the system down, but the chassis and shell had been ripped off. This meant we had to clear the debris and run again without the top.

This time, Chris stayed in with her. He switched on the power and she just shot off!! I didn't even move the stick. This time she out-ran Chris and eventually smashed into the wall on the far side of the arena. DOH! The batteries were torn from their mountings and Chris had to carry the pieces back.
— Pete Collier of Team Panda, recollecting the initial control issues Panda Monium had without a failsafe[5]

A failsafe was ultimately added to Panda Monium following the audition, significantly improving its control ahead of its eventual selection as a Series 2 reserve. It subsequently displayed very few control issues during its televised appearance in Heat A.[6]

However, as the main Robot Wars arena and pit area were filmed in a television studio, competitor machines were subjected to many sources of radio interference - cameras, power cables, lights and internal combustion engines installed in many of the House Robots. Consequently, radio signal was often difficult to maintain, and many teams - particularly in earlier series - had problems with their failsafes cutting in and making the robot stop unexpectedly under normal battle conditions, which was frequently a cause for complaint.

Furthermore, the implementation of failsafes did not entirely prevent robots from losing control during various stages of filming. Roboteers such as Rex Garrod expressed strong concerns that the rules regarding these and other safety devices were not being properly enforced, and called for improvements for these in subsequent series in order to minimise the risk of potential accidents.

"...I got a rollicking from a so called health and safety man (for drilling a hole in a piece of plastic, half a mm thick with half mm drill bit ,without goggles and leather gloves), I told him that serious accidents would occur because of their lack of proper real safety precautions like checking the all important failsafe devices that MUST be fitted on ALL robotic machines AND PROPERLY TESTED BY AN EXPERT WHO UNDERSTANDS THE DEVICES AND THEIR FAILINGS. He merely walked away. That advice fell on deaf ears, only for a serious accident (hospital case) to occur almost immediately."
— Rex Garrod, criticising Series 2's implementation of failsafe rules[7]

Despite Garrod's warnings, an accident subsequently occurred shortly after his communication with a member of the production crew about this issue. During filming for The Third Wars, a number of behind-the-scenes accidents were also linked to radio interference as well as a mix of ineffective safety switches and failsafes. Dissatisfied over the show's safety standards at the time, Garrod immediately retired from Robot Wars in response.

"The next year I arrived at the studio, only to find another robot had run amok, and injured another stagehand (machine fell off a trolley and the switch shorted out and an inefective failsafe didn't stop the machine)."
— Rex Garrod, citing improperly-prepared failsafes as a cause of one of the Series 3 incidents.[7]

Series 4-7 and International Series[]

From The Fourth Wars onwards, more detailed rules regarding failsafes were issued, stressing the importance of them being fitted to any 'dangerous' circuits such as drive and weapon systems.[8] This was one of a number of measures to ensure that earlier incidents could not be repeated. A 'failsafe check' was also in place for all applicants, involving robots being placed on their stands, operated in full drive (forward/reverse/left/right) and having their transmitters switched off mid-drive to prove the device's functionality.[9]

During filming for Season 1 of Robot Wars: Extreme Warriors, a competitor robot, The Wife, was forced to withdraw and be replaced by a loanerbot after its team could not resolve issues with its failsafe.[10]

The rules regarding failsafes by the time of The Seventh Wars were as follows:

"i) On Middle and Heavyweight robots all operating circuits that are deemed to be 'dangerous' (normally the drive and weapons) must have an approved failsafe device fitted to each circuit.
ii) This MUST bring that circuit to a pre-set 'off' or 'zero' position if the transmitter (TX) signal is lost, to prevent further operation.
iii) The fail-safes may take the form of plug-in commercial devices; electronic circuitry incorporated into some receivers - e.g. PCM-type- or other devices - e.g. Vantec speed controllers.
iv) Whichever device(s) is selected it MUST operate to the Organiser's satisfaction before the Robot will be allowed to compete. (See Technical Sheet No. 1).
Robot Wars Rules and Regulations, Series 7 (2003)[11]

Series 8-10[]

For Series 8, 9 and 10, the rules regarding failsafes remained largely similar to those of The Seventh Wars, with additional requirements regarding receiver batteries and digital switches:

"All systems that are deemed to be 'dangerous' (normally the drive and weapons) must have a 'failsafe' device. This MUST bring the systems to a pre-set 'off' or 'zero' position if the transmitter signal experiences interference or is lost. These devices should also failsafe when the receiver battery is low or if power is completely lost."
— Series 10 Build Rules, Section 4.2.1[12]
"The failsafe(s) may take the form of plug-in commercial devices; electronic circuitry incorporated into receivers or other devices. It could also consist of digital switches, which return to pre-set off position on loss of power."
— Series 10 Build Rules, Section 4.2.2[12]

Failsafe devices or capability continue to be compulsory to be fitted to all robots in FRA competitions today, but are most commonly a feature of the transmitter/receiver pairing and not a separate component within the robot.

Comparison with removable links[]

When Behemoth's receiver crashed during its Series 7 battle against Mute, the failsafe was unable to perform its intended function as the robot was left stuck in forward drive and was largely unresponsive to control inputs from Team Make Robotics. Behemoth's removable link thus provided a backup method of removing power from its drive and weapon systems prior to returning to The Pits

Failsafes are often confused with removable links, a separate switch device also used to cut off power entirely and made mandatory from The Fourth Wars onwards.[8] The term "failsafe" began to be used interchangeably with "link", even in the televised series, owing to both devices being used to immobilise robots and thus making them safe for maintenance and transportation.

The main difference between the two components is that while failsafes only cut off power when a robot loses radio signal, a removable link cuts off power as soon as it is detached from the robot's drive and weapon systems. This renders the robot and its weapon(s) inactive under all circumstances. In the event that a failsafe is not able to perform its intended function – for example, when Behemoth's receiver crashed and left it stuck in forward drive against Mute in The Seventh Wars – the link provides an effective backup solution by removing all power from the robot upon extraction.