- "A four-bar mechanism gets the tip of the arm to move with a slight forward arc while it travels up. This seemed like a good motion for flipping other robots over. Four-bar mechanisms are very popular in machine design. The trick is to determine the optimum length for each of the four bars to get exactly the motion you want."
- — Carlo Bertocchini on BioHazard's iconic lifter[1]
Four-Bar Lifters are a specific type of lifting arm which makes use of a four-bar linkage to move the arm up and forwards and tip opponents over.
Design and History[]
BioHazard demonstrating its four-bar lifter against Killbborg in 1996.
The four-bar lifter was first introduced by Carlo Bertocchini, the builder of BioHazard. Inspired by mechanical devices which make use of the same concept, he debuted BioHazard in the 1996 US Robot Wars competition. It proved to be an instant success, using its revolutionary weaponry to control and overturn opponents, many of whom had no answer to being flipped. BioHazard won the heavyweight competition by defeating Vlad the Impaler in the semi-finals and La Machine in the final. In its semi-final win, BioHazard's four-bar lifter mechanism proved to be an effective self-righter as well, becoming the first combat robot ever to right itself from being flipped onto its back.[2] In 1997, BioHazard was joined by another robot using a very similar mechanism - a smaller robot called Defiant. Defiant won the lightweight championship that year, replicating the success of Carlo Bertocchini's machine in its own division, who also won its second heavyweight competition.
Defiant flipping over Endotherm during the 1999 Long Beach event.
BioHazard lifting Center Punch in Season 5.0.
As BattleBots hosted its first ever competitions in 1999, BioHazard and Defiant returned to defend their respective titles. Both fought in the 1999 Long Beach event and whereas Defiant lost in the kilobot final to Ziggo, BioHazard defeated KillerHurtz by lifting it over and claimed the Gigabot championship. While Defiant would not compete again, BioHazard returned for the Las Vegas event that same year, but could not replicate its success. Vlad the Impaler earned its revenge by flipping BioHazard over, who did not appear able to self-right with the addition of hinged skirts around the sides and rear for protection from wedges.
Gamma Raptor in Season 5.0.
BioHazard returned for all five seasons of Comedy Central BattleBots and maintained its dominance, winning three further heavyweight titles before the show's cancelation after Season 5.0. In the meantime, Team Raptor had upgraded their Long Beach entry W.L.O.W. and revised its lifting mechanism, converting it to a four-bar mechanism. This was seen throughout Alpha Raptor's run to the lightweight finals in Season 1.0, its Season 2.0 semi-final finish as Beta Raptor and runner-up and semi-final finishes as Gamma Raptor between Season 3.0 and 5.0. Jeff Vasquez - later of Whiplash fame - entered Deb Bot into the final three seasons of the Comedy Central era.
OverDrive's chassis with its four-bar lifting mechanism raised.
Four-bar lifters were scarcely seen on the show following its 2015 revival on ABC. With BioHazard not returning, the only lifter of its kind came in the form of OverDrive. However, Christian Carlberg's then most recent build struggled to perform, losing in the Round of 16 to Witch Doctor. OverDrive returned for the following competition, but with a vertical bar spinner replacing its lifter. Although not a lifter by definition, Lucky and Vault also utilized a very similar four-bar mechanism for their pneumatic flippers, as well as the multi-time superheavyweight RoboGames champion Ziggy.
Outside BattleBots[]
Away from the US, numerous four-bar lifter designs have been attempted with varying degrees of success. In the UK television series Robot Wars, Series 2 and 3 competitor Griffon sported this weaponry. However, it suffered a short career and a 2-1 overall record. Following its Robot Wars New Blood tournament win, six-wheel drive robot Storm 2 sported a four-bar lifter at the producers' request for Team Storm to add active weaponry to their robot for Series 7. Storm 2 would place second overall in the subsequent series and win the Third World Championship tournament. After several live event appearances, the four-bar lifter was swapped out for a front-hinged lifting arm, and the four-bar lifter was absent as Storm 2 returned for Robot Wars Series 8 in 2016.
Deb Bot appeared in Season 2 of the TLC show Robotica and enjoyed considerably more success than in BattleBots, making the final four before losing to Flexy Flyer.
King of Bots competitor Bullfighter sported a pneumatically-powered four-bar mechanism inspired by that of Lucky and Ziggy, but lost its only fight to Mist Lion.
Notable Competitors[]
| Robot | Seasons | Image |
|---|---|---|
| BioHazard | Long Beach 1999 Las Vegas 1999 Season 1.0 Season 2.0 Season 3.0 Season 4.0 Season 5.0 |
 |
| Deb Bot | Season 3.0 Season 4.0 Season 5.0 |
 |
| Defiant | Long Beach 1999 |  |
| Gamma Raptor
(also Alpha Raptor |
Season 1.0 Season 2.0 Season 3.0 Season 4.0 Season 5.0 |
 |
| Killjoy | Season 2.0 |  |
| OverDrive | World Championship I |  |
References[]
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