In November 2020, French driver Romain Grosjean had a fiery crash that he was lucky to escape from relatively unscathed. In September 2021, rivals Max Verstappen and Lewis Hamilton collided, and the Dutch driver’s rear wheel skidded across the Briton’s helmet.
If it hadn’t been for the precision engineering, manufacturing and testing of the halo safety device, a wishbone-shaped structure that is fitted to the chassis of open-wheel racing cars, these incidents could have been life-changing, if not fatal.
The halo caused controversy with fans and drivers – including Grosjean – when it was introduced. Fans called it “ugly” and complained that they couldn’t identify drivers because it obscured their helmets. In a video message from his hospital bed after his crash, Grosjean retracted his opposition to the halo: “I wasn’t for the halo some years ago, but I think it’s the greatest thing that we brought to Formula 1. Without it I wouldn’t be able to speak to you today.”
Halo trio
UK-based SS Tube Technology (SSTT) is one of three companies that manufactures the halo head protection device.
Upon hearing that motorsport’s governing body the FIA intended to introduce halos onto open-cockpit cars in 2017, Nick Henry, engineering director at SSTT, emailed Charlie Whiting, then FIA director and safety delegate, and introduced himself and what his company could do.
“He replied much quicker than I thought,” Henry said. “We managed to get a meeting with him and Andy Mellor, who was heading up the project at the FIA, at the British Grand Prix that year.”
The FIA was impressed with SSTT’s capabilities and in August 2017 approved SSTT, Germany’s CP Autosport and Italy’s V System to produce halos for F1, Formula 2 and Formula E for the start of their next championships in March 2018.
The FIA stipulates the design of the halo, from the materials it is made from (titanium alloy Ti6Al4V grade 5) to the overall weight of the device (13.5kg ±0.1kg), as well as set dimensions and tolerances. “The halo is made up of four key components,” Henry explained. “There’s the central pylon, which is the part that mounts to the monocoque ahead of the driver, then the V-transition that connects the central pylon to the main hoop. Then two billets are gun drilled and machined into tubes, which are each bent to 90° and welded together to create the 180° main hoop.”
The reason for machining a billet, rather than simply sourcing pre-made tubing, is that grade 5 titanium drawn tube is hard to make and source within the lead times required. Also, the FIA’s dimensional tolerances are exacting, and unlikely to have been met with drawn tube. Machining allowed SSTT to have better control of the halo’s dimensions.
Where the halo mounts to the chassis behind the driver’s head and in front of the steering wheel, there are fittings that are also machined from grade 5 titanium and welded onto the halo and bolted and doweled into the chassis by the teams.
Henry added: “The tolerances were extremely tight between the mounting points, ±0.1mm, there was also a weight tolerance that was critical and, obviously, tolerances on the inside/outside diameter of the tubes. That was quite a challenge. It took a final machining step to hit those tolerances.”
Tricky to bend
Aside from the tolerances, Henry said that the timeframes and the tube bending were also challenging, because grade 5 titanium has high strength, low ductility and exhibits spring back.
“It has to be bent very slowly, as there’s a strain rate factor to bend it successfully,” he continued. “Also, the V-transition is complicated to machine. It’s an expensive lump of titanium to start with so you don’t want to get it wrong. It takes 30 to 40 hours of machining for each part.”
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