Why the halo’s central pillar doesn’t hinder driver vision, and why it’s so integral to the concept

Our question this month comes from John Dunne, who asks if it would ever be possible to design a halo strong enough such that it doesn’t need the central pillar.

It may seem a simple question, but it leads me to think about exactly what the halo has to do and therefore explore a little bit of the science of structures, as well as some interesting aspects of human perception and why our eyes can indeed sometimes deceive us.

Firstly, let’s examine if there would be any advantage in removing the central pillar. You might think that the pillar obstructs vision or at the very least distracts the driver just as they need their visual perception to accurately place the car at the apex of a corner.

In reality the driver is not aware of the presence of the central pillar and this is due to something called retinal disparity. If we have two well-functioning eyes, we are able to use the separate images that each eye sees to form a three-dimensional image and hence judge both the position and the distance of the object we are viewing.

This occurs because the separate images that each eye sees are very slightly different as each one sees the object from a slightly different angle. Our brain then combines these images to give us the depth perception necessary to judge distance. 

Retinal disparity occurs because your dominant eye will see an object directly in front of, and close to, it while at the same time your non-dominant eye will concentrate on the background. Again, the brain processes these two bits of information in a different way, making the object in front of the dominant eye appear transparent or at least translucent.

Williams released a cockpit video in February 2018 of Robert Kubica’s first run in the halo-equipped FW41 at Aragon. Seems the camera captures a different view than the human eye…

Photo by: Williams Racing

So it may be that there is actually no advantage in removing the central pillar. Indeed, the opposite is true and one of the many factors that led to the introduction of the halo was the incident in Hungary in 2009 when Felipe Massa was knocked unconscious when hit on the head by a spring that fell off the car he was following.

While the halo central pillar may not stop all missiles that approach the driver, research by the FIA at the time showed that it was capable of stopping the majority of objects and specifically would stop an errant wheel that may otherwise strike the driver.

It was this latter case that led to much of the testing of the halo and the aeroscreen devices that were evaluated at the same time. It was appreciated that the driver’s head remained the most vulnerable part, but the task of stopping a wheel and tyre was going to require a serious structure.

It’s a device that aerodynamicists hate. It is in the direct path of airflow to the engine intake and the rear wing

The halo project started in 2011 but it was not introduced into Formula 1 until 2018, which gives some measure of the difficulty of finding the best solution. A lot of experimentation was done, which consisted of firing a 20kg wheel and tyre assembly at 140mph at the candidate solutions.

The aeroscreen performed well but suffered from degradation of vision due to rain, oil and rubber, as well as having some distracting reflections that the drivers did not like. Eventually the halo was the chosen solution.

The halo consists of a fabricated construction of titanium. It needs to withstand a load of 125kN (14 tons) applied to it, about the weight of a half-full double-decker London bus.

Mercedes boss Toto Wolff reckoned the halo “definitely” saved Lewis Hamilton’s life at the 2021 Italian Grand Prix

Photo by: Zak Mauger / Getty Images

Obviously, such a device is not light. It weighs around 7kg, but the real weight comes from the increased chassis structure needed to support the loads that the halo can transfer to the monocoque. This leads to a further mass increase probably similar to that of the halo itself. 

It’s also a device that aerodynamicists hate. It is in the direct path of airflow to the engine intake and the rear wing, and could be very destructive, but luckily the FIA allows some mitigation by means of lightweight fairings that reduce the otherwise detrimental effects.

While all of this explains the intricacies of the halo, I have not yet answered the question. To do so I could go into some relatively simple maths to show the difference in stress under a given load between a halo with and without the central support, but let me try and illustrate it practically.

If you take a standard school-type ruler and clamp it over the edge of a table and then press down on it somewhere in the middle of the overhanging part, you will see it deflect. Now support the free end, say on the arm of a chair, and press down in the middle again. The deflection is considerably less and, as stress is proportional to strain, the stress is also much less. 

So yes, you could make a halo without a central support, but it would be considerably heavier to return the stress to an acceptable level and would be less effective as it would still leave a large opening in front of the driver.

Want to ask Pat a tech question for a future issue? Let us know on autosport@autosport.com

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Engineers have been given ways to mitigate the aerodynamic impact of the halo with the use of fairings

Photo by: Giorgio Piola