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With Formula E proposing to drop the minimum mid-race car swap time, the concern that a driver might inadvertently leave the pit without their belts properly tightened, has already been countered with a FIA Belt Tension Device.

The first four seasons of Formula E have been marked by the unique mid-race swap to another car with a fully charged battery, to ensure safety and unforced errors in tightening the seat belts, there has always been a minimum stop time, that gives a margin for error and double checking the belts. Albeit the car-swap practice will stop in Season5, the remainder of the 2018-2019 season will now enjoy no minimum time. But, the danger of an unsafe release without the belts being duly tightened is monitored by more than just the mechanics checking the belt during the swap. Since Season3 Formula E has run a FIA Belt Tension Device (BTD) that senses if the belts have been tightened enough. This was part of the FIA Global Institute for Motorsport Safety (GIMS) campaign that identified the issue of untensioned seat belts and directed development for the solution that now races on every FE car.

Although being a FIA safety project, the device was made in partnership with Prodrive, I spoke to David Lapworth about the BTD’s development. With Prodrive delivering the BTD to its FE customers, the project, as mentioned was not of their own making, in fact it goes back to one specific individual, as Lapworth explains “We had a FIA request, but it was actually a Peter Wright project that came out of GIMS, to see if they could come up with a device that could ensure that seat belt was correctly tensioned”. Many of this Drivetribe’s readers will know the name Peter Wright, the Lotus designer that famously came up with ground effect underfloor aerodynamics and latterly moved on to direct safety initiative’s in the wake of Senna’s death. Wright, now semi-retired, continues to work with the FIA on safety initiatives, although the Institute has its own large group of engineers working on a wide range of motorsport safety initiatives.

As a background, the BTD wasn’t initially envisaged for Formula E, rather other categories with driver swaps, according to Lapworth “it was driven by various incidents in endurance and all sorts of series, where they have pitstops and there have been issues with drivers leaving without their seatbelt properly fitted, people slackening off their belts during safety car periods or when a driver coming into the pits slackens the belts and the next driver who jumps in could be tempted be tempted to drive off before he’s tensioned the belts”.

With this remit to check for belt tension, the project began “Peter was given the project three years ago, to see if he could come up with a device. He had a bit of a brainstorm with himself and had some ideas. Then he came down to sit with ourselves. To see if we could help him with some more brainstorming and some prototyping. To see if we could come up with a viable concept together”.

Racecar seat belts

All modern Racecars require the driver to wear what’s known as a six-point seat belt set up. Thus, there are two shoulder belts and two waist belts each connecting into a quick release buckle. There’s then two crotch straps, these loop around the waist straps to prevent the steeply reclined driver ‘submarining’ under the main belts with sudden deceleration in an accident. With the six straps clipped in, there are tensioning devices in each shoulder belt to pull the entire harness tight. Such is the tension in the system, that drivers are unable to pull hard enough on the tensioning straps from their seat position. So, a mechanic leans in to tighten them, using their better position and weight to put the load into the straps.

While seatbelts are primarily a safety item, given the forces the racing driver is subjected through braking, acceleration and cornering, the belts serve a secondary function to hold the driver’s torso tight in their seat, leaving only the limbs able to move in order to operate the steering wheel and pedals. The requirement for very tight belts actually aids the driver’s ability to race, as they are not having to brace themselves from the car’s dynamic G-forces.

Removing or loosening the belts is the reverse process, often loosening the tension by lifting the tension device and twisting the quick release to detach the belts from the buckle. Should I driver suffer loose belts, either because they loosened them, or they have inadvertently come loose, the driver could not retighten them alone, especially when driving.

FIA Belt Tension Device

Given this safety critical process, Formula E car-swaps raised the concern that rushed stops could lead to drivers racing with loose or unbuckled belts. Thus, the minimum pit stop time was enforced, but now the sport is happy to allow the team’s a competitive advantage with faster swap times. The BTD will help the team and allow the FIA to enforce safety through the car swap.

A simple housing mounted to the strap triggers when the belt is pulled tight enough to close the spring and press the micro switch

So, how does it work? Surprisingly the solution doesn’t actually detect the buckles being clipped in or the measure belt tension directly, “Originally it was an idea to see if you measure the belt tension, when you’re wearing the belts it quickly became evident from measuring the tension in the belts, that the belt tension when you’re in the car and driving was all over the place. It’s not any kind of reliable indication that the belts were tightened properly”. Thus, the solution moved to another aspect of the belt tensioning process, “the idea moved on to we will put it in the tail of the belt, the bit of the belt you pull on when you tighten the belts. That will indicate that the belts have been tightened”. While this might not seem like a full solution, Lapworth goes on to explain the thinking and benefits of this method, “It can’t prove that the belts remain tight, unless you deliberately wanted to cheat it and I can’t imagine why anybody would, but it will prove you have pulled on that tensioning strap with more than X newtons and then the belt can reasonably be assumed to be tight. Off the top of my head, its 100 newtons, there’s an agreed target that’s regarded as ‘that’s a good tug on the belts’”.

With the concept agreed it then moved on to finding a solution, direction for this came from a surprising source! “It started off with Peter, who got this idea after being inspired by a mouse trap and said do you think we could do something based on this?”. “We knocked it around then came up with a microswitch and the spring idea from the mouse trap, which puts a kink in the belt, when its tight enough the belt goes straight and the switch operates and the light goes off. We rapid prototyped a little housing and went from there”.

As the device fits to the tensioning strap itself and not the tensioning buckles on the shoudler straps, its agnostic to which make of belts are used and needs no modification to the seat belt system, brilliantly simple!

So, with the requisite tension put into the belt, the driver/mechanic gets a visual indication with a LED lighting up on the tensioning device, there is also a connection for the FIA Safety Data Recorder mounted to every car, to record the tension target being achieved, this can be reviewed by the FIA when the telemetry is downloaded in the pits.

You can’t beat the system

Mounting the tensioning strap, the BTD works with any make of seat belt

When Formula E announced it would scrap the minimum pit stop time, the concern was an unclipped belt could allow a driver to leave with unsafe belts, but the force required to trigger the sensor counters this. Equally a team trying to gain time by purposely cheating the system is of no benefit either “We’ve thought this thing through, it’s difficult to see how you could cheat it, the way it is, without wasting more time than you’re saving. The quickest and easiest way to trigger the device is to put on the belt and pull on the tails as you’re supposed to”. Although Lapworth is happy “it kind of just works!” it’s not meant to be entirely foolproof. It’s just to ensure you don’t leave the pits with the belts loose” adding “it’s not worth leaving the pits with the belts loose”. As the BTD has been running since Season3, it’s a proven device “as far as I know I’m not aware of any reliability issues or where a driver hasn’t had the signal and the driver said, ‘I did pull the belts on’.

Wider spread use?

The wire from the BTD gives a tell-tale signal to the FIA safety Data Recorder

With Formula E pioneering this safety add-on, where is the next stop for the device? “We want to roll something similar out to world endurance, you add that together with in-car camera and you’re pretty much going to be bang to rights if you don’t tighten the belts. If the light doesn’t trigger, then they look at the in-car camera and its obvious the belts are loose”. Plus, Lapworth explains the next generation of BTD “There’s work going on Mk2 even a Mk3. For the further iterations there’s thoughts about whether you could somehow detect if the driver had loosened the belt. Some of the drivers apparently are tempted to loosen the belts behind the safety car because they tension the belts so tight they are uncomfortable when they are not racing and maybe they don’t re-tension them. There’s talk of taking the Mk1 further and making it wireless, which it not exactly too challenging these days”.

With the FIA investment and ownership of the BTD, Prodrive are still the supplier of the solution, “It’s an FIA product, they own the right. We manufacture it and we provide them to Formula E. We pay a royalty for everyone to the FIA to pay back their initial investment, we get paid for the hardware”.

Being such a simple and cheap solution, plus all championships are now running FIA’s Safety Data Recorder, there seems little reason not to run these in every top-level category. Obviously prioritising categories with driver swaps. In the meantime, Formula E can be happy the last races with car-swaps, can go on safely, until the new era of Season5 with cars and batteries that will last the full race.

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