What It Takes To Drive A Car Upside Down, From A Man Who Aims To Try It

It’s something you’ve probably heard a million times as a Formula 1 fan—that the cars make enough downforce that they could theoretically drive upside down. Of course, nobody’s ever actually done it, because practical concerns make proving the theory incredibly difficult. Regardless, one man is eager to achieve such a feat, and he’s stumped up the money to fund the necessary engineering work to make it happen.

Scott Mansell, known on YouTube as Driver61, has made it his mission to drive a car upside down, solely relying on aerodynamic downforce to keep him stuck to the roof of a tunnel. As he’s explored the project, and engaged engineers to work on the problem, he’s come up with a believable plan to pull it off. This involves a custom car and a custom tunnel, built specifically for the purpose of achieving this stunt.

Choosing The Right Car

You might think that a Formula 1 car would be ideal for the job, but as far as Mansell and his team are concerned, that’s anything but the truth. For a start, F1 cars are incredibly expensive to buy and run, assuming you can even lay your hands on one. Modern examples are also rather heavy, pushing up towards 1800 pounds. The heavier the car, the more downforce you need to generate to drive it upside down, and thus the faster you have to go. This tends to complicate the whole enterprise. By virtue of adhering to the rules of competition, F1 cars are also compromised in the amount of downforce they actually make.

For all these reasons, Mansell chose to go an entirely different route, instead choosing an open-wheel formula-like car for the job. He selected the Empire Wraith from the world of hillclimb racing, where restrictions on things like weight, horsepower, and aerodynamics are minimal. The Wraith, with significant modification, should be able to generate large amounts of downforce at a much lower speed in order to make driving upside down as easy and safe as possible. In running trim, it typically weighs under 700 pounds, making it perfect for the job.

To customize the car for the job, Mansell enlisted Willem Toet as his chief aerodynamicist. Toet has an impressive resume, having worked with Ferrari, Bennetton, and Sauber during his career in Formula 1. Drawing on that experience, he has designed an aerodynamic package for the Wraith to help it create double its own weight in downforce at just 80 miles per hour, down from 100 miles per hour in initial estimates.

That figure might sound excessive, but it’s actually around the bare minimum you want for driving upside down. That’s because of how gravity and grip work when you flip your entire frame of reference upside down. For example, when a car without downforce is driving along the ground, it has its own weight pressing its tires into the ground to generate mechanical grip. To generate that same grip when driving upside down, you actually need to generate the entire vehicle’s weight just to overcome the gravitational force pulling the car down, and then actually press the vehicle up to generate grip to that same degree. It’s also obviously desirable to have some safety factor. If, for example, you were generating just barely enough downforce to stick the car to the ceiling of a tunnel, you wouldn’t want a gust of wind or a small bump to cut your downforce and see you falling to the floor.

How To Make It Work

To achieve maximum downforce at low speed, Toet has reworked the aerodynamic elements of the Wraith design. He put a great emphasis on generating downforce with wings in addition to using ground effect. That choice was due to the fact that the car will be running on a round tunnel surface. In this situation, because the tunnel curves away under the car’s body, the car is effectively running at a much higher ride height than it would be over a typical flat road. This compromises the ground effect aerodynamics moreso than it does the wings.  To that end, Toet designed a huge five-element rear wing, with extra wings either side that pick up the flow over the rear wheels. The front wing is also extremely deep to generate the maximum possible downforce. The design also uses skirts along the side of the body to try and make the most of the ground effect downforce available.

Cutting the speed down nets huge savings in the cost of the overall stunt. That’s because Mansell is having to construct a tunnel from scratch specifically for this feat. There’s also a safety bonus, too. “It’s much better to have an upside-down crash at 80 miles per hour rather than 150,” Mansell chuckles.

The Tunnel Is A Key Element

In fact, the tunnel is one of the most difficult and expensive parts of the whole thing. The simple fact is that there aren’t really existing tunnels in which you could achieve driving upside down. Even if you could convince a government authority to give you dedicated access to a major road tunnel, you’d need to take it out of commission for months to remove all the lighting and ventilation fixtures on the ceiling. Plus, regular road tunnels tend to have huge bumps and gaps between sections, and just generally aren’t suitable for driving in. Most of all, though, none have been built with a convenient smooth transition for allowing a car to transition from driving on the flat ground, up the walls, and on to the ceiling.

Instead, Mansell tapped engineering agency Expedition Enginering to design an open-sided C-shaped tunnel specifically for purpose. This has the dual benefits of both saving resources and allowing better viewing of the stunt by spectators and cameras. The basic calculations have determined that the tunnel needs to be approximately 2300 feet long to allow Mansell to drive upside down for 5 seconds at 80 miles an hour, and this includes the necessary transitional areas.

Figuring out the best diameter for the tunnel was more complicated. After an initial pass at the aerodynamics involved, Toet determined that a 54-foot diameter tunnel would be suitable for the task. This was chosen as the larger diameter tunnel would see the surface of the tunnel curve away from the car less underneath, reducing the loss of downforce compared to driving on a flat surface. However, at this enormous size, the tunnel would be very expensive to construct, and present a huge fall if the car happened to come into trouble. Eventually, the team decided on a tunnel 7.5 meters, or 24.6 feet in diameter, which was a good balance between cost and performance. The camber of the car’s wheels also comes into the matter, with a 24.6-foot diameter tunnel requiring the wheels to be mounted at a very significant angle to maintain the best possible contact patch on the curved surface.

As a temporary structure that will only be used on a one-off basis, the engineering team developed a plan to construct the tunnel using something called VarioKit. These are large off-the-shelf building blocks typically used to construct support frames for large building projects like bridges, tunnels, and buildings. Imagine an Erector Set, but at civil engineering scales, and you’re on the right track.

The build rests on concrete sleepers which are to form a solid base for the tunnel and keep it anchored in place. Large water tanks along the back edge of the tunnel will further serve as ballast to weigh the structure down. The red VarioKit C-shaped frames act as the main vertical support structures of the tunnel, with the white steel perlins acting as a subframe to support the road surface tie everything together in the horizontal direction. Four layers of curved plywood will be used to construct the road surface itself, since it can readily be shaped to suit during the construction process. The construction will require a bespoke solution for expansion joints that can help manage the structure’s size change in warming or cooling conditions, which could see the whole structure grow by as much as 15 inches from night to day.

Ultimately, if Mansell is to pull this feat off, he’ll need serious sponsorship to build the car, build the tunnel, and find somewhere big enough to actually do it. The basic engineering is there, though, and all that really remains is to put this madcap plan into action. We can’t wait to see what happens.

Image credits: Driver 61, YouTube screenshots, Tunnel image – Lucasbosch, CC BY-SA 4.0