For decades people have been pointing out that since many modern race cars (Formula 1, Indy Car, etc.) have more aerodynamic downforce than they weigh, theoretically they would stick to the ceiling of a tunnel if you could get one up there going fast enough. But obviously easier said than done.
Race driver Scott Mansell (no relation to F1 and Indy Car champion Nigel Mansell) has just announced that he’s going to do it, and that he has already spent hundreds of thousands of pounds to develop the car and the track to drive upside down on the top of a tunnel for five seconds, using only “organic” downforce. No fans, no centripetal force, like a Hot Wheels loop, or Jeremy Clarkson’s lark with a Renault in a sewage tunnel. Only the downforce generated by the car at speed.
The “tunnel” will be C-shaped, open on one side, so that spectators can watch. He’s aware of the difficulties of running an IC engine upside down, although the video doesn’t explain how he plans to solve it. (I’m thinking aerobatic aircraft engines would be worth a look.)
I find the big deal Mansell is making this out to be a a bit OTT. It’ll be fun to watch, but it’s not as though there’s anything controversial or complicated about the physics.
It’s a significant engineering challenge, sure. But I guess what I’m getting at is that it strikes me as like a scaled-up mythbusters except that we know the answer already. But I guess you could say that about going to the moon, so I’ll stop harshing the vibe!
It’s more like dropping the hammer and the feather on the moon. We know the result in advance but it’s still remarkable to see because it’s viscerally counterintuitive.
Yeah. A solved problem. Ensuring you have positive fuel supply and positive oil supply are the two biggies. Most current piston aero engines are air cooled, so liquid coolant flow isn’t an issue. That one probably needs work for this car too.
The usual technique is to have multiple pickup points around the header tank for the fluid. Another one is to have a single pickup on a flexible hose with a weight on the end. The pickup will tend to end up wherever the fluid is, whether it’s moving under the influence of gravity or centripetal force.
Most of these systems are only good for a short time inverted, maybe a minute or so. So not truly agnostic as to which way is local “down”, but good enough to keep the engine healthy and happy through transitions and thrashing and some amount of fully -1G compared to normal ops…
It’s not quite that simple. Downlift depends on speed. Speed is a balance between friction on the tires and drag. Friction on the tires depends on normal force, and normal force depends on orientation. In other words, if you have a car that, at maximum speed, has a downlift of 1.1 times its weight, that’s achieved with a normal force of 2.1 times its weight. Try driving that car upside down, and now the normal force is only 0.1 times its weight, which means that friction is now much lower, which means that drag is now greater than friction, which means that the car slows down, which means it can no longer maintain that downlift, and so it falls.
It’s still possible to engineer it, of course. You just have to make sure you have enough surplus. But it takes more than just having a car with more downlift than weight under normal racetrack conditions.
That’s what I was thinking; the car not only needs to stay on the ceiling, but with enough force that it has traction to overcome the aerodynamic drag.
Formula 1 cars have well over twice as much downforce as weight, and Mansell and his team are designing their car for that much surplus as well, as he mentions in the video.
And we should probably suggest this to them as well, just for an additional safety margin. Thanks, Beck.
