Jon Peddie sent me a link to this clever commercial for the Mercedes SLS, showing it roll 360-degrees around the inside of the China Bar Tunnel in British Columbia, Canada (Supposedly). Watch it closely, and see if you can tell if it’s CG?
I’m pretty sure it is, but it’s quite well executed. One giveaway I noticed was that the beginning of the curve (the 2:15 mark) is shot from a wall-mounted camera just narrowly missed by the passing car, however this camera doesn’t actually appear in the driver’s view. In fact, I don’t see any cameras at all.
Of course, there is also the matter of physics, where it doesn’t matter how fast forward you go, Gravity still pulls Down so you have to generate Lift to counter it. If they were generating that kind of lift, the car would fly off the road.
Update: Commenter pboin points out the dangers of posting before coffee, as the real physics effect here would not be lift but downforce (eg. a force pulling the car ‘down’ towards the wall, or up towards the ceiling when it’s upside down). Certain race cars, like F1 racers, generate pretty substantial downforce to increase traction and improve handling, but I doubt the Mercedes SLS is in that class.
It is a clever ad, but surely a fake, for one simple reason.
The car as it is upside down on top of the tunnel, is shown passing over a group of people who watch the attempt.
No person in his right of mind would be positioned between the beginning of the roll, up to the well beyond the “landing” point.
Also, the ramps on the beggining and ending of the roll, as well as the “erased” line of lights may add to the realism, but they are clearly a photoshop work.
This is old, but the physics effect is actually not downforce either, at least not primarily. Downforce would refer to the aerodynamic forces created by fins and what not on the car and the force would not be nearly enough to hold the car to the ceiling on their own. The car could not just drive along on the ceiling no matter how fast it was going.
They are implying that the car is going so fast, and turns up the wall at such a high angle that the momentum of the car going up the wall keeps pushing it up on to the ceiling and then keeps it on the wall on the way down. This is called centrifugal force.
I doubt this is truly possible as it was set up, but I can’t say absolutely not either. No doubt though, this is fake.
It’s an awesome vid though.
@ pboin Ah yeah you’re right, brain fart on my part, the dangers of posting before sufficient coffee.
When I typed that, I figured a Formula1 car is probably the only thing to create enough downforce to pull this off, but probably doesn’t have sufficient ground clearance to allow that tight of a turn (unless you have a pretty big tunnel, which probably would defeat the whole project).
First of all, I’d agree that this is CG, for no other reason that logistics and finance make it the obvious choice.
I think you might have the physics backwards. Race cars generate *down*force, to have better grip on the track, not upforce. Therefore, they wouldn’t actually fly up in the air at all. Grand prix races that run in cities sometimes require manhole covers to be welded, so that the cars don’t suck them out of place!
Wikipedia regarding F1 cars: “while an F1 car achieves the same downforce:weight ratio of 1:1 at 125 to 130 km/h (78 to 81 mph), and at 190 km/h (118 mph) the ratio is roughly 2:1”
So, it can be done, at least theoretically. I doubt anyone is going to loan their F1 out for experiments though!