What's the max speed a stunt person could hold on to a moving vehicle?

July 25, 2019 4:26 AM

Let's assume they are not roped on but that there are decent hand and foot holds on the vehicle. At what speed does it become uncomfortable? Impossible to move around? Impossible to hold on?

This is for something I'm writing. I am thinking of stunt people hanging on to vehicles at high speeds.

Additional question, at what speed does it become difficult to climb out a window or a sun roof of an accelerating vehicle. When does it become impossible?

Additional additional question, what would be the max speed that a stunt person could jump from one moving vehicle to another, assuming they were going at the same speed.

All of this is assuming infinite track length and no limitations on vehicle speed.

Rough guesses are fine for my purposes. I have no clue about any of this, obviously!

posted by einekleine to Grab Bag (10 answers total)

Best answer: Well, motorcycles are one way to look at this. You have a way to hang on, but you are otherwise pretty exposed unless there is a fairing. It becomes difficult to see without eye protection at about 20mph. Not only do bugs go in your eyes, but your eyelids flutter and your eyes dry out. Anything over 100mph is pretty uncomfortable. Without a jacket and a face shield on your helmet, the skin on your face and arms will start to flap, which is not a good look. Above about 120, without protection from the wind it would be pretty difficult to hang on. Above that, it is possible to hang on, if you have a fairing to duck behind. Moto GP riders regularly hit 200+ mph, but they have the full power rangers getup and a faring to duck behind. Not sure about the jumping from vehicle to vehicle, but I would guess a lot slower, like bicycle speed. The wind drag would slow you down really quickly- humans don't have such good aerodynamics- and would make it difficult to match speeds correctly.
posted by Maxwell's demon at 5:01 AM on July 25, 2019 [2 favorites]

There was a recent road rage incident in the Boston area where a guy jumped on the hood of another car, which then sped away. The driver was going highway speeds while the, um, rider clung to the front. If an amateur can do that, I imagine a professional could do better.

(No one was injured and both guys were arrested.)
posted by backseatpilot at 5:04 AM on July 25, 2019 [4 favorites]

Also worth thinking about the road surface - if you’re on something really smooth it’s probably easier to stay put at higher speeds, but if you’re hitting holes or rocks and have to keep trying to regain your balance to stay on, you’ll be off sooner.
posted by penguin pie at 5:10 AM on July 25, 2019 [1 favorite]

The limiting factor is going to be relative air speed ('wind'). A vehicle at constant speed, whatever it is, exerts no force on the person; that only happens during acceleration/deceleration. What matters is the resistance of the moving air.

If there were a tail wind exactly matching the speed of the vehicle, then there's no relative air movement, and the speed is only limited by the vehicle. That's probably going to give you the upper limit. The person hanging on, assuming these ideal conditions, will be as comfortable as they'd be if the car weren't moving.

If the car is moving at 70mph on a still day, then the force of air on the person is about the same as if they were at rest in a 70mph wind - in a wind tunnel, for example.

You could do some maths based on the mass of air (about 1.3 kg / cu. m), and the area of the person's body (say 1 sq. m) in various orientations to calculate the force they'd need to hold on with.
posted by pipeski at 5:45 AM on July 25, 2019

I've traveled in a few places where people (young men mostly) without the money for a ticket for an inside seat ride on the backs and tops of vans and buses, hanging on to the luggage piles or standing on the back bumper. (See also the photos of people hanging off of trains.) They mostly* stay on at highway speeds, including turns and speed changes.

* We came around a corner right after someone fell off, and it was not a pretty sight. This is a thing that can be done, not something that should be done.
posted by Dip Flash at 6:30 AM on July 25, 2019

For reference only, a cat was recently filmed after being accidentally left unnoticed on the roof of its owner’s car as it cruised at interstate speeds in Nebraska. The car was fine. But it’s a cat. They’re used to aerodynamic precarity.

The cat makes it, the video is safe to watch. Here’s an update and cute safe kitty.
posted by spitbull at 7:17 AM on July 25, 2019 [1 favorite]

I have ridden in the back of a pickup truck at 100+ mph, standing up in the bed. You could still move around, but it's very windy and dreadful if you ride for more than a few minutes. (oh deadly youth!) So upwards of that with good hand and footholds. I'd guess you could ride until you got too tired to hold on.
At 100, the wind is annoying but still manageable. Maybe 120-150 mph, it'd become too much to bear for a long (30 mins) period of time without protection. And as speed increases every movement becomes more risky.
posted by The_Vegetables at 8:45 AM on July 25, 2019

Best answer: With respect to jumping from one vehicle to another, as Maxwell's demon points out, humans are not highly aeronynamic and would tend to lose velocity alarmingly fast once they are no longer getting a boost by being in physical contact with hthe car's surface. Between two ordinary-length passenger vehicles traveling the same speed and horizontally aligned with each other, I'd venture that even a moderate speed of, say, 40mph would make this straight-up impossible --- even jumping forward on a diagonal from for leading edge of the vehicle, the person would slow enough in transit to end up behind the target. Longer vehicles like tractor-trailers would be more forgiving on this front, although even then, the faster they're going, the more air resistance is going to seriously impact a free-flying human with that forward velocity and I doubt you'd gain much in terms of viable speed. OTOH, if the vehicles weren't horizontally aligned, higher-speed jumps would be possible (since slowing down wouldn't be a problem if the target was behind you), although at some point you'd reach a point where the force of air-resistance would be such that the speed differential on landing would be too large to be done well --- i.e., the jumper loses speed to drag while in the air, and in trying to land on or catch a vehicle going the original speed simply slips off because there's not enough friction (if landing) or exceeds the physical capacity of their bodies (if grabbing). Landing in something like the bed of a pickup truck or (if the timing worked really right) a sunroof could mitigate this last limit, although there'd still be serious trauma in slamming into, say, the back of the pickup truck's bed with relative speed equal to your drag loss.

So the answer to that question ranges a lot, depending on the relative position of the vehicles, the jumper's technique, the suitability of the landing area, and whether you cared if the jumper is still uninjured/conscious/living afterwards. Like, it's a physical possibility to pitch a human body horizontally from on top of a car at standard human jumping speed and have it land in the bed of a pickup truck one lane over and some distance behind no matter how fast both vehicles are going. But if you want the jump to be something a normal human could do notwithstanding the wind, and you want the body not to be completely pulverized on impact, then there are limitations after all.

To get real numbers you'd need a sense of (a) how much time a human is likely to be in the air during a horizontal jump between two cars, and (b) how much force a relative windspeed of X mph imparts on a human body. Then it would be pretty easy to determine exactly both the position shortfall and relative velocity difference at the end of the jump.
posted by jackbishop at 9:10 AM on July 25, 2019 [2 favorites]

Motorcycle sidecar racers typically top out at 150mph or so, and the monkey (sidecar rider) is attached to the vehicle purely by holding on. To be fair, at top speeds, they're usually tucked down on the straights, but for turns they're crawling all over their car. Here's some footage from the IMO TT that might give you an idea of what that looks like. Keep in mind the IOM course is run on (closed) public streets, and therefore slower than racetrack speeds.
posted by mollymayhem at 11:11 AM on July 25, 2019

This show has people jumping from cars to trucks and back at approximately 22 miles per hour. It seems hard even then.
posted by tacodave at 3:30 PM on July 25, 2019