There’s been a new Chevy “American Revolution” ad playing on TV, which features a car carrier truck driving around, and cars that drive up behind it, and then up the ramp. I also saw this on Knight Rider all the time when I was a kid, and I always called bs on it. If I’m driving at 60 mph, then I go to drive up the ramp, either I zoom up the ramp at 60 mph (which should launch me through the truck, and my demise, real fast), or right before the ramp I slow down, in which case the timing is probably a huge pain in the ass.
I would have thought you would just get the car going at 5-10 mph faster than the truck, aim up the ramp, hit the clutch and coast up (probably not real good for the tires as they hit the ramp, but otherwise I don’t see any problems).
However, the last guy in the link above says that (according to a film he saw), it was done by keeping the car in gear the whole time and just slamming the brakes (and clutch I presume) quickly once the driver felt the acceleration. (He says it was because the target ramp is so small you have to be movely very slowly relative to the truck to hit the ramp correctly).
Not much else useful in the thread linked.
I wouldn’t be surprised if there was a lot of speeding up the film going on too, but I have no real knowledge.
I wonder if it’d be easiest if the stunt car was a rear wheel drive with the brakes disconnected from the back wheels, and operating on the front only. The hand brake would still operate on the rear wheels only.
Front foot hits the ramp, and with some heel and toe, you can get the front wheels’ spin under control fairly rapidly, whilst maintaining rear wheel acceleration on the road . Once the front wheels are spinning only at the relative ramp speed, foot off the brake again, and go up the ramp until the rear wheels hit it, at which point you’d apply the hand brake to stop the rear wheels from spinning. Then release the hand brake and just drive on up the ramp.
IIRC, in The Italian Job, the front-wheel-drive Minis lurched forward as they mounted the ramp, jumping into the bus and braking sharply. I guess the implausible or impossible action in that case was the stopping distance.
Stunt drivers are able to corner a car on two wheels without tipping it over. I think they wouldn’t have a lot of difficulty driving up the ramp of a moving truck.
I don’t think this would be a good thing for most of us to try.
There’s no reason why the car would immediately accelerate to 60mph in relation to the truck (it wouldn’t, after all, be able to accelerate 0-60mph on a piece of flat road the length of the truck+ramp, would it?) - the wheels are quite likely to spin on the ramp as they leave the road and this could be a problem in that they could shimmy off the side, but I don’t think this is anything that proper design and an experienced stunt driver couldn’t handle together.
I think the Knight Rider sequence may have been filmed at a lower speed and replayed at a faster rate; they did this for other parts of the footage.
The thread Astro posted is informative but it does have a lot of crap to wade through.
I used to work as a mover and have driven cars onto a truck many times, but never while it was moving ;). The moving truck I drove was about one foot lower than a normal freight truck. Even with 14 foot long ramps we had to be very carefull that the front and back of the car did not scrape, and at higher speeds the suspention would compress when you hit the ramp causing even more scraping.
Even with long ramps it will be like driving up a very steep hill, so the car would slow down very quickly just from the grade. Most car carriers sit very close to the ground so this would not be as big of a problem.
As others have said the car is not going to instantly double its speed when it hits the ramp. With very long ramps or a low truck the biggest problems would be the change in speed of the drive wheels when they hit the ramp, probably not that big of a deal for an experienced stunt driver. The speed difference between the car and truck would probably have to be more than a couple miles per hour to overcome the steep grade and ‘coast’ through the period when the drive wheels are changing from (for example) 70 mph to 10 mph.
The problem is not unlike that of a human walking onto a moving walkway (like the sort you get at airports - if you’re walking on the stationary ground at 3mph and the walkway is moving away from you at 3mph, you’ll eventually end up moving at 6mph relative to the stationary ground, but in the transition, there’s an awkward moment of acceleration when it feels like your legs are being pulled forward.
Well, the only thing moving relative to the truck is the wheels. So you would just need to first stop the speed of the front wheels and then the back wheels. If you assume the mass of the wheels are ~0 then this should work perfectly. Of course, the wheels have mass (which gives rotation momentum) which will make the car jump forward just a little bit when it touches the ramp.
You can pretty accuratly calculate the increase in speed mathematicly. Just divide the momentum of the wheels by the mass of the entire car.
It’ not just the mass of the wheels, the wheels are connected to the transmission and engine. The transmission is in the appropriate gear to turn the wheels at 70 so when the car makes the transsition (sp?) from road to ramp something is going to happen until the driver shifts down to an appropriate gear (or until the automatic transmission gets things sorted out). Most likley there will be some wheelspin when this happens.
If you coasted onto the ramp in neutral than you would be correct but as I mentioned above the ramp will be very steep so if you where in neutral you would lose speed very quickly and start to roll back.
When the front wheels touch the ramp you’ll (hopefully) get a big enough boost to negate the slope for long enough to get the car out of neutral. If that isn’t enough you could try driving a bit faster before hitting the ramp.
But of course, I don’t have a driver’s licence and I’ve never been interested in cars at all.
Just like to add that the first time I saw this done was before Knight Rider, in the goofy 70s film The Gumball Rally. Definitely no fancy special effects, a stunt driver just carefully did it. Didn’t look speeded up either. Rolled out of the truck & back down the ramp too!
