Is it possible to..?

Natorgator · Post by **Natorgator** » 2004-01-01 10:27pm

I assume you've all seen the new GM commercials, in which the Corvette among other cars drives onto a trailer that is moving. Would the car not lunge forward from it moving onto a stationary surface (relative to it, of course) with the tires still traveling 55mph or however fast it was going?

Could you actually park it in a casual manner as depicted in the commercial?

Darth Yoshi · Post by **Darth Yoshi** » 2004-01-01 10:46pm

I think it would depend heavily on whether the car is forward or rear wheel drive. Plus, you're forgetting that in the end, all that matters is the speed of the two vehicles relative to each other. The relative momentum would pretty much suck the speed away from the tires, though there would be a pretty nasty jerk as the car compensates.

Now I'm reminded of Knight Rider.

Lt. Dan · Post by **Lt. Dan** » 2004-01-02 12:24am

Maybe it would be like a plane landing.

Hethrir · Post by **Hethrir** » 2004-01-02 12:29am

I'm guessing you would have to throttle up so that you go up to the trailer, and just before the wheel with drive hits it, you go into angel.

Nathan F · Post by **Nathan F** » 2004-01-02 12:47am

No, you couldn't, at least not at the speed's their travelling. You see, the wheels are turning at the speed that the vehicle is going. As soon as the drive wheels hit the trailer, they are going to shoot the vehicle forwards. Sort of like if vehicle A is going 60mph and vehicle B is going 70mph, if vehicle B decides to ramp up on vehicle A, it's going to appear to be travelling 10 mph in relation to vehicle A. As soon as it touches vehicle A, it's forward velocity rockets to 130mph.

So, unless you had a way to brake the wheels (stop them completely) as soon as they hit the trailer, then no, it's impossible.

Post by **Darth Wong** » 2004-01-02 01:12am

Nathan F wrote:No, you couldn't, at least not at the speed's their travelling. You see, the wheels are turning at the speed that the vehicle is going. As soon as the drive wheels hit the trailer, they are going to shoot the vehicle forwards. Sort of like if vehicle A is going 60mph and vehicle B is going 70mph, if vehicle B decides to ramp up on vehicle A, it's going to appear to be travelling 10 mph in relation to vehicle A. As soon as it touches vehicle A, it's forward velocity rockets to 130mph.

With all due respect, that's the dumbest thing I've seen in quite a while. Do you think the only requirement to massive acceleration is a high rotation rate for the wheels? If you have a car suspended a foot off the ground and its wheels are spinning at a rate commensurate with a ground speed of 70mph and you drop it to the ground, do you think it will instantly accelerate to 70mph? Or do you think it will accelerate slightly, while its wheels burn a lot of rubber and fishtail?

Please review basic Newtonian kinematics. Particularly a fairly well-known equation which looks like this: F=ma.

So, unless you had a way to brake the wheels (stop them completely) as soon as they hit the trailer, then no, it's impossible.

Wrong. The real problem is maintaining control at the moment the wheels touch the ramp, not any fears of instantaneous, physically impossible accelerations.

kojikun · Post by **kojikun** » 2004-01-02 03:02am

The vehicle is also likely to be frontwheel drive, or atleast was in the commercial, so when the backwheels hit the trailer, they would slow down pretty quickly. Hitting the breaks while moving onto the trailer also helps prevent burning rubber so you get a nice clean shot.

Howedar · Post by **Howedar** » 2004-01-02 03:48am

I don't think it would be achievable without either a very large trailer or else front and back brakes that could be engaged independantly.

Crayz9000 · Post by **Crayz9000** » 2004-01-02 03:52am

That is one commercial that should have, in large lettering: KIDS, DO NOT TRY THIS AT HOME.

You'd have to be one hell of a driver, and have one hell of a vehicle, to pull that off. And even then you're not guaranteed.

So how'd they do it? *points at renderfarm*

Post by **Darth Wong** » 2004-01-02 04:13am

Howedar wrote:I don't think it would be achievable without either a very large trailer or else front and back brakes that could be engaged independantly.

Not really. The Corvette is a rear-drive car, or at least it always has been in the past. The front wheels of a Corvette spin freely, and are not engaged by the car's propulsion system. They would stop of their own accord upon contact with the ramp.

The problem is what happens when the rear wheels hit the ramp, in terms of control.

Howedar · Post by **Howedar** » 2004-01-02 04:35am

Oh, rear drive makes it easier then. I didn't know we were talking about a Corvette.

Still you'd need a big trailer, because I expect the driver would not mantain positive control throughout the maneuver.

Hethrir · Post by **Hethrir** » 2004-01-02 06:17am

Nathan F wrote:No, you couldn't, at least not at the speed's their travelling....

That why i said you should hit neutral just before the wheel with drive hits the trailer.

Nathan F · Post by **Nathan F** » 2004-01-02 12:31pm

Darth Wong wrote:With all due respect, that's the dumbest thing I've seen in quite a while. Do you think the only requirement to massive acceleration is a high rotation rate for the wheels? If you have a car suspended a foot off the ground and its wheels are spinning at a rate commensurate with a ground speed of 70mph and you drop it to the ground, do you think it will instantly accelerate to 70mph? Or do you think it will accelerate slightly, while its wheels burn a lot of rubber and fishtail?

Please review basic Newtonian kinematics. Particularly a fairly well-known equation which looks like this: F=ma.

Don't worry, Mike, I know all about that. I guess I should have worded it better, but it IS going to accelerate rapidly (along with your mentioned fishtailing and burning rubber). I never said it would instantly accelerate, I said it would rocket forward, which was the bad wording.

Wrong. The real problem is maintaining control at the moment the wheels touch the ramp, not any fears of instantaneous, physically impossible accelerations.

See above.

Nathan F · Post by **Nathan F** » 2004-01-02 12:32pm

Hethrir wrote:
Nathan F wrote:No, you couldn't, at least not at the speed's their travelling....
That why i said you should hit neutral just before the wheel with drive hits the trailer.

Which would rip the transmission out of your vehicle, and you still have inertia to worry about.

Post by **Darth Wong** » 2004-01-02 12:41pm

Nathan F wrote:
Hethrir wrote:
Nathan F wrote:No, you couldn't, at least not at the speed's their travelling....
That why i said you should hit neutral just before the wheel with drive hits the trailer.
Which would rip the transmission out of your vehicle, and you still have inertia to worry about.

No, you don't. The best way to do it is to accelerate hard toward the trailer, put your foot in the clutch just before you touch the ramp, and let your momentum carry you into the trailer. Don't you people know how to drive standard?

Post by **Darth Wong** » 2004-01-02 12:42pm

Nathan F wrote:Don't worry, Mike, I know all about that. I guess I should have worded it better, but it IS going to accelerate rapidly (along with your mentioned fishtailing and burning rubber). I never said it would instantly accelerate, I said it would rocket forward, which was the bad wording.

You said it would rocket forward to the sum of its velocity and the truck's velocity. This is simply not true. A considerable extra energy input is required in order to accomplish that.

The Cleric · Post by **The Cleric** » 2004-01-02 12:43pm

Yes, some of us do.

And wouldn't you have to break fairly hard to not slam into the back of the trailer? And wouldn't that breaking cause steering problems that would most likely take you off the trailer?

aerius · Post by **aerius** » 2004-01-02 12:47pm

Nathan F wrote:
Hethrir wrote:That why i said you should hit neutral just before the wheel with drive hits the trailer.
Which would rip the transmission out of your vehicle, and you still have inertia to worry about.

How? Look at the reverse situation, reving the engine and then dropping the clutch at say 4000rpm which is done all the time by car magazines when they're doing acceleration tests. The driveline & wheels go from 0 to 20-30 mph in an instant depending on the gearing, and the fact the the wheels & driveline are under load makes it a lot harder on the tranny than stopping a pair of spinning wheels which are just freewheeling. Dropping the clutch like that ain't the best thing for a tranny but it's not going to kill it unless you do it all the time.

If the clutch pedal is pushed down or the tranny's in neutral, the only things that have to stop spinning are the wheels, rear differential, driveshaft, and the output shaft on the tranny. There are no real loads being put on any of the gears in the driveline since the engine is disengaged from it.

Crayz9000 · Post by **Crayz9000** » 2004-01-02 12:49pm

StormTrooperTR889 wrote:And wouldn't you have to break fairly hard to not slam into the back of the trailer? And wouldn't that breaking cause steering problems that would most likely take you off the trailer?

Relative velocity. If you're talking about the truck doing 55 and you're catching up to it at 65, then there's only a 10 MPH difference in speeds. How fast can you stop in a parking lot?

Post by **Darth Wong** » 2004-01-02 12:49pm

StormTrooperTR889 wrote:Yes, some of us do.

Good; I was starting to wonder

"Shift into neutral"

And wouldn't you have to break fairly hard to not slam into the back of the trailer? And wouldn't that breaking cause steering problems that would most likely take you off the trailer?

Once you jerk onto the trailer from momentum, your free-spinning wheels will rapidly slow down to match your velocity relative to the truck. Their rotational inertia is insignificant next to the mass of your vehicle, so you will experience very little forward acceleration upon contact. You will still have to brake so you don't hit the back of the trailer, but if you have good brakes that should not be a problem; your velocity relative to the trailer should be fairly minimal.

Mind you, this would still require a good stunt driver; if you put your foot in the clutch too early you won't have enough inertia to coast into the trailer, and if you do it too late you'll suffer a pretty bad jolt when your rear wheels hit the ramp.

The Cleric · Post by **The Cleric** » 2004-01-02 12:54pm

Crayz9000 wrote:
StormTrooperTR889 wrote:And wouldn't you have to break fairly hard to not slam into the back of the trailer? And wouldn't that breaking cause steering problems that would most likely take you off the trailer?
Relative velocity. If you're talking about the truck doing 55 and you're catching up to it at 65, then there's only a 10 MPH difference in speeds. How fast can you stop in a parking lot?

It's only 10 mph while you're approaching. When you hit it's different.

Darth Wong wrote:Mind you, this would still require a good stunt driver; if you put your foot in the clutch too early you won't have enough inertia to coast into the trailer, and if you do it too late you'll suffer a pretty bad jolt when your rear wheels hit the ramp.

So trying it with my Saturn wouldn't be a good idea

?

Crayz9000 · Post by **Crayz9000** » 2004-01-02 01:24pm

StormTrooperTR889 wrote:It's only 10 mph while you're approaching. When you hit it's different.

That's right. You'll drop to almost nothing very quickly. Not a pleasant experience.