Driver fails to leap retracting bridge


#1

[Read the post]


#2

He had a full tank of gas, and half a pack of cigarettes, but he forgot to put his sunglasses on.


#3

I hesitate to point out that the bridge did not appear to be retracting, in fact, but closing.

I guess it’s possible the bridge operators saw what was going to happen and reversed the controls in case it was going to make a difference, but my money’s on the driver just being too stupid to wait for the bridge to close properly and running the lights.


#4

Looks like someone’s been watching too many action adventure films.


#5

I wonder if he’d make it if he’d go faster.

…any math/physics geeks here able and willing to run the numbers? What’d be the necessary speed to jump this gap?


#6

The necessary speed to clear this gap is more than this minivan can likely muster.

I determined this scientifically, of course.


#7

I was gonna say too many cartoons, but they’re pretty much the same thing.


#8

I don’t know the math, but I’m pretty sure he’d have to clear the gap before gravity had a chance to pull the vehicle down. So maybe a lot faster than the vehicle can go?

To quote The Tick: “Gravity is a harsh mistress.”


#9

Assuming the curvature of the bridge is an illusion caused by lens distortion, then likely no speed will result in the car jumping the gap. The reason being that the front of the car will begin to fall as soon as the front axle is unsupported. Hmm…

If, I say if, the front wheels will climb a five centimetre difference, then the front axle needs to dip no more than 5cm in its trajectory. From s=1/2 at^2, rearranged to t=√(2s/a), t is √(2 * 0.05/10) = 0.1 seconds.

If the gap is 5 metres, then the car has to clear 5 metres in a tenth of a second, for a velocity of 50m/s or 112mph. I don’t see any station wagon making that speed unmodified. At a guess I’d say that car was going about 30mph (plus or minus a wide margin for guesstimation).

In short, don’t try this, kiddies, or mom is going to ground you for a century.


#10

Added complications: once the rear axle has left the road, the front wheels will have no traction when they contact the retracted bridge, so they’ll have to rely on forward momentum to carry the car over. Which will probably result in some loss of speed. Not to mention that climbing the 5cm gap may introduce a further pitching motion to the car, possibly resulting in the chassis grounding before the rear axle meets the bridge.

Mom is going to be so pissed with you.


#11

But not watching them closely enough!

A minivan? Seriously?


#12

JATO would solve that!

…paging Mythbusters…?


#13

I had a dachshund that tried something similar once.

There was some food on a table that she wanted, and she through if she crawled up onto a side table and balanced herself precariously on a pile of magazines that she could jump the three foot gap, from a standstill.

She made it about six inches before crashing to the ground. It was one of the silliest things I’d ever seen.

Fortunately only her pride was hurt.


#14

Except that the suspension will push the front wheels down to maximum extension as soon as they are un-weighted. This is a variable in the equation that we don’t have a number for, but the short version is that the car has to clear the gap faster than the front springs/struts/whatever can push the wheels down (more than 5cm).

I suspect that will be considerably faster than 112mph…


#15

There are many, many station wagons that will do 112mph.
Indeed, there are more than one station wagons easily capable of ~175mph stock (with a few capable of 200+ while retaining their usability & road legal-ness).

I’d be more concerned with the axels dropping as the suspension unloads. 5cm is a fairly normal amount of sag…


#16

Hmph. Speed Racer can do it.


#17

Maybe those voracious beasts you have in Americaland can achieve those speeds, and more importantly accelerations, straight out of the showroom, but I’m kinda doubting that their more gracile cousins here in Europe could do as well typically, especially after a year or two on the road. My old hatchback had a speedometer that went all the way up to 110ish, as I recall, but I only ever went above 90 going downhill on the motorway. (And I slowed down as soon as I realised I was breaking the speed limit, honest, gov.)

As to the suspension, as roomwithaview points out, the suspension has to react to being unloaded in realtime; would they reach full extension in a tenth of a second?


#18

Came for the Dukes of Hazzard reference. Left disappointed.


#19

I think the most interesting thing is how he survived the crash with no injuries, then severely injured himself getting out of the water :smile:


#20

Would have worked if it were a bus