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Pole vault car

i was listening to the show today 3/7/09 and you told a lady that she needed her car looked at right away because it was possible for the car to pole vault and flip over catasrophically. mythbusters did a show on this and while the youtube clip i found is horrible it shows the meat of the debunk


thanks :slight_smile:

                                                   The Pole Vaulting Flathead

When I was in highschool, my friend Mike had an early morning rural paper route that he drove 7 days a week. He drove a beat up ?51 Ford Tudor at high speeds, breaking hard to slip a paper into a paper box and than speeding to the next one while pulling a paper from the back seat, tucking it into a roll for the next box. I want to establish that Mike was a very good driver despite his thick glasses. His non-paper route car was a ?52 Ford Coupe with a Ford-O-Matic transmission that the rest of us car nuts poked fun at periodically. Mike would show the superiority of F-O-M by inviting us to ride with him. He would wind up to 60 MPH plus and then slip it into reverse and floor the gas pedal. It was pretty impressive! The car would rise up and slow down in a hurry. Mike repeated this maneuver
plenty of times, thumbing his nose at us stick-shifters. ?Try that!? he?d say.
One cold winter Sunday morning Mike called me. ?I need a tow,? he said. He gave me directions, a rough road about a mile from his house. When I drove up, Mike was standing in the road, grinning at a hidden joke. As I backed up and hooked my tow chain, I asked him if the Ford had quit. ?Naw, runs fine, but take a look underneath, at the back end.?
At first I couldn?t see anything wrong, then:. ?The drive-shaft is missing!? ?Look some more,? said Mike. Then I saw that the differential had spun around within the spring ?U? bolts, the front was buried into the bottom of the gas tank. Laying on the ground, I tried to imagine what had happened here.
The Clues: The road was full of deep chuckholes. Mike loved to throw this car into reverse.
?Mike, did the drive-shaft break at the front?? ?Yep.? ?And it fell into a chuckhole?? ?Yep.? ?You pole-vaulted this Ford?? ?Yep.?
Imagine this: the car was speeding down the rough road, he threw it into reverse, the drive-shaft broke at the front, fell into a large hole and vaulted it about five feet into the air.
?What did you say when this happened??
?Whoooopie! Until it landed…hard! Then I said somethn’ else.?

I kind of doubt a car is going to “pole vault” and go end-over-end even if the front of the driveshaft does get nicely planted. However, I’m sure a lot of damage can be done to the back half of the car, including ripping loose the rear axle and shredding the gas tank (with resulting fireball). It’s not something to neglect.

I can see it as a possibility. History is repleat with tall, short wheelbase, front heavy RWD cars of very light overall weight with enough overhang for the front to dig in if the rear got lifted.

Note that I’m alluding to vintage cars. With the added weight of today’s safety equipment and the crash testing requirements today I can’t envision it happening to a modern car.

I’ve never seen it, but it’s theoretically possible.

Sometimes you have to shake people up a bit in order to rouse them to action. While it is true that a modern car is unlikely to actually “pole-vault”, the fact remains that when the front u-joint on a driveshaft snaps and the front of the driveshaft hits the pavement, it is not a good thing.

I can recall an acquaintance going through this with his '58 Ford–on the West Side Highway in NYC, during a torrential rain storm, circa 1964. The driveshaft dug into the bad, pothole- studded pavement in such a way that the car came to a stop almost instantaneously, and the occupants were all injured when they hit the windshield. Major damage to the rear axle and the rear suspension took place, due to the circumstances.

Luckily, he was able to avoid being hit by other cars when his car came to an abrupt stop in the left lane, but an incident like this has the potential to result in real tragedy, depending on the specific vehicle, its speed, the condition of the road surface, etc.

I see this as a distinction without a significant difference.

MythBusters did it. Devised a rig to dislodge the U-Joint on the drive shaft, timed it just so that the shaft dropped on the ground, snagged a pot-hole and caused the car to jump. It didn’t flip end-over-end, but it sure did a number on shoving the whole rear-end into the trunk / back-seat. Kind of scary to see the differential and axle sticking out.