Demolition Derby Special

Episode #115

OAD: April 8, 2009

Myth: Need For Speed

In the movie “Speed”, when a city bus needs to make a right-hand turn at 50 MPH (80.5 KPH), Keanu Reeves tells all the passengers to move to the right side of the bus so it won't tip over.  Would this really make a difference?

The Expert:

Stuntman George Sack gives Adam and Jamie a driving lesson.

Memorable/Quotable Moments:

Adam: Here comes chaos!

The Action/Results:

The team gets a standard city bus, and brings it back to M5 for preparation.  The insurance company has given Adam and Jamie the green light to drive the bus in these tests, so they install a roll cage, a safety harness for the driver, and plastic replacement windows.  A course is marked out on the Alameda runway that duplicates the turn from the movie.  Seven metal drums are strapped into the right-hand seats, and filled with roughly 450 pounds (204 kg) of water each, to simulate the weight of the 19 passengers from the movie.

Adam does the first test run, and at 50 MPH, barely makes the turn.  Jamie, in the chase car, sees the tires come slightly off the road.  This result duplicates the movie scene.  But did shifting the passengers really make a difference?  To find out, the barrels are rearranged to simulate people sitting throughout the bus.  Jamie takes the wheel, and pulls off the high-speed turn twice.  There isn't any real difference between how the bus handled with the weight evenly distributed and with the weight on the right, so this myth is Busted.

Now it's time to see what it takes to roll a city bus, and for that it's time to R/C it.  Brakes and throttle will be simple switches – either they're off or they're on full power.  Steering will be a big issue on this test; instead of the usual hand-held unit Adam uses a steering wheel as his controller.  The final R/C rig is mounted in the bed of Jamie's pickup (complete with a seat for Adam).  Initial testing at Alameda looks good.  With Jamie handling brakes and speed from inside the bus, Adam is able to drive it down the runway from the chase pickup.  The water barrels from before are strapped into the left-hand seats, and 4000 pounds (1814 kg) of metal sheets are strapped to the bus roof to make it top-heavy.  A valve on the air shocks will let the guys dump all the air from one side, tipping the bus.

When they're about to start the final run, Adam's throttle switch fails.  Jamie goes for the simple solution, and jumps into the bus to override the R/C and manually set the throttle.  Then Adam's brake control fails to disengage.  The Jamie Solution works again, and as the bus heads off Jamie dashes for the truck so he can get Adam back in range.  Steering, fortunately, does not fail, and the bus rolls onto its side on cue.

Myth: Hollywood Crash Test

In TV and movie chase scenes, cars plow through obstacles without a scratch and keep going.  Would this really happen?

The Experts:

E-Tech Testing Services lets the team come back to play on their crash track.

Memorable/Quotable Moments:

Grant: Which way to the destruction?

Tory: Now how the **** are we going to get this car out of here?

Kari: Just throw it back over the fence.

The Action/Results:

Kari, Grant, and Tory take several cars and assorted obstacles out to E-Tech, last seen in the first Alaska Special when they ran over a fake moose.  There are two things to test on each run – does the impact look like what we've seen in Hollywood chase scenes, and is the car still drivable afterwards?  Since all these myths involve high-speed chases, they decide to run all the tests at 70 MPH (112.6 KPH).  The test car will be released before impact, so any destruction is purely from momentum, not from being towed through the target.

Sub-Myth 1: Fruit Stand

Kari sets up large wooden bins loaded with fruits and vegetables on the test track, and the first car crashes into them.  It definitely passes the first criteria, as food flies everywhere.  Unfortunately, the impact severely damaged the front end of the car and smashed the windshield.  This is ruled Busted, you couldn't continue the chase with the resulting car damage.

Sub-Myth 2: Gate Crash

Another common Hollywood obstacle is the gate of a chain-link fence.  The team sets up a steel fence across the track, and padlocks the gate closed.  Kari expects another Busted result, but the car plows through easily.  The impact triggers the air bags, and does some damage to the bumper, but Grant is able to drive the car around.  You don't see airbag deployment when this happens in a movie, but many older cars don't have airbags – the team agrees to call this Plausible.

Sub-Myth 3: Trailer

One scene from the movie “Mad Max” features a cop car punching a hole through a camping trailer and continuing to drive.  An RV is parked across the track, and test car 3 heads out.  This test fails both criteria.  Instead of punching neatly though the trailer, the car destroys it.  The car also takes enough damage in the process to be undrivable.  This myth is Busted.

Sub-Myth 4: Instant Convertible

We've all seen it in the movies – semi pulls across the road, car can't stop in time, car goes under the semi trailer and emerges on the other side without a roof.  Kari backs a semi trailer into position, and Buster is placed on the seat of the final test car, “ducking” the way a live driver in this situation would.  The car goes under the trailer, leaving its roof behind ... and then leaves E-Tech behind.  The test cars were all fitted with a remote brake for safety, but this one failed.  The car launches itself off the earth berm at the end of the track and over the fence on the other side.  Buster came through apparently undamaged, and the team agrees that the car must have been still drivable to take off like that even though the bonus crash wrecked the front end, so this one is Plausible.

Myth: Car Drop Chaos

An ad for a luxury car shows a driver outrunning gravity over a 4000 foot (1220 meter) course.  A driver on the ground passes a target before a duplicate car dropped from a helicopter lands.  But is this really possible?

Memorable/Quotable Moments:

Kari: Did we get the rental insurance on this?

Grant: I'm not going to say, like Luke down the Death Star trench ... but it was like Luke down the Death Star trench, and then the X comes up, YEAH!

The Action/Results:

The first thing the team needs to test is how a car would fall in this situation.  The ad shows the car falling level, which maximizes wind resistance and lowers the terminal velocity.  To see if cars really fall that way, they take three test cars out to the Teichert Aggregates quarry where a bamboo ultralight almost flew.  Each car is given the same rigging as the car from the ad, hoisted 400 feet (122 meters) into the air on a crane, and dropped.  The first two cars hit nose-first. Grant and Kari point out that this doesn't necessarily bust the myth, because the types of cars MythBusters can afford to drop off cranes have 60 percent of their weight in front of the center line.  Luxury cars are evenly balanced front to back to improve the ride.  Before the third car is dropped, the team loads enough junk into the trunk to balance its weight distribution.  This time, the car falls level.

For the full-scale test, the team obtains two identical luxury cars, capable of matching the top speed of the car from the ad.  Because it would be too dangerous for one of them to drive Car A while Car B is falling overhead, Grant sets up an R/C rig that should allow him to control the car from as much as 2 miles away.  He adds a small video camera to the hood, so he'll be able to follow a guide line on the test track.  Meanwhile, the designated drop car is balanced to match the car from the ad exactly.

Once everything is ready, testing moves out to the Mojave Desert.  While Grant finishes R/C setup, Tory and Kari mark the test track and lay out a large target X with plastic snow fencing.  While the remote control appears to be working normally, Grant's video feed keeps cutting out.  Without that, he can't steer the car accurately.  So, they bring in a second helicopter.  Instead of steering from the start line, Grant and Tory will be chasing their car in the chopper.  Tory will keep a directional antenna aligned on the car, while Grant drives.  The next problem is speed.  The car from the ad has a top speed of 142 MPH (228.5 KPH), and on pavement so does their test car.  On a dry lake bed, they can only hit 105 MPH (169 KPH).  Grant does the math and adjusts their test track to the distance their car can cover in the same amount of time as the original car: 2950 feet (899 meters).  The falling car will still travel 4000 feet.

Finally, it's time to go.  Grant and Tory bring their car up to speed.  As it crosses the start line, Kari in the lift chopper drops the second car directly over the X, and the race is on.  The dropped car hits the ground 300 feet (91 meters) away from the X, over two seconds before the driven car reaches the target.  While the ad may have been filmed under different atmospheric conditions, affecting the rate of fall, the team calls this one Busted.

------

Myth: Compact Compact Supersized

The Compact Compact myth from Episode 41 is revisited.

The Experts:

Mike Stanley and the rest of the crew from New Mexico Tech

Memorable/Quotable Moments:

The subtitled “translation” of Jamie's comments after the runaway truck incident.

A speechless Adam in the rocket sled bunker.

Jamie: So, our goal was to fuse metal and pancake the car.  Did we achieve that?  _What_ car?

The Action/Results:

Jamie and Adam agree that Compact Compact needs a revisit – they didn't get the crash timing right last time, and the trucks were traveling too slow.  They head back to Alameda to set up a modified version of the original rig.  The modifications should not only make it easier to ensure simultaneous collision, but will let the tow trucks get up to highway speeds.  As before, the tow cables will be attached to the tow trucks with a breakaway blue rope, which leads to some disagreement.  Adam thinks two lengths of rope will be plenty to handle the load, Jamie wants to use four.  They finally compromise on three.  The test begins, and promptly ends as the rope breaks prematurely and both semis head off the course.  One almost lands in the Bay, both take a lot of damage to their steering rigs.

Once everything is repaired and reset, the test runs again (with four lengths of blue rope).  This time, everything goes perfectly.  The semis smash into the compact simultaneously at 50 MPH (80 KPH), crushing it far more than the car in the original test.  However, the semis aren't fused together, and the car wasn't “lost” between them.

But the guys want to see what it would take to get the results of this myth, and for that they head to New Mexico Tech to borrow their rocket track.  Jamie and Adam assemble two rocket sleds, each one carrying 12 rockets, and set them up in a two-stage arrangement.  At the far end of the track, a steel plate is set against a concrete backstop to simulate one truck grille, and a compact car is placed against it.  A second steel plate, standing in for the other truck grille, is on the front rocket sled.  The rear sled will fire first, bringing the rig up close to 400 MPH (644 KPH), then the lead sled will fire its rockets for further acceleration.  When the lead sled hits the car, it's going 650 MPH (1046 KPH), and there's nothing left but scraps that would easily be lost between two wrecked semis.

Even that didn't produce fusion between the two metal plate “trucks”.  There is a procedure, called “explosive welding”, that will bond two pieces of metal together with an impact.  Before leaving New Mexico, Jamie and Adam get a demonstration of what it takes.  One sheet of steel is placed on a flat patch of ground, and a second plate placed over it at a measured distance.  Five hundred pounds (almost 227 kg) of high explosives goes on top of that, and everyone heads for the bunker.  When the explosives are set off, the two sheets of metal are forced together and fuse.

Back in San Francisco, Jamie and Adam agree that while pancaking and fusion are both possible, they call for conditions that you're not going to get on a highway.  This myth is still Busted.