Human dummy takes a beating
Strange but true

Published: October 7, 2008

Q: What’s it like to be involved in 846 car crashes, a world record? Wouldn’t only a "dummy” do this on purpose?

A: The human "crash test dummy” is Rusty Haight, a former California policeman who taught accident investigation before opting for some hands-on investigation of his own, says Justin Mullins in New Scientist magazine.

Artificial dummies are designed for high-speed crashes and are built to last, with stiff necks and other features to prevent breaking. But at lower speeds they are of limited use because they respond differently than a real person.

Enter Haight. In a typical low-speed crash, he is subjected to about 10 g’s on average — 10 times the force of gravity — as if his 200-pound frame momentarily weighed 2,000 pounds.

(That’s why a car occupant can’t really brace against a crash.) On one day alone, Haight did nine crashes before noon, making his ribs and shoulders sore and tiring him out, victim of what biomechanicists call the "third collision,” where internal organs slam ahead into the ribs or inside of the skull.

The key variable here is not velocity but delta-v, or change in the car’s velocity (slowing impact). A change of speed of 10-25 mph is a moderate crash, and 25-35 mph is a moderate to severe crash.

Haight has personally taken it to 43 delta-v but has dodged injury by staying mostly with lower-speed crashes: 846 and counting.

Q: What can the rider of a wild bull (or even a mechanical bull in a bar, for that matter) do to help stay mounted other than just holding the strap around the animal’s chest?

A: With each sudden move of the bull — twisting, pitching, running, stopping — the rider’s momentum and angular momentum tend to send or rotate her from her perch, says Jearl Walker in "The Flying Circus of Physics.”

Instead of holding on to the strap tightly with both hands, she can do better by throwing one arm high, far from her rotational center, in a direction to counter any sudden rotation of the more massive upper body of the bull. If she also holds a large hat with her free hand, the air drag on the hat as it is waved might give an extra measure of resistance to the rotation of the upper body.

A first-time roller or ice skater does something similar to partially correct a problem with imbalance.

"During my first time on roller skates, when the skates tended to roll out in front of me, I automatically rotated my arms in vertical circles back over my shoulders (like a windmill) to keep my center of mass positioned over the skates and thus to maintain my balance and what little was left of my pride.”

Send questions to strangetrue@compuserve.com.

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