Technology is no match for really big snow

February 20, 2003|By MIKE HIMOWITZ

EVERY NOW and then, I'm reminded of the limits of technology. For example, consider what happens when your corner of the world is buried in 28 inches of snow, as ours was over the past weekend.

If you live in Minnesota, this kind of "weather event" is known as flurries. But here in the Mid-Atlantic, it happens very rarely - rarely enough that you've almost forgotten about the last really big snow when the next one rolls around. And you're surprised to find out what a pain in the keister it is.

This time, I certainly thought I was prepared. The snowblower was gassed up and ready to go. We had plenty of melting crystals on hand, and this year, for the first time ever, a car that was designed to go in the snow.

We picked out the Toyota Highlander 18 months ago with vague memories of 1996 on our minds. This was our last real Winter of Discontent, with a series of major snowfalls that culminated (for us) in 8 inches on the morning of my younger son's Bar Mitzvah.

The Highlander is known in the trade as a mid-size SUV. That means it's something less than a truck, and certainly nowhere near as large, expensive or obnoxious as, say, a Lincoln Navigator or a Hummer.

On the other hand, it's boxier than the average car. If not exactly designed for off-roading, it does sit a higher off the ground than my pokey little Buick. More important, it has all-wheel drive and a button for something called Electronic Traction Control, a term that has the wonderful ring of redneck tech.

Which brings me around to the physics of driving in the snow and to a lesson I learned very painfully this week. Here goes:

In virtually all cars today, a device called the differential gear determines how much torque (a force that operates in a rotating motion) is actually applied to the driving wheels. This is a tricky business because, when you turn, the outside wheel has to travel further and spin faster than the inside wheel. The differential gear handles this disparity nicely.

Now it gets a bit more complicated. A standard differential applies the same torque to both driving wheels. More important, for ice and snow, it makes sure that the engine applies only enough torque to keep the wheel with the least traction from slipping.

If one wheel is on ice and starts spinning, a standard differential won't apply more torque to the other wheel, even if it's on solid ground.

This defies logic at first glance, but there's a reason for it. Let's say you're driving on a patch of highway where one wheel is on ice and the other is on dry ground. If your car routinely applied additional torque to the wheel with traction, the vehicle could easily make an unexpected turn or go into a skid.

In any case, you've seen this system in action if your car has ever been stuck on a patch of ice. One driving wheel spins like crazy, while the other doesn't move at all.

That's why many cars today come with a limited-slip differential, known by a variety of fancy names including Positraction and electronic traction control. Unlike its standard cousin, the limited-slip differential will eventually apply additional torque to the wheel with better traction if it senses the other wheel spinning too much.

So, theoretically, it will help get you moving in icy conditions as long as one wheel has some grip on the road.

That's about as good as it gets on two-wheel-drive cars because the engine is hooked up to only one set of wheels. In passenger cars today, this is typically the front wheels; larger vehicles are still likely to use rear-wheel drive.

Four-wheel-drive vehicles up the ante in the get-up-and-go game by doing just what their name suggests. Instead of applying power to just one set of wheels, they apply power to both sets, which doubles the amount of traction available at any time. This is useful both in snowy conditions and off-road, where the footing and traction conditions are very uneven.

Needless to say, a car or SUV with all of these things going for it is a complex machine, full of extra gears, clutches, sensors and computerized controls. In a normal snow, they will probably do their job. But this wasn't a normal snow. This was a hell of a lot of snow.

As I found out Monday morning, with the last flakes still blowing. My wife and I made one last pass over the driveway with the snowblower and got it close to bare pavement. Then I opened the garage door, climbed into the SUV, and blasted into the street, with all those wheels, gears, clutches and sensors doing their thing.

About 20 feet into our court I came to a dead stop. The snow was flying, and all the wheels were turning but I was going nowhere. I backed up, started forward, backed up, turned the wheel, gunned the engine. Nowhere.

A couple of chuckling neighbors helped me dig out, and I backed up dejectedly into my driveway.

I'd learned the hard way about another factor known as ground clearance.

If the snow is above the bumper, churning your way into it, even with four-wheel drive, is just going to pile the stuff up under the car till you wind up with your wheels spinning on nothing. So there I was, stuck along with everybody else. For the first time in 32 years in this business, I missed a day of work because of the weather.

It took another 24 hours to get the blankety-blank SUV out of the driveway, and a few hours after that, the snowplow finally arrived and freed all of us.

But it could have been worse. A young colleague told me today that he was snowed in for three days with a broken XBox and a pile of new games he couldn't play. Like I said, there are limits to technology.

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