How safe are ski lifts and cable cars, anyway?

Brian Yarvin/FTWP - The Aiguille du Midi cable car in service with Mont Blanc in the background in Chamonix, France.

By Brian Yarvin,

There’s a metallic clang, and the door slams shut. Seconds later, the crammed cable car whisks upward, heading for La Flegere, a mountain just outside Chamonix in the French Alps.

A pit forms in my stomach as the car starts rocking. After a few moments, it’s swinging so enthusiastically that one man almost falls, and the kids on board are squealing with delight.

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Most of the other passengers focus on the stupendous views. It seems as though I’m the only one who doesn’t calm down quickly and enjoy my day on the mountain. But not being a cable car regular, I find a host of unsettling questions popping up in my mind: How do these contraptions work? How did they get all this stuff up the mountain in the first place?

And the all-important query: Are these things safe?

A few days later, I took another cable car from Chamonix up to Aiguille du Midi, a far more frightening-looking ride to a much higher spot. When we reached the mountain, all the other passengers ran out to the viewing terraces. But I was stopped dead in my tracks by a diagram that explained exactly how the whole thing works. This is what I wanted to know.

I studied the diagram carefully. There’s a motor, of course, but it alone can’t simply lug the car up as dead weight, so each cabin going up is counterbalanced by one going down. This is done by mounting each one halfway around a loop of steel cable. Now, obviously, most lifts have more than two cabins, but the idea of even spacing and counterbalancing cleared things up for me in a big way.

At the top and bottom of the lift, the cable spins around large discs called bull wheels. One of those wheels is powered, and it pulls the cable along as it turns. The other wheel is known as the return, and it sends the car back the other way. Drum brakes, not unlike those in older cars, can stop the wheels that carry the cables, and emergency brakes on the bull wheels offer a backup.

There was one more piece to the puzzle: What keeps the cables on the bull wheels in the first place? Wouldn’t they just pop off when they expanded in warm weather? And what corrects for a heavily loaded car going one way and an empty one going the other?

It turns out that this is handled with huge underground counterweights that pull back on the bull wheels and keep the cables at just the right degree of tension.

All in all, a pretty nifty piece of engineering.

In fact, it was the invention of lifts that made skiing popular. Before then, people would have to hike up mountains to ski down them. The idea that you could have more than a few downhill runs a day was revolutionary.

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Although skiing has existed in one form or another for thousands of years, motorized lifts have been around for only about a hundred. The first known working lift was apparently in the Black Forest town of Schonaich, Germany, where a water-powered tow rope for skiers and toboggans operated during the winter of 1908. It took a bit longer for lifts to catch on in the United States, but by the mid-1930s, tows rigged from old auto parts were fairly common in New England.

 
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