by Chris Woodford. Last updated: August 21, 2014.
Snow problem? 'sno problem if you have a snowmobile! If you live somewhere warm, like California, your only chance of seeing one of these brilliant little machines is in wildlife documentaries or James Bond films. If you live nearer the Arctic, in Alaska or northern Quebec, snowmobiles (often called snow machines) will be as familiar to you as motorcycles are to people living further down south. Given how useful they are, it's hardly surprising that engineers spent much of the early 20th century trying to develop the perfect machine for speeding over frozen terrain. The small, light, modern snowmobile finally appeared in the 1960s thanks to pioneering Canadian engineer Joseph-Armand Bombardier, who named his machine the Ski-Doo®. So how do these funky little snow bikes actually work? Let's take a closer look!
Photo: A convoy of US Marines on Ski-Doo snowmobiles in Alaska. Photo by Airman 1st Class Jack Sanders courtesy of US Marine Corps.
What is a snowmobile?
Photo: Right: A snowmobile makes light work of this frozen track in Alaska. Note how far apart the front skis are compared to a skier's: this gives a snowmobile stability and a lower center of gravity, which helps to stop it tipping over. Photo by Jonathan Snyder courtesy of US Air Force.
Think about an ordinary motorcycle: you have a heavy engine in the center with the rider balanced on top of it and two narrow wheels with rubber tires just in front and behind. Now in theory you can ride a machine like this through snow, providing the snow is soft enough to compact as you move over it (and you can get some grip) and not so hard and frozen that it's turned to super-slippery ice. In practice, motorcycling on snow and ice is incredibly dangerous and best avoided: steering fluctuates between tricky and impossible and there's a high risk your bike will slide right out from under you. The problem is that relatively little of your bike is actually touching the road—just two tiny patches of rubber under the front and rear tires—and that's simply not enough to give you good traction and grip.
Artwork: Left: A snowmobile gets much more traction in snow than a motorcycle using a large, wide track with deep rutted treads. A belt-drive and clutch system transfers power from the engine (in the center of the machine) to the track at the back. Compare this with Bombardier's early, 1944 snowmobile design (below) and you'll see that the basic idea hasn't changed very much.
If you had to rebuild a motorcycle for snowy terrain, what would you change? You might fit skis at the front to spread your weight and give reasonable steering. A wide, rutted track at the back would give you plenty of speed and lots of grip, no matter what kind of terrain you had to deal with. What you'd end up with would be something like a modern snowmobile. It's very similar to a motorcycle, with the engine in roughly the same place and power transmitted to the rear track through a drive belt.