Snowmobile tracks are like tank tracks, with some key differences. They are made of light materials like rubber for added mobility and speed, while tank tracks are made of rigid materials because they must withstand concussions and explosions while carrying heavy weights. Tank tracks usually serve to steer as well as propel the vehicle, while a handlebar/ski mechanism steers snowmobiles.
In both cases, tracks succeed where wheels often fail -- they spread the vehicle weight over a greater surface area, allowing it to move on soft, slippery or unstable terrain where wheeled vehicles are unable to gain traction. Tracks keep a heavy snowmobile from sinking in soft snow, just as long, flat skis and wide, flat snowshoes spread a person's weight over a larger area.
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Snowmobile tracks also provide traction on slippery surfaces like snow and ice, where regular wheels would slip and slide. The large surface area and the roughness of the treads create friction between the snowmobile and the surface, giving the snowmobile a better grip. Most snowmobilers add sharp studs to their tracks; these act like cleats on athletic shoes and sink a short distance into the ice or hard snow, gouging small holes that enable the tracks to grip the ice even tighter on particularly slippery terrain.
You steer a snowmobile by turning the handlebars, in much the same way as you steer a bicycle or motorcycle. The handlebars connect to a stem mounted near the front of the snowmobile, which in turn connects to skis mounted on a bracket at the bottom of the snowmobile. Turning the handlebars turns the skis in the same direction.
Snowmobile skis come in varying widths and sizes for different terrain, as well as single or double-ski models. Wider skis displace the snowmobile's weight over a larger area, enabling it to "float" higher over the snow, while narrower skis allow for sharper turns.
Shock absorbers play a large part in providing a comfortable and stable ride. Springs and dampers are used in a manner similar to mountain bikes, enabling the rider to pilot their vehicle with the mobility of skis, but the stability of a tracked vehicle.
In the next section, we'll look at some of the environmental concerns associated with snowmobiles.