To set the bobsled in motion, team members sprint while pushing the sled forward. They run for about 50 m (164 ft) and then leap into the sled just before the first turn, assuming streamlined positions for the remainder of the run. The driver occupies the front position and steers the sled. The brakeman, in the rear position, operates the brake. On a fourman bobsled the two middle sledders contribute mostly during the start, although they also shift their weight during turns.
On the course, drivers try to steer through the turns smoothly and to prevent the sled from skidding into the walls. The greatest challenge is to maintain a tight line on the banked curves, not allowing the sled to drift high up the turn. After the finish, the brakeman pulls up on the brake to stop the sled.
The basic techniques used in twoman and fourman bobsledding are the same, but because fourman sleds have two extra sledders, they are faster. They gain power from the extra push provided by the middle sledders at the start, the sledders additional weight, and the increased weight of a larger sled. The increased speed and weight make fourman sleds harder to steer than twoman sleds.
Bobsled competitions involve training runs and two or four heats, with the lowest combined time winning. Racers often use the training runs to experiment with different strategies.
Bobsleds are made of aluminum and steel, although synthetic materials such as kevlar and carbon are becoming increasingly popular. All sleds must fit international specifications. The maximum length for twoman sleds, sometimes called boblets, is 2.7 m (8 ft 10 in). Fourman sleds can be 3.8 m (12 ft 6 in) long. Maximum weights, including crew, are 390 kg (860 lb) for twoman sleds and 630 kg (1389 lb) for fourman sleds.
The sled slides on four runners, two on the front axle and two on the rear. The front axle is connected to a steering mechanism of pulleys and ropes that the driver handles. The back axle is bolted to the sled and does not move. The sled also has a brake, a sawtoothed bar that comes down between the back runners. An aerodynamic hood, or cowl, covers the front of the sled. The back is open, which allows the brakeman to jump in easily at the start (the other sledders jump over the side). Handles extend from the back, where the brakeman pushes at the start. The other sledders use handles along the sides; these handles retract once the sledders jump into the sled.
Bobsleigh crews once consisted of five or six people, but were reduced to two and fourperson sleighs in the 1930s. A crew is made up of a pilot, a brakeman, and, only in 4man heats, two pushers. Athletes are selected based on their speed and strength, which are necessary to push the sleigh to a competitive speed at the start of the race. Pilots must have the skill, timing, and finesse to steer the sleigh along the path, or, line, that will produce the greatest speed.
In modern bobsleighs, the steering system consists of two metal rings that actuate a pulley system located in the forward cowling that turns the front runners. For example, to turn left, the pilot would pull the left ring. Only subtle steering adjustments are necessary to guide the sled; at speeds up to 80 miles per hour (130 km/h), anything larger would result in a crash. The pilot does most of the steering, and the brakeman stops the sled after crossing the finish by pulling the sleds brake lever.Women compete in Womens Bobsleigh (which is always twowoman), and men in both two and fourman competitions. .....