A bull wheel is a major wheel or gear in a mechanical system like a chairlift. It is typically the largest wheel in the system and is very strong. It can provide a source of power to drive the system, moving other components. The bull wheel design can be seen in a number of settings, ranging from farm equipment to lifts used to maneuver heavy machinery on the factory floor. Depending on the system, the wheel may be of custom manufacture for a very specific need, or produced generically.
In the case of a gear, the bull wheel has large teeth designed to intersect with neighboring gears to move them, powering the system. It may be reinforced to make sure it can withstand heavy loads. Other bull wheels are designed as cylinders or wheels wrapped with rope, cable, and other materials. As the wheel turns, the rope moves, and can be used to haul objects.
On a device like a chair lift, one bull wheel rotates with power, and another bull wheel, connected at the other end of the cable, rotates freely as the cable moves along. Chairs attached to the cable are moved up and down a mountainside or over a river or ravine. The same device can be used to move equipment, logs, and other objects in outdoor and indoor settings.
Bull wheels can also be employed on other types of pulley systems in a variety of settings. In all cases, this component of the system is easy to spot because of its large size. It may be centrally located for maximum efficiency and tends to be noticeably heavier and sturdier than other system components, as it is subjected to much more stress. A failure of the wheel could be particularly catastrophic, especially for systems under tension, and thus it is installed and maintained with care.
People working around a bull wheel must exercise caution. Crush injuries are possible if body parts become trapped in the wheel and they are often difficult to stop, making it hard to take action in an emergency. If someone is caught in the wheel, it is important to resist the temptation to pull the person out, as this could injure the person more and the rescuer could also get caught in the wheel. The emergency stop should be activated, and emergency services should be called immediately to extract the person and provide appropriate medical aid.