Cranes have played an important part in constructing houses, buildings, cities, and nations throughout history. What would take hundreds of people and hours to accomplish, one of these cranes can do in just minutes. Mobile cranes generally operate a boom from the end of which a hook is suspended by wire rope and sheaves. The wire ropes are operated by whatever prime movers the designers have available, operating through a variety of transmissions. Steam engines, electric motors, and internal combustion engines (IC) have all been used. Older cranes’ transmissions tended to be clutches. This was later modified when using IC engines to match the steam engines’ “max torque at zero speed” characteristic by the addition of a hydrokinetic element culminating in controlled torque converters. The operational advantages of this arrangement can now be achieved by electronic control of hydrostatic drives, which for size and other considerations is becoming standard. Some examples of this type of crane can be converted to a demolition crane by adding a demolition ball, or to an earthmover by adding a clamshell bucket or a dragline and scoop, although design details can limit their effectiveness. The standard in mobile cranes, hydraulic truck cranes can lift thousands of pounds using hydraulics that rely on forces transmitted through oil pushing the boomas pistons in opposite directions. Hydraulic truck cranes are essential to building major projects like bridges, buildings, airports, roadways, and more.
