Boom

The design of the boom determines the height and reach of the crane. Mini crane booms are usually made up of telescoping sections. This boom has three sections of which two are telescoping.

Unlike most other cranes, pick and carry mini cranes are designed to allow the boom to be retracted or extended while under load.

This is a key advantage in terms of operating in confined spaces. The length of the boom defines its operating radius. The longer the boom, the greater the mini crane’s potential operating radius.

Boom rams

The telescoping sections of mini crane booms are extended or retracted using hydraulic rams and, with some machines, chain drives, located inside the boom.

There are single ram systems, where one ram is used; and multi-ram systems, where two or more rams are used, of which one design is a double-acting ram, where one ram can be extended inside another ram.

Hydraulic rams can also be used in tandem with chain drives. This configuration is most commonly used on larger mini cranes, which have more than three telescoping sections.

Wear pads

The telescoping boom sections on mini cranes, as on all cranes, have wear pads. These are pads made from a hard-wearing material, such as neoprene, which hold the sections in place as they are extended or retracted.

As such, the steel sections of a mini crane boom never touch. The wear pads can be replaced once they become worn.

Electric motor / hydraulic tank

The electric motors operates two systems – the drive system and the function system. The drive system controls the movement of the mini crane. The function system controls the hydraulic pumps, which lift and lower the boom, and operate the boom rams.

Hook

Rigging chains or nylon strops are attached to the mini crane’s hook. This hook has a safety catch to ensure the rigging load cannot slip.

Lift ram

A mini crane’s lift ram, or derrick ram, is used to lift and lower the boom. It is hydraulically powered. Pick and carry mini cranes do not slew. This is a key design feature, which allows them to remain compact and able to work in confined spaces.

However, the load can be moved side to side because the articulating single rear drive wheel gives the mini crane such a tight turning circle.

Foot

The foot is the point at which the boom is attached to the main body of the mini crane. Mini cranes are designed so the foot is to the rear of the machine.

This ensures the weight of the load is distributed effectively between the drive wheel at the back, and the two front wheels, maximising the mini crane’s stability.

Tip Height

The tip height is the maximum height the crane can reach when fully telescoped out, and the boom is as far back as possible. The tip height is calculated using data for the boom angle and boom length generated by the recoil drum.

Recoil drum

The recoil drum is another key part of the mini crane’s load monitoring system (LMI). The boom length is measures by a wire which extends from a drum as the boom is extended, which gives the device its name.

Data from the recoil drum is stored by the 3B6 LMI system and displayed on the driver tiller control panel. This data is important because the further the load is from the crane, the less weight the crane can lift.

Jib head

The jib head is a device attached to the end of the boom, from which the rigging cable, chain or strap is hung.

On the Valla 22E mini crane (shown), the orientation of the jib head can be adjusted, depending on the nature of load and objective of the lift.