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 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. One design is a double-acting ram, where one ram can be extended inside another ram.
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 motor operates the cranes hydraulic pump system, which in turn then operates the lifting functions as requested by the operator, Thus lifting the crane jib up and down and also extending or retracting the length of the jib.
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. Most pick and carry mini cranes do not slew. This design feature, 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.
Transducers
Mini cranes have two transducers on the base of the boom. These are devices that measure the pressure in the mini crane’s hydraulic system to calculate the weight of the load.
These transducers, when combined with the recoil drum, form a vital part of the mini crane’s 3B6 load monitoring indicator (LMI) system.
The 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.
Safe working load + load chart
Every mini crane must carry two clearly-visible signs. One gives its maximum safe working load (SWL). The other displays its load chart. A load chart provides data that defines each mini crane’s capabilities.
The data can be used to calculate safe lifting capacities, depending on the distance the crane is from the load and the angle of the boom. The information given by these signs are used by the operator to ensure the mini crane is always set up to carry out a safe lift.
All cranes with a SWL over 1,000kg must be fitted with a LMI (Load Moment Indicator) or SLI (Safe Load Indicator). At 95% of the SWL, an amber warning light comes on, to alert the operator. At about 105% of SWL, a red warning light is activated. At this point, the mini crane’s function is automatically restricted.
When this happens, the mini crane can only be operated in a way that brings the load back into radius, or lowers it off.
Non-marking tyres
Mini cranes can be fitted with non-marking tyres, as this one is. These are ideal for working inside buildings and clean environments. The tyres are solid, but are designed to flex under load, increasing the surface area in contact with the ground.
This maximises the mini crane’s stability.
Recoil drum
The recoil drum is a key part of the mini cranes safety system, know as the LMI (load moment indicator) The boom length is measured by a wire which reels from a drum as the boom is extended. Data from the recoil drum is measured by the 3B6 LMI system and is displayed to the operator via a digital screen.
This data is very important because the further the load is from the crane, the less weight the crane can actually lift.
Driver tiller
Mini cranes can be driven and operated in a number of ways. Some larger cranes have a built-in seat for the driver / operator to sit on. This particular mini crane has a drive tiller. This has levers and buttons used by the mini crane operator to move the machine and control the lift functions. The drive tiller also has a digital screen which provides the operator with lift information.
This mini crane has an emergency bump stop. If there is a risk that the operator could become trapped while reversing the mini crane, this stops the machine and moves it away from the operator. This is designed to prevent crush injuries. Many mini cranes can also be operated remotely using a hand-held controller, which may be radio-controlled.
Radius
Radius is the measurement from the centre of the front wheels on a Valla mini crane to the centre of the load, or to the centre of where the load is to be positioned.
On a mobile road crane, the centre of the radius is calculated from the centre of the slewing ring.
Battery pack and battery charger
The mini crane’s battery pack forms part of the machine’s counterweight system. No additional weight can be added to a mini crane.
Valla pick and carry mini cranes have battery packs of differing power, depending on the size and lift capability of each machine. They are made up of series of 2 volt wet cells. This particular mini crane has a 24 volt battery pack, made up of 12 x 2 volt cells. Valla pick and carry mini cranes can have an on-board battery charger.
Articulated rear axle
Most pick and carry mini cranes have a fixed boom. So, to slew a mini crane, the entire machine must move. Because the crane has an articulating rear axle, it can slew with ease in either direction. Mini cranes turn on their front axles.
The weight of the crane acts as the counterbalance.
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 type of load and objective of the lift.
Anatomy of a Mini Crane
It’s the mini crane that can make a big lifting impact.
Hird mini cranes like this Valla pick and carry crane are in big demand as clients such as glass installers, construction firms and facilities management specialists realise that they increase productivity, cut out manual handling safety risks and reduce overall lifting costs.
They are also impressive pieces of kit, packed full of clever technology to make any lifting project easier and safer to manage. So take a look around, and acquaint yourself with the anatomy of a mini crane.
For mini crane hire or mini crane sales, call Hird. We offer a national mini crane hire and mini crane sales service through three UK regional operating centres.