Truck-Mounted Crane

What a Truck-Mounted Crane Is

A truck-mounted crane is a hydraulically powered lifting appliance integrated onto a commercial road truck so that one unit both transports and lifts. The crane is bolted to a subframe over the chassis rails, its hydraulic pump is driven by a power take-off (PTO) from the gearbox or engine, and stabiliser legs (outriggers) extend before lifting to widen the support base. Because the crane shares its carrier with the load, the machine is fundamentally a compromise between three competing demands: lifting capacity, payload still left to carry, and a footprint small enough to fold up and drive on public roads.

Functionally there are two distinct product families under the same name. The first is the articulating loader crane, often called a knuckle-boom crane, lorry loader, or by the genericised brand name Hiab. Its boom folds at hydraulic knuckle joints, mimicking a human finger, so it stows in a compact package directly behind the cab and leaves the bed clear for cargo. The second is the telescopic boom-truck crane, sometimes called a boom truck or self-propelled telescopic crane, which carries a straight boom that extends like a fishing rod and lifts with a rope and hoist winch over a head sheave. Loader cranes are rated by lifting moment in tonne-metres; boom trucks are rated by capacity at radius like a small mobile crane.

The two families also live under different safety standards, which is more than a paperwork detail. In Europe, loader cranes are governed by EN 12999, a harmonised standard under the Machinery Directive whose current edition is EN 12999:2020+A1:2025. In North America, articulating boom cranes follow ASME B30.22, while telescopic boom trucks follow ASME B30.5 (Mobile and Locomotive Cranes); ASME B30.5 explicitly excludes knuckle-boom cranes from its scope, confirming the split. China uses the GB/T 9465 series for lorry-loading cranes. The standard that applies changes the required overload device, the test-load factor, and the inspection regime, so the family question is the first selection decision, not a marketing label.

The commercial value of the configuration is self-sufficiency. A delivery of building materials, steel, precast concrete, glass, or plant can arrive, unload itself, place the load where it is needed, and leave without a second machine or a crew waiting on a hired mobile crane. That eliminates the standby cost and the coordination risk of two assets on one timeline. The trade-off is that every kilogram of crane and subframe is payload the chassis can no longer carry, and the lifting capacity at long radius is modest compared with a dedicated mobile crane of the same gross weight.

In scale, the category spans a very wide band. Compact loader cranes start at a few tonne-metres for light delivery vehicles. Mid-range loader cranes of 20 to 60 tonne-metres dominate construction supply and utility work. At the top, Palfinger's PK 200002 L SH reaches about 150 tonne-metres with roughly 48 m of outreach, and Fassi's F2150RAL runs to about 160 tonne-metres. Telescopic boom trucks range from roughly 2 t up to 65 t capacity, with sheave heights above 60 m on the largest swing-cab machines. No single crane covers this range, so engineering selection means matching a specific duty to a specific class and chassis.

Types and Classification

Truck-mounted cranes are classified first by boom architecture, then by mounting position, drive, and control. Boom architecture is the decision that drives everything else, because it sets the reach geometry, the rating method, and the governing standard. The table below compares the two principal families on the metrics that matter at selection.

The articulating loader crane is the most common truck-mounted crane in materials delivery, utilities, and general construction supply. Its folding boom lets it reach down below grade, lift over a wall and lower into a courtyard, and fold into a small stowed package that leaves almost the full bed available for cargo. Hydraulic extension booms slide telescopically from the outer knuckle to add horizontal reach, and a fly jib can be fitted for extra outreach. Because the hook hangs directly from the boom tip, the load follows the boom precisely, which is excellent for placing material accurately but offers less gentle vertical lowering than a free rope.

The telescopic boom truck trades folding compactness for reach and rope handling. The straight boom telescopes to height, and a hoist winch raises and lowers the load on wire rope over a head sheave, exactly as a mobile crane does. This gives high vertical reach, the ability to reach over an obstacle and lower a load gently to grade regardless of radius, and a winch that is permanently affixed to the crane. The penalty is that the boom stows along the bed, consuming cargo length, and the machine behaves and is rated like a mobile crane rather than a loader.

Beyond boom type, a second axis is the mounting and control arrangement. Loader cranes mount behind the cab (most common, keeping weight forward over the chassis), behind the body, or as a rear-mount. Control can be by manual levers at a stand-up or seated station, or by proportional radio remote control, which is now standard on mid and large cranes and lets the operator stand clear with a full view of the load. EN 12999 sets the requirements for these control systems and for the overload safety device that arbitrates between operator command and the load chart.

A third axis is hoisting class and duty class, defined by EN 12999. Cranes are assigned a hoisting class HC1 or HC2 according to their dynamic and elastic behaviour: HC1 for a crane mounted on a vehicle or a structure of equivalent flexibility, and HC2 for rigidly mounted cranes such as those on a static foundation or vessel. A rigidly mounted crane fitted with a device limiting peak pressure in the first boom cylinder, for example an accumulator, may also qualify for HC1. The duty class (for example HD4 or HD5) reflects how the load is picked up, with faster pickup demanding a higher safety factor in the structural calculation. These classes feed directly into the fatigue and strength design of the crane, so a vehicle-mounted crane and a stationary crane of the same nominal capacity are not interchangeable.

Lifting Moment, Reach, and the Load Chart

The single most misread number on a truck-mounted crane is the maximum capacity. A loader crane is rated by lifting moment, the product of load and horizontal radius, expressed in tonne-metres (t-m). One tonne-metre is approximately 9.81 kN-m. A crane rated at 30 t-m does not lift 30 t; it lifts roughly 3,000 kg at a 10 m radius, about 6,000 kg at 5 m, or about 1,500 kg at 20 m, in each case after deducting the weight of the extension booms in use and the structural safety margin. The headline maximum capacity is achieved only at the shortest radius, close to the column, where the crane is rarely actually working. The load chart, not the brochure number, is the contract.

The table below shows the published lifting-moment classes of representative manufacturer models, illustrating how outreach grows with the class. These are nominal catalogue figures for orientation; the governing document for any lift is the specific model load chart at the actual configuration and outrigger spread.

Reading the chart correctly means understanding why capacity collapses with radius. As the boom extends, the lever arm grows, so the same lifting moment yields a smaller permissible load: load equals moment divided by radius. At the same time, each metre of deployed extension boom adds dead weight that the moment budget must also carry, so the usable load falls faster than the simple inverse-radius curve near full extension. This is why a crane that lifts several tonnes near the column may only lift a few hundred kilograms at full reach with a jib fitted.

A telescopic boom truck is read differently. Its chart is tabulated like a mobile crane: rows of radius against columns of boom length, each cell giving a capacity in tonnes for a stated outrigger condition. The hoist winch line pull and the number of falls of rope also cap the load, independent of structural capacity, so a deep multi-fall reeving is needed for the heaviest lifts and a single fall for fast light hook speed. Sheave height and available boom length set the vertical reach, with large swing-cab boom trucks reaching sheave heights above 60 m.

Two practical reach concepts complete the picture. Horizontal outreach is the working radius from the slewing centre to the hook, the number that decides whether the crane can place a pallet on the far side of an excavation. Vertical lifting height is how high the hook can go, which matters for stacking, loading high vehicles, or lifting over a structure. A loader crane usually wins on horizontal outreach for its weight and a boom truck usually wins on vertical height; choosing between them starts from which of the two governs the job.

Finally, never size to the chart edge. Good practice keeps the working load comfortably inside the rated curve, allows for slings, lifting beams, and dynamic effects during pickup, and accounts for the duty class that governs how fast the load may be lifted. A crane operating routinely at the very limit of its chart wears faster, trips its overload device on minor dynamic peaks, and leaves no margin for the wind, the swing, or the slightly heavier-than-expected load.

Stability, Outriggers, and Standards

A truck-mounted crane lifts loads that would otherwise tip the vehicle, so stability is the central safety problem and the reason outriggers exist. Outriggers, also called stabiliser legs, are retractable hydraulic legs that extend out from the chassis and press down onto the ground, widening the effective support base so the tipping line moves well outside the wheels. The published load chart is valid only when the outriggers are deployed as the chart specifies; lifting on wheels alone, or on a narrow outrigger spread, sharply reduces what may be lifted.

Outrigger spread is the geometry that sets stability. Many cranes publish capacity for both full spread and reduced or partial spread, because a kerbside or confined site may not allow the legs to extend fully on one side. Partial spread can cut rated load by 30 to 60 percent in the direction of the narrow base, and asymmetric deployment is one of the most common causes of loader-crane overturns. Advanced rated-capacity systems read the actual leg positions and automatically derate the chart for the deployed geometry rather than trusting the operator to pick the right column.

Ground bearing pressure is the second half of stability and the part the crane cannot control. Each outrigger pad concentrates a large share of the combined crane and load weight into a small footprint, and pressures of several hundred kilopascals are common. Soft, wet, or made ground, buried services, and unseen voids can let a pad punch in and collapse the support base even when the crane itself is within its chart. The remedy is engineered outrigger pads or timber cribbing sized to spread the load to within the ground's allowable bearing pressure, assessed before the lift.

The governing standards translate these physics into testable requirements. The table below summarises the principal documents an engineer specifying a truck-mounted crane will encounter.

Under EN 12999, the stability check is performed with a test load equal to 125 percent of the specified carrying capacity, and an overload safety device is required for loader cranes with a carrying capacity above 1,000 kg. The device limits the load moment, typically by adapting the lifting force in the crane hydraulic system so that an over-moment command is blocked rather than allowed to proceed. ASME B30.22 sets parallel requirements for articulating boom cranes in North America, including load-rating charts that show capacity by configuration. These device and test requirements are not optional extras; they are why the load chart can be trusted, and they are part of what is being purchased.

Key Specification Parameters

A loader-crane or boom-truck datasheet can list dozens of figures, but a manageable set drives the selection decision. Read these in order, and read each against your actual duty rather than the brochure best case.

Lifting moment and capacity at radius. The lifting moment in tonne-metres is the headline rating for loader cranes, but the operative number is the capacity at the radius and configuration you will work at, taken from the load chart. For boom trucks, read the capacity-at-radius table for your boom length and outrigger condition. Treat the maximum capacity as a marketing figure achievable only at minimum radius.

Maximum hydraulic outreach and vertical height. Outreach is the working radius at full extension; vertical height is the maximum hook elevation. A jib or fly extension increases outreach but reduces capacity and adds dead weight. Confirm both the with-jib and without-jib figures, because the catalogue maximum outreach is usually the jib-fitted number at very low capacity.

Number of hydraulic extensions and slewing angle. More extension booms give finer reach control and longer outreach but more dead weight. Slewing angle ranges from limited arcs to continuous 360-degree rotation on larger cranes; continuous slew via a slewing gear and worm or rack drive is preferred for repeated full-circle work, while limited-slew rack-and-pinion cranes are lighter and cheaper.

Outrigger spread and ground pressure. Note the full and partial spread dimensions and the rated capacity for each, plus the maximum outrigger leg load that sets the required pad area for the ground you will work on. A crane that cannot achieve full spread on your typical site must be sized on its partial-spread chart.

Hydraulic system and PTO. Working pressure is commonly in the range of about 16 to 35 MPa, with pump flow matched to the crane size. The system pressure, flow, and the PTO type the chassis can provide must be compatible. Higher flow gives faster crane speeds but demands more from the PTO and pump.

Crane and subframe weight. This is payload the chassis loses. The crane self-weight plus the subframe, plus a margin, must leave the cargo payload you still need to carry within the chassis gross vehicle weight rating and axle limits. This single line often decides which crane class the chassis can legally carry.

Control and safety electronics. Manual levers versus proportional radio remote; the rated-capacity limiter or load-moment indicator and its features such as automatic outrigger-based derating, oil-temperature display, overload alerts, and data logging. EN 12999 requires the overload device above 1,000 kg carrying capacity, so its presence is a baseline, and its sophistication is a differentiator.

The summary table below collects the typical ranges across the truck-mounted-crane category for quick orientation. Use it to bracket a search, then verify each value on the specific model datasheet.

Selection Decision Factors

To move from category knowledge to a specific model and chassis, work the decision sequence below in order. Most selection failures come not from a single wrong number but from deciding the chassis or the crane class before the duty is defined. These steps double as an RFQ template.

1. Define the worst-case lift first. State the heaviest load and the longest horizontal radius you must reach together, then add slings, lifting beam, and a margin. Find that point inside the load chart, not at the crane maximum. If you also lift over an obstacle, state the required vertical height at that radius.
2. Choose the boom family. If you need compact stowage, a clear bed, kerbside access, and accurate placement, choose an articulating loader crane (EN 12999 / ASME B30.22). If you need high vertical reach and gentle rope-lowered placement, choose a telescopic boom truck (ASME B30.5 / EN 13000). The family also fixes the governing standard and overload regime.
3. Match the lifting-moment class to the chassis. Add crane self-weight plus subframe plus a margin and confirm the remaining payload, rear-axle load, and gross vehicle weight stay within the chassis ratings. Verify the chassis frame strength and wheelbase suit the crane mounting position behind the cab or rear.
4. Confirm the outrigger spread against your sites. Compare full and partial spread dimensions with the typical work area. If sites often prevent full spread, size the crane on its partial-spread chart and check the per-leg ground pressure against the ground's allowable bearing, specifying outrigger pads where needed.
5. Specify reach details and accessories. Number of hydraulic extensions, fly jib if extra outreach is needed, slewing angle (limited versus continuous 360 degrees), and any winch option on a loader crane for rope lowering. Each accessory adds dead weight that the moment budget must carry.
6. Set the hydraulic and PTO requirements. Confirm the crane working pressure and pump flow, and that the chosen chassis can supply a compatible PTO. Specify crane speed expectations, since higher flow buys faster cycles at the cost of PTO and pump demand.
7. Specify control and safety electronics. Proportional radio remote control for operator visibility and safe stand-off; a rated-capacity limiter or load-moment indicator that automatically derates for partial outrigger spread; data logging and oil-temperature display for fleet maintenance. Confirm the overload device meets the governing standard.
8. Total cost of ownership. Crane and installation, subframe fabrication, PTO and pump, periodic statutory inspection (thorough examination), spare parts and service network, operator training and certification, and downtime cost. A crane that is one class too small forces repeated near-limit lifts that wear it out early; one class too large eats payload and capital for capacity rarely used.

One dimension that is easy to overlook at purchase but dominates the asset's life is serviceability and inspection support. Truck-mounted cranes are safety-critical lifting equipment subject to periodic thorough examination, so local availability of spare parts, certified inspectors, field hydraulic service, and load-chart and software support determines uptime over a 10 to 15 year service life. Palfinger, Hiab, and Fassi maintain broad dealer and service networks across Europe, North America, and Asia; XCMG, SANY, and Zoomlion anchor the Chinese market and increasingly export with regional support. A slightly cheaper crane with no nearby service can cost far more in downtime than the purchase saving over its working life.