Knuckling down

7 December 2022

Knuckleboom cranes have found their niche as loader cranes for trucks. They are becoming quieter, greener and easier to use. Julian Champkin reports on developments.

Knucklebooms can be mounted on all kinds of chassis. On crawlers they generally count as mini-cranes - see page 28. On static mounts the small space taken up by their foldable jibs makes what is essentially the same concept especially well-suited to ships, docks, offshore rigs and the like where they are generally classified as marine equipment and can be fitted with deep-sea winches, pipe grabbers and other specialised maritime extras such as heave compensation.

In these applications they can reach very large capacities and sizes: Liebherr’s RLK series, intended for deep sea operations, goes up to 250t capacity and 7,500tm overturning moment. And they can be equally useful when mounted on railway cars.

But the prime application, and indeed the name used by several manufacturers of these cranes, is as a loader crane. Mounted on a truck, either behind the cab as is usual in Europe, or at the rear of the vehicle – a layout more favoured in the US - it loads the truck, frequently with construction materials such as bricks, tiles or timber, at the yard and, more crucially, unloads it at the jobsite either onto the ground or, for those with longer booms and reaches, into a first or even second-floor area of the project.

They are workhorses, perhaps considered an adjunct of the truck – the operator is more likely to consider himself a truck driver than a crane operator and will spend much more of his time at the wheel of the vehicle than at the levers of the crane control - but a vital adjunct nevertheless.

As with almost all crane sectors, recent developments in knuckleboom loaders include digital analytics and remote control. Electric power, as opposed to hydraulics powered from the truck’s diesel engine, is also making inroads, as are other emissions-saving technologies. Danish knuckleboom makers HMF have gone perhaps furthest along this road, fitting their electric-powered loader crane to a truck which is itself powered by biogas rather than diesel.

Danish builders' merchant Bygma came up with the idea and are operating what they say is a first in the industry.


For the past 15 years, Bygma has been using HMF cranes, which means, given the size of the company’s fleet, that hundreds of Bygma trucks are driving around with a red HMF crane fitted to help with the unloading of all kinds of building materials. According to Bygma's purchasing director, Preben Nielsen, the investment is an important part of the company's goal to reduce CO2 emissions from its own operations.

"A biogas truck contributes significantly to CO2 reduction; in fact, as much as 90% compared to diesel depending on the type of gas used. That's why we made this investment," he says.

"Bygma's new trucks will run on biogas, which offers the greatest savings on CO2. As the truck is stationary while work is being carried out with the crane - which is often used many times a day - we think it’s obvious to combine the two technologies."

An electric or biogas truck may be more expensive but there are advantages to switching to the greener technology: "The electric HMF crane is almost completely silent, and since the truck doesn’t emit CO2 when it is switched off, we significantly reduce both emissions and engine noise. The new trucks therefore offer a significant noise reduction compared to traditional trucks, which is very important in connection with construction sites in urban areas."

"We’ve been using HMF cranes for about 15 years, so it goes without saying that we’re satisfied with them," he says. “Our drivers are pleased with the crane's extra 'bend in the back' which makes it flexible to work with. Our close cooperation with the company is also crucial, and the reason for us to continue our work with HMF.

“The construction industry of the future is undoubtedly green. We support the Danish government's goal of reducing greenhouse gas emissions by 70% by 2030. That's also why we're investing in these biogas trucks. We consider ourselves pioneers in this field and look forward to gaining some experience with our new biogas and electric-powered trucks before deciding on the next step."

All Bygma's forklift trucks are already electrically powered, and the distribution trucks are currently being replaced by electric versions.

Hiab are major players in the field and it too has a new electric knuckleboom. In October 2022 it launched the ePTO 44, its second generation Electric Power Take-Off machine.

The plug-in system has more power and longer battery life with less weight than its predecessor. As an electric, emission-free, alternative to drawing power from the vehicle’s engine it allows the crane operator to work with the engine switched off – quietly and free from exhaust fumes.

Hiab says that using electricity reduces energy costs by up to 90% compared to diesel alternatives, and that the ePTO 44 offers further energy efficiency as it only delivers the energy that is required to move the crane: no energy is lost by idling the truck engine while the crane is not moving. The operating hours of the vehicle are increased as the ePTO allows the crane to be operated with the truck engine switched off so unloading hours no longer count in the truck’s useage time.

The setup consists of a battery, an electric motor, a hydraulic pump and a smart electronic control system, all of it packaged on the truck chassis. The status of the ePTO 44 is visible in the CombiDrive4 remote control display or on a display mounted on the crane.

The ePTO 44 can be used with any Hiab HiPro loader crane. The crane capacity is the same, and the already-familiar Hiab operational response is even enhanced. When the crane is not in use the electric pump is automatically switched off to save energy and battery capacity; the ePTO 44 starts up again with the control lever. As with the HMF electric knuckeboom the Hiab crane is virtually silent, enabling safe communication and a greatly improved working environment for operators.

UK timber and builders’ merchant Lawsons has already been using Hiab’s ePTO system. According to one of its delivery drivers, “from an operator’s point of view, using the crane is far less tiring. We’re not fatigued because we’re not working with the constant drone of the truck’s engine running all the time when we’re unloading. After a ten-hour shift, you really notice the noise difference.

Working with the ePTO makes our environment a happier place.”

Since the cranes are zero-emissions at the point of use working areas can be extended: the crane can be operated in emission-restricted zones such as indoor and tunnel operations, urban areas, early morning or night-time deliveries, or other areas where noise is a concern.

The company has been busy. To compliment the ePTO44 in September this year Hiab also launched its new medium range loader, the Hiab iX.162 HiPro. It is up to 370kg lighter, depending on configurations, than its predecessor, the X-HiPro 162, and the maximum lifting capacity has been increased by more than 10%. Pipes and hoses have been integrated into the crane body to make it less vulnerable to the elements and wear during transport and use, maximising uptime and productivity.

It comes equipped with the new SPACEevo control and sensor safety system which offers smart functionalities and smooth and rapid crane movements. SpaceEvo supports many new stabiliser leg configurations and options. It is based on an open platform, so upgrades and new features can be added over time.

A Hiab iX-162 HiPro version with ePTO (electric power take-off) integrated into its base will be available for order in early 2023. The battery pack and electric power unit will be placed directly on the crane base itself. This will make the installation process faster and leave more room on the truck chassis for other equipment.

“The Hiab iX.162 HiPro BSS-2 with an integrated ePTO and hydraulic tank, all in one unit, weighs the same as its conventional diesel-powered predecessor," says Mattias Berglund, director, global product management, special applications and digital products, loader cranes, light and medium, Hiab. "No additional weight is added when you go electric — this makes it a real sustainable option.”


Palfinger, too, is moving to electric power and electronic sophistication. The company has completely redesigned its core product, the Knuckleboom loader crane, to focus, it says, on three key cores: smart solutions, smart services, and eco-efficiency.

Its stated rationale is that inner-city jobsites and lifting tasks can now present complex challenges and require long reaches, and intelligent technologies – plus longer booms. Hence its new TEC range. The new design, it says, combines the advantages of its predecessors with digital systems such as the Paltronic 180 control system and the LX-6 control valve.

All models in the TEC series feature Palfinger’s Smart Control to control the crane tip. Palfinger claims the system is revolutionising the work process, uniting the crane with the operator. Instead of moving up to three different levers, Smart Control only requires one lever to move the crane tip horizontally or vertically. The operator therefore only needs to specify the direction of the crane tip, while the intelligent technology combines the necessary crane movements to reach the target position exactly.

There is also a Memory Position crane positioning system, which can store up to four crane positions, and the Levelling Assistant which helps optimally to level the cranes. “The future of construction is high-tech and interconnected,” says Palfinger. “These smart systems enable a faster start to operations as well as more efficient and simpler work processes.”

The first of the new models to be seen out on the road will be the 60-metre-tonne PK 580 TEC. When used with Palfinger’s mobile hybrid power unit it becomes emission-free with a minimum of noise emissions; an integrated tilting crane fork on the fly jib creates a high degree of safety for challenging work for example in narrow spaces.

Its sister introduction, the PK 1050 TEC, goes for the large crane segment. With a fly jib and enormous lifting capacity and reach, it stands out in its metre-tonne class with a reach of 37 metres. With DPS-C the lifting capacity is continuously maximised in every position because the intelligent system knows exactly where the crane tip is at any given moment. Palfinger is going small as well: its new PK 250 TEC — currently the smallest P-Profile crane — is a compact crane but even so has hydraulic reach of almost 20 metres and a maximum lifting capacity of 23.5-metre-tonnes.

Palfinger’s goal is to digitise its product range. Electrification also creates sustainable added value. At Bauma 2022, the company presented its eDRIVE technology for energy-efficient and completely emission-free operation of loader cranes. With eDRIVE operators can choose between a Li-Ion battery pack, a cable connection to the power grid, or the vehicle engine at the press of a button while operating the crane. Depending on requirements the best drive option can then be selected. The batteries of this smart system can be charged between jobs using the integrated generator. eDRIVE again operates almost silently, making it possible to work in noise-sensitive areas and at night.

Meanwhile Hyva earlier this year added a 40tm family to its successful Edge Line loader cranes which combine knuckleboom geometry with telescopic jib sections. There are five models, three of them rack and pinion, the other two with endless slewing. All are double linkage.

The basic model is the HC 401 rack and pinion with 430-degree slewing; the HC 401K is the short boom version; the HC441 proportional has a proportional lift control system (P-LCS) and the HC 405e and HC 445e proportional are the endless-slewing versions.

The cranes have from two to eight extensions, giving 8.02 to 20.90 metres maximum outreach and, except for the K-boom version, 10m jibs.

“Their high performance levels and wide range of innovative features and accessories and attachments make these cranes ideally suited to applications from construction to logistics, oil and gas, and mining, and for maintenance or rental,” says Giuseppe Bevacqua, Hyva’s product manager for cranes. The Edge Line is produced in a new dedicated crane assembly line in Poviglio, Italy.

The lesson might be that knucklebooms are developing from truck accessories to intelligent lifting machines in their own right. At any rate they are becoming quieter, greener and easier to use.

Liebherr’s RLK dockside crane: knuckleboom on steroids?
HMF’s electric-powered knuckleboom on a biogas truck
Palfinger’s PK 1050 TEC has a 37m reach
The new medium-range iX.162 HiPro from Hiab
Hiab’s second generation electric-powered ePTO
Hyva Edge-line 40tm has up to 21m outreach
Smart Control eases operation of Palfinger loader cranes
HMF’s electric-powered knuckleboom on a biogas truck