In a bid to reduce manufacturing costs in the automotive industry car manufacturers have for years been asking suppliers for ever more complete and ready-built sets of components. Having been led by high volume car producers, this phenomenon is spreading to commercial vehicle manufacturers and, because these component suppliers also serve crane manufacturers, it is increasingly being seen in the on- and off-highway mobile crane manufacturing industry despite the relatively small numbers of components involved. The net result is that the number of separate component suppliers that a crane manufacturer uses is being reduced.
For the crane manufacturer, reducing the number of component suppliers lowers costs, means fewer parts need to be held in stock and simplifies such things as ordering, product development, and other supply chain management issues. Grove in the USA, for example, reduced its number of component suppliers from around 1,500 at the end of 1999 to 539 today. By the end of September it expects to have just 350 suppliers. This has been achieved partly by rationalising its product line but mostly by reorganising its approach to manufacturing. Instead of the former assembly line structure, Shady Grove now has a hub and spoke operation where components are transported from different halls around the 123ha factory site to a central final assembly hall. Two years ago there were 365 pieces of rolling stock (fork lifts, etc), now there are 130. Productivity has improved from 70% to 91%. On-time shipping performance has improved from 65% to 100% for 22 straight months. Average build time for an E series rough terrain was reduced from 58 days to 22 days.
Grove has reduced the number of its suppliers by having a greater commonality of parts in the reduced product range and by greater use of outsourcing. A smaller number of suppliers provide components as larger pre-assembled sections. Control panels, for example, now arrive at the factory with all electrical wiring, gauges and switches already installed. Previously Grove would have assembled them in-house from individual components.
Liebherr also keeps outside suppliers to a minimum but, unlike other crane manufacturers, many components come from companies within the Liebherr group. The drive technology philosophy is to have a system solution for future construction machinery requirements, down to producing its own engines and hydraulic pumps, for example.
As a component supplier to crane manufacturers DaimlerChrysler’s PowerSystems division has broadened its range from previously just supplying engines. An example for mobile cranes is a power pack consisting of an OM 502 LA V8 engine coupled with a G 240 transmission. This ‘custom-made drive train’ means the engine and transmission are ‘ideally’ matched to each other and communicate electronically, the company says, which results in ‘harmonious gear changes with operating convenience and little stress on the clutch. It also prolongs the useful life of the drive train and saves fuel’.
One of the world’s largest suppliers of components, modules and complete systems to industrial vehicle manufacturers is Dana Corporation. New products launched by Dana at this year’s Las Vegas ConExpo are designed to persuade major customers to purchase more of their drive train components from the company, says Albert Huevel, product manager at its Spicer Off-Highway Products division.
Launches included a new Powershuttle transmission, the PSR08, that can be used in small cranes and compact vehicles up to 120hp (90kW). There is also a complete drive line system available as a package that includes the suspension system. Components for cranes made by Dana include single-reduction and planetary axles, transmissions, transfer cases, multiple brake options, torque converters, driveshafts and end fittings.
Integration In their turn, along the supply chain, component and system manufacturers also outsource components such as alternators, starters, even entire electrical systems from component sub-suppliers (see Cool technology, p41). Seamless integration of all these components and sub-assemblies into the total vehicle system needs a close working relationship between component suppliers and the crane manufacturer. Increasingly this integration and optimisation happens electronically, via computer software, rather than mechanically. Components are also being ‘simplified’ mechanically. For example, instead of mechanical actuators to synchronise gears in its transmissions ZF Friedrichshafen does it electronically.
Cranes are built in relatively low numbers which can mean higher component costs, particularly for items that are produced specifically for use in cranes. Crane manufacturers can reduce costs by using higher volume ‘standard’ drive train components and use software tailored to their specific requirements to control it and integrate it with the rest of the vehicle. In this way, it is the software of each crane manufacturer that becomes the way to differentiate between a product from one manufacturer or another.
Take the ZF AS Tronic transmission (Shift to automatic Sept 00, p35). Production volumes are high because AS Tronic is used by several major truck manufacturers and bus and coach builders as well as crane manufacturers, including Liebherr and Tadano Faun. The control software specifications for a gearbox used in a road haulage vehicle differ from that used in an all terrain crane so manufacturers have their own versions. Variations include axle ratios, transfer box ratings, engine characteristics, etc. This same transmission is given names like Tipmatic, Optidriver, Eurotronic, Ecogit and Freedomline by various commercial vehicle manufacturers but they are all the same basic product.
For mobile cranes ZF offers ‘customised system concepts that take account of specific manufacturer requirements.’ These are the AS Tronic automatic transmission system, The ZF-Intarder retarder system, the new TC Tronic combined transmission system, Ecomat automatic transmissions and ZF power takeoffs.
Whereas ZF specialises in transmission systems Liebherr promotes its own complete system solution for drive technology. Liebherr has to cater for a wide range of construction machinery that imposes differing demands on the drive technology. In construction and civil engineering loads must be lifted, moved and positioned. In mixing technology various materials have to be mixed and batched. An efficient and reliable drive train with a series of drive and control components is necessary for this mechanical work.
The drive train includes diesel engines, multiple-output pump transmissions and hydraulic pumps and motors; coordination takes place by using components of the control and management electronics. To ensure that an intelligent and optimally tuned system solution is available for every aspect of drive technology, Liebherr says, it manufactures the various drive train components itself. Liebherr Machines Bulle in Switzerland, founded more than 20 years ago specifically for such tasks, develops and produces the drive systems.
With a view to optimising the entire drive train, Liebherr has developed a series of hydraulic pumps and motors, covering six different sizes. These new hydrostatic components are notable for their improved efficiency, reduced noise levels, longer service life and greater reliability, the company says.
Considerable potential for reducing fuel consumption is seen by matching individual components within the entire drive train. A prerequisite for this is full electronic management of the diesel engine and the hydraulic pumps and motors. A CAN bus system is used to communicate between the components which means the entire drive train operates at maximum overall efficiency at every point so fuel consumption is further improved.
Systems integration on Caterpillar engines comes through a CAN Data Link, allowing bi-directional communication between engine and machine electronics. ‘This simplifies the installation of transmission, hydraulics and monitoring systems,’ says Roberto Dionisio, Power Systems manager at Caterpillar. ‘It also lowers installation costs and significantly improves machine performance.’
The new industrial version of Volvo Penta’s D12 engine has EMS (Engine Management System) which improves performance and allows full integration with the vehicle. D12 engines can be delivered as a component of the customer’s system either partly integrated or free-standing.
COOL TECHNOLOGY
An area of significant recent development is engine cooling. Bosch Rexroth, Denison Hydraulics and Horton are all promoting cooling fan systems that are claimed to have benefits including, for the manufacturer, design flexibility, easier manufacturing and, for the equipment’s end user, better operating efficiency, reliability and lower running costs. These cooling options can be supplied by the engine manufacturer as part of a power package.
Denison Hydraulics claims that its digitally controlled, hydraulically powered fan drive system for heavy duty engine cooling applications improves vehicle emissions, gives better fuel efficiency, more precise thermal control and better reliability. Controlling engine coolant temperature is only one of several tasks performed by today’s cooling systems, says Denison Hydraulics marketing manager Paul Newnham. ‘We are seeing today that a single multi-path radiator is used to cool engine oil, air conditioning refrigerant, transmission, drive train and hydraulic fluids, [to] pre-condition combustion charge air and even [to] control the ambient temperature inside the engine compartment,’ he says.
A traditional direct drive fan system is not flexible or controllable enough to do all these things efficiently, he says, ‘because their performance is almost entirely determined by engine speed. But engine speed and cooling load are not generally well coordinated in these kinds of applications, with the result that a lot of fuel is wasted turning a fan at much higher speeds than necessary. If more cooling is needed while the engine is idling, perhaps due to high ambient temperatures, the only way to get it is by increasing engine speed but running the engine faster increases the thermal load on the system while increasing fuel consumption and exhaust pollution. Conversely, when the vehicle is moving, the fan might not be needed but the direct drive fan continues to consume engine power.
Various devices have been developed to overcome this basic problem. Clutch systems disconnect the fan blade from its input shaft, and there are temperature sensitive viscous couplings. But fan speed is still dependent on engine speed, regardless of thermal requirements, and so the system is still wasteful. Denison’s system runs the fan at optimum speed across the duty cycle and so consumes only as much power as is needed to do the job. The fan’s electronic controller monitors signals from temperature sensors in the various cooling circuits and adjusts the speed of the fan to keep all the systems within programmable temperature limits.
Available data allows graphing and data logging via a PC and there are diagnostic and status display LEDs. Windows based software is used for programming the unit by connecting it to a PC with a Denison OptoLink interface. This is an infra-red unit so there are no standard connectors that can be damaged or that will corrode in harsh environments. Up to three simultaneous inputs from temperature sensors such as standard thermistors are accepted by the controller which processes them according to preset parameters and then sends signals to operate the valves that control the motor speed of the fan drive. Denison designed the manifold to be freestanding or mounted on the ports of the motor for maximum space efficiency.
Programmable features include accelerated warm-up where the fan is off, a delay that keeps the fan off to reduce load during a hot start. The fan can even be asked to run in reverse to blow dirt and debris out of the radiator.
Since the fan and its control system are self-contained and do not rely on a mechanical drive such as a belt from the engine, the radiator can be mounted almost anywhere on the vehicle. This allows improved machine ergonomics, new body design possibilities and better access for maintenance. Even if the radiator is mounted conventionally, in front of the engine, the radiator and fan assembly can be moved to give access to the front of the engine.
Another new fan drive that promises to increase performance and efficiency of heavy duty off highway diesel-engined equipment is Horton’s MagForce. It is a two speed electromagnetic drive – the fan alternates between eddy current for low speed and electric current for high speed – giving more precise temperature control, fuel savings, noise reduction and reduced maintenance needs. Mag Force is suitable for fans up to 26in (660mm) diameter on engines between 50hp and 200hp (37kW and 150kW).
Improvements are also possible by changing the cooling fan itself. Horton claims that its new WindMaster increases airflow by 15% and uses 20% less power than other fans.
