When the truck fits

Ergonomics – the human factor in design – has played a major role in the development of modern industrial equipment.

What’s the first thing you do when you get into the car to drive after someone else has been driving it? Chances are you adjust the seat and the rear view mirror. This is an everyday example of ergonomics in action.

The birth of ergonomics can be traced back to the Second World War, when designers began to realise that products would have to take account of many human and environmental factors if they were to be used safely and effectively.

To illustrate what can go wrong if you ignore the human factor, it is only necessary to look at the statistics: work-related sickness in the UK costs industry £11bn every year.

Some years ago, researchers compared the relative positions of the controls of a lathe with the average size of a male worker. It was found that the lathe operator would have to stoop and move from side to side to operate the controls. An ideal-sized person to fit the machine would have to be 4½ ft tall, 2ft across the shoulders and have an arm span of 8ft.

Industry progress

This may be an extreme example, but it shows how things can go badly wrong when no account has been taken of the user of a system. In addition to looking at human physical properties, ergonomists also take into account strength, compatibility of controls, vision, sound, thermal comfort, motion, vibration and workloads.

One area in the materials handling industry where ergonomics does appear to have made major inroads is in forklift truck design. Most of the major companies boast of having some degree of ergonomic features especially within the driver’s cab. Making a forklift safe and comfortable is not as easy as it sounds. Manufacturers are caught between the constraints of volume production and the need to meet the local needs of a worldwide market.

For instance, US truck users demand a no-frills, rugged machine, putting durability before comfort. In much of the developing world, where labour is cheap, there is less emphasis on high productivity, driver-friendly equipment and its associated cost. By contrast, most European firms will probably insist that the forklift operator is involved in the selection process. Here the selling price of the truck is less important compared to the total operating costs. Also, safety is a bigger concern, especially in the light of increasing regulation and legislation.

Designers are also faced with widely varying individual demands. A male Scandinavian operator might, typically, be over 6ft tall and weigh 16 stone. By comparison, his Latin counterpart may be no more than 5ft and weigh considerably less. Add to this the fact that in many countries there is a growing number of women drivers, whose body shape, limb proportions and muscle structure are different again, and the problems the designers face become apparent.

As part of the design of its LJ/MJ counterbalanced truck range, Yale called in New York-based Ergonomics Technology Corp (ETC) to carry out a series of tests.

Testing situations

ETC’s goal was to identify and quantify the ergonomic issues relating to several of the truck’s design components in an aim to locate potential stresses. Tests were carried out on static mock-ups of the proposed truck cab and on functional trucks. The testers were fitted with electrodes to measure and record muscle stresses in arms, torso and legs when mounting the truck and operating the controls.

The testing procedure included evaluating functions such as lever location, seat rotation effects, and pedal layout, as well as evaluation of the overall cabin design and dynamic testing of pedal effort and anthropometric measures of the test subject’s’ body size.

The physical effort required to operate controls, pedals and levers was measured, and the results proved critical to the final product with brake and pedal geometry being redesigned to minimise ankle flexion and reduce effort.

For the steering wheel, further changes were made. Roger Penfound, Yale Europe’s strategic products development director says: ‘We looked at the comparison between the height of the steering wheel and that of the operator’s shoulder, to minimise any reaching above shoulder height. The team looked at the shoulder height of the fifth percentile female and as a result improved reach by fitting a steering column with a tilt which extended downwards.’

In another piece of research for Yale, Professor Dr Hans Jurgens, head of the Anthropological Institute at the University of Kiel, tested the company’s new tiller handle. This encompassed the ergonomic evaluation of components including grip, butterfly type handle, controls for operating functions, and traction reversing button, as well as the general properties of the vehicle.

‘Ergonomic testing can reveal a great deal,’ says Jurgens. ‘Solutions arising from testing are already making life much easier for operators. The tiller handle is a promising example of the benefits that can be realised from testing.’

3D-motion tracking and measurements of independent angles were employed as test methods on small mixed groups of users. Operator feedback was sought at the prototype design stage by interviewing 70 people in the US and Europe. The group consisted of a wide range of both male and female operators, tall and short, who used forklifts in a variety of different situations.

Movement sequences on all operators were analysed with a mock-up in the ergonomic laboratory in order to acquire a database for measures of components and the tiller handle. International anthropometry databases, pressure and force measurements and procedures for contact area analysis supplemented these. Mitsubishi is currently working with Delft University of Technology to research new ways of improving ergonomics.

The company is also drawing on the work of the aerospace companies within Mitsubishi Heavy Industries to find new ways of suppressing noise and vibration. This is already in evidence with the launch of fly-by-wire technology employed in the fingertip controls introduced on its IC engine trucks.

Reducing noise and vibration has two major effects: first, it reduces the stress on the operator and second, it means that the vehicle has less effect on its environment. Some trucks are so quiet that they can be used in urban areas around the clock, without disturbing the neighbours. At 55dB(A), the power steering on Mitsubishi’s FBK T three-wheeled electric counterbalanced truck is quieter than that of a top-of-the-range executive car.

Safe in sound

Rogier Tonies, product manager for counterbalanced trucks of Mitsubishi Forklift Trucks, in Almere in the Netherlands, says: ‘Research shows that excessive and constant noise is an important stress factor in any workplace. A warehouse or docking station is most certainly no exception. Due to the constant noise factor people aren’t able to focus on what they are doing or when they need to start another activity. This causes a lack of concentration and motivation and a less productive driver.’

In Scandinavia, BT Rolatruc picked up the Fork Truck Association’s Annual Award for Excellence in the ergonomics category this year for its Orion range of powered pallet trucks. The trucks feature an ergonomically designed steering arm and handle which incorporates much of the truck’s technology. It is designed for one-handed operation (either right or left) and features a display which provides information on the truck’s status.

The message is: with health and safety issues becoming an ever-greater priority, ergonomics cannot be ignored.