Safety at speed

Aids to optimum forklift driving.

For any forklift truck activity, there’s a right speed and there are wrong speeds. Moving too quickly can be risky – and moving too slowly reduces productivity. Mark Nicholson looks at lift truck features designed to achieve optimum motion.

In the classic Cat® Lift Trucks forklift safety animation, 7 Deadly Sins, ‘Driving too fast’ comes in at number 3. Most obviously, excessive speed is a danger to any pedestrians in a lift truck’s working area. It also increases the risk of dangerous and damaging collisions with structures and objects, including walls, racking and equipment. Careful cornering is a special concern, as a speeding truck may become unstable – leading to overturning in the worst-case scenario.

Another aspect of speed to consider is whether any of the truck’s movements are too quick and jerky. Sudden steering actions, speed changes, starts or stops can cause instability. Your load may be thrown from the forks, resulting in damage to valuable goods. This kind of rough ride may be uncomfortable and counterproductive for the driver as well.

Improve output and save money

For all the above reasons, trying to go faster may reduce your output and add to your costs. Smooth motion in materials handling, rather than a frantic rush, is a key to higher productivity. It also reduces your forklift’s energy consumption.

We’re not suggesting that you should do everything slowly. The ideal is to move at the optimum speed for each situation – not too fast, but not too slow. Thankfully, there are advanced lift truck features and technologies which can help with that.

We will illustrate them here with reference to the Cat® EP40-55(C)N(H) 4.0 to 5.5 tonne electric forklifts. However, similar capabilities can be found throughout the Cat counterbalance forklift, reach truck and warehouse product ranges.

Programming

One of the most basic aids to safely controlling speeds is a programmed speed limit. In the models shown, you can choose between pre-programmed ECO and PRO performance modes.

In ECO mode, performance is restricted in certain ways. For beginners, trainees, part-time workers and other less experienced users, this lowers accident risks. ECO mode can also be chosen to save energy or when handling delicate goods.

PRO mode gives experienced operators more complete control of the truck’s high performance – including higher speeds.

Alternatively, a service engineer can set various parameters – including speed and acceleration – according to your specific needs.

Responsive Drive System (RDS)

These Cat trucks do more than just allow you to choose between contrasting performance modes. They continuously make automatic adjustments to operating characteristics according to the driver’s changing needs. This is achieved through the Cat Responsive Drive System (RDS).

RDS monitors and responds to changes in the driver’s speed of accelerator pedal and hydraulic control movement. These indications of the driver’s behaviour let the system know when a new situation or need arises. In response, parameters are altered accordingly. Drivers say that these forklifts feel totally in tune with them. The truck seems to know exactly how the driver wants it to behave at any moment. One important outcome is that all drive and hydraulic actions, including starts and stops, are carried out very smoothly.

Intelligent curve control

Automatic cornering control systems prevent drivers from taking turns too fast. In simple terms, the forklift’s maximum speed is reduced according to the angle of steer. The larger the steering angle, the more the speed is reduced. In practice, however, the performance of simpler systems is far from perfect.

Cat lift truck designers have taken intelligent curve control to a much higher level. Automatic reduction of travel speed takes place much more smoothly. The initial deceleration, as the turn begins, is relatively small. As the steering wheel turns further, braking increases more strongly – but still with a smooth progression. The driver experiences no sensation of sudden speed change, or of the truck tilting, as he or she turns. The motion feels natural and comfortable.

In addition, the Cat intelligent curve control system uses traction speed cutback to minimise side forces. It addresses an issue that forklifts face when straightening up after a high-speed tight turn. In this situation, the counterweight may continue to move sideways, under the influence of centrifugal forces. This is sometimes called ‘snake-tailing’. It can lead to a loss of rear-end grip for the truck – and it’s uncomfortable for the driver. The Cat system counters this with a combination of dual-drive motor control and a small limitation of the steering angle.

Importantly, these advances enable drivers to turn optimally – at the maximum safe speed for the circumstances. It means they can make quick and confident turns, rather than slowing excessively and over-cautiously.

Adaptive steering

Adaptive steering automatically adjusts steering force and steering ratio according to the truck’s travel speed. At fast speeds, it helps to keep motion steady by becoming ‘stiffer’. If the driver wants to steer, he or she must then apply a larger force to the steering wheel. At the same time, the steering wheel must be turned further to make the steered wheels turn.

When travelling fast and straight, this feature prevents small movements of the steering wheel from making larger-than-necessary changes to the truck’s course. Without adaptive steering, drivers may find they are constantly turning the steering wheel back and forward to correct unwanted deviations.

The same system helps to maintain steering stability when cornering at high speeds. Conversely, at low travel speeds the steering becomes lighter. It then requires less turning of the steering wheel to manoeuvre the truck.

Driver behaviour

While technological aids like these are welcome, we should always continue to stress the value of good driving habits. In particular, drivers must slow down when cornering. They should also drive smoothly. That means taking off gently, avoiding abrupt accelerations and turns, and anticipating stops with gradual deceleration.

You must supervise, monitor and enforce these practices. Today’s forklift telematics systems can be a useful aid in that respect. They will record data on driving characteristics such as speeding, harsh acceleration and braking, and fast cornering. If you detect any problem behaviours, you can support your drivers with extra training or refresher courses.