Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering
Transport Technology

J.H.D. Luiting Maten Container-lifting at the front. An introduction to reach stackers and front lift trucks.
Literature survey, Report 2000.TT.5358, Transport Engineering and Logistics.

This study is focussed on the role of the reach stacker and the front lift truck in container and intermodal freight handling. Both machines carry the loads in front of the truck. Because of this, the load causes a forward moment, which has to be compensated by a counter balance at the rear of the truck. The way the load is lifted has a large impact on the stability of the truck. A front lift truck has a fixed mast and its lift capacity is constant. The forward moment caused by the load is constant. A reach stacker, with its extendable boom, can reach beyond the first row. However, the further the load distance (the distance from front axle till the centre of gravity of the load) gets, the higher the forward moment, caused by the load, will be. The counter balance has a constant mass, so the lift capacity will decrease with an increasing load distance. Because the reach stacker can stack containers in the second and third row, the stacking density at a terminal served by reach stackers is higher than terminals served by front lift trucks. However, a higher stacking density has its effect on the accessibility of the containers, the so called selectivity. The selectivity refers to the number of moves that is needed to pick up a certain container. When a large number of moves is needed, the handling times will increase and the overall productivity will be lower. The selectivity is also less due to the fact that a reach stacker can not pick up every container in the second row, because of the decreasing lift capacity at larger load distances. This means that when a heavy container is needed, the entire first row has to be removed. With terminal planning software the situation can be improved, but it will always be difficult to predict when the shippers will pick up their cargo. Thus a front lift truck scores better on selectivity, but a reach stacker scores better on stacking density.

To make the machine more competitive with other types of terminal equipment, manufacturers try to improve handling time and to reduce operation costs. One of the major exploitation costs is the tyre cost. Tyres are very expensive and when a tyre has to be replaced, the machine is not productive. If a tyre fails during operation, the truck can also be damaged. The efforts of the manufacturers have to lead to longer tyre life, so the cost per kilometre can be reduced as well as the downtime. Better tyres can also absorb shocks, which will lead to less damage of the machine and more comfort for the driver. The comfort of the driver is the next point of attention for the manufacturers. They have concluded that it is not easy to design faster machines. Therefore, a lot of effort is put into the design of the interior of the cabin, to make it more ergonomic, so that the driver can operate it more easily and can work faster. Furthermore, the manufacturers try to improve the visibility.

Reports on Transport Engineering and Logistics (in Dutch)
Modified: 2006.01.23; , TU Delft / 3mE / TT / LT.