Design Challenge - ALT 2011

RKad Engineering

Stability of container-handling forklift trucks is defined by ISO 10525 for which there are four criteria: longitudinal stacking (container raised to maximum height); longitudinal travelling (container raised to a height allowing operator to see under container and mast tilted fully back); lateral stacking (container raised to maximum height and mast tilted fully back); lateral travelling (usually container raised to a height allowing operator to see under it and mast tilted fully back). These criteria require the truck to be tested by tilting on a test platform until it tips over. Optional calculations or simulations can be used.

Adding additional counterweight improves longitudinal stability but it affects lateral stability. Increasing the mast’s back tilt angle will improve longitudinal stability for travelling but, at the same time, would reduce lateral stability for stacking and travelling. One obvious solution is to provide fine control of mast tilt, reducing maximum back tilt while the container is raised for improvement of lateral stacking stability, and increasing it when it is lowered for longitudinal travelling. Mast tilt angle control could be achieved quite easily by employing angle sensors or tilt cylinder stroke sensors to control operation of the hydraulic tilt cylinders’ valve.

Traditionally, container-handling forklifts have their cabin positioned relatively high above the ground and towards the rear so that the driver can see high stacks, as well as carry the container low enough for the operator to still be able to see under it. Another option is to position the cabin quite high but have it moving back for high stacking, and moving forward to see over the container, which would be in the lowest position for travelling (of course, this would not be a good solution for empty container handlers that handle two containers at the same time).

So perhaps the most viable solution would be to design a mobile cabin support that would raise the cabin for high stacking and lower it, as much as practical, for travelling. Moving the cabin from the rear high to the front lower position would require a hydraulically operated mechanism with cabin mounting structure.

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BIOGRAPHY

Owner & principal engineer Richard Kowalczyk has 30+ years’ experience in mobile equipment engineering. His most recent role was chief design engineer for Clark Equipment Australia.

CONTACT DETAILS

Email: richard@rkad.com.au

Web: www.rkad.com.au