FEATURE | GANTRY CRANES
A 50-ton semi-gantry at a pulp and paper factory (Credit: Sclaferriere, Wikimedia Commons)
so using one wall of that building to support the hoist makes sense: it is close by and no space is wasted since the loads can be stored right up against the wall. As lifting solutions go the gantry design does seem an obvious one - a beam supported on legs at either end – and it has been used since earliest times. A travelling gantry though does though
have a weakness, or at least a consideration that designers must address. For smooth movement along the ground the leg structures and the wheels at either end must be kept aligned and parallel to each other. But the beam is large and long: if the legs were to be fixed rigidly to it, then any deflection, twist or expansion of the beam – from load, or from wind, or from thermal expansion in hot weather, - would transmit itself, magnified, to the legs and wheels; rubber-tyred wheels would then not travel in a straight line, and rail-mounted wheels might jam.
of Chesterfield Crane Company based in Derbyshire, are currently, and conveniently for this article, illustrating the ‘flexibility’ part of that statement. They are in the process of transporting an existing 12.5 t SWL gantry crane some 60 miles to a new site in South Wales (See box.) For completeness we should mention also the semi-gantry crane, which has a slight crisis of identity being both a gantry crane and an overhead bridge crane. One end of it has legs that run on tracks or tyres along the ground so qualifying as a gantry; the other end runs on an elevated runway fixed to the wall of the building, so
qualifying the machine as an overhead or bridge crane. Semi-gantries are found in roughly equal numbers inside fabrication plants and outside. The advantages of the hybrid are clear and apply indoors or out: it saves on space, the footprint is large, rectangular, and obstructed, if at all, only by a single rail on the ground. It is economical, since a wall of an existing building provides half the structure that gives height; and geography is on its side as well since storage yards, for components going in or for finished products coming out of a building, are most conveniently sited alongside that building,
KULI CRANES
Kuli Hebezeug Cranes have been making cranes in Remscheid in North Rhine-Westphalia for a hundred years. They recently delivered a gantry crane to a customer also in Remscheid, very close to their own facilities. The new crane replaces an existing one. The customer’s needs for the new equipment were higher speeds, greater capacity, and better hook approaches, together with more sensitive operation and smoother running. The new crane has a lifting height of 14m and a runway length of 90
m. It has two 3,2t hoists, mechanically coupled, to give a maximum span is 20m with a cantilever at one end which has a usable length of 0,5m. All movements are frequency inverter driven with stepless speed adjustment to give lifting speeds of 0-10m/min and cross- travel speeds of 3.6 - 36 m/min. Longitudinal travel is from 4 - 60 m/ detection, and a load summing device to keep to the maximum 5t capacity. There is a crane activity signal inside the building to show that the outside gantry crane is in motion. Operation is by radio
The solution is some kind of flexible
joint where the top of the leg meets the beam. Only one set of legs needs such a join. (If both ends were flexible, the whole thing would collapse sideways; it would be a mechanism, not a structure). That is the reason that large gantry cranes, where wind load and thermal expansion of the beam become significant, are frequently asymmetrical. The legs at one end are larger, more rigid, of a quite different design that legs at the other. A related problem afflicts small – even the smallest- of portable gantries such as those used in repair shops. These
remote control. The design is to DIN 15018 for lifting class H3B4. The total crane weight was around 20t. Two 50t and one 35t truck- mounted cranes were needed for the on-site erection.
26 | March 2025 |
www.hoistmagazine.com
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