A brief history of lifting gantries1 November 2000
David Duerr P.E. reviews the development of hydraulic gantries
Telescopic hydraulic gantries were born in the early 1960s not as the commercial products available today, but as one-of-a-kind pieces of equipment used by rigging contractors for machinery handling. The basic concepts and designs of gantries came from the minds of imaginative riggers and engineers who needed to solve unusual lifting problems. Here we trace the beginnings of hydraulic gantry systems from specialty one-off pieces of lifting equipment to the diverse array of products available on the market today.
The first hydraulic gantries
The first pure hydraulic gantry was designed and built in 1963 by Hartley Belding, then the chief engineer of Belding Engineering Company in West Chicago, Illinois, USA. The company was awarded a contract to relocate a manufacturing plant owned by Elkay Sink Company in Illinois. Among the equipment to be moved were a number of large presses. Belding conceived the gantry system as a practical method of lifting the tall presses and laying them down to the horizontal position for transport.
Each leg of this system consisted of three 102mm (4in) bore, single stage, dump truck cylinders arranged in a straight line and welded to a simple structural base. Although the bases were not fitted with wheels, the system could be moved if necessary by setting the bases on machinery skates. The system was powered by a gasoline engine pump with an output pressure of 69,000kPa (10,000psi). The lifting capacity per leg was 34t (37.5 US ton) and the stroke was 2.44m (8ft).
Later gantries built by Belding used cylinders with larger bore diameters, longer strokes, and capacities of up to 91t (100 ton) per leg. A variation of the three-cylinder gantry was developed in 1967 in which the cylinders were arranged in a triangle, thus providing greater stability. The first gantry system of this configuration retained the performance specifications of the original gantry: a capacity of 34t (37.5 ton) per leg and a stroke of 2.44m (8ft). In addition, around this time, gantries were constructed with wheels integral to the base, thus allowing the gantry to be more easily moved while supporting a load.
In the years following, Belding designed and constructed a variety of gantry systems of various capacities and lift heights. These gantry systems, all of which were of the single stage, bare cylinder style, were (and in some cases, still are) used exclusively by Belding in its rigging contracting business.
The first commercial hydraulic gantry product was a system manufactured by Modern Hydraulics, also of West Chicago, Illinois, from the mid 1960s to the early 1970s. This gantry was of the single stage boom type and was manufactured with capacities ranging from 23t (25 ton) to 91t (100 ton) per leg.
The Modern Hydraulics gantry is shown in its simplest form in Figure 2. Each leg consisted of two concentric square structural tubes inside of which was a single hydraulic cylinder. The long and narrow base was also fabricated from a structural tube shape, as were the diagonal longitudinal braces. The header beams were simple S or wide-flange shapes.
Longitudinal stability was provided by the long bases and the diagonal braces that supported the bottom section of the boom. The header beam was rigidly bolted to the tops of the two legs, thus creating a rigid frame that provided lateral stability. This rigid frame design presented an operational constraint in that the extension rates of the two legs of the gantry had to be synchronized relatively closely to avoid introducing unwanted bending into the system. The internal hydraulic cylinders acted only in compression to lift the load. Bending stiffness to resist horizontal forces was provided by the square tube leg sections.
The gantry in Figure 2 serves only to lift and lower loads through a vertical stroke of 1.22m (4ft). More sophisticated models were later available that featured bases equipped with wheels for travel with a suspended load and with hydraulically powered lift links that could shift the load from side to side. Modern Hydraulics discontinued manufacture of these gantry systems in the early 1970s.
The principal design work of this product line was performed by Robin Renshaw, then president of Modern Hydraulics. Belding Engineering Company, a part owner of Modern Hydraulics, provided input into the concept and design and was the first buyer of a Modern Hydraulics gantry system.
A variation of the rigid-frame gantry was built by Williams Crane & Rigging of Richmond, Virginia. In 1971, Williams Crane was faced with the challenge of unloading from barges the steam supply system components for the North Anna nuclear power plant in Virginia. The remote location and configuration of the barge landing did not allow for the use of any type of land-based lifting equipment. The most practical solution was to ground the barge, lift the components straight up, position the hauling equipment beneath, and then drive the components off the barge.
The method chosen to accomplish the lifting utilized a hydraulic gantry system. This system, shown in Figure 3 lifting a steam generator, consisted of two independent gantries, each of which was built up from two single stage cylinder legs and a pair of wide flange shapes as a header beam. Extensions to the cylinders, each 1.83m (6ft) long, could be used as shown in Figure 3 to increase the gantry’s overall height. As with the Modern Hydraulics gantry, the header beam was rigidly attached to the cylinders, thus creating a rigid frame that was designed to resist lateral loading and provide transverse stability. A unique design feature of this one-of-a-kind system was the use of pinned connections at the ends of the longitudinal braces and at the bottoms of the cylinder legs. This allowed the gantries to be easily dismantled for shipping.
The basic concept of this bare cylinder gantry system was developed and all of the design engineering was performed by Daniel DeYoung, P.E., then with the Richmond, Virginia-based engineering firm of Torrance, Dreelin, Farthing, and Buford. The system provided a rated capacity of 545t (600 ton) and a vertical stroke of 2.44m (8ft). The large bases imposed relatively low bearing pressures to the underlying surface, thus making this system practical for use on light barge decks and on soil.
The next development in the evolution of the hydraulic gantry incorporated two concept changes: the elimination of the dependency of rigid frame behavior to resist lateral loads and the use of multiple stage, telescopic cylinders. This configuration of system, like the original Belding gantries, used legs with bases that are wide enough relative to their extended heights to provide an adequate stabilizing moment from gravity loads only. The multiple stage cylinders provide a retracted height to extended height ratio that is superior to that possible with single stage cylinders. The hydraulic legs of the first such gantry were constructed in the late 1970s by Edgar Engler, a former employee of Belding Engineering Company who was involved in the development of the Modern Hydraulics gantry.
Each leg consisted of a base constructed from structural steel shapes that supported three five-stage dump truck cylinders. A steel header plate joined the tops of the three cylinders and provided a support platform for one or two header beams. This gantry had a retracted height of 2.44m (8ft) and a stroke of 4.88m (16ft) that gave a fully extended height of 7.32m (24ft). The lift capacity was 68t (75 ton) per leg.
The basic pair of gantry legs was purchased from Engler by Daniel Hamm Heavy Rigging & Transport Company of St. Louis, Missouri, of which Gary Lorenz was president. Lorenz then built a power pack for the system and modified the jacks to include safety devices such as counterbalance valves to allow holding and controlled lowering of the jacks under load. Calculations to determine the capacities of the system were provided by Roger Johnston, P.E. through his consulting firm, J&R Engineering. Lorenz and Johnston were previously acquainted at Sargent Engineering and P&H Harnischfeger.
A period of transition
Lorenz established Linden Industrial in Davenport, Iowa in 1980. This company performed rigging work using the gantry system rented from Daniel Hamm. Linden Industrial ordered the first gantry to be built by Riggers Manufacturing Company, which was formed in 1980 by Engler, Johnston, and Lorenz to build and sell this new type of multiple stage cylinder gantry. The company’s product was based on Engler’s original concept, but was built to Linden’s order to include wheels, propel cylinders, and a leveling system.
The Daniel Hamm gantry (Figure 4) was of a fixed base design. That is, the bases could not be moved while supporting a load. Riggers Manufacturing improved the product by introducing a gantry system that featured a wheel-mounted base (Figure 5). This gantry could be rolled along structural steel track beams while supporting a lifted load. Movement was powered by hydraulic cylinders fitted between each gantry base and the track assemblies. The gantry system was moved by extending or retracting these propel cylinders.
A configuration change was made to the Riggers gantry in 1984. Each jack unit was made with four cylinders, rather than three. By 1984, three different models were produced with capacities ranging from 91t (100 ton) to 272t (300 ton) per jack unit.
The lifting gantry business became a two-company industry in 1983 when Gary Lorenz left Riggers Manufacturing and founded 4-Point Lift Systems in Davenport, Iowa. Lift Systems designed and began manufacturing a line of bare cylinder gantries using only one or two cylinders per base. These models were most commonly used in arrangements of four legs. Depending on the requirements of the lift to be made, the Lift System could be set up as two independent gantries (four legs, two header beams), as is seen in Figure 7, or as one four-legged system with a header beam arrangement that tied all four legs together.
Roger Johnston left Riggers Manufacturing Company in 1984 and, with Ron McCarthy, founded Hydratech Systems in Milwaukee, Wisconsin, to manufacture hydraulic gantries. Johnston was also associated at the time with Hydra-Power Products, a manufacturer of hydraulic cylinders.
Hydratech produced two styles of gantry system. The company’s basic system was a bare cylinder model (Figure 8) that used one multiple stage cylinder per base. Each base was fitted with a planetary drive system that provided continuous travel. The company also produced a telescopic boom gantry (Figure 9) in which each base supported two booms and was powered by two cylinders located outboard of the booms. The booms were equipped with locking devices that could support the load mechanically in case of a hydraulic failure. Hydratech discontinued the manufacture of gantry systems in 1986.
With this discontinuation of gantry manufacturing at Hydratech Systems, Johnston returned to J&R Engineering. Johnston had founded J&R in 1978 as a consulting engineering firm serving the crane and rigging industry. In 1986, the company became the newest manufacturer of telescopic hydraulic gantries.
The lifting gantry industry today
J&R Engineering resurrected the telescopic boom gantry of the Modern Hydraulics style. Like the Modern Hydraulics gantries, the J&R products used square structural tubing as the boom sections and placed the hydraulic cylinder inside the boom. Like the Hydratech gantry, the J&R gantry also provided mechanical boom locks. Where the Hydratech design used stepped latches that could lock the boom sections together only at set intervals along the length of extension, the J&R gantry used cam locking mechanisms between boom sections that enabled the load to be supported mechanically at virtually any position of extension.
By this time, three companies remained as the primary manufacturers of commercial gantry products: J&R Engineering, Riggers Manufacturing, and 4-Point Lift Systems. They remain today as the only commercial manufacturers of telescopic hydraulic gantry systems.
By 1988, J&R Engineering was producing three-stage telescopic boom gantries with cam locks. Later, a manual section was added to the boom, thus giving a four-stage boom powered by a three-stage internal hydraulic cylinder. A 408t (450 ton) J&R boom gantry is shown in Figure 10.
In 1992, 4-Point Lift Systems added a line of telescopic boom gantries to its product mix. The first of these products used a combination of internal and external cylinders to provide powered extension of all stages of the gantry. Typically, the lower two or three stages are controlled by two or four external cylinders that are mounted on the base and that are tied to the boom by means of a yoke weldment. The upper one or two stages are controlled by a single internal cylinder.
A four-stage two-legged gantry of this style is shown in Figure 11.
A second noteworthy feature of the Lift Systems telescopic boom gantries was the use of welded four-plate boom sections, rather than the then-dominant structural tube boom sections. This allows the use of high-strength alloy steels for boom construction as well as a ‘fine tuning’ of the proportions of the boom sections for structural efficiency. (Editor’s note: David Duerr himself developed a detailed method for telescopic boom design to support the design of this product line.)
Later versions of the Lift Systems telescopic boom gantries were developed using one internal cylinder per leg (Figure 12). Some gantries so configured included a manual boom section and others had all boom sections powered. Other enhancements included pin locks to mechanically lock boom sections together at specific intervals of extension and wedge locks to lock boom sections together at any extension position.
Today, telescopic hydraulic gantries are available in a variety of capacities ranging from 9t (10 ton) to 363t (400 ton) per base and systems with greater capacities are in the design pipeline. Multiple stage cylinders and booms are used on the vast majority of the systems available and electronic control systems enhance safety and ease of use.
Just as this type of equipment has grown from one-of-a-kind machines and specialty products in the 1960s to the broad array of sophisticated gantry systems we see today, there is every reason to expect that the products will continue to evolve in years to come as user demand spurs new design efforts and the manufacturers continue to take advantage of advancing technology.