Gantry systems in one form or another have been around since the 1960s, as the previous article explains. But this year marks the 20th anniversary of the birth of the commercial manufacturing industry. The market for commercially produced hydraulic lifting gantries is today dominated by three US manufacturers: Riggers Manufacturing, Lift Systems, and J&R Engineering. And the three share common roots – all can claim, in one way or another, to have been in at the beginning.
In 1979 Gary Lorenz, who was then president of Daniel Hamm haulage company of St Louis, Missouri, bought an unfinished three-stage telescopic gantry that Ed Engler had built, using dump truck cylinders, for his own rigging company in Chicago. Lorenz finished it, had the engineering checked by Roger Johnston, and put it into service. “It was crude, but it worked,” he recalls. Lorenz then teamed up with Bill Linden, owner of Illinois-based Linden Industrial, to set up Linden Industrial in Iowa. Unable to procure the necessary equipment for this new venture, Lorenz also joined with Engler and Johnston to form Riggers Manufacturing.
In 1980 Riggers produced its first hydraulic gantry, the EZ Lifter, for Linden Industrial.
About a dozen units of the EZ Lifter (still a production model) were sold by Riggers Manufacturing up to 1983 before the partnership broke up. Lorenz was first to leave. “I think it was a question of rigging philosophy,” he says. Lorenz says that he wanted to build ‘more flexible’ machines with four jacks, while Engler wanted to build bigger units.
Lorenz set up Lift Systems and shipped his first unit, a four leg design, in 1984. This was the first 4-Point Lift System. The following year Johnston split from Engler. Johnston had had his own engineering company for many years, J&R Engineering, and now began building his own gantries, the Lift-n-Lock, in association with a cylinder manufacturer. Three pioneering partners were now in competition. Engler has since retired, but Riggers Manufacturing still goes strong, under owner-manager Dave Pokraka.
Technical divergence
There remains a strong competitive rivalry between the three manufacturers, each of which claim performance and safety advantages for their systems over the others’. The rivalry is not totally without ill-feeling, it seems, and there have been intellectual property disputes between Lift Systems and J&R.
Key differences of approach centre on how man legs or housings are best, how many hydraulic cylinders per housing should there be and whether boom type legs or plain cylinders are best, either with cylinders inside or outside the boom, if there is one. Riggers, which still uses a two leg system, claims that its design is more stable than either the Lift Systems or the J&R solutions. J&R and Lift Systems products follow a similar design principle and prefer four housing lifting.
Riggers argues that two legs are safer. The most common cause of gantry accidents is an out-of-level condition and it is much easier for an operator to keep two legs level rather than four, the company says, even when a self-levelling system is fitted, as it is to all Riggers gantries. Competitors either do not offer such systems or they are options, according to Riggers. Easier set up is also claimed for a two leg system because there are only two legs to handle, set and level.
As for the number of cylinders, Johnston says that adding a fourth to the original three cylinder design was intended to increase strength but it actually had little effect, even though this machine is still in production. Riggers and Lift Systems both use multi-cylinder systems (more than one per lift housing) but Johnston argues that there can be control problems. If the load forces are not perfectly equal to all of the cylinders (almost impossible to achieve) the less loaded cylinder will extend faster and further than the more loaded cylinder, Johnston says. As a consequence, he continues, this will cause the cylinders to become out of parallel and load the head glands to a point where there are side loading forces which can damage seals or rupture the cylinder. Some multi-cylinder models have correcting systems that stop the unloaded cylinder until the loaded cylinder catches up. This stopping and starting can cause a suspended load to swing dangerously, says Johnston.
J&R uses single lift cylinders inside the boom of its octagonal boom Lift-n-Lock model. Lift Systems also offers single cylinder models in addition to twin and four cylinder types. Riggers claims that its 800 ton (725t) capacity EZ Lifter 804, with four cylinders per leg and load holding valves on each cylinder, means four times the safety of single cylinder gantries.
After a fourth cylinder was added to the original three cylinder design, J&R concluded that a cylinder-only gantry did not have suitable strength and several different models of gantries with booms were built. Booms are designed to take the side loading, otherwise borne by the hydraulic cylinders, so that there is no cylinder deflection and possible leakage or worse, a bending failure. Lift Systems offers two boom type systems, with either inside or outside cylinders, Lorenz says. The current J&R version was first built in 1988 and has proved successful, according to Johnston, who adds: “Some of the competition has tried to copy them but fortunately for us they are poor copiers and we do have some patent protection.”
Lorenz credits J&R with the first boom type gantry, with the Cam Lock load holding system. Instead of cams Lift Systems offers a choice of wedge locks, pin locks or cylinder lock valves to hold the load in case of hydraulic failure. Riggers claims that any three of its four cylinders can hold the load and therefore it does not need mechanical locking devices. Johnston, however, says that by their very nature, all holding valves, pistons or head gland seals can lose some of their pressure holding capacity, causing cylinders to lose a small amount of hydraulic pressure. A reduction in cylinder pressure would mean the load would be unable to be supported and could begin to inadvertently lower, he says.
J&R’s Lift-n-Lock design means a slight amount of lowering automatically engages concentric elliptical cams onto the boom structure to hold the suspended load. The Cam Lock system is automatically applied by a spring which positions the cam each time hydraulic pressure is reduced in the system. When lifting resumes, the cams are opened by a small hydraulic cylinder. Johnston says that competing systems have a wedge type locking device used in contact with a thin plate boom section where the non-concentric lock can become wedged to the point of becoming unlockable, even with the lift cylinder.
Roger Johnston makes a further strong claim that his company’s Lift-n-Lock hydraulic boom gantries have a “proven superiority” to any other system available. “We are far more advanced in engineering and field usage than the competition. Our machines have many features and benefits that others do not have; all of which were developed for increased safety and ease of operation,” he claims.
Lorenz says that his competitors cannot match the dynamic testing that Lift Systems puts its products through, while Riggers still maintains that two legs is best. Also, Riggers gantries are electrically powered, and all the motors, pumps, hoses and connections are housed in the gantry legs. Four leg gantries are powered by gasoline/propane engines located in the operator’s console, which means that they are noisier and their hydraulic hoses are exposed.
Whatever one’s view of the competing systems, the lifting industry has benefited from the fierce rivalry between the three companies, Lorenz suggests. “Some people say that it is too bad that the three people – Lorenz, Engler and Johnston – didn’t stay together,” says Lorenz today. “But I believe that the separation into three competitive companies is the reason for the growth in new types, models and ideas that has benefited all our customers.”
