A short history of tower crane remotes24 April 2008
Radio remote controls are now standard equipment on most self-erecting tower cranes, and are even becoming common in some parts of Europe for top-slewers. Will Dalrymple asks how they have come to be like a complete crane cab in a box.
Almost all self-erecting tower cranes come with a remote control. A growing number of top-slewing tower cranes use them as well. For example, the Potain Igo series of self-erecting cranes, and the new Igo T and MCT city-class tower cranes all use remote controls. All of the Liebherr Litronic cranes, and the EC-HM range and EC-B range can be used with remote controls. "In Europe, remote controls are used only with small top-slewing tower cranes, up to 100tm or 120tm," says Hans-Martin Frech, marketing director at the Liebherr Biberach tower crane factory. The limiting factor, he says, is that operators of larger cranes need to feel the crane reacting to the load so they do not operate too roughly.
With digital readouts wedged in between the controls, remote controls have started to look more and more like the load-moment indicator inside the cabin of a mobile crane. They tell users how much the load weighs, and what percentage of the maximum it is, how high the load is, and even how strong the wind is blowing.
What is remarkable is how quickly this has happened. Tower cranes have moved from simple electric machines to computer-control in about 20 years- perhaps half the development time of mobile cranes.
Remote controls have played a key role in this development. Early on, crane owners realised that small cranes are not busy all the time, and so operators who use remote controls can help out with rigging and other site jobs during down time. Although of course it costs more, adding a remote control could save an entire salary.
Frech explains: "Sometimes nothing is happening, and then it is possible for the driver to do other things. If you have a remote control, you can walk beside the load. If you have to put a load down softly, you can stand beside the load, and see everything very well."
These early remote controls would have only replicated the main levers of the crane. Remote controls were an aftermarket business.
"Remote controls have evolved away from being a specialty thing," says Hetronic Europe key account manager Josef Scheuerer. "Twenty years ago, a crane operated by remote without a cable was some kind of magic. Now it is becoming standard for all crane applications, especially tower cranes, and loader cranes and mobile crushers."
A key milestone was the manufacturers' decision to start to work directly with remote control vendors in the development of the crane. In 2000, Potain teamed up with German remote control manufacturer Hetronic, according to Potain global product manager David Havard. About the same time, Liebherr's Biberach tower crane factory also started working closely with HBC-Radiomatic.
Havard explains: "The decision was taken with the Igo range in 2000, that because of the evolution in the market toward radio remote controls, we should offer it as standard. It was then a gradual process to roll out standard remote controls. This was not about cost; the market was pulling for a solution, and we thought we should follow."
This move was important because it integrated the remote control into the technical architecture of the crane. Since the manufacturers were buying one unit for every crane, remote control manufacturers could expect much larger orders. By moving from an aftermarket addition to an OEM business, radio remote controls reached the mainstream.
The other feature of this new arrangement was technical cooperation. When OEMs started to work together with radio remote design engineers, remotes became much higher-performance products.
"The trend in the industry is for radio remotes to move from being simply transmitter-receivers to going toward the receiver having the features of a PLC," Scheuerer says, referring to a programmeable logic controller (a computer). "Receivers need to become more intelligent, and programmeable."
"It is necessary to have a long-term partner," Frech at Liebherr says. "You have to give many things to the partner so that they can provide control signals to the PLC, and give them the possibility to log into our control system. You don't give someone you don't know such access."
A remote control unit based on a computer is also more efficient to manufacture. Instead of having to make 50 different circuit boards for different customers, Hetronic can, for argument's sake, make five, and adapt each one of those 10 different ways using its H-Link configuration software. The H-Link software can assign buttons to outputs, and program speed increases or decreases, for example. He hints that the next generation of Hetronic remotes will be even more programmeable.
The structural changes in the business - concentrating on a few key OEM customers, and an increasing emphasis on computer hardware and software - may be reflected in changes of business structure of at least one company, Hetronic. Founded in Germany, the firm reorganised a few years ago, moving its headquarters to the USA, and its biggest factory to the fringes of Europe, on the Mediterranean island of Malta. The company's remote control for the recently-launched Potain Igo T85 crane, for example, was engineered at its global headquarters in Oklahoma City, and made in Malta. A Hetronic Asia factory in the Philippines is the company's main factory, Scheuerer says.
Now on the small screen
The Hetronic control for the Potain T85 displays trolley radius, hook height, weight, percentage capacity remaining, battery power, signal strength, wind speed, whether the crane is in two-fall or four-fall configuration, and warnings at 90% and 100% of crane capacity. The first models displayed one piece of information; now screens display all of it.
Remotes with data feedback have become something more than just levers connected to the crane by a wireless radio link. Now a computer- or several computers - sit between the levers and the crane motors. The software that interprets the signals that display the information also moderate the crane operator's actions.
David Havard gives an example. In the old days, if an operator was unsure of the weight of a load, he would try to raise it on the crane. If the crane's limit switches cut out the hoisting motion, then he would know that it was too heavy to lift. Now, control software available in the Potain Igo T and MCT ranges will interpret the crane's load chart and warn the operator before the limit switches cut out. This same software will help crane operators determine how far they can trolley out a given load on the hook.
In at least Liebherr's case, the remote control does not actually consult the crane's brain, but rather one resident in its own computer. "If something goes wrong with the remote, you can at least drive it manually," Frech says. Most of the time, however, the users would not know that the remote control system works independent of the crane control system, because they are identical. So the end effect is the same.
The stage looks set to make tower cranes more computer-controlled in the future. "If you look at the market generally, there wasn't a computer network on the crane; there wasn't CAN-Bus architecture," Havard says. Now, on the latest cranes, there is, and optional extras such as site signalling lamps or zone limits can be slotted in without detailed set-up, extra programming, or complex troubleshooting. "That is pretty recent, and I have not seen that elsewhere on self-erectors." Tooled-up end users or dealers will configure the crane using an input screen inside the electrical cabinet of the crane itself. Havard describes the interface as similar to a mobile phone's menu-type system.
"What is most interesting in tower cranes now is the control system," Frech says. "A tower crane is a steel construction, but there are more and more control and monitoring systems."