Are knuckle-boom cranes sticking it to stick-booms?

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Some companies manufacturing cranes for mechanic service trucks are knuckling a bit more leverage into their products.

Knuckle-booms, also known as articulating cranes, have long been favored by service truck operators in Europe, while stick-booms, sometimes referred to as telescopic booms and stiff-booms, have generally held sway in the U.S.

But times are changing. Hiab brought one of its knuckle-booms to the 2017 Work Truck Show in Indianapolis while Iowa Mold Tooling Co. Inc. trucked a knuckle-boom to the International Construction and Utility Equipment Exposition in Louisville, Ky., in October.

While knuckle-booms seemed poised to gain traction on this side of the Atlantic, manufacturers say there’s a role for each variety of crane in a fleet of service trucks. And, in many cases, it simply boils down to user preference.

Choice depends on operation

Brian Heffron, national sales manager with Omaha Standard Palfinger, told Service Truck

Magazine he estimates U.S. market preference at roughly 85 per cent for stick-booms and 15 per cent for knuckle-booms.

“Picking between the two depends on what your operation is,” Heffron said. “If you’re in the construction market and doing material handling, you’re more likely going to go with a knuckle-boom because you’re either having to lift into a building or up and over to the top of the building, or a long reach across a work site. And a telescopic just doesn’t make sense for that. Whereas if you’re doing service work on-site, say you’re working on a Cat dozer or an excavator, a knuckle-boom would be overkill — it would use up a good portion of your payload, leaving a limited amount of weight for tools and equipment.”

Palfinger offers both varieties, and Heffron said each has notched new developments in recent years.

On the knuckle side, models such as the PK 165.002 and PK 200.002 — with numbers referring to tonne-metres — have new boom sections Palfinger calls the P-Boom. “The thing about large Grove or National cranes is that kind of reverse-teardrop look,” Heffron said. “Now, imagine viewing that with one piece of metal and one weld. That’s the P-Boom.”

Heffron calls this a load lightener. “It allows you to go to larger cranes and stay within a weight limit that won’t affect your chassis choice too much,” he said.

Stick-boom with a twist

One area where stick-boom technology has advanced is remote technology, where users can see data pertaining to a load that can help an operator gauge lifting capacity. “It’s a fairly new development, and we’re all searching to try to figure out how we want to do it,” Heffron said, adding that Palfinger offers this enhancement as an optional upgrade.

Garner, Iowa-based Stellar Industries Inc. does not offer knuckle-boom cranes in the classic sense of the term — that is, where it folds into a figure-four position. However, it does sell stick-booms with a bit of a twist. These include cranes that articulate specifically for tire-service applications. “These are specialty cranes designed to be a tool as well as a lifting device,” sales and marketing manager Sean Moran explained. Stellar also offers a small line of T-boom cranes, which Moran described as a variant of a telescopic crane that has a high mast.

Moran said remote-control systems are also catching on at Stellar. A line of light-duty hydraulic

cranes has options for proportional and non-proportional radio remote controls, and a line of heavy-duty telescopic cranes up to 14,000 pounds lifting capacity features proportional radio remote control.

“In regards to the stick-boom cranes, the use of operator feedback through the radio remote is becoming more common,” Moran said. “Stellar introduced this feature in 2010 with the introduction of the Stellar CDT radio remote, which alerted the operator through LED alerts as well as a tactile vibration when the crane was nearing its rated capacity.”

Stellar furthered the design in 2014 with the Stellar CDT and CDTplus radio remote, which added a visual display with real-time information such as load weight, boom angle, horizontal reach and how much more load the crane could handle at a given load or reach. “This gives the operator critical information to be more productive when using the crane,” Moran said.

As Moran sees it, the two varieties differ distinctly in their design and intended use. “A knuckle-boom crane is intended to be a material handling crane — to load and unload, to pick and place material. A stick-boom crane is intended to act as a lifting tool and specifically incorporates a winch to allow more precise lifting and holding of components while servicing equipment. Its stick design also allows for better reach into enclosed areas, such as cabs, while using the winch to lift and lower component parts.”

Praising the T-boom

Ironically, perhaps, Hiab builds a small number of stick-booms but for outside the U.S. where there’s some market demand. However, in addition to knuckle-booms, the company offers a T-Boom, which crane product manager Terry Fidler described as kind of an in-between.

“Instead of having that second knuckle, it has a first knuckle quite high, and just one boom instead of two booms,” Fidler said. “And it telescopes in a live situation, so you can do it while lifting the load.”

Hiab’s T-Boom can lift close to the hook. And, whereas a stick-boom traditionally has a winch and tends not to lift so close to the head of the crane, the T-Boom and knuckle-boom don’t require a winch, so operators can position the head of the crane right next to a load, Fidler added.

Fidler said the T-Boom wasn’t introduced to deliberately steer users towards a knuckle-boom. “The first-ever hydraulic lifting crane was built by our company in 1944 in Sweden, and that was a T-type boom. The knuckle-boom was a kind of improvement that came later. Today we put fly jibs and third and fourth elbows onto our knuckle-booms — they’re big cranes.”

Gaining in popularity

Tom Wallace, sales manager with Iowa Mold Tooling, said the company builds stick-booms and a handful of specialty knuckle-boom cranes at its Garner, Iowa facility but most of its articulating lines are manufactured by HMF in Denmark and private-labelled to IMT specifications.

“Articulating cranes are gaining popularity because they’re very versatile,” Wallace said. “They fold differently then telescopic cranes, so this gives them a lot of versatility of where they can reach and grab a load. They can come in real close and sometimes even underneath a flatbed, grab a load, and start lifting, whereas a telescopic crane does not have versatility.”

For example, Wallace said, a mechanic might need to gain access through the interior of the cab of a large excavator to pull something out. “A telescopic crane works very well there,” he explained. “You can go in perfectly horizontal and extend your crane right into that cab. The boom tip is small enough that it can slide right in, and as long as your product will go out the door it gives you some real advantages.”

As far as new developments, Wallace said, one area both crane varieties are gaining something in common is enhanced attention to safety.

Overload prevention systems that warn an operator when a load is reaching its maximum capacity are available on both, while interlock systems, already on articulating cranes, are on the near-horizon for telescopic cranes.

These prevent the operator from running a crane without the stabilizers being completely deployed and down, and also prevent any lifting over an operator who is standing and manually running the crane by the truck, Wallace said. “This prevents the operator from getting in between the load and the truck, and the possibility of getting injured.”

— Saul Chernos

Saul Chernos is a freelance writer based in Toronto.

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