Manitowoc unveiled the mobile crane industry’s first commercially available 24-ft. carbon fiber composite stinger (the fly section of the jib) at the ConExpo-Con/Agg trade show in Las Vegas, Nev., earlier in March.
The composite stinger offers the same 8,600-lb. maximum capacity as its steel counterpart and can lift up to 12-15% more than the steel version at high reach, long reach, and some jib offset angles. Sid Shreiner, VP of engineering at Manitowoc Cranes, confirms that starting in the fourth-quarter of this year Manitowoc will offer the composite stinger as an option for Grove 700 Series truck-mounted (TMS) cranes, and for its new Grove TMS9000-2 truck crane, which was unveiled at ConExpo.
Dr. Sammy Munuswamy, a senior principal engineer who led the development of the composite stinger, explains why he describes the stinger as one which “captures the power of ‘light’.” “Cranes in general need to get lighter and lighter to be more transportable and efficient,” he says. “The use of a carbon fiber stinger helps with both and we now offer a lighter crane component without compromising structural performance. The composite stinger is made of carbon fiber reinforced polymers (CFRP), which give strength and stiffness comparable to its steel counterpart but at 35% lighter weight. If a user combines it with a synthetic fiber rope, they can lighten a crane significantly.”
Munuswamy says that weight is always an important factor in crane design, and minimizing weight becomes even more crucial for units such as the taxi crane, which travels over public roads and must transport itself as a self-contained unit.
Ronald Joven, an engineer who is also a part of the composite team, confirms that the stinger measures just over 24 ft. long, 8.7 in. wide, and 13 in. high. It mounts the same way as the more-common steel version. It stows at the side of the lattice jib and swings out front before being pinned into working position. Mounting and stowing can be managed entirely by a single operator.
Munuswamy explains that the ends of the composite stinger are the same steel components used on the existing steel stinger. “We wanted to retain the proven sheaves and shafts of the steel stinger so that users will be able to leverage their existing mounting procedures.”
Despite featuring the same steel end design, Munuswamy explains that the main carbon fiber body drastically differentiates it from its steel counterpart. “One of the advantages of carbon fiber is that it allows for a more efficient design,” he says. “Stinger design necessitates the flexibility to vary the amount of material along the length based on the amount of reinforcement needed at higher and lower stress sections. Because steel is generally used in standardized plate sizes, granularity suffers and you end up adding more material than needed. Carbon fiber, in contrast, provides finer control over the amount of material, which can be added wherever needed. This allows us to create a structure that is both stronger and more efficient,” he says.
While designing, the Manitowoc team examined vital factors like strength, modulus, impact resistance, UV resistance, compatibility with adhesives, manufacturability, cost, and other field considerations in order to design a structure that would reduce weight and improve lifting capacity without increasing its footprint.
Tests of the final prototype included the required SAE standard tests for structural integrity, stability, stiffness, fit, function, resistance to deflection, and other key criteria. In addition, Manitowoc also put it through tens of thousands of cycles on a test bench to ensure its fatigue life and strength met expectations.
The resulting stinger is stronger, lighter, easier to handle, more efficient, and helpful when working with projection edges, such as high buildings. Compared to a steel stinger, it improves load capacity, reach, and tip height. Other features include resistance to rusting and internal dampers to reduce noise and vibration.
Munuswamy says that this is just the first step in using carbon fiber technology for structural lifting components. “This design success opens the door for investigations into how carbon fiber can be utilized to redesign other structural components in the hope of realizing similar performance gains,” he says.
Not just better equipment; a better lifting experience
A crane with new carbon fiber stinger and synthetic fiber rope is an example of what Munuswamy calls Manitowoc’s “design of experience (DoEx)” philosophy, which aims to provide not just tools, but designs that give users a memorable lifting experience.
“Design of experience as a philosophy seeks to understand a customer’s inherent difficulties while using a product, even if the customer can no longer explicitly recognize the pain points they continually face because complacency has set in,” he says. “The goal is to ease this pain using a better experience which blends technology with humanity.”
He adds that in the 21st century, experiences, more than anything else, drive the global economy, and that innovative products and services need to engage customers emotionally. Customers don’t just buy a product; they buy into the reason behind the product and the experience it brings.
In the case of the new carbon fiber stinger, a great customer experience comes from the ability to handle a unit that is up to 35% lighter than a similar steel structure, not rusting, enjoying the smooth feel afforded by stronger vibration dampening, experiencing lower fuel costs that come with transporting a lighter unit, and the satisfaction of being able to lift more at longer radii and higher tip heights.
It is safe to say that the new carbon fiber stinger is just the latest in a long line of innovative products and services that will help Manitowoc crane owners and users enjoy the benefits of an amazing “lifting experience.”