The Shuttle Buggy’s ability to save time and costs while improving road quality has made it a crucial piece of equipment on road construction, maintenance and rehabilitation projects around the world. One of the most advanced and innovative Shuttle Buggies on the market, the Astec SB-3000, is currently enhancing roadworks on the N2 at George in the Western Cape.
The machine, which Astec Industries has supplied on a rental basis to longstanding customer Road Milling and Sweeping (RMS), is proving its mettle on this important South African road project, and demonstrating how superior equipment ensures success and road surface quality, says Astec product sales manager Philip Saunders.
The Shuttle Buggy is a Material Transfer Vehicle (MTV), which was a novel concept when Astec Roadtec introduced its first Shuttle Buggy in 1989. Before this, road surface failure due to asphalt segregation was a recurring problem. Delivery trucks would have to dump hot mix asphalt (HMA) directly into the paver, which caused numerous problems. Engineers realised that being able to re-mix the HMA before feeding it to the paver was the key to increasing road surface quality. This prompted the development of the earliest Shuttle Buggy to transport and remix HMA between the asphalt truck and paver.
“Thermal segregation is one of the reasons that asphalt road surfaces fail prematurely,” explains Astec product sales manager Philip Saunders. “Another reason is aggregate size segregation, which is caused by the same movement of the delivery vehicle as thermal segregation. Even a new road surface can show segregation spots - both thermal and aggregate size segregation - caused in great part by the delivery truck.”
Offering an unrivalled solution to this problem, the Astec Shuttle Buggy is a mobile silo and on-site mixer for hot mixed asphalt road surfacing material. It stands between the delivery vehicle and the paver, receiving and remixing the hot material to make the temperature homogeneous. “By eliminating the effect of 'end of load' segregation, the Shuttle Buggy doubles the road life and dramatically reduces maintenance costs,” Saunders states.
The SB-3000 can unload a truck at a rate of 1000 tons per hour and re-blend the material to a uniform temperature and stone size gradation. The benefits of this state-of-the-art machine include seamless material transfer for uninterrupted surfacing and reduced thermal segregation, resulting in longer-lasting roads. Time and money are also saved. Saunders expands: “A fully laden SB-3000 holds 30 tons of mix. By using a hopper insert in the paver, that can be increased by 15+ tons when combining the capacities of the Shuttle Buggy and the paver. This enables nonstop surfacing while remixing, resulting in the best possible mat. Each truck costs money, and every minute it waits costs money. With the SB-3000, the time needed to unload dump trucks can be reduced by 25%. In addition, this an eco-friendly solution as the SB-3000 features electric-drive technology,” he notes.
Since the launch of Astec Roadtec’s first Shuttle Buggy 35 years ago, other manufacturers have jumped onto the Shuttle Buggy bandwagon, but not all Shuttle Buggies are created equal, Saunders stresses. The Astec Shuttle Buggy has evolved, advanced and improved over the years. “Astec Industries has worked closely with customers to optimise user experience and safety, transportability and the jobsite performance of its Shuttle Buggy. The result is the SB-3000, a powerful and manoeuvrable MTV that combines superior mixing technology with ultimate operator comfort and unparalleled safety.
“The SB-3000’s superior Astec remixing technology results in uniform HMA with a consistent material size and constant temperature. The SB-3000 uses a triple pitch auger design to eliminate segregation issues caused by single pitch augers. A single pitch auger pulls material from the sides of the bin, which causes the spaces between flights to remain full of material. This material is unable to be properly remixed, which leads to uneven temperatures and inadequate integration of small and large particles. By contrast, Astec’s triple pitch auger remixes across the entire width of the storage hopper as the material moves through, continuously blending and yielding a consistent mix. This technology eliminates the common issues of thermal and material segregation that compromise the resulting asphalt mat. With the SB-3000, road builders can be assured of thoroughly remixed material that is evenly distributed as it is paved.”
The ideally sized augers on the Astec SB-3000 also set it apart. “Their 26-inch diameter is ideal to reduce wear and tear,” Saunders explains. “This smaller diameter is the ideal size for remixing the material while keeping the conveyor chain out of the mix. Moving the same amount of material with smaller augers also results in less wear. The machine requires less torque, resulting in a lower total cost of ownership.”
Operator comfort is enhanced in the Astec SB-3000. It offers improved control stations with dual seats that hydraulically swing out 90 degrees. The platform pivots out from the side of the machine, allowing the operator to sit perpendicular to travel. Seats can be easily pulled in at the touch of a button.
Exceptional visibility, simple operation and a slew of safety features are further benefits, Saunders adds. “The swing out seats provide excellent sight lines. From the safety of the operator seat, the operator can see clearly back to the paver as well as to the front of the machine. The operator also has clear sight lines to the C2, rear tire, dump hopper, and paver. While seated, the operator has an unobstructed view of the groundperson, making for a safer and more efficient work site. The SB-3000 boasts clear and intuitive controls. Its safety features include lights, cameras and display screens. The ground crew control panel includes a patent-pending seat that ensures safety and productivity.
“Lighting and access are brighter and better on the Astec SB-3000,” Saunders states. “The lighting package includes bigger, brighter LEDs that are designed for night work as well as safe transport and manoeuvring. The ladder on the SB-3000 provides access to the operator station and also acts as a bridge across the machine.”
Obstructions like islands and medians are no barrier to this MTV, he notes. “Challenging areas, such as parking lots, intersections, underpasses, and tunnels can be managed easily because the dump truck can unload at a convenient spot and the SB-3000 can shuttle the mix to the paver. Large wheels with a shorter sidewall offer an improved ride and better float on the machine. The low-profile tyres provide stability, protecting the crew when surfacing the road and when transporting the machine off the road at the end of the shift,” Saunders explains.
The SB-3000’s engine is at ground level, so performing daily inspections and maintenance is safer and easier, he says. Easy access to the engine, hydraulic pumps, fuel and DEF tanks save time and improve safety. The Shuttle Buggy also has a wash down system. Regular cleaning is vital to prolonging the life of all asphalt paving equipment.
“This exceptional machine is the result of Astec constantly striving to improve on its Shuttle Buggy concept, taking in feedback from designers as well as operators across the sector over many years. The SB-3000 is the perfect blend of Astec’s history of manufacturing top quality, robust equipment with the latest road surfacing technology and innovation. We are delighted to have had the opportunity to supply an SB-3000 to support our customer RMS on the N2 road rehabilitation project,” Saunders concludes.
