What Speed Bump?

By Walt Moore, Senior Editor | September 28, 2010


ASV considers its SR-Series Posi-Track loaders the most significant product development in its 20-plus years of building rubber-track loaders. The SR-Series features a new chassis, new undercarriage and new operator's station, along with such design details as high-intensity working lights and a cab door that lifts vertically and stores in the roof.
ASV's director of product development, Brad Lemke, convincingly demonstrates the SR-80's aggressive digging power, traction and ability to negotiate rough terrain.


Click to enlarge.
This photo illustrates the independent suspension of the four bogie assemblies. A timber under the rear wheels of the foreground bogie tilts the assembly toward the front of the machine. A timber (not visible) under the front wheels of the corresponding background bogie tilts the assembly rearward. Four rows of rubber lugs on the track's inner surface guide the wheels and provide engagement points for the roller-cage sprocket (upper left).

ASV's Brad Lemke
ASV's Brad Lemke tilts up the SR-80's cab, which can be raised with the loader in any position. Controls stay with the cab, making the cab far easier to seal, says ASV. Lift-cylinder plumbing (right side) is more robust in design. Hydraulic fittings on the left lift arm provide low-flow and high-flow auxiliary circuits and a case drain. An integral pressure-relief button dissipates residual pressure before installing attachments. Also included is an electrical-control connector.
The redesigned SR-Series chassis has loader towers that are an integral part of the structure. The rotational-molded fuel tank (black component) and hydraulic tank (white component within the chassis) make the most of available space. The fuel-tank sender is solid-state and has no moving parts.
The brush ring between the shroud and fan blades closes up this annular space for more efficient airflow and protects the fan blades when the engine flexes. (This is not an actual installation.)
New features in the SR-Series operator's station include a two-piece lap bar with integral gauges, redesigned joystick controllers, new suspension seat, set-position foot throttle, variable low-flow control and selectable bucket positioning.
Photos: George Pfoertner©


On a chilly afternoon some six weeks ago, we watched Brad Lemke, director of product development for ASV, as he spared no horsepower in demonstrating the aggressive performance of the company's new SR-80 Posi-Track loader.

Working the new machine in a remote area of ASV's extensive proving grounds — near its Grand Rapids, Minn., factory, Lemke excavated deeply into the site's heavy sandy clay and ran the new tractor up, down and across the site's imposing grades and rutted surfaces. Then, on a concrete test pad, he repeatedly drove the new model at top speed over a 4×4 timber placed across one track's path. We were impressed at how calmly the SR-80's new four-bogie undercarriage rippled across this impediment.

"The SR-Series is the most significant model introduction in ASV's history," says Lemke. "Just about every idea, wish and want we as a manufacturer have had in 20-plus years of building rubber-track loaders is reflected in this new design. We've invested more in manufacturing tooling for these machines than we invested in all our previous models — combined. Not counting nuts and bolts, there are, literally, only five or so part numbers that are common with our existing models."

The new series, which includes the 80-hp flagship model, the SR-80, and a 70-hp companion model, the SR-70, was three years in development, says Lemke. And although the new machines don't replace any of the company's current nine models, the technology they embody, he says, eventually will work its way through the entire line. That transfer of technology likely will include the stellar feature of the SR-Series — its new "single-rail" undercarriage.

The single-rail concept

ASV has been building rubber-track vehicles since the early-1980s, and the hallmark feature of its loaders has always been a suspended undercarriage that flexes as it encounters obstacles in its path. The new SR-Series undercarriage, which ASV calls a "single-rail" design, is the company's fourth-generation concept, and according to Lemke, the best yet.

Similar to the preceding undercarriage generations, the single-rail system retains the essentials of ASV's undercarriage design: proprietary rubber tracks that contain no steel; multiple wheels to spread the tractor's weight evenly over the tracks; torsion axles to provide the desired suspension qualities; and a roller-cage sprocket.

That said, however, the new single-rail system represents a significant departure in overall design from its predecessors. We've included a couple of computer-generated illustrations from ASV's engineering files to help you understand the fundamentals of the single-rail design,

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