Earthmovers do more with less

Innovative design allows making earthmoving equipment more versatile without resorting to a lot of sophisticated electronics.

By Richard T. Schneider, contributing editor

SR-80 loader's multi-level suspension has four wheel carriages on each side that flex independently to maximize ground contact over uneven terrain.

Pilot-operated joysticks use hydraulic oil to shift drive pumps and to control lift-arm functions, giving the operator smooth, precise control of the machine without cables, linkages, or more complex electrical systems.

Over the past 20 years, compact loaders have taken the construction industry by storm. It's difficult to find a job site today without these little one-man work forces . . . as contractors realize that these versatile loaders can bring the power of hydraulics to operations that once depended on expensive manual labor.

ASV Inc., Grand Rapids, Minn., focuses on rubber track loaders — machines with undercarriages that allow them to crawl over tough excavating sites as well as sensitive terrains, such as lawns and asphalt surfaces. ASV's new SR-80 loader runs on a purpose-designed suspended rubber-track undercarriage with the widest tracks in the industry (20 in.) and an independent, multi-level suspension. Four-wheel carriages on each side flex independently — in multiple directions — to maximize ground contact over uneven terrain. The 41/2-ton machine produces only 2.84-psi ground pressure, and the chassis provides 15 in. of ground clearance.

A turbocharged Perkins diesel engine — rated at 80.5 gross hp — drives a dual hydrostatic pump, which supplies a pair of 2-speed drive motors that power the tracks. The machine is capable of travel speeds from 0 to 12.5 mph in its high-speed range and 0 to 7 mph in the low-speed range.

Plush, automotive styling for the SR-80 cab gives operators a high level of comfort — along with precision control. A single foot pedal controls engine speed. Two joysticks are configured in a " Caterpillar" pattern: left hand for drive; right hand for attachments. Both control flow of fluid to pilot-operated valves. The operator selects either low-or high-range speed for the drive circuit with a button on the right-hand joystick.

A variable-displacement pump — piggybacked to the hydrostatic pump — supplies the separate attachment circuit. A wide variety of attachments has been developed for these loaders. (With its hydraulic quick attach, the SR-80 can be fitted with virtually any industry-standard attachment.) Some of them — drive-motor attachments such as snow-blowers, cold-planers, and brush-cutters — perform best at high speeds and thus call for high flow. Others — cylinder attachments such as grapples, multi-purpose buckets, backhoes, and dozer blades — are difficult to control at high flow. ASV accommodates these two situations with options of high flow or variable low flow in the attachment circuit. A high-flow switch selects 30-gpm for the circuit, or a rocker thumb switch lets the operator vary flow between 0 and 20 gpm. (The thumb switch operates a proportional, electric pressure-reducing valve.)

Brad Lemke, director of new product development at ASV Inc., provided details on these loaders.

TAGS: Construction