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This file type includes high resolution graphics and schematics when applicable. | American Piledriving Equipment (APE), Kent, Wash., forms the foundation of large construction projects. Literally. Among the many heavy-duty machines the company designs and manufactures are top-drive augers, which drill holes into the ground for foundations. Once the auger has drilled to the required depth, grout, concrete, or other material is pumped into the bottom of the hole through the hollow center of the auger as it is withdrawn from the hole. The contractor then inserts preformed, caged
rebar assemblies into the just-cast material to form a reinforced column.
Hydraulics was chosen for this application because of its high power density. A low-speed, high-torque motor transmits the high torque and provides the speed control needed for the varying conditions typically encountered when drilling into the ground. The systems can be used on mobile excavators, so the mobility and flexibility of hydraulics made it the most practical choice.
A big advantage to APE’s top-drive auger is that it can shift on the fly. Contractors can drill, retract the auger, and spin off dirt and mud without stopping the operation. Other machines use gearboxes to accomplish drive functions, which requires stopping the auger to shift from one drive mode to another.
Simple, powerful hydraulics
The machine can drill at two speeds: 0 to 30 rpm at 5,500 psi or speeds to 60 rpm at 3,000 psi. Operating speed is determined by soil and ground conditions; speed can be changed automatically to give the machine the highest rate of productivity possible. All functions can be done on the fly without stopping the drilling operation.
Design of the top-drive auger’s hydraulic system was a team effort, led by Dan Miller, chief engineer at APE, working in conjunction with Kris LaVigne, of Hydra Power Systems, Portland, Ore. Hydrapower supplied all the hydraulic components, including a wide variety of cartridge valves from Sun Hydraulics, Sarasota, Fla.