A new kind of swing

摘要

WHEN Joe Stevens first ventured into geothermal drilling 10 years ago, he soon spotted a stumbling block. "It's hard to get the rig around," says Mr Stevens, president of TL Stevens Well Co in Maple Plain, Minnesota."You're drilling multiple holes, pulling the rig-from hole to hole, and sometimes ending up with mud ruts that are knee-deep." But he was not about to turn his back on a lucrative new market just because of a little mud. After about eight years in the geothermal field, he had an idea: to mount a rig on tracks, which would be gentler on the ground and easier to move around. Mr Stevens soon discovered that tracks were pretty expensive, so he looked to salvage yards for something more affordable. After four months, he found what he was looking for: a set of nearly new tracks on a fire-damaged excavator. The tracks had everything Mr Stevens wanted: they were the right size (not so wide to require a special permit, but big enough to enable him to haul the rig on a tag trailer instead of a low-boy), and they were heavy enough to handle the weight of the drill rig that was to be mounted on top.