Cradle Boring: Old Technology Becomes New Again

By Jeff Griffin, Senior Editor | June 2011 Vol. 66 No. 6

The McLaughlin Group has introduced two new cradle boring machines -- the first new models manufactured in this product category since the late 1960s.

Unlike conventional earth boring equipment which initiates bores from a pit, a cradle boring machine (CBM) is suspended above a starting trench by a “cradle” held by two or more sidebooms. By eliminating the need for starting pits, the process speeds making bores under roads to lengths of 140 feet.

“Reduction in setup time helps contractors complete more bores in a day,” said Dave Gasmovic, McLaughlin president. “More bores in less time means less cost per bore.”

The McLaughlin CBM 48 is powered by a 175-horsepower, air-cooled, turbocharged diesel engine and develops 170,000 foot pounds of rotary torque for installing in one pass steel casings in diameters of 12 to 48 inches.

The CBM 42 has a 106-horsepower diesel engine and 138,000 foot pounds of rotary torque for making one-pass installations of 12- to 48-inch diameter steel casings.

Transmissions of both models have five forward and one reverse speed. A centrally-positioned, fully-adjustable seat provides the operator with easy access to the control console with joystick and switch functions and a clear view of the boring process. A patented, operator presence control, hydraulic clutch ensures quick drive-line shutdown in an emergency.

Both models are available now through authorized dealers or directly from McLaughlin.

For set up, typically one sideboom supports the CBM and the second holds the casing. Three hydraulic chain vises hold the steel casing firmly in place with chains running over the casing attached to one of the hydraulic cylinders which tightens the casing to the unit. To maintain even pressure during the bore, cylinder pressure is monitored via a pressure gauge. CBMs are designed to install a continuous length of casing. A powerful winch pulls the machine forward in the bore hole. When the exit point is reached, the CBM is disconnected, augers are backed out of the casing, and the product is inserted.

History
Tracing the history of cradle boring, Gasmovic said their popularity developed during the 1960s and ’70s, a time when many cross-country pipelines were being constructed.

“They could cross county and state roads in one pass, and do it in less time than with conventional equipment,” he explained. “Contractors generally would have cradle boring crews work ahead of the regular pipe crew. They would cross a road and then move to the next, so work wasn’t slowed when excavation came to a road.”