DEADHEADING— Traveling without a load, except
when traveling from the dumping area to the loading
point.
DENSITY— The ratio of the weight of a substance to its
volume.
DIESELING— In a compressor, explosions of mixtures
of air and lubricating oil in the compression
chambers and/or other parts of the air system.
DOLLY— A unit consisting of a draw tongue, an axle
with wheels, and a turntable platform to support a
gooseneck trailer.
DOUBLE-CLUTCHING— Disengaging and engaging
the clutch twice during a single-gear shift (change
of gears) to synchronize gear speeds.
DOWNSTREAM FACE— The dry side of a dam.
DOZER— Abbreviation of bulldozer.
DRAFT— Resistance to movement of a towed load.
DRAGLINE— A crane with a dragline attachment, used
to excavate material from below the grade on which
the crane is sitting.
DRAWBAR— A fixed or hinged bar, extending to the
rear of a tractor and used as a fastening for lines and
towed machines or loads.
DRAWBAR HORSEPOWER— A tractor’s flywheel
horsepower minus friction and slippage losses in the
drive mechanism and the tracks or tires.
DRAWBAR PULL— The pull that a tractor can exert on
a load attached to the drawbar. Depends on power,
weight, and traction.
DRILL COLLAR— Thick-walled drill pipe, used
immediately above a rotary bit to provide extra
weight.
DRILL, PERCUSSION— A drill that hammers and
rotates a steel and bit. Sometimes limited to large
blast hole drills of the percussion type.
DRILL PIPE— The sections of a rotary drilling string,
connecting the kelly with the bit or collars.
DRIVE SPROCKET— A drive roller with teeth that
engage matching recesses or pins (bushings) in the
track assembly.
DROP HAMMER— A pile-driving hammer that is
lifted by a cable and that obtains striking power by
falling freely.
DRUM, SPUDDING— In a churn drill, the winch that
controls the drilling line.
EJECTOR— A clean-out device, usually a sliding plate.
EMBANKMENT— A fill whose top is higher than the
adjoining surface.
EROSION— Wear caused by moving water or wind.
FACE— (1) The more or less vertical surface of rock
exposed by blasting or excavating or the cutting end
of a drill hole. (2) An edge of rock used as a starting
point in figuring drilling and blasting. (3) The width
of a roll crusher.
FACTOR OF SAFETY— The ratio of the ultimate
strength of the material to the allowable or working
stress.
FAIRLEAD— A device which lines up cable so that it
will wind smoothly onto a drum.
FEATHER— To blend the edge of new material into the
old surface smoothly.
FIFTH WHEEL— The weight-bearing swivel
connection between highway type of tractors and
semitrailers.
FILL— An earth or broken rock structure or
embankment. Soil or loose rock used to raise a
grade. Soil that has no value except bulk.
FLOAT— In reference to a dozer blade, to rest by its own
weight or to be held from digging by upward
pressure of a load of dirt against its moldboard.
FOOT— In tamping rollers, one of a number of
projections from a cylindrical drum.
FOOT-POUND— Unit of work equal to the force in
pounds multiplied by the distance in feet through
which it acts. When a 1-pound force is exerted
through a 1-foot distance, 1 foot-pound of work is
done.
FOUR BY FOUR (4 x 4)— A vehicle with four wheels
or sets of wheels, all engine-driven.
FREE FALL— Lowering of the hook (with or without a
load) without it being coupled to the power train
with the lowering speed being controlled by a
retarding device, such as a brake.
FRONT-END LOADER— A tractor loader with a
bucket that operates entirely at the front end of the
tractor.
FROST— Frozen soil.
FROST LINE— The greatest depth to which ground may
be expected to freeze.
AI-4
