4
Brake Valve
— A hydraulic counterbalance valve should be connected to the reel-in port of the hydraulic motor. It allows
oil to flow freely through the motor in the winching direction. When oil pressure tries to rotate the motor in the reel-out
direction, the brake valve blocks the flow of oil out of the motor until the internal static brake is released. It then controls
reel-out speed based on the load and flow of oil to the motor. All the heat generated by controlling the speed of the load
is dissipated by the hydraulic system, not by the internal static brake.
Sprag or Overrunning Clutch
— A mechanical one-way clutch on the input shaft of the winch, between the input shaft
and the static mechanical brake. The clutch allows the input shaft to turn freely in the direction required to spool cable
onto the drum, then immediately locks the winch gear train to the mechanical brake when the winch is stopped, holding
the load in place.
Static, Mechanical, or Load-holding Brake
— A multidisc, spring-applied, hydraulically released brake that works
together with the sprag clutch to hold a load. This brake is not designed to stop a load being lowered, but holds the load
in place when the winch is not in operation.
First-layer Line-pull Rating
— The maximum rated line pull (in pounds or kilograms) on the first layer of cable. The
maximum rating for any particular winch is based on maintaining an acceptable structural design factor and service life.
Certain combinations of drum, gear ratio, motor and hydraulic pressure, may reduce this rating.
First-layer Line-speed Rating
— The maximum rated line speed (in feet or meters per minute) on the first layer of
cable. Certain combinations of drum, gear ratio, motor, and hydraulic flow may reduce or increase this rating.
D/d Ratio
— The ratio of cable drum barrel diameter (D) to wire/synthetic rope diameter (d). Current SAE standards
require a minimum of 8:1.
EXAMPLES:
If you know the cable diameter you want to use, multiply it by 8 to get the MINIMUM cable drum barrel diameter (such
as 1/2-inch wire rope X 8 = 4 inches — this is the minimum winch barrel diameter).
If you know the barrel diameter, divide it by 8 to get the MAXIMUM wire/synthetic rope diameter.
(such as 8-inch barrel diameter / 8 = 1 — this is the maximum wire/synthetic rope diameter)
Cable Drum Dimensions
—
a
b
First sheave
or load
First sheave or load should be cen-
tered between the drum flanges, so
that angles A and B are equal.
Angles A and B should be a minimum
of 1/2 degree and a maximum of 1-1/2
degrees.
Wrap
— A single coil of wire/synthetic rope wound on a drum.
Layer
— All wraps of wire/synthetic rope on the same level between drum flanges.
Freeboard
— Amount of drum flange that is exposed radially past the last layer of wire/synthetic rope. Minimum freeboard varies
with the regulatory organization. ASME B30.5 requires 1/2-inch minimum freeboard. SAE J706 requires minimum freeboard of 0.7d,
where d is rope diameter.
Grooved Drum
— A cable drum with grooves on the barrel to ensure the
first layer of cable spools properly onto the drum. The grooves can be cast
or machined into the drum, or cast or machined into separate pieces that are
mechanically fastened to the drum.
NOTE:
Only one size cable can be used on a grooved drum.
Barrel
Diameter
Flange
Diameter
Distance
Between
Flanges
Fleet Angle
— The angle between the wire/synthetic rope position at the extreme end wrap on a drum, and a line drawn
perpendicular to the axis of the drum, through the center of the nearest fixed sheave or load attachment point.
GLOSSARY
