Planetary Hoist Common Terms

Brake Valve- A hydraulic counterbalance valve is usually bolted to the hoist port of the hydraulic motor. It allows oil to flow freely through the motor in the hoisting direction. When oil pressure tries to rotate the motor in the lowering direction, the brake valve blocks the flow of oil out of the motor until the internal static brake is released. It then controls lowering 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.

D/d Ratio- The ratio of cable drum barrel diameter (D) to wire rope diameter (d). Current ANSI standards require a minimum of 17:1.

  • If you know the cable diameter you want to use, multiply it by 17 to get the MINIMUM cable drum barrel diameter. (i.e. 1/2" wire rope x 17 - 8.5" - this is the minimum hoist barrel diameter).
  • If you know the barrel diameter, divide it by 17 to get the MAXIMUM wire rope diameter. (i.e. 10" barrel diameter / 17 = 0.588, or 9/16" - this is the maximum wire rope diameter).

‚ÄčWinch Cable Drum dimensions D/d Ratio

First Layer Line Pull Rating- The maximum rated line pull (in pouds or kilograms) on the first layer of cable. The maximum rating for any particular hoist is based on maintaining an acceptable structural design factor and service life. Certain combinations of drum, gear ratio, motor and hydraulic flow may reduce or increase this rating.

First Layer Line Speed Rating- The maximum rated line speed (in feet or meters per minute) on the first lay of cable. Certain combinations of drum, gear ratio, motor and hydraulic flow may reduce or increase this rating.

Fleet Angle- The angle between the wire rope's 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.

Winch fleet angle diagram


Freeboard- The amount of drum flange that is exposed radially past the layer of wire rope. Minimum freeboard varies with the regulatory organization. ASME B30.5 requires 1/2" minimum freeboard.

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 separate pieces that are mechanically fastened to the drum. Note:Only one size cable can be used on a grooved drum.

Layer- All wraps of wire rope on the same level between drum flanges.

Sprag or Over Running Clutch- A mechanical one-way clutch on the input shaft of the hoist, 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 (i.e. lift a load), then immediately locks the hoist gear train to the mechanical brake when the hoist is stopped, holding the load in place.

Static, Mechanical, or Load-Holding Brake- A multi-disc, spring applied, hydraulically released brake that works together with the sprag clutch to hold a suspended load in place when the hoist is not being operated.

Wrap- A single coil of wire rope wound on a drum.

Basic Components of Planetary Hydraulic Winch

Planetary Hoist Hydraulic System

Planetary Hoist Winch Diagram

brake piston brake plates sprag clutch, planetary hoist terms