Worm Gear Common Terms

Worm Gear Terms Diagram

Bull Gear- Bronze ally gear powered by the steel worm. Braden refers to the "bull gear" as the worm gear.

Capstan- Usually a small removable drum used to apply force to fiber rope wrapped around the barrel with tension applied by hand. Most have a nominal barrel diameter of 7" (178 mm).

CR Reel- Collapsible recovery reels are used for picking up and coiling power and telephone lines which have been removed from the poles and lowered to the ground. Most CR reels have a nominal barrel diameter of 20" (508 mm).

Drum Clutch- Also known as a "dog-clutch" or "jaw-clutch," consists of two or more drive lugs which engage in similar driven lugs to transmit torque to the cable drum.Winch Grooved Drum Diagram

Drum storage Capacity- The maximum length of wire rope which may be wound on a cable drum without exceeding the maximum number of layers. It is expressed in feet or meters.

Extension Shaft- The standard cable drum shaft is extended or replace by an extra long shaft which permits the use of capstans or CR reels at the side of the vehicle, most extension shafts are limited to a standard lengh of 44 to 46 1/2" (112-118 cm) from the cable drum center-line.

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.

Freeboard- The amount of drum flange that extends radially past the last layer of wire rope.

Free Spooling- The operation of manually unspooling wire rope from the cable drum by pulling on the free end of the rope while the cable drum is disconnected (declutched) from its power.

Full Drum or Maximum Layers- A drum containing the maximum number of cable layers which would leave a freeboard of 0.7 x the cable diameter below the drum flange.

Gear Set Efficiency- The relationship between the input horsepower transmitted to the winch by the prime mover and the output horsepower transmitted by the winch to the wire rope. Expressed as a percentage.

Largest Recommended Wire Rope size- shoud be no larger than 1/8th the cable drum barrel diameter for most recovery applications.

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

Mean Drum- A theoretical point located midway between the first layer of wire rope on the cable drum barrel and the top layer. Often used as a reference point in measuring winch performance.

Rated Input Speed- The maximum permissible input speed at rated load expressed in RPM. Exceeding rated input speed may cause damage to the worm gear set.

Rated Line Pull- The line pull on any layer that results from the output torque which produces maximum rated line pull on the first layer. Rated first layer line pull is based on maintiaing an acceptable structure safety factor while providing an acceptable component service life. Line pull is expressed in pounds or kilograms.

Rated Line Speed- The line speed on any specific layer that results from rated input speed. It is expressed in feet/minute or meters/minute.

Running Input Torque- The torque applied to the winch input shaft required to maintain upward movement of rated load. It is expressed in pound-feet, pound-inches, kilogram-meters or Newton meters. May also be referred to as dynamic torque.

Starting Input Torque- The torque applied to the winch input shaft required to start a rated load upward from a suspended position. It is expressed in pound-feet, pound-inches, kilogram-meters or Newton-meters. May be referred to as static force.

Thermal Rating (Duty Cycle)- The result of a test, expressed as the distance (feet or meters) a load travels up and down while hoisting and lowering a specified weight until the lubricating oil rises from 100° F to 250° F (38° C to 121° C). 250° F (121° C) is the maximum intermittent gear oil temperature allowed. Most gear oils "break down" rapidly at higher temperatures and seals may be damaged.

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