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FUNCTION IN REVERSE ROTATION:
RAPID REVERSE
When the hydraulic motor is pressurized for rapid reverse, the rotation of the motor drive shaft causes the sprag
clutch to lock, resulting in a solid assembly between the motor drive shaft and the connecting shaft. Rotation of
the connecting shaft causes the sprag clutch between the connecting shaft and the brake hub to lock making
a solid assembly between these two components. Hydraulic pressure is automatically transmitted to the brake
piston, forcing the brake piston to release brake against a series of brake springs. The friction plates, which are
engaged in the brake hub, can now rotate between the divider plates. Since both sprag clutches are locked, the
friction plates, brake hub, connecting shaft, internal gear and primary sungear turn at the same revolution as the
motor drive shaft. Thus, the primary drive is eliminated, resulting in a reversing speed 4.67 times faster than low
forward speed.
If a load on the cable drum tends to affect the reversing speed, the resulting pressure drop in the brake piston
causes friction between the friction plates and the divider plates. Thus, a completely smooth reversing speed can
be controlled in a stepless operation by modulation of the winch control handle. When the control is returned to
neutral position, rotation stops and the disc brake applies automatically. The pressure in the brake piston is vented
to the reservoir by the motor spool of the winch control valve.
During reverse operation of the winch, or when a load is being lowered, the friction created by the brake disc
results in temperature. On the standard Model HL25 this temperature is dissipated by a circulation flow of
hydraulic fluid, supplied from an external source (see HYDRAULIC CIRCUIT). For efficient cooling of the
automatic brake, the external circulation flow should be adjusted to 7 (US) gpm (26 l/min). This circulation flow
must be returned directly to the reservoir with a permissible back pressure of 30 psi (2 bar) (see HYDRAULIC
CIRCUIT).
IMPORTANT: Under no circumstances must the back pressure in the brake housing be permitted to exceed
30 psi (2 bar). Excessive pressure in the brake housing will damage the oil seals separating the
brake housing from the drum interior. Damage to this seal will cause the cable drum to fill up with
hydraulic fluid. In order to prevent potential damage to the drum seals and the end cover of the
winch, when the cable drum fills up with hydraulic fluid, a breather relief (see PARTS
REFERENCE, item 130) is installed on the end cover. The breather relief bleeds to atmosphere
and serves as a warning signal that the oil seal between the brake housing and drum has been
damaged.
CONTINUED
DESCRIPTION OF THE MODEL HL25
313 REV.970901
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