Why the first layer matters
The first working layer places the rope closest to the drum core and gives the smallest effective radius. For a given output torque, this is normally where theoretical line pull is highest. A first-layer rating is useful for comparing winches, but it does not describe the pull available when the drum is partly or fully loaded with rope.
What changes on the outer layers
Every additional rope layer increases the effective drum radius. Line pull decreases because the torque acts through a longer radius, while line speed increases because each drum revolution moves a greater circumference of rope. Rope diameter, drum geometry and the actual number of layers determine the change; a single catalog headline cannot replace the application calculation.
Start from the required working condition
Define where the critical pull occurs. A recovery system may need its highest pull with most rope paid out, while another machine may need a verified load at a particular installed rope length. Also distinguish pulling duty from lifting duty. Hoisting requires additional safety, brake, control and regulatory review and cannot be approved from a simple pull calculation alone.
Connect line pull to the hydraulic drive
Required drum torque is established from working pull and effective radius, then related to the gearbox, hydraulic motor and mechanical efficiency. Required rope speed is related to drum speed at the same layer. The available hydraulic pressure and flow must be checked against both demands, including starting, acceleration, reversing and continuous-duty conditions.
Rope and drum details that affect selection
- Required working pull and whether it is a pull or hoist
- Required speed at the stated rope layer
- Rope diameter, construction and total usable length
- Drum core diameter, flange diameter and usable width
- Expected number of working layers and fleet angle
- Duty cycle, environment, brake and control requirements
Provide the machine layout and any existing drum drawing so JST engineering can review capacity, interfaces and the complete drive arrangement.
This guide supports preliminary discussion. Final selection must be confirmed from the specific model data, hydraulic circuit, installation drawing and machine safety requirements.