KEVOS® MAKEOS · Mechanics
Rope Drum and Fleet Angle Check (Fleet Angle, Rope Capacity by Layer, D/d Ratio, Drum Torque)
For a winch or hoist drum feeding a rope to a lead sheave, is the fleet angle small enough for even spooling, does the drum hold enough rope, and what torque does the top layer need?
Check of a rope drum and its lead: the fleet angle from half the drum width and the distance to the first sheave, the drum-to-rope diameter ratio, the turns per layer and the rope each layer holds, the rope length needed for the lift and falls plus dead turns, the layers used, and the drum torque on the outermost layer used (as the rope winch drum tool), against your fleet angle limit, least D/d ratio and the layers allowed.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Rope pull at the drum | kN | Line pull on the rope where it leaves the drum. |
| Drum barrel diameter | mm | Diameter of the drum barrel (under the first layer). |
| Rope diameter | mm | Rope diameter. |
| Drum width between flanges | mm | Width of the drum between its flanges. |
| Distance from drum to the lead sheave | mm | Distance from the drum to the first (lead) sheave, centred on the drum. |
| Rope needed | ||
| Lift height | m | Height the hook travels. |
| Falls of rope (reeving) | Number of rope falls between the drum and the hook block. | |
| Dead turns left on the drum | turns | Turns that must stay on the drum at the lowest hook position. |
| Limits | ||
| Largest fleet angle | ° | Largest fleet angle you accept for even spooling (often 1.5° for grooved and 1° to 2° for plain drums). |
| Least drum ÷ rope diameter | Least drum-to-rope diameter ratio from your rope or crane code. | |
| Most layers allowed | layers | Most rope layers allowed on the drum. |
Method and formulas
- Fleet angle = atan ((drum width ÷ 2) ÷ distance to the sheave), lead sheave on the drum centre line.
- Turns per layer = drum width ÷ rope diameter; layer i holds π (D + (2i − 1) d) × turns; rope needed = lift × falls + dead turns × π (D + d).
- Drum torque = pull × layer pitch radius (as the rope winch drum tool at that diameter).
- Example: fleet angle 1.4321°; 42.922 m of rope in 1 layer(s); 1,550 N·m on the top layer.
Limitations
- Rope wound tightly with no gaps; loose spooling needs more drum.
- Fleet angle for a sheave on the drum centre line; an offset sheave makes one side worse.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Lay out a winch and its lead sheave
- Check rope capacity before fitting a longer rope
- Find the torque on the top layer of a drum
Who it is for
- Lifting engineers
- Riggers
- Machine designers
What you get
- Fleet angle and D/d ratio
- Rope needed and capacity by layer
- Layers used and top-layer torque
Interpreting the result
- Each extra layer raises the torque and speed of the rope and crushes the layers below; most crane codes limit layers for that reason.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 165–168, 2455–2459. Topic reference; no source tables or recommended settings are reproduced.
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