BIZOMAT 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. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Rope pull at the drum
- What it is
- The tension in the rope where it leaves the drum, which with the working layer diameter gives the drum torque.
- Units and format
- Enter a number in kN: kilonewtons (1 kN = 1000 N). The form accepts 0.000001 kN to 10000 kN. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 kN as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Drum torque rises in direct proportion.
- Get it right
- Enter kN; with several falls this is the line pull, not the hook load.
What this means: Drum barrel diameter
- What it is
- The diameter of the bare drum barrel, under the first rope layer.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 10000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 300 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger drum raises the D/d ratio and holds more rope per layer.
- Get it right
- For a grooved drum use the diameter at the groove bottoms.
What this means: Rope diameter
- What it is
- The nominal diameter of the wire rope.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 200 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A thicker rope fits fewer turns per layer and lowers the D/d ratio.
- Get it right
- Use the nominal rope size from the rope certificate.
What this means: Drum width between flanges
- What it is
- The width of the drum between its flanges, over which the rope spools from side to side.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 500 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A wider drum holds more turns per layer but raises the fleet angle.
- Get it right
- Measure inside the flanges, the usable winding width.
What this means: Distance from drum to the lead sheave
- What it is
- The distance from the drum to the first sheave the rope runs to, with that sheave on the drum centre line.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 1000000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10000 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A longer distance lowers the fleet angle.
- Get it right
- Measure from the drum axis to the lead sheave axis.
Rope needed
What this means: Lift height
- What it is
- The height the hook travels from its lowest to its highest position.
- Units and format
- Enter a number in m: metres. The form accepts 0.000001 m to 10000 m. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 m as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The rope length to store rises in direct proportion, with the falls.
- Get it right
- Use the full hook travel, not the height of the structure.
What this means: Falls of rope (reeving)
- What it is
- The number of rope parts supporting the hook block between the drum and the block. Each metre of hook travel winds this many metres onto the drum.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 24. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Count the rope parts holding the hook block, not the sheaves.
What this means: Dead turns left on the drum
- What it is
- The turns of rope that must stay on the drum with the hook at its lowest point, to take strain off the rope anchor.
- Units and format
- Enter a number in turns: a number of turns. The form accepts 0 turns to 50 turns. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 3 turns as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Take the number from your crane or hoist standard.
Limits
What this means: Largest fleet angle
- What it is
- The largest fleet angle you accept: the angle between the rope and a line square to the drum axis when the rope is at a flange.
- Units and format
- Enter a number in °: degrees of angle. The form accepts 0.1° to 10°. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.5° as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Take the limit from the rope or crane standard; grooved and plain drums have different limits.
What this means: Least drum ÷ rope diameter
- What it is
- The least ratio of drum diameter to rope diameter allowed, to limit bending fatigue of the rope.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 100. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 18 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Take it from your crane or rope standard for the duty class.
What this means: Most layers allowed
- What it is
- The most rope layers you allow on the drum, compared with the layers needed to store the rope.
- Units and format
- Enter a number in layers: layers. The form accepts 1 layers to 20 layers. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 3 layers as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Take it from your crane standard or the drum and rope makers.
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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