Measure the usable barrel
Use the barrel diameter below the rope and the length actually available for winding, rather than the flange outside diameter.
HOISTING & TRAVEL / TOOL 18
Wire Rope Drum Capacity Calculator
Check whether a proposed drum has enough geometric rope storage for the required payout and retained wraps.
Before you start: required inputs
- Use the drum drawing for the barrel core diameter and effective winding length between the actual end clearances.
- Obtain rope diameter, winding pitch, permitted layer count and required retained wraps from the proposed drum arrangement.
Calculation diagram
A PRACTICAL WALKTHROUGH
How to use this calculator
Set the winding arrangement
Specify rope diameter, pitch, full layers and retained first-layer wraps.
Separate storage from payout
Compare total stored length and usable payout. Convert rope travel into hook travel using the actual reeving arrangement.
Single-layer 16 mm rope drum
THE INPUTS
400 mm core, 16 mm rope, 18 mm pitch, 900 mm winding length, one layer and three retained wraps.
THE RESULT
The barrel fits 50 wraps. Estimated storage is 65.345 m, including 3.921 m retained, leaving 61.424 m of rope payout.
What does the result mean?
01
Each complete layer uses its rope centre-line diameter, so outer layers store more rope per wrap.
02
Usable payout is rope movement. It is not the same as hook travel on a multi-part hoist.
03
Flange freeboard, rope anchorage, crossovers, groove geometry and drum strength are outside this storage estimate.
Watch for this
Using the flange diameter as the core diameter, which overstates rope length on every wrap.
Formula & model conditions +
D_i = D_core + (2i − 1)d
L_stored = N_wraps × π × ΣD_i
L_usable = L_stored − N_retained × π × (D_core + d)
- Wraps per layer = floor(effective length / winding pitch).
- Each layer is estimated as circles at the rope centre-line diameter. Crossovers, helical correction, compression, flange freeboard and rope anchorage details are excluded.
- Usable payout subtracts the entered retained first-layer wraps. Payout is rope travel, not hook travel.
Common questions
Why is the number of wraps rounded down?
The model counts only complete wraps that fit within the effective winding length.
Does this tool verify that multilayer spooling will work?
No. Fleet angle, crossover arrangement, groove profile, crushing, rope behavior and flange clearance need separate checks.