Include the moving block
The mass must include everything carried by the reeving, not just the goods on the hook.
LIFTING & RIGGING / TOOL 10
Hoist Reeving Line Pull Calculator
Use this for an initial comparison of rope line pull when the supported mass, number of load-supporting rope parts and overall reeving efficiency are known.
Before you start: required inputs
- From the reeving diagram, count the rope parts that directly support the moving block.
- Find the complete supported mass, including the lower block, and obtain a suitable overall reeving efficiency from the mechanism data.
Calculation diagram
A PRACTICAL WALKTHROUGH
How to use this calculator
Count supporting rope parts
Count load-supporting parts of rope in the diagram. The number of sheaves is not a substitute for this count.
Apply the system efficiency
Use one overall efficiency between zero and one. Compare the frictionless and estimated raising line pulls to understand the entered loss allowance.
Four-part reeving carrying 10,000 kg
THE INPUTS
Supported mass 10,000 kg; 4 load-supporting rope parts; overall reeving efficiency 0.9.
THE RESULT
The ideal line pull is 24.5166 kN. With the entered overall efficiency, the estimated raising line pull is 27.2407 kN.
What does the result mean?
01
Ideal line pull divides static weight by the number of supporting rope parts.
02
Estimated raising line pull is higher because the entered overall efficiency accounts for a system-level loss.
03
Neither value selects a rope diameter, breaking strength, drum attachment or permissible working load.
Watch for this
Entering a single-sheave efficiency as the overall reeving efficiency, or counting sheaves instead of load-supporting rope parts.
Formula & model conditions +
Ideal line pull = mass × 9.80665 / supporting rope parts
Estimated raising line pull = ideal line pull / overall reeving efficiency
- Quasi-static raising, equal ideal load sharing and one user-supplied overall reeving efficiency are assumed.
- Acceleration, rope self-weight, rope bending, unequal tension and shock loading are not modelled.
- This estimates line pull only; rope selection, reeving layout, drum attachment and breaking-force requirements are separate.
Common questions
Can I enter 90 for 90% efficiency?
No. Enter 0.9. The supported range is greater than zero and no more than one.
Does twice as many rope parts mean twice the lifting capacity?
This equation changes ideal line pull only. The complete hoist, rope, structure, speed, drum and duty still require coordinated design.