This page now follows the actual form (c) diagram: a fixed standing end, one load-attached movable sheave, and an overhead-redirected haul line. Those two vertical cord parts support the moving block, fixing the ideal force ratio at 2:1.
Form (c) Ideal Standing-End/Haul-Line Explorer
Enter a declared load and load lift. The connected view keeps the fixed standing end, movable sheave/load, overhead redirect and downward haul line together while reporting the exact ideal 2:1 force, travel and work ledger.
Equation Used
- One standing end is fixed overhead.
- The standing end and haul line are the two vertical cord parts acting on the load-attached movable sheave.
- Both parts belong to one ideal continuous cord and carry equal tension T.
- The overhead redirect changes hauling direction but adds no support at the moving block.
- Cord and sheaves are massless, inextensible and frictionless in the ledger.
- Friction, bending loss, acceleration, shock, ratings, inspection, guarding and safe operation are excluded.
Locks form (c) to its fixed standing-end and haul-line two-part topology and removes the unrelated variable-fall model.
The standing end and haul line are the two supporting parts
The cord is fixed at the standing end, passes under the load-attached movable sheave, rises as the haul line and is redirected overhead for a downward pull. The two vertical parts at the movable sheave each carry ideal tension T, giving W=2T.
The overhead redirect changes pull direction only.
Use this page only for the depicted ideal form (c) ledger
The worksheet reports ideal effort, hauling-rope travel and work closure for declared load and lift. It cannot select, rate, inspect or authorize a real lifting system.
The fixed two-part force trade closes the work ledger
Real effort is higher because bending, bearing friction and alignment introduce loss.
A transparent form (c) example
For W=1000 N and h=1 m, ideal hauling effort is 500.00 N and hauling-rope travel is 2.00 m. Ideal input and output work are both 1000.00 J.
No component rating follows.
Two-to-one geometry is not actual lifting capacity
Official Army and Navy guidance counts only the rope parts acting on the movable or traveling block and distinguishes theoretical from actual advantage because friction reduces performance.
The former arbitrary fall-count input, unsupported loss rates, capacity, human-effort, sizing, deployment, maintenance and troubleshooting claims are removed.
Form (c) questions
What is the standing end?
The fixed end of the continuous cord.
Why is the ideal ratio 2:1?
The standing-end part and haul-line part both support the movable sheave.
Does the overhead redirect add advantage?
No.
Can this rate hardware?
No.
Movable-pulley references
- US Army TC 4-13.17, Block and Tackle: theoretical advantage is found by counting parts at the movable block.
- US Navy Salvage Manual, Volume 1: supporting tensions sum at the traveling block; actual advantage is lower because of friction.
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