This page now follows the actual form (b) diagram: two vertical equal-tension cord parts support one load-attached movable sheave, while a small fixed guide turns the hauling end through 90 degrees. The guide changes direction only; the ideal advantage remains exactly 2:1.
Form (b) Ideal 2:1 Right-Angle-Haul Explorer
Enter a declared load and load lift. The connected view keeps the fixed anchor, two vertical supporting parts, movable sheave/load and right-angle hauling guide together while reporting the exact ideal force, travel and work ledger.
Equation Used
- Exactly two vertical cord parts act upward on the movable block.
- Both parts belong to one ideal continuous cord and have equal tension T.
- The upper-right fixed guide changes hauling direction by 90 degrees but does not support the movable block.
- The load and movable sheave translate together.
- Cord and sheaves are massless, inextensible and frictionless in the ledger.
- Fleet angle, bending loss, friction, acceleration, shock, ratings, inspection, guarding and safe operation are excluded.
Locks form (b) to its two vertical supporting parts and direction-only 90-degree hauling guide, removing unrelated free segment-count and angle inputs.
Two vertical parts support the moving block; the small guide redirects the haul
The continuous cord is anchored overhead, descends around the load-attached movable sheave, rises vertically, and then turns through the fixed upper-right guide to the hauling end. Only the two vertical parts act upward on the movable block.
With ideal equal tension T, vertical equilibrium is W=2T. The direction-changing guide adds no supporting part.
Use this page only for the depicted ideal form (b) ledger
The worksheet reports ideal effort, hauling-rope travel and work closure for declared load and lift. It cannot select, rate, inspect or authorize any real lifting system.
Direction changes without changing the ideal 2:1 ratio
Real effort is higher because cord bending, sheave bearings and alignment introduce loss.
A transparent form (b) 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 hardware rating follows.
Ideal geometry is not lifting capacity
Official Army and Navy guidance counts the rope parts acting on the movable or traveling block and distinguishes theoretical from actual advantage because friction reduces performance.
The former arbitrary segment-count and free angle selectors, generic loss percentages, human-effort, capacity, sizing, deployment, maintenance and troubleshooting claims are removed.
Form (b) questions
Does the small upper guide add mechanical advantage?
No; it changes hauling direction only.
Why is the ratio fixed at 2:1?
Exactly two vertical parts act upward on the movable block.
Why does rope travel equal 2h?
Both supporting parts shorten by h.
Can this rate a lifting system?
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 and friction makes actual advantage lower.
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