A combination of two fixed pulleys and one movable pulley

Only the input is driven; every other part of this model moves by physics (MuJoCo), and its ratios are measured. Run it live, change its parameters, or switch the friction off to see the output stop.

Modelled as

one rope of 120 links (friction on the sheaves): from the hand over the upper fixed sheave, down and under the movable sheave, up over the middle fixed sheave and down to the movable block, where it is lashed

Measured

block/hand 0.336 (three parts: 1/(2 + cos 8.9°) = 0.335), sheaves upper −8.38, middle −3.91, movable −7.87 rad/m (strand speeds: −8.40, −3.94, −7.92), pull 64.6 N against W/2.988 less the hand's weight 63.9 N, pen ≤ 0.04 mm

Notes

Only the hand is driven (a slide in a guide along the rope's strand, 20° off plumb, 6 cm/s). The upper sheave is drawn larger, as in the plate, so the fall to the movable sheave clears the middle one. The lashing leaves the middle sheave 8.9° off plumb to reach the block's centre. Negative control: the rope's contact switched off → the block does not rise (0.000; it drops to its stop while the hand still hauls).

Film (MP4) · GIF · Still (PNG) · Spec (YAML) · Model (MJCF)