Two treble blocks: power × 4½.
Whip upon whip (single Burton): trebled.
When one tackle is applied to another, the power obtained is found by multiplying their respective values together.
No advantage is gained by using a greater number of sheaves than two treble blocks in one fall.
The power is equal to the weight divided by the number of ropes (standing parts) attached to the lower block, or by twice the number of rising pulleys (sheaves).
KNOTS, HITCHES, ETC.
Thumb-knot ([Fig. 108]).—Used to prevent the end from unfraying, or to prevent its slipping through a fall.
Figure-eight Knot ([Fig. 109]).—Used to prevent the end from unfraying, or to prevent its slipping through a fall.
Fig. 108.