A gun tackle consists of two single blocks with fall fixed to the one, then rove through the other, and then through the first. Power = ½ weight (or 2 to 1): or Power = ⅓ weight (or 3 to 1). Vide [Fig. 3, and 4.]
Two double blocks are generally used for very heavy guns.
A luff tackle, or half watch tackle, consists of one double and one single block: the fall is fixed to the single, then rove through first sheave of the double, then through sheave of single, and lastly through second sheave of double block. Power = ⅓ weight (3 to 1): or Power = ¼ weight (4 to 1). Vide [Fig. 5, and 6.]
A runner tackle is the same as a luff tackle, applied to the end of a large rope, called a runner, which is rove through a single block attached to a fixed point, or to a body that is to be moved, or raised; the standing end of the runner being secured to another point.
Power is either 6 to 1, or 7 to 1, or 8 to 1.
A gyn tackle consists of one triple and one double block: the fall is fixed to the double, then rove through first sheave of triple, then through first sheave of double, then through second sheave of triple, then through second sheave of double, and lastly through third sheave of triple block.
Power = ⅕ weight (5 to 1): or Power = ⅙ weight (6 to 1). Vide [Fig. 7.]
If the moveable block of a tackle be strapped with a tail, it is called a tail, or jigger block: and the tackle a tail, or jigger tackle: a block with a hook strapped to it, and attached to a selvage, answers the same purpose.
Two double blocks, with fall fixed to one of them, and then rove through the sheaves of both blocks, will either give Power = ¼ weight (4 to 1): or Power = ⅕ weight (5 to 1). [Fig. 8.]
Two triple blocks, with fall fixed to one of them, then rove through sheaves of both blocks, will either give power = ⅙ weight (6 to 1): or Power = ⅐ weight (7 to 1). [Fig. 9.]