All of the above tackles/purchases are designed to increase the power utilised to the effect achieved. Because of friction between the ropes and sheaves, the actual (theoretical) weight lifted can be roughly calculated as being: Weight + (1/10 x weight) for each sheave. The mechanical advantage gained can be found…
Purchase. A purchase is a combination of blocks or pulleys rove with a rope, wire or chain. Tackle. A tackle is a purchase consisting of a rope rove and through two or more blocks, in such a way that any pull applied to the hauling part, is increased by an…
In order to lift heavier weights, a system of blocks and tackles was gradually introduced. Originally they were made out of wood, but as the loads got heavier and they had to withstand harder work they were made out of steel. It is very rare these days to find a…
Cargo working gear consists of shackles, cranes, derricks and their associated equipment, masts and Sampson posts and the wires/ropes used to connect them all together. Shackles. Types: Shackles are named according to their different shapes, ie “D” or “Straight backed”, “Bow” or “Harp” shackles. One other type which is not…
Until now we have been looking at the loading and discharge of what is known as General Cargo. There has been a large shift away from general cargo vessels with the introduction of containers. Containers are very large steel boxes with lockable doors at one end. Thr idea is that…
The loading and discharging of cargo is greatly eased with the help of the proper equipment for its handling. In this chapter we will be discussing the various items of equipment and their uses. Rope slings. Rope slings are constructed by joining the ends of a piece of 25 to…
