Types
Breast
A breast derrick is a derrick without a boom with a mast constructed from two upright members. The upright members are more spread at their bottom ends than their top ends. There are crossbars to join the two members from the bottom to the top to form a mast..Chicago boom
A Chicago boom derrick is a derrick with a boom which is attached to an external structure. The external upright member of the structure serves as the mast, and the boom is stepped in a fixed socket clamped to the upright. The boom is connected to at least three pulley systems to control the position of the boom. For example, a pulley system is connected to the top of the boom and the higher area of the external structure and two pulley systems near the top of the boom connected on either side of the boom to the external structure. The position of the top of the boom can be controlled by manipulating these pulley systems. The load is lifted from a separate pulley system that is connected to the top of the boom.Gin pole
Gin pole derrick (also known as standing derrick or pole derrick) is a derrick without a boom with single tower or mast supported by 4 guy wires (two side guys, fore guy and rear guy). Its guys are so arranged from its top as to permit leaning the mast in any direction. The base of the tower is hinged and the top of the tower is connected to a pulley system for load lifting. As this is a simple derrick system, it is considered to be used by some agencies as an improvised rescue derrick in an emergency situation where no suitable rescue derrick or crane is available.Guy
Guy derrick (also known as boom derrick) is a fixed guyed mast derrick that can be rotated and connected to a boom. The mast is in upright position with the base that can make the mast rotate, but not to be lean in any direction. The top of the mast is connected to many guy wires which are anchored to the ground to support the load. At the base, the mast is also connect to the bottom end of the boom. The boom extends outward and upward to the desired position. The top of the boom is a pulley system that is connected to the top of the mast to control how far the boom is to be from the mast. When the mast is rotated, the connected boom is swung from to the side. The control of the lifting location is done by the manipulation of the top pulley system and the rotation of the mast at the base. The load is lifted by another pulley system connected to the top of the boom. In a medium load lifting, another construction method can be used. In this case, the mast is fixed without being rotated, but the boom can be swung around the mast. This can be done by connecting the bottom of the boom with two boards on the opposite sides around the surface of the boom to form a fork. The fork and the bottom part of the boom is lashed to secure them together. Another lashing is between the fork area and the mast at a higher position to support the weight of the boom. The fork is put around the mast such that the bottom of the boom is rested on the mast without permanently fixed to it. The fork prevent the boom to come off the mast while swinging up to 180 degrees.Shearleg
Shearleg derrick is similar to breast with an exception that instead of fixed guy wires that secure the top of the mast, it is secured by multiple reeved guy to permit handling loads at various radii by means of load tackle pulley system suspended from the mast top. In a simpler construction, a shearleg derrick can be assembled from two posts to form A-frame shear legs without any crossbar. The bottom of the legs are set in two holes on the ground spreading them apart. There is a rope to tie the two legs together near the bottom to prevent them from spreading apart further. On the top side, the two legs are connected together by aStiffleg
The Stiffleg derrick, also known as a Scotch derrick, is a derrick with a boom similar to a guy derrick, but instead of using guy wires to secure the top of the mast, it uses two or more stiff members, called stifflegs, which are capable of resisting eitherOil derrick
Patent systems
Hallen
TheVelle
The Velle derrick is quite similar to the Hallen but without use of outriggers. On top of the boom is a T-shapedStülcken
See also
* Crane *References
Further reading
* A swinging derrick white.External links
*{{Commonscatinline, Derricks Industrial equipment Lifting equipment