conclisions of motorized screw jack and advantages of motorized screw jack
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advantages and disadvates of screw jack
A jackscrew is a type of jack that is operated by turning a leadscrew. In the form of a screw jack it is commonly used to lift moderately heavy weights, such as vehicles. More commonly it is used as an adjustable support for heavy loads, such as the foundations of houses, or large vehicles. These can support a heavy load, but not lift it.A screw jack is a simple machine. It is used to lift cars or heavy automobiles. It consists of a long screw rod which passes through a threaded block B and a handle . The distance between two consecutive thread is known as pitch of screw.
When an effort is applied to the handle , the effort moves in a circle of radius “d” while “d” is the length of the rod and the block “B” moves up equal to the pitch of the screw jack. If the handle is turned through one complete revolution in a circle of radius “d” the effort moves through a distance 2pd and consequently the load is raised through a height h. Hence, the mechanical advantage is given by:
M.A. = 2pd/h
M.A. = Distance through which the effort is moved/height through which the load is raised
We know that the pitch of the screw is very small as compared to the length of the rod, so the mechanical advantage should be very large. Due to frictional force between the different parts of screw jack, the efficiency is less than one. It is due to the reason that a lot heat energy is used for over coming the frictional forces.
It should be remembered that in case of screw jack friction is a necessary part of operation, because in the absence of friction, it would unwind at once when applied force is removed.