Mechnical Jacks vs. Hydraulic Jacks
What is the difference between a mechanical jack and a hydraulic jack? With the number of jack types that are available, it is important to understand the difference between the two. Additionally, each type of jack offers its own benefits and drawbacks. Knowing which jack type to use involves understanding the differences in the two types of lifting devices.
In contrast to hydraulic jacks, mechanical jacks use only physical means of raising and lowering their loads. Using mechanical advantage, these jacks are commonly seen in the automotive industry for lifting vehicles and other loads.
A common type of mechanical jack is known as a “screw jack.” With the use of a motor, or a lever that is cranked by an operator, a screw uses the shape of its threads to raise or lower the jack. Depending on the type of jack, the screw itself may raise or lower the load, or a traveling nut does the raising while the screw turns in place.
These jacks have many applications that include moving platforms on stages, changing settings on woodworking machinery, and adjustments of radio telescopes. Other applications also involve the use of mechanical jacks and they provide some advantage over hydraulic systems.
Mechanical systems are normally self-locking. This means that when power is removed from the jack, the screw remains in the same position until power is reapplied. Self-locking properties make these jacks safer to use than hydraulic units, since operators need not worry about loss of power.
Drawbacks of a mechanical system include the fact that they are not capable of lifting the same loads as hydraulic lifts. Additionally, levers that provide mechanical advantage for manual operations can only reach a certain length before bending and becoming useless.
Jacks using hydraulic power operate on the phenomenon that fluids produce the same pressure at all points when contained in a closed system. With these types of jacks, a fluid is contained within a large and small container, both of which are linked by tubes. When a small amount of force is applied to the smaller tube, the pressure on the fluid increases. This means that, within the larger tube, the same amount of pressure per square inch is applied over a larger surface, resulting in an increased amount of force.
While these jacks are capable of lifting heavier loads than mechanical jacks, they also have the drawback that the load will be lowered if the hydraulic power is removed from the jack. Operators must take care to ensure that hydraulic power remains in place while they are working with the jacks.