the smaller surface. This pressure is then transferred, by means of
the fluid, to the larger surface where a proportional force (output)
The rate mechanical advantage is produced by hydraulic
means is in direct proportion to the ratio of the size of the smaller
(input) area to the size of the larger (output) area.
pounds of force applied to one square inch of surface of a confined
liquid produces 100 pounds of force on a movable surface of 10 square
inches. This is illustrated in Figure 1-5. The increase in force is
not free, but is obtained at the expense of distance. In this case,
the tenfold increase in output force is gained at the expense of a
tenfold increase in distance over which the initial force is applied.
Some hydraulic components require air as well as hydraulic oil for
Other hydraulic components do not, and instead
their performance is seriously impaired if air accidentally leaks
into the system.
Familiarization with the basic principles of pneumatics aids in
understanding the operation of both the hydraulic components
requiring air as well as those that do not.
It aids, also, in
understanding how air can upset the normal operation of a hydraulic
system if it is present in the system where it must not be.