22 Fluid Power
Flowing water in rivers and streams was also
used to assist in transporting boats and materials.
The Egyptians, Persians, and Chinese built dams,
ditches, and gates to form elaborate water-control
and irrigation systems. These various applications
eventually led to the development of variations of
the waterwheel to lift water for irrigation purposes
and turn simple mills. These early uses of fluid
power were dependent on vast quantities of low-
pressure air and water supplied by nature. They
also were subject to variations in the weather,
which made them somewhat unpredictable and
only partially under the control of the operators.
The windmill and waterwheel were exten-
sively used as power generating devices before
and through the early years of the Industrial Revo-
lution. Their power-generating capabilities were
very limited, however, usually in the 5–10 horse-
power range with a maximum of 30 horsepower.
The development of large industrial complexes
needed a larger and more-controllable power gen-
erating system, such as the steam engine devel-
oped by James Watt. This steam engine was not
constructed until 1775.
It is doubtful whether the physical principles
associated with modern hydraulics and pneu-
matics were fully understood in early history or
even at the beginning of the Industrial Revolution.
The physical principles and design features that
we consider basic to the operation of fluid power
systems were developed over several centuries.
Many of these developments were the products of
tinkerers more than due to an understanding of
advanced scientific principles. Application of the
scientific method played an ever-increasing role in
the development of both fluid power theory and
machinery design. The scientific method dictates
accurate measurement, controlled testing, repro-
ducibility of results, and systematic demonstration
and reporting of results.
Individuals in History
The identity of individuals involved in the
original development of the significant fluid
power scientific principles has been lost to time.
One of the factors that makes the identification
of individuals difficult is that many of the prac-
tical solutions were considered below the dignity
of “pure” science and, therefore, never recorded.
Several individuals, however, need to be recog-
nized as having made important discoveries. Other
individuals contributed by bringing together a
group of known elements to form a principle that
has become basic to the fluid power field.
Archimedes is credited with the discovery
of the principle of buoyancy in the third century
BC. Folklore relates that discovery to the need to
establish the amount of gold in the king’s crown.
Archimedes did extensive work with mathemat-
ics and other scientific principles. Two volumes of
his known manuscripts deal with hydrostatics and
floatation. He is also credited with the invention of
the water screw, Figure 1-11. This device has been
used to lift and move water for centuries. It has
also greatly influenced the development of pump-
ing devices in the fluid power field.
Hero is another individual who is recognized
as contributing basic knowledge to the area of fluid
mechanics. His work appears to have been done in
the second century BC, although no specific dates
have been established. Historians often considered
him to be a recorder of information, rather than an
originator. Nevertheless, Hero is popularly identi-
fied with a rotating, steam-jet device. At the time,
Figure 1-10. People have used the natural move-
ment of both air and water throughout history to
reduce work and aid in transportation. Using sails
on ships is an example of using fl uid power (wind).
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