24 Fluid Power
An Italian, Evangelista Torricelli (1608–1647),
is recognized as having identified the principles
that affect fluid flow. He also did extensive work in
the field of mechanics and had an influence on the
development of many scientific principles. Today,
he is generally associated with the development of
the barometer. However, close analysis of histori-
cal data indicates the basic principles were tested
by others with Torricelli properly interpreting the
results.
The French scientist Jacques Charles (1746–
1823) provided another key element to under-
standing fluid power principles. He developed a
law relating to the effect of temperature on the vol-
ume of a gas:
All gases expand or contract in
direct proportion to the change in
absolute temperature.
Charles’ law combined with Boyle’s law form the
general gas laws, which are fundamental to any
calculations done for gases today.
Daniel Bernoulli (1700–1782) is credited with
laying the foundation of hydrodynamics. Although
his name is applied to the Bernoulli theorem, some
historians contend that his 1738 publication Hydro-
dynamics does not include specific formulas. He
extensively studied both static and dynamic fluid
phenomena. His contemporaries and successors
considered his work to be the first specific prin-
ciples on fluid movement.
James Watt (1736–1819) was a productive
inventor who is usually thought of with respect
to the steam engine, Figure 1-13. His inventive
genius went well beyond this device, however. He
impressed his contemporaries as the individual
who provided mankind with devices that had
the potential of producing unlimited power. As
new designs were developed to meet the power
demands of the Industrial Revolution, Watt devel-
oped, or caused to be developed, new manufac-
turing techniques that greatly influenced the
Industrial Revolution.
English engineer Joseph Bramah (1748–1814),
with his assistant Henry Maudslay (1771–1831),
invented the cup seal. This seal greatly contributed
to the practical application of fluid power devices.
The cup seal enabled the development of devices
requiring pressurized liquids and gases to oper-
ate with little leakage. Bramah went on to build
the first functional hydraulic press, which had
extensive application in the fluid power industry.
Maudslay went on to develop numerous devices
and is generally considered to be the father of the
machine-tool industry.
Lord William Armstrong (1810–1900) devel-
oped a hydraulic accumulator that made a major
contribution to the development of the early fluid
power industry. An accumulator stores excessive
pressurized fluid from the pump until needed
during peak system operation. The Armstrong
accumulator was basically a large, vertically
positioned cylinder with a weighted ram. These
devices were extensively used during the late
nineteenth century in large, centralized, pressur-
ized-fluid systems found in major cities through-
out Great Britain.
Osborne Reynolds (1842–1912) established by
direct observation that two types of fluid flow
exist: laminar (smooth and steady) and turbulent
(chaotic and rough). The observations he made
in 1883 eventually led to the development of a
formula that produces a dimensionless number
today called the Reynolds number. The Reynolds
number is considered one of the basic parameters
of fluid mechanics.
Figure 1-13. James Watt perfected the steam
engine and greatly infl uenced the development of
the Industrial Revolution. Many of his ideas were
used in the development of pumping devices.
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