Birth of Mechanical Engineering and a Glimpse …
15
Fig. 14 Watt’s original
crank rocker design and the
alternative sun and planet
arrangement
constructing a double-acting engine, it was necessary to eliminate the circular sectors
on the rocking beam and connecting it with the piston rod that required a rectilinear
oscillating motion. He designed a straight-line generator with a four-bar mechanism
that is still known as ‘Watt’s Straight-Line Generator’ shown in Fig. 15. Generating a straight-line motion with the help of only hinge joints in a mechanism was
a design challenge and Watt considered this mechanism to be his best work. Slowly
the subject of mechanism theory started achieving maturity as the steam engines
started taking modern shapes with the introduction of high-pressure steam engines
by Richard Trevithick in 1801. For controlling the speed, a governor mechanism was
also introduced by James Watt, and the centrifugal governor designed by him is still
called ‘Watt Governor’. Figure 16 shows Watt’s design of the centrifugal governor
he employed. Figure 17 shows a double-acting rotary engine constructed in 1788. It
shows the introduction of the straight-line mechanism and the governor. Figure 18
shows the drawing of a Watt’s double-acting rotary engine. Since the piston moved
in a straight line, in this case, its connecting point driving the rocking beam needed
rectilinear motion. The use of the straight-line mechanism and a Watt governor is
clearly visible. The sun and planet mechanism to convert oscillatory motion to unidirectional continuous rotary motion is also conspicuous in the drawing. It is to be noted
how gradually the steam engine started looking as a product of mature ‘Mechanical
Engineering’ as time progressed.
As mentioned earlier, the real steam engine employing the expansive force of
high-pressure steam could not be developed since Watt was against it, and his claim
no. 4 in the patent use of high-pressure steam was mentioned. Only after the expiry of
the patent period, Richard Trevithick developed the first high-pressure steam engine
15
Fig. 14 Watt’s original
crank rocker design and the
alternative sun and planet
arrangement
constructing a double-acting engine, it was necessary to eliminate the circular sectors
on the rocking beam and connecting it with the piston rod that required a rectilinear
oscillating motion. He designed a straight-line generator with a four-bar mechanism
that is still known as ‘Watt’s Straight-Line Generator’ shown in Fig. 15. Generating a straight-line motion with the help of only hinge joints in a mechanism was
a design challenge and Watt considered this mechanism to be his best work. Slowly
the subject of mechanism theory started achieving maturity as the steam engines
started taking modern shapes with the introduction of high-pressure steam engines
by Richard Trevithick in 1801. For controlling the speed, a governor mechanism was
also introduced by James Watt, and the centrifugal governor designed by him is still
called ‘Watt Governor’. Figure 16 shows Watt’s design of the centrifugal governor
he employed. Figure 17 shows a double-acting rotary engine constructed in 1788. It
shows the introduction of the straight-line mechanism and the governor. Figure 18
shows the drawing of a Watt’s double-acting rotary engine. Since the piston moved
in a straight line, in this case, its connecting point driving the rocking beam needed
rectilinear motion. The use of the straight-line mechanism and a Watt governor is
clearly visible. The sun and planet mechanism to convert oscillatory motion to unidirectional continuous rotary motion is also conspicuous in the drawing. It is to be noted
how gradually the steam engine started looking as a product of mature ‘Mechanical
Engineering’ as time progressed.
As mentioned earlier, the real steam engine employing the expansive force of
high-pressure steam could not be developed since Watt was against it, and his claim
no. 4 in the patent use of high-pressure steam was mentioned. Only after the expiry of
the patent period, Richard Trevithick developed the first high-pressure steam engine