Birth of Mechanical Engineering and a Glimpse …
13
by Wilkinson. This was the first step toward achieving accuracy in machining that
was another founding stone of emerging discipline—‘Mechanical Engineering’. It
may be interesting for today’s mechanical engineers to note the status of accuracy
of machining in those days. In April 1775, Wilkinson delivered a cylinder which in
Boulton’s language “— does not err the Thickness of an old shilling at any part —”.
Later Wilkinson improved his technique and in Watt’s language “— a 72 inch cylinder
being not further from absolute truth than the thickness of a new sixpence in the worst
part —”. The thickness of a coin may be a monstrous error by today’s standard BUT
THE ENGINE RAN after a decade of unsuccessful continuous struggle.
At this stage, it is desirable to get a glimpse of the historical patent taken by Watt
on January 29, 1769 for “Lessening the Consumption of Steam and Fuel in Fire
Engines.” It is given below:
First, that vessel in which the powers of steam are to be employed to work the engine, which
is called the cylinder in common fire engines, and which I call the Steam Vessel must, during
the whole time the engine is at work, be kept as hot as the steam that enters it; first by
enclosing it in a case of wood, or any other materials that transmit heat slowly; secondly, by
surrounding it with steam or other heated bodies; and thirdly, by suffering neither water nor
any other substance colder than the stream to enter or touch it during that time.
Secondly, in Engines that are to be worked wholly or partially by condensation of steam, the
steam is to be condensed in vessels distinct from the steam vessels or cylinders, although
occasionally communication with them; these vessels I call Condensers; and; whilst the
engines are working, these condensers ought at least to be kept as cold as the air in the
neighborhood of engines, by application of water, or other cold bodies.
Thirdly, whatever air, or other elastic vapor, is not condensed by the cold of the condenser and
may impede the working of the engine, is to be drawn out of the steam vessels or condensers
by means of pumps, wrought by the engines themselves, or other wise.
Fourthly, I intend in many cases to employ the expansive force of steam to press on the
pistons or whatever may be used instead of them, in the same manner as the pressure of the
atmosphere is now employed in common fire engines; in cases where cold water cannot be
had in plenty, the engines may be wrought by this force of steam only, by discharging the
steam into open air after it has done its office.
It is to be noted that in his fourth claim Watt included the concept of using the expansive force of steam, instead of the atmospheric pressure working against vacuum.
This prevented others in developing real ‘steam engines’ as Watt never allowed such
attempts as in his opinion use of high-pressure steam was dangerous. This delayed
the steam engine technology by almost 20 years. Although with a separate condenser
the efficiency of the engine increased drastically, the basic concept was still the same
as that of Newcomen’s engines. The configuration also remained the same consisting
of a typical rocking beam as shown in Fig. 13.
It was John Wilkinson who gave Watt the idea of a rotating steam engine instead
of generating only a reciprocating motion. Such an engine can drive machineries and
mills directly. Watt had to conceive of a mechanism and thought of a crank rocker
mechanism for converting the reciprocating motion into a continuous unidirectional
rotation. But his idea of a crank rocker mechanism was leaked by one of his assistants to some Mr. Pickard who took a patent. This became a stumbling block for
13
by Wilkinson. This was the first step toward achieving accuracy in machining that
was another founding stone of emerging discipline—‘Mechanical Engineering’. It
may be interesting for today’s mechanical engineers to note the status of accuracy
of machining in those days. In April 1775, Wilkinson delivered a cylinder which in
Boulton’s language “— does not err the Thickness of an old shilling at any part —”.
Later Wilkinson improved his technique and in Watt’s language “— a 72 inch cylinder
being not further from absolute truth than the thickness of a new sixpence in the worst
part —”. The thickness of a coin may be a monstrous error by today’s standard BUT
THE ENGINE RAN after a decade of unsuccessful continuous struggle.
At this stage, it is desirable to get a glimpse of the historical patent taken by Watt
on January 29, 1769 for “Lessening the Consumption of Steam and Fuel in Fire
Engines.” It is given below:
First, that vessel in which the powers of steam are to be employed to work the engine, which
is called the cylinder in common fire engines, and which I call the Steam Vessel must, during
the whole time the engine is at work, be kept as hot as the steam that enters it; first by
enclosing it in a case of wood, or any other materials that transmit heat slowly; secondly, by
surrounding it with steam or other heated bodies; and thirdly, by suffering neither water nor
any other substance colder than the stream to enter or touch it during that time.
Secondly, in Engines that are to be worked wholly or partially by condensation of steam, the
steam is to be condensed in vessels distinct from the steam vessels or cylinders, although
occasionally communication with them; these vessels I call Condensers; and; whilst the
engines are working, these condensers ought at least to be kept as cold as the air in the
neighborhood of engines, by application of water, or other cold bodies.
Thirdly, whatever air, or other elastic vapor, is not condensed by the cold of the condenser and
may impede the working of the engine, is to be drawn out of the steam vessels or condensers
by means of pumps, wrought by the engines themselves, or other wise.
Fourthly, I intend in many cases to employ the expansive force of steam to press on the
pistons or whatever may be used instead of them, in the same manner as the pressure of the
atmosphere is now employed in common fire engines; in cases where cold water cannot be
had in plenty, the engines may be wrought by this force of steam only, by discharging the
steam into open air after it has done its office.
It is to be noted that in his fourth claim Watt included the concept of using the expansive force of steam, instead of the atmospheric pressure working against vacuum.
This prevented others in developing real ‘steam engines’ as Watt never allowed such
attempts as in his opinion use of high-pressure steam was dangerous. This delayed
the steam engine technology by almost 20 years. Although with a separate condenser
the efficiency of the engine increased drastically, the basic concept was still the same
as that of Newcomen’s engines. The configuration also remained the same consisting
of a typical rocking beam as shown in Fig. 13.
It was John Wilkinson who gave Watt the idea of a rotating steam engine instead
of generating only a reciprocating motion. Such an engine can drive machineries and
mills directly. Watt had to conceive of a mechanism and thought of a crank rocker
mechanism for converting the reciprocating motion into a continuous unidirectional
rotation. But his idea of a crank rocker mechanism was leaked by one of his assistants to some Mr. Pickard who took a patent. This became a stumbling block for