Watt had been asked in 1763 to…
1765 CE
Even after repair, the engine barely works.
After much experimentation, Watt demonstrates that about three-quarters of the thermal energy of the steam is being consumed in heating the engine cylinder on every cycle.
This energy is wasted because later in the cycle cold water is injected into the cylinder to condense the steam to reduce its pressure.
Thus by repeatedly heating and cooling the cylinder, the engine wastes most of its thermal energy rather than converting it into mechanical energy.
Watt's critical insight, arrived at in May 1765, is to cause the steam to condense in a separate chamber apart from the piston, and to maintain the temperature of the cylinder at the same temperature as the injected steam by surrounding it with a "steam jacket."
Thus very little energy is absorbed by the cylinder on each cycle, making more available to perform useful work.
Watt has a working model later this same year.
Despite a potentially workable design, there are still substantial difficulties in constructing a full-scale engine.
This requires more capital, some of which comes from Black.
More substantial backing comes from John Roebuck, the founder of the celebrated Carron Iron Works near Falkirk, with whom he now forms a partnership.
Roebuck lives at Kinneil House in Bo'ness, during which time Watt works at perfecting his steam engine in a cottage adjacent to the house.
The shell of the cottage, and a very large part of one of his projects, still exist to the rear.
The principal difficulty is in machining the piston and cylinder.
Iron workers of the day are more like blacksmiths than modern machinists, and are unable to produce the components with sufficient precision.
Much capital is spent in pursuing a patent on Watt's invention.
Strapped for resources, Watt is forced to take up employment—first as a surveyor, then as a civil engineer—for the next eight years.
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