Two centuries of shipbuilding by the Scotts at Greenock

84 Engines of Thames Steamers.
facing this page, showing one of the Clyde-built vessels
ready to steam from Greenock to London.
The engines for all of these vessels are of the compound,
diagonal, surface-condensing type, the two cylinders being
16 in. and 31 in. in diameter, with a stroke of 3 ft.
One set of engines is illustrated on Plate XXXV.,
adjoining page 85. They have forged steel guide columns,
to bind the cylinders to the three entablature frames. The
crank-shaft is a solid steel forging, 6f in. in diameter,
coupled to the steel paddle-shafts by flexible couplings.
The surface-condenser, cylindrical in form and constructed
of light brass sheets, is placed below the guide bars close
to the cylinders. The water-ends are of cast brass, arranged
for double circulation of the water. The air-pump, of the
trunk type, is driven by bell-crank levers off the low-
pressure connecting-rod. Two independent feed-pumps are
driven off the same crosshead.
The auxiliary machinery includes a circulating pump
with auxiliary air-pump attached, a direct-acting feed and
bilge pump, a fan and engine for the forced draught, and
an electric engine and dynamo.
Each steamer has one cylindrical steam boiler, 9 ft. in
diameter by 9 ft. 3 in. long. The working steam pressure is
110 lb. The boilers are also illustrated on Plate XXXV.
The twenty sets of engines and boilers were completed
in a remarkably short space of time.
These steamers were designed for a service speed of
12 statute miles per hour, and a trial speed of 13 miles
per hour, or 11.285 knots. The best trial performances
were attained by the FitzAilivin and the Turner, both
built on the Clyde; they attained a speed of 14.1 miles
per hour, or 12^ knots, with the engines making 69.8
revolutions per minute, and indicating 360 horse-power.
This is nearly 1 sea mile per hour more than was required
by the contract.