The Locomotive - Lighthouse Survival Blog

1901.] THE LOCOMOTIVE. 123
1839 — about a year before the experiments — and the boilers then placed on board
remained in use until 1892, or about thirty-three years. The steam pressure carried was
about twenty pounds above the atmosphere, and the greatest economy was found to be
when the steam was cut off at four-ninths of the stroke, which, allowing for clearance,
meant an expansion ratio of about two. This was quite contrary to what the advocates
of extreme expansion had claimed, for, according to calculation based on Boyle's law
alone, the greatest degree of expansion should have given the highest economy. [On
this point the theory of nearly all text-books on steam engines, up to within a few years,
has o-one wrong. As good an authority as Rankine neglected to take account of the
effect of condensation in the engine cylinder. If the condensation be neglected, theory
shows that the shorter the cut-off and the greater the expansion of the steam in an
engine cylinder the more economical the engine. At present steam pressures, about one-
third cut-off gives the best results with simple non-condensing engines, there being less
condensation in the cylinder and consequent waste of steam when running under these
conditions that when the cut-off is very early in the stroke. In the case of the Michigan,
where the steam pressure was only twenty pounds per square inch, it was found, as
stated above, that the most economical point of cut-off was at nearly half-stroke. The
steam lost through condensation upon the cylinder walls when cutting off at this point
was less than half the condensation when cutting off at about one-tenth stroke. —
Editor.]
It would seem that the results of these experiments should have been absolutely
convincing as to the limiting ratios of expansion with low steam pressures and slowmoving
engines, but such was not the fact, and during the Civil War and thus right
after the publication of the experiments there was a heated controversy on this question
of expansion between Mr. Isherwood and a famous patent lawyer of New York named
Dickerson. Mr. Isherwood was accused by Dickerson of willful waste of government
funds by designing engines with very little expansion, and, indeed, after the war was
over these charges were investigated by a Congressional committee, which, after taking
testimony from many eminent engineers, found, in accordance with the facts, that Mr.
Isherwood had been, entirely right. However, during the war, Dickerson was given
permission to put machinery of his own design on two vessels, Pensacola and Algonquin.
The machinery of the Pensacola was an absolute failure, and had to be removed to make
the vessel of any service. After the war was over a competitive trial was made of the
Algonquin and a vessel called the Winooshi with Isherwood's machinery. This resulted
in a marked victory for the latter. The trial was conducted by civilian experts, whose
report concluded
machinery he has failed, and we are of the opinion that it is totally unfit for the naval
: "In every point guaranteed by the contractor for the Algonquin
service."
During the Civil War the depredations of Confederate privateers, notably the
Alabama, had driven American merchantmen off the ocean, and towards the end of the
war it was decided by the Navy Department to build a class of vessels which would be
faster than any others afloat, either in naval or merchant service. The most famous of
these vessels was the Wampanoag, whose machinery throughout was the design of Chief
Engineer Isherwood, who also laid out the lines of the hull. This vessel was not com-
pleted until after the conclusion of the war, but in February, 1868, she was given a full
power trial at sea from Sandy Hook to near Cape Hatteras. The performance was the
most wonderful record for a steamer in the history of marine engineering up to that
time, and in some ways it is still the most remarkable that has ever occurred. The
average speed for the whole trip was 16.7 knots; for twenty-four consecutive hours 17