Scientific American Supplement, No. 492, June 6, 1885 — John Shaqi
Scientific American Supplement, No. 492, June 6, 1885Various
Science
Scientific American Supplement, No. 492, June 6, 1885
Various
Science -- Periodicals
After making a voyage or two to the Baltic, and finding that everything
was working satisfactorily, the Kovno was loaded with 2,400 tons dead
weight, and sailed in January, 1883, for Buenos Ayres; the Draco was
loaded with 2,425 tons dead weight, and sailed March, 1883, for Bombay,
the distance in both cases being about 6,400 miles. It was thought
advisable, for purposes of comparison, that the ships should steam at as
near as possible the same speed; and to attain this object, we considered
the safest plan was to instruct the engineers as to the average amount of
coal they were to burn per day, and experience with these ships on their
Baltic voyages had fixed this at 12 tons in the case of the Kovno and 10
tons in the case of the Draco. During the voyage each ship seems to have
had fair average weather, and equal care was taken in getting the best
results possible. The average speed of the Draco was, however, 8.625
knots, or 207 miles per day, the engines making on the average 57.5
revolutions per minute, while the Kovno did only 8.1 knots, or 194 miles
per day, the engines making 55.5 revolutions. The coal used was ordinary
South Yorkshire, just as it comes from the pits for bunker purposes. The
indicated horse power in each case would average about 600. The total
coal consumed was 326 tons in the Draco and 405 tons in the Kovno, or a
saving of 19.5 per cent. over the ordinary compounds, with an increase of
speed of 6.5 per cent.
In December, 1883, one of the others, the Grodno, sailed from Bombay, and
attained an average speed of 8.5 knots, or 204 miles per day, the engines
making 57 revolutions, with a coal consumption of 12.8 tons per day, or
469 tons on the voyage. The Draco's consumption is therefore 30.5 per
cent. less than that of the Grodno on the round voyage, and 20.3 percent
per day.
The success of the triple compound engine was in these instances more
than had been anticipated, and induced Mr. Wilson to go a step further.
The S.S. Yeddo had been refitted with boilers made for a working pressure
of 90 lb. per square inch, but owing to the size of the shafting the
working pressure was limited to 70 lb.; the average consumption of coal
under these circumstances on two voyages was 17 tons per day. These
boilers had a margin of safety beyond what was required by the rules when
made, and as the Board of Trade rules had been modified in the mean
while, it was found that they could with safety be worked at 100 lb. per
square inch. A third cylinder was now fitted on the top of the original
low pressure, and the safety valves loaded to the 100 lb., and the ship
was dispatched to Cronstadt. After making two voyages under similar
circumstances to the two previous ones, the average consumption was 13.5
tons per day only. In this case it was the same ship, same boilers, same
engines, same propeller, and same men, the only difference being the
addition of a third cylinder and the increase of pressure.
Public-domain text, read in full here on John Shaqi.
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