Scientific American Supplement, No. 458, October 11, 1884 by Various
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Various >> Scientific American Supplement, No. 458, October 11, 1884
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* * * * *
SCREW STEAM COLLIER FROSTBURG.
[Illustration: NEW STEAM COLLIER.]
Our diagram shows the screw steam collier Frostburg, built by Henry H.
Gorringe (the American Shipbuilding Co.), Philadelphia, Pa. Length, 210
ft. Beam, 33 ft. Depth, 17 ft, Register tonnage, 533. Carrying capacity on
14ft., 1,100 tons, and 100 tons coal in bunker. Cubical contents of cargo
space, 55,168 cub. ft. Carrying capacity on 16 feet draught, 1,440 tons.
Engines, compound surface condensing. High pressure 26 in. diameter, low
pressure 48 in. diameter, stroke 36 in. Two boilers, each 13 ft. diameter.
10 ft. long, and one auxiliary 5 ft. diameter and 10 ft. high. 100 lb.
working pressure. Sea speed with full cargo, 11 knots.
* * * * *
A thirteen year old girl, who is perfect in other ways, but who has simply
little blue spots that puff out slightly where her eyes should be, is said
to be living at Amherst, Portage County, Wisconsin.
* * * * *
DESTRUCTION OF THE TARDES VIADUCT.
The railroad from Montlucon to Eygurande, which is being constructed by
the state engineers, crosses the valley of the Tardes in the environs of
Evaux (Creuse).
At the spot selected for the establishment of the viaduct the gauge is
deep and steep. The line passes at 300 feet above the river, and the total
length of the metallic superstructure had to be 822 feet. To support this
there was built upon the right bank a pier 158 feet in height, and, upon
the left, another one of 196 feet. The superstructure had been completed,
and a portion of it had already been swung into position, when a violent,
gale occurred and blew it to the bottom of the gorge. At the time of the
accident the superstructure projected 174 feet beyond the pier on the
right bank, and had to advance but 121 feet to reach the 33 foot
scaffolding that had been established upon the other pier.
It blows often and violently in this region. For example, a gale on the
20th of February, 1879, caused great damage, and, among other things, blew
the rear cars of a hay train from the top of the Louvoux viaduct to the
Bouble.
The superstructure of the Tardes viaduct had already withstood the tempest
of the 23d and the 24th of January, 1884, and neither any alteration in
its direction nor any change in the parts that held it upon the pile could
be perceived. But on the night of January 26-27 the storm doubled in
violence, and the work was precipitated into the ravine. No one was
witness of the fall, and the noise was perceived only by the occupants of
the mill located below the viaduct.
The workmen of the enterprise, who lived about 325 feet above this mill
and about 650 feet from the south abutment, heard nothing of it, the wind
having carried the noise in an opposite direction. It was not until
morning that they learned of the destruction of their work and the extent
of the disaster.
One hundred and sixty-nine feet of the superstructure, weighing 450 tons,
had been precipitated from a height of nearly 200 feet and been broken up
on the rock at 45 feet from the axis of the pier. The breakage had
occurred upon the abutment, and the part 195 feet in length that remained
in position in the cutting was strongly wedged between walls of rock,
which had kept this portion in place and prevented its following the other
into the ravine.
Upon the pier there remained a few broken pieces and a portion of the
apparatus used in swinging the superstructure into place.
Below, in the debris of the superstructure, the up-stream girder lay upon
the down-stream one. The annexed engraving shows the state of things after
the disaster.
Several opinions have been expressed in regard to the cause of the fall.
According to one of these, the superstructure was suddenly wrenched from
its bearings upon the pier, and was horizontally displaced by an impulse
such that, when it touched the masonry, its up-stream girder struck the
center of the pier, upon which it divided, while the down-stream one was
already in space. The fall would have afterward continued without the
superstructure meeting the face of the pier.
[Illustration: DESTRUCTION OF THE TARDES VIADUCT.]
Upon taking as a basis the horizontal displacement of the superstructure,
which was 45 meters to the right of the pier, and upon combining the
horizontal stress that produced it with that of the loads, the stress
exerted upon the body may he deduced. But this hypothesis seems to us
scarcely tenable, especially by reason of the great stress that it would
have taken to lift the superstructure. On another hand, it was possible
for the latter to slide over one edge of the pier, and this explains the
horizontal distance of 45 feet by which its center of gravity was
displaced. It is probable, moreover, that the superstructure, before
going over, moved laterally upon its temporary supports.
The girders were, in fact, resting upon rollers, and the roller apparatus
themselves were renting upon wedges, and there was no anchorage to prevent
a transverse sliding.
Under the prolonged thrust of a very high wind, the superstructure, by
reason of its considerable projection, must have begun to swing like a
pendulum. These oscillations acquired sufficient amplitude to cause the
superstructure to gradually move upon its rollers until the latter no
longer bore beneath the webs. The flanges therefore finally bent upward
where they rested upon the rollers, through the action of the weight which
they had to support, and the entire superstructure slid off into space.
An examination of the bent pieces seems to give great value to this
hypothesis.--_Le Genie Civil_.
* * * * *
JOY'S REVERSING AND EXPANSION VALVE GEAR.
[Footnote: A paper read before the Mechanical Section of the British
Association, at Montreal, August, 1884.]
Four years ago, in August, 1880, a paper was read on this subject before
the Annual Summer Meeting of the Mechanical Engineers' Society of Great
Britain, then held in Barrow-in-Furness, describing this valve motion and
its functions, which was then comparatively new. It was, however,
illustrated by its application to a large express goods (freight) engine,
built by the London and North-Western Railway Company (England) specially
to test the advantages and the endurance of the gear. This engine had
cylinders of 18 inches in diameter and 24 inch stroke, and six wheels
coupled 5 feet 1 inch diameter, and was designed by Mr. Webb, the
Company's chief engineer, for their heavy fast goods traffic on the main
line. The engine has been running this class of traffic ever since. In
January, 1884, it was passed through the repair shops for a general
overhauling, when it was found that the valve motion was in such good
condition as to be put back on the engine without any repairs.
The main object of this present paper is to deal with the advantages of
the valve gear and its application to various classes of engines both on
land and at sea, and with the results of such applications, rather than
treating it as a novelty, to give an exhaustive description of its
construction and functions, which was done in the paper above referred to.
A very short description of its action and main features will, however,
be necessary to the completeness of the paper, and as a basis from which
the improved results to be recorded should necessarily be shown to spring.
The essential feature of this valve gear is that movement for the valve is
produced by a combination of two motions at right angles to each other;
and by the various proportions in which these are combined, and by the
positions in which the moving parts are set with regard to each other, it
gives both the reversal of motion and the various degrees of expansion
required. Eccentrics are entirely dispensed with and the time-honored link
gear abandoned, the motion is taken direct from the connecting rod, and by
utilizing independently the backward and forward action of the rod, due to
the reciprocation of the piston, and combining this with the vibrating
action of the rod, a movement results which is suitable to work the valves
of engines, allowing the use of any proportions of lap and lead desired,
and giving an almost mathematically correct "cut-off" for both sides of
the piston and for all points of expansion intermediately, as well as a
much quicker action at the points of "cut-off" and "release" than is given
by a link gear.
The machinery for accomplishing this is both less costly and less
complicated than the ordinary link motion, and is shown in elevation on
cut, which is a view of the complete motion as on the first London and
North-Western locomotive. Here E is the main valve lever, pinned at D to a
link, B, one end of which is fastened to the connecting rod at A, and the
other end maintained in about the vertical by the radius rod, C, which is
fixed at the point, C. The center or fulcrum, F, of the lever, E,
partaking of the vibrating movement of the connecting rod at the point, A,
is carried in a curved slide, J, the radius of which is equal to the
length of the link, G, and the center of which is fixed to be concentric
with the fulcrum, F, of the lever when the piston is at either extreme end
of its stroke. From the upper end of the lever, E, the motion is carried
direct to the valve by the rod, G. It will be evident thus that by one
revolution of the crank the lower end of the lever, E, will have imparted
to it two different movements, one along the longer axis of the ellipse,
traveled by the point, A, and one through its minor axis up and down,
these movements differing as to time, and corresponding with the part of
the movement of the valve required for lap and lead, and that part
constituting the port opening for admission of steam.
[Illustration: JOY'S REVERSING AND EXPANDING VALVE GEAR.]
The former of these is constant and unalterable, the latter is
controllable by the angle at which the curved slide, J, may be set with
the vertical.
It will further be evident that if the lever, E, were pinned direct to
the connecting rod at the point, A, which passes through a practically
true ellipse, it would vibrate its fulcrum, F, unequally on either side of
the center of the curved slide, J, by the amount of the versed sine of the
arc of the lever, E, from F D; it is to correct this error that the lever,
E, is pinned at the point, D, to a parallel motion formed by the parts, B
and C. The point, D, performing a figure which is equal to an ellipse,
with the error to be eliminated added, so neutralizing its effect on the
motion of the fulcrum, F.
The "lap" and "lead" are opened by the action of the valve lever acting as
a lever, and the port opening is given by the incline of the curved slide
in which the center of that lever slides, and the amount of this opening
depends upon the angle given to that incline. When these two actions are
in unison, the motion of the valve is very rapid, and this occurs when the
steam is being admitted. Then follows a period of opposition of these
motions, during which time the valve pauses momentarily, this
corresponding to the time when the port is fully open. Further periods of
unison follow, at which time the sharp "cut-off" is obtained.
The "compression" resulting with this gear is also reduced to a minimum,
owing to the peculiar movement given to the valves (_i. e._, the series of
accelerations and retardations referred to), as, while the "lead" is
obtained later and quicker, the port is also shut for "compression" later
and quicker, doing away with the necessity for a special expansion valve,
with its complicated and expensive machinery, and allowing the main valve
to be used for expansion, as the "compression" is not of an injurious
amount, even with a "cut-off" reduced to 15 per cent., or about 1/6 of the
stroke.
Thus, so far as the distribution of the steam and its treatment in the
cylinder is concerned, a marked advantage is shown in favor of this valve
gear. But next in its favor, as before said, is that the above advantages
are not gained at the cost of added complication of parts or increased
cost of machinery, but the reverse, as this gear can be built at a less
cost than link gear, varying according to the circumstances, but reaching
as high as a saving of 25 per cent., or, if it be compared with a link
gear supplemented by the usual special expansion valve and gear as
employed on marine engines, then the total saving is fully 50 per cent.,
and an equally good result is obtained as to the distribution and
subsequent treatment of the steam.
After accuracy of result and reduction in cost may rank saving room and
the advantages arising therefrom (though for steamships perhaps this
should have come first). Taking locomotives of the inside cylinder type,
which is the general form in use in England and the continent of Europe,
by clearing away the eccentrics and valves from the middle of the engine,
much larger cylinders may be introduced and a higher rate of expansion
employed, and this is being done. Also room is left for increasing the
length and wearing surfaces of all the main bearings with even less
crowding than is now the case with engines with the smaller cylinders.
But this advantage of saving room comes much more prominently forward in
marine engines, especially in war ships, where every inch of room saved is
valuable; and in the new type of triple-cylinder engines now coming so
much into vogue in the mercantile marine, whether those engines be only
the ordinary three-cylinder engines with double expansion, or the newer,
triple expansion engine, expanding the steam consecutively through three
cylinders--the form of marine engine which promises to come into use
wherever high-class work and economy are required. On this system, by
placing all the valve chests in front of the cylinders instead of between
them, or in a line with them, sufficient room is saved to get the new-type
three-cylinder engine into the space occupied by the old form of
two-cylinder engine.
Besides these prominent advantages there are others which, though of minor
importance, are still necessary to the practical and permanent success of
any new mechanical arrangement, such as the accessibility of all the
working parts while in motion, for examination and oiling; the ease with
which any part or the whole can be stripped and cleaned, or pinned up out
of the way in case of break down or accident, or got at and dismantled for
ordinary repair; the ease with which the whole may be handled, started,
reversed, or set at any point of expansion--all these being
recommendations to enlist the care and attention of the engineers in
charge by lightening their duties and rendering the engines easy to work.
With those advantages it is perhaps not surprising that this valve gear
has been very considerably adopted for many classes of steam engines,
especially where a high result has been required, with economy of space,
and a minimum of complication.
Having crucially tested the original engine on the London and
North-Western Railway, Mr. Webb proceeded to build others similar, and on
his bringing out his Compound Express Engine--notably the most advanced
step in locomotive design of the present day--he adopted this valve gear
throughout. There are now a number of these engines running some of the
fastest trains on the London and North-Western Railway, with the most
satisfactory results.
Following these, others of the leading railways took up the system, and
prominently among these Mr. Worsdell, of the Great Eastern Railway, built
a number of large express engines for his fast and heavy traffic, and is
now building a number of others similar as to the valve gear for his
suburban traffic, which is specially heavy. Also the Lancashire and
Yorkshire and the Midland and others of the chief railways are employing
the system specially for large express engines; the Midland engines having
cylinders of 19 inches diameter by 26 inches stroke, and four coupled
wheels of 7 feet diameter. A number of the above-named engines have run
large mileages, in many cases already exceeding 100,000 miles per engine.
For other countries also a number of locomotive engines have been built or
contracted for--both of inside and outside cylinder types--making a total
of nearly 800 locomotives built and building, many of them being of
special design and large size, up to 20 inches and 21 inches diameter of
cylinder.
In all these the absence of wire-drawing may be specially noted by the
full line at the top of the diagram, showing the admission of steam--this
fullness arising from the rapid and full opening of the port for
admission.
Passing now to the other great type of engines, those covered under the
general designation of marine engines, this gear has been applied to
nearly 40,000 H.P. indicated, built and building, and to all classes and
sizes, from the launch engine with cylinders 8 inches by 9 inches, running
at 600 to 700 revolutions per minute, up to engines for the largest class
of war ships, such as her Britannic Majesty's steel cruiser Amphion, of
5,000 H.P., with cylinders in duplicate of 46 inches and 86 inches
diameter, and 3 feet 3 inches stroke, running 100 revolutions per minute.
An examination of the indicator diagrams taken from these engines shows
that no wire-drawing takes place, and that, though the expansion is
carried to a point beyond the ordinary requirements, the compression is
but slightly increased. In all the diagrams taken from this valve motion
there is seen the clear, full upper line showing an abundant admission of
steam without any wire-drawing, and also the distinctly marked points
where "cut-off" or "suppression" and where "release" takes place, showing
the rapid action of the valves at those points.
It is well known to engineers that to obtain the maximum advantage out of
compounding, it is necessary to cut off in the low pressure cylinder at a
point corresponding to the relation between the low and the high, and that
point should be unaltered, whereas the point of cut-off in the high may at
the same time be varied to suit the work to be done.
In an ordinary link motion engine (where both links are connected to the
same weigh shaft), when linking up the high pressure cylinder to cut-off
short, the same change is necessarily made in the low. By the use of the
Joy gear, cut-off valves may be fitted to both cylinders, that for the low
pressure being fixed at the constant position required by the proportion
of the cylinders, while that on the high is adjustable; of course, in this
case, the position of the quadrants must be only changed for reversing. In
arranging the independent cut-off on the Joy gear, it is only necessary to
increase the length of the vibrating link beyond the point of attachment
for the main valve spindle connection to obtain a point from which motion
may be taken to actuate the cut-off valve; even then the cost of the Joy
gear for both cylinders is but little more than for a single set of link
gear.
This arrangement gives an absolutely perfect distribution of steam for
compounding, also equalizes the power developed by both cylinders, and is
far more simple and inexpensive than any other gear in existence.
* * * * *
THE STEAM BELL.
[Illustration: FIG. 1.]
[Illustration: FIG. 2.]
The secondary railways in rural districts in Austria having no gates or
bars at the level crossings, or guards at such points, but being open like
tramways, special precautions are required to avoid accidents, and the
public has to be warned of the approach of the train from a sufficient
distance. This is done by ringing bells preferably to sounding whistles,
as these are more likely to startle horses. The steam bell shown by our
illustrations has been adopted for this purpose on the Austrian lines, and
is a simple contrivance. It consists of a cylindrical chamber, a, ending
in a narrower tube, c, which forms the seating for a flap valve, d, to
which the hammer or clapper, e, is fixed. Steam is admitted through a
small pipe, b, at the bottom, and after a certain interval attains
sufficient pressure to lift the valve. The opening being large compared
with the pipe, b, steam escapes more rapidly than it arrives through the
small orifice; the pressure falls, and the valve drops down and causes the
hammer to strike a bell surrounding the cylinder. The valve is provided
with an internal collar as shown, so that it has to rise for the width of
this before the steam is let out, and thus determines the swing of the
clapper and the force of the blow. To intensify the latter and multiply
the number of blows, the clapper spring is prolonged over the fulcrum and
bent back so as to form a spring, which is tightened by the lifting of the
flap, and sends the clapper down on the bell with increased force. The
hinge of the flap does not require any lubrication besides what it gets
through the steam. The bell is fixed upon the roof of the driver's cab, so
that the steam does not interfere with his lookout, and fastened by three
bolts or screws. The diameter of the steam-pipe is from 1/4 to 1/2 inch
according to the size of the bell, and the distance of the clapper from
the bell is a little less than the diameter of the corresponding cock. The
steam cock is perforated as shown by the illustration to drain the pipe
when shut, and a small hole, b, in the bell cylinder drains the latter.
The steam-pipe is made with a bend as usual, to allow for contraction and
expansion. The number of blows given varies according to the steam
pressure, and the opening of the steam cock; it is
With 90 lb. pressure, and cock 1/2 open, 170 blows per min.
" " " " 1/3 " 136 "
105 " " " 1/2 " 240 "
" " " " 1/3 " 156 "
" " " " 1/5 " 136 "
120 " " " 1/3 " 228 "
135 " " " 1/5 " 200 "
To start the bell, the cock is opened full, and afterward partly closed.
The blows follow in such rapid succession that a kind of uniform sound
with louder intervals is produced, but not of the same shrill character as
by a steam whistle. The same kind of bell is used on the shunting engines
in goods yards, where roadways have to be crossed on which lurries and
handtrucks circulate, and the results as far as prevention of accidents is
concerned are stated to be very satisfactory.
* * * * *
LIEUT. GREELY BEFORE THE BRITISH ASSOCIATION.
Lieuts. Greely and Ray were received with distinguished honors at the
meeting of the British Association in Montreal. A complimentary luncheon
was tendered him by the members of the British Association for the
Advancement of Science, at the Windsor Hotel. General Sir Henry Lefroy
presided. In response to the toast "Our Distinguished Guests," coupling
the names of Lieuts. Greely and Ray and Mrs. Greely, Lieut. Greely said:
"_Mr. President, Ladies and Gentlemen_: I need scarcely say that this
flattering reception from representative men of one of England's most
distinguished societies touches deeply my feelings as a soldier and as a
man. It is not alone that you represent the science and learning of
England and the world, but that you are all countrymen of those daring
seamen and explorers whose names and whose deeds have become household
words throughout the world. Hudson, Baffin, Cook, Nelson, Parry, Franklin,
and a score of others among the dead; McClintock, Nares, and Markham, and
last, but not least, the man whose name was oftenest on our lips when
praying for relief during the past terrible winter--Bedford Pim. What
those men have done the whole world knows. That you should deem aught that
I have done worthy to placed with the deeds of those illustrious men must
always be a source of pride to me. For three centuries England maintained
against the world the honors of the farthest north. Step by step every
advance was made by Englishmen. Now England's grandest colony presses to
the front; but none the less is the honor England's, for at the price of
her sons' lives and by their toil the path was cleared. But for Beaumont's
dauntless pluck and indomitable energy in 1876, Lockwood would never had
made his great northing in 1882. I have during a quarter of a century's
service, as becomes a soldier, been jealous of my honor. I have striven to
maintain it in the field, fighting and bleeding for my country, and at my
desk studying and discussing scientific data; in the Arctic Circle, when
pursuing scientific and geographical work, or later, when stranded by
adverse fate, and starving and freezing upon the barren coast. This marked
and public testimonial of your approval cannot fail to make me doubly
jealous of it in days to come."
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