Burlington, New Jersey
We thought you folks would be interested in this experimental
locomotive and for that reason we give it a prominent place and
much detail. Editor
Locomotive 60,000, the subject of the present publication, was
designed and built by the Baldwin Locomotive Works as an experiment
steam and high ratios of expansion. Opportunity was also taken to
try out certain novel details of construction.
Through the courtesy of the Pennsylvania Railroad the locomotive
was submitted to an extensive program of tests on their locomotive
test plant at Altoona (Pa.), and it was subsequently given road
tests on this line and on a number of other prominent
railroads.
DESIGN AND CONSTRUCTION
The locomotive forming the subject of this bulletin is the
60,000th locomotive built by The Baldwin Locomotive Works. It was
built during the early part of the year 1926 as an experiment to
ascertain the possible economies which can be effected by the use
of high steam pressures and a high ratio of expansion.
Up to a certain period, development of locomotive design brought
with it mainly an increase in, weight of individual locomotives,
the increase in power being proportionate to the increase in
weight. This increase in power made possible notable economies in
railroading. Of late years, however, the demand for still further
economies has led locomotive) designers to strive to increase the
efficiency of the locomotive, and thus give increased power per
unit of locomotive weight. Among the means adopted successfully to
this end, are the use of superheated steam, various fuel and
labor-saving devices, improved boiler design, more efficient steam
distribution, and refinements in design and materials for
locomotive parts.
At present much thought is being given to the possibility of
using higher steam pressures and higher ratios of expansion to give
greater cylinder efficiency and consequently greater horse-power
per unit of weight.
The great advantage of high pressure steam is that a combination
of adequate cylinder force and a high ratio of expansion can be
obtained with cylinder of moderate dimensions.
GENERAL DIMENSIONS | ||||||||
CYLINDERS | Boiler Tubes | DRIVING WHEELS | WEIGHT | |||||
High-pressure (1), inside | 27′ x 32′ | Diameter | 5?’ | 2?’ | Diameter, outside | 63?’ | in working order | |
Low-pressure (2), outside | 27′ x 32′ | Number | 50 | 206 | ‘ center | 56′ | On driving wheels | 338,400 lb. |
Valves | Piston, 14′ dia. | Length | 23’0′ | 23’0′ | Journals, main | 12′ x 13′ | ‘ truck, front | 57,500 lb. |
‘ others | 11′ x 13′ | ‘ back | 61,600 lb. | |||||
Total engine | 457,500 lb. | |||||||
‘ ‘ and tender | 700,900 lb. | |||||||
BOILER | ENGINE TRUCK WHEELS | |||
Type | Wagon top | |||
Diameter | 84′ | Diameter, front | 33′ | |
Working pressure | 350 lb. | Journals | 7′ x 12′ | |
Fuel | Soft coal | Diameter, back | 45?’ | |
Firebox | Heating Surface | Journals | 9′ x 14′ | TENDER | |||
Type | Water-tube | Firebox | 745 sq. ft. | Wheels, number | Twelve | ||
Length, total | 1991/2′ | 51/2′ flues | 1645 sq. ft. | ‘ diameter | 33′ | ||
Width | 96′ | 21/4 tubes | 2775 sq. ft. | WHEEL BASE | Journals | 6’x 11′ | |
Length of grate | 1381/4′ | Firebrick tubes | 27 sq. ft. | Driving | 22′ 10′ | Tank capacity | 12,000 U. S. gal. |
Width | 86′ | Total | 5192 sq. ft. | Rigid | 16′ 9′ | Fuel | 16 tons |
Water-tubes, number | 100 | Super heater | 1357 sq. ft. | Total engine | 45′ 2′ | ||
Diameter | 4′ | Grate area | 82.5 sq. ft. | Total engine and tender | 86′ 11?’ | Tractive force | 82,500 lb. |
The figures here given are based on the outside diameters of the | |||||||
In view of the limits set to steam temperatures by the method of
producing the steam and by difficulties of lubrication, locomotive
designers must, at least for the present, aim at a steam
temperature of approximately 650 degrees F., with a maximum of say
700 degrees, irrespective of the pressure used. Now, if the
pressure is increased while the temperature remains constant, the
superheat and the heat content per pound of steam fall off as the
pressure is increased. For example, a steam temperature of 650
degrees F. gives, at 200 pounds per square inch, about 263 degrees
superheat and 1340 B.T.U. per pound of steam, and at 350 pounds per
square inch about 217 degrees superheat and 1332 B.T.U.
If steam of 200 pounds per square inch and of 350 pounds per
square inch is expanded from the same temperature under such
conditions in each case respectively that the exhaust steam escapes
at the same pressure and temperature, and with the same heat
content in both cases, it follows that the heat taken from the
steam in the cylinders and converted into mechanical work will be
slightly less with the high than with the low pressure steam. That
is, with the same heat content in the exhaust steam, the higher
pressure will not give greater thermal efficiency. To reduce the
heat content of the exhaust steam and thus increase the thermal
efficiency, it is necessary to increase the ratio of expansion.
An increase in the ratio of expansion results in a reduction in
the mean effective pressure obtained from a given boiler pressure,
and this requires an increase in cylinder dimensions if the same
power is to be developed. Now in a large modern locomotive of
conventional design, an increase in cylinder dimensions to permit
of higher expansion would lead to difficulties in design, and it is
advantageous to use a higher boiler pressure so that the increase
in expansion can be obtained without involving a loss in power or
an abnormal increase in cylinder dimensions.
As a means of obtaining the higher expansion necessary to give
economy with steam of 350 pounds per square inch, Locomotive 60,000
was designed with three cylinders compounded, the high-pressure
steam being first admitted to the middle cylinder. After expansion
there, the steam passes through the receiver in the cylinder saddle
to the two outside cylinders where further expansion takes
place.
Steam pressure of 200 to 215 pounds per square inch have been
currently used for a number of years, and in the last two or three
years a considerable number of locomotives have been built for
working steam pressures of 240 and 250 pounds per square inch. This
latter is probably about the maximum pressure which can be carried
successfully in boilers of conventional design with fireboxes
having flat sides braced by staybolts. The stayed firebox is the
weakest point in a locomotive as ordinarily designed, and with
pressures carried above 250 pounds per square inch a change in
design is necessary to eliminate excessive trouble with staybolt
breakage. The decision to use a pressure of 350 pounds per square
inch in Locomotive 60,000 led to the adoption of a water tube
firebox, and the elimination of all staybolts.
GENERAL DESCRIPTION
The locomotive is of the 4-10-2 type, built for freight service,
with driving wheels 63 inches in diameter, and three cylinders each
27 inches in diameter by 32 inch stroke. The total weight in
working order is 457,500 pounds, of which 338,400 are on driving
wheels. Full detailed dimensions are given on page 6. (Ed. note.
The dimensions are found under one of the accompanying
pictures).
Apart from the modifications necessary to the use of the water
tube firebox and the high pressure, the boiler does not differ in
principle from that of the conventional locomotive. The boiler
barrel is of the usual fire tube type having 206 2-inch tubes and a
type A super heater carried 50 5-inch flues.
The barrel consists of three courses, having plates respectively
1 and five-sixteenths, 1 and three-eighths and 1 inches thick. The
third course is sloped on top, increasing the shell diameter from
84 inches at the front end to 94 inches at the back. All
circumferential seams are double riveted, and the longitudinal
seams are of the so-called ‘saw-tooth.’ octuple riveted
design, which provides a short caulking distance between rivets. At
the rear, the barrel is closed by a tube sheet, which is riveted to
the shell in the same manner as the front tube sheet. The boiler
tubes and flues are welded into the rear tube sheet.
None of the studs tapped into the boiler passes all the way
through the sheets, hence there can be no leaky studs or stays.
The firebox is of the water-tube type, each side wall consisting
of 48 tubes 4 inches in diameter connecting a hollow cast steel
mud-ring at the bottom to one of the horizontal cylindrical drums
at the top. Outside of these side tubes a firebrick shell is built,
over which are applied removable cover plates which are covered
with magnesia sectional lagging and jacketed. The front and back
walls of the firebox are of firebrick, and the opening between the
two drums forming the crown of the firebox is also closed with
firebrick.
This construction provides a boiler entirely free from staybolts
and from flat surfaces requiring staybolts. This feature of the
design gives it an important advantage when high steam pressures
are to be carried.
The depth of the firebox from the top of the mud-ring to the
center line of the drums is 6 feet 6 inches. The total volume,
including combustion chamber, reaches the large figure of 683 cubic
feet. This gives 8.3 cubic feet of volume for each of the 82.5
square feet of grate area, which is a high relative volume for a
modern locomotive, and aids in securing effective and efficient
combustion.
The two drums are each 26 inches in diameter, and the transverse
distance between their centers is 31 inches. They have a total
length of 23 feet 6 inches, and extend into the boiler barrel a
distance of 5 feet 6 inches ahead of the back tube sheet. The
openings in this sheet, through which the drums pass, have flanges
65/8 inches in depth, to which the drums are double riveted. Each
drum is closed, at the rear, by a cover plate which is secured to
an internal ring by means of studs, and is fitted with a copper
gasket to keep the joint tight. By removing these covers the drums
can be entered for purposes of inspection, and the water tubes can
be ‘turbined’ during washing-out, to remove any scale. This
can be done without removing any of the lower plugs, one of which
is placed in the mud-ring opposite each tube end for rolling the
tubes.
Evidence obtained in road tests with different kinds of water
shows very light accumulation of scale in the drums and
water-tubes. This indicates that less frequent turbining and
cleaning are necessary than with conventional type of stayed
firebox.
The third course in the boiler barrel is sloped on top, and the
two upper drums are so located that their forward extensions come
in contact with this course and are riveted to it. This acts as a
support for the drums, and tend to counteract the cantilever effect
of the long overhanging firebox. Furthermore, to balance the effect
of the pressure on the covers at the back ends of the drums, three
longitudinal stay rods are run from the forward end of each drum to
the front tube sheet. These rods are anchored to internal braces
which are riveted to the drum. This construction, together with a
system of braces connecting the front end of the mud-ring and the
boiler barrel, relieves the back tube sheet of any tendency to
distortion, due to the firebox overhang and the pressure on the
drums heads.
The hollow cast steel mud-ring is connected to each upper drum
by 48 tubes each 4 inches in diameter; and there are also four
tubes connecting the drums to the back section of the mud-ring. All
these tubes are swedged to a diameter of 3 inches at the mud-ring
end, where they are rolled and belled, while at the drum end they
are rolled, belled and welded. The tube holes in the mud-ring have
two depressions rolled into them, into which the tubes lock
themselves firmly when being rolled in. Water connection between
the bottom of the boiler barrel and the front end of the mud-ring
is made by two elbow pipes, each 9 inches in diameter, and placed
right and left.
The mud-ring, which has a total length of 18 feet 2 inches and a
width of 8 feet 5 inches, is cored throughout to permit water
circulation. The rectangular outer frame is crossed by a central
longitudinal member and also a transverse member located about six
feet back of the front end of the firebox. From this transverse
member, which lies at the front end of the grate, five water tubes
extend to the upper drums, and serve as supports for the brick
arch. That portion of the firebox which is forward of the arch
constitutes a combustion chamber and is closed, at the bottom, by a
horizontal steel plate, and floored with firebrick. A Y-shaped
cinder pocket is applied for cleaning this combustion chamber.
The locomotive is at present arranged for burning coal, and is
equipped with a Duplex stoker. It has, however, also been operated
as an oil burner.
The dome is placed on the second barrel course, and is connected
with the super heater header by an internal dry-pipe. A smoke box
throttle of the multiple type is applied, and there is a shut-off
valve for the steam supply in the dome.
The three cylinders, with their steam passages and steam chests,
are formed in a single grey iron casting. The high-pressure steam
chest is placed in the saddle, on the right-hand side, and is
connected with the super heater by a single steam pipe. All the
piston valves are 14 inches in diameter, that for the high-pressure
cylinder being arranged for inside admission, while the valves for
the low-pressure (outside) cylinders are arranged for outside
admission. The high-pressure exhaust is conveyed to the
low-pressure steam chests through passages cored in the cylinder
casting; while the exhaust from the low-pressure cylinders passes
to the smoke box through outside pipes which terminate in a single
exhaust nozzle. A Worthington feed-water heater is applied to this
locomotive, and a branch from each exhaust pipe conveys the steam
to the heater.
For starting purposes, live steam is admitted to the
low-pressure cylinders through a 1-inch pipe leading from a
manually-controlled valve in the cab. This creates a back pressure
or. the high-pressure piston, relieving the same from the full
effect of 350 pounds’ pressure.
The two outside cranks are placed 90 degrees apart, so that
there are four even exhausts per revolution, and the inside crank
is placed at 135 degrees from each outside crank. The high-pressure
piston is connected to the second pair of driving wheels, and the
two low-pressure pistons to the third pair. All three piston heads
are of the built-up type, with spiders of open hearth cast steel.
The main and side rods are of carbon vanadium steel, while the
driving axles, main crank pins and piston rods are of open hearth
steel, heat treated, oil quenched and hollow bored. The crossheads
are of the underhung multiple bearing type, as developed by Mr. J.
T. Wallis, now Assistant Vice President in Charge of Operation of
the Pennsylvania Railroad, and adopted as standard for heavy power
by that road. They work in guides having two inwardly projecting
horizontal ribs on each side.
Walschaerts valve gear is used, with an independent motion for
each cylinder, but all controlled by one type B Ragonnet power
reverse gear. The valve for the left-hand cylinder is operated from
the left-hand main pin and crosshead in the usual way. The
right-hand valve receives its lead from the right-hand crosshead,
but the link for this cylinder is operated through a transverse
shaft, by means of a connection to the left-hand cross-head. The
return crank on the right-hand main pin is set to operate the valve
from the inside cylinder, and this valve is given lead through a
connection with the inside crosshead. The valve motion bearer is a
single steel casting supporting practically the entire valve
gear.
This locomotive, designed to traverse curves of 17 degrees, has
flanged tires on all the wheels. Lateral motion boxes are applied
to the first driving axle. The front truck has a swing bolster
suspended on heart-shaped links, while the rear truck of the Delta
type, and is so designed that a booster can subsequently be applied
if necessary. There is a continuous equalization system on each
side of the locomotive, from the leading drivers to the rear
truck.
The accessories are all operated by superheated steam at a
pressure of 350 pounds, except the feed-water heater and injector,
which use saturated steam at the same pressure.
The tender is carried on two six-wheeled trucks, and is of the
Vanderbilt type with capacity for 12,000 gallons of water and 16
tons of coal.
DISCUSSION OF TESTS
After a few preliminary runs on the road, Locomotive 60,000 was
turned over to the Pennsylvania Railroad to be tested on the
locomotive testing plant at Altoona.
The locomotive test plant is too well known to require detailed
description. On it a locomotive under test is supported on carrying
wheels which are controlled by hydraulic friction brakes so that
the power developed can be absorbed, while the tractive effort is
measured by a dynamometer.
On the test plant it is possible to run a locomotive
continuously for an hour or more with perfect uniformity of speed
and cut-off. At the same time water and coal measurements, and
observations of draft and temperature, can be made with an accuracy
unattainable in road tests.
While all test measurements can be made with much more facility
and accuracy on the test plant, this is particularly true of
indicator diagrams. In. the case of road tests, corrections are
necessary for acceleration due to grades or change of speed, and it
is always possible, by a change in throttle or reverse lever, to
produce a card which does not in any way correspond to the speed at
which the engine is running. On the test plant such irregularities
cannot occur, and the indicator cards are far more reliable than
those obtained in road service.
The tests made by the Pennsylvania Railroad on Locomotive 60,000
covered speeds from 80 to 200 revolutions per minute (15 to 37.5
miles per hour), and cut-offs from 50 to 90 per cent in the
high-pressure, and 20 to 70 per cent in the low-pressure cylinders.
The indicated horse-power developed ranged from 1500 to 4500, at
which figure the capacity of the test plant was reached, otherwise
a higher power could have been developed.
Maximum power was developed at 200 revolutions per minute with a
cutoff of 80 per cent in the high and 50 per cent in the
low-pressure cylinders. With these conditions held constant during
a test run of one hours’ duration, the following results were
obtained
Indicated horse-power | 4515 |
Equivalent evaporation, pounds per hour | 83,769 |
Coal fired, total dry coal, pounds per hour | 11,827 |
Coal fired, dry coal per square foot of grate, pounds per | 143 |
Boiler efficiency, per cent | 51 |
Steam per indicated horsepower hour, pounds | 14.9 |
Dry coal per indicated horsepower hour, pounds | 2.7 |
Draw bar pull, pounds | 35,000 |
During this test the boiler pressure averaged 344 pounds per
square inch, with a temperature of 683 degrees F. or 257 degrees
superheat in the branch pipe. The horse-power and equivalent
evaporation of this test are both higher than have been reached
with any other locomotive on the test plant. They represent
approximately the maximum values likely to be reached by Locomotive
60,000 in regular operation, although as stated elsewhere, they
could have been exceeded if the capacity of the test plant had not
been reached.
On a repeat test with the same cutoff and speed a similar
horse-power was obtained with the same coal rate and a water rate
of 15.4 pounds. This gives an average water rate of 15.15 pounds
per indicated horse-power hour for a working rate of 4500
horse-power indicated.
BOILER PERFORMANCE
The evaporative capacity of the boiler was high and so far as
published records show, is higher than that of any other locomotive
boiler tested at Altoona. This is due to the largo dimensions of
heating surface, grate area and combustion space.
When plotted against the rate of firing per square foot of grate
per hour, the boiler efficiency is well represented by a straight
line ranging from about 67 per cent at 40 pounds or dry coal per
square foot of grate per hour to about 53 per cent at 140 pounds of
dry coal per square foot of grate per hour.
More detailed information on the boiler efficiency is given by
the heat balances and by the determination of the efficiencies of
heat production and heat absorption. The efficiency of heat
absorption is about 82 per cent at all rates of working, while the
efficiency of combustion fall off as the rate of firing
increases.
Comparison of these efficiencies with those obtained from modern
boilers with fireboxes of the conventional type shows little
difference in the overall boiler efficiency. The tests show that
the water-tube firebox has little effect on steam production. Its
purpose is to eliminate the necessity for flat stayed surfaces in a
high-pressure boiler.
The temperature of the steam in the branch pipe ranged from 568
degrees F. at the lowest power to 683 degrees at high power. These
figures compare closely with those usually obtained with other
locomotives. The superheat corresponding to the foregoing figures
varies from 135 to 257 degrees.
ENGINE PERFORMANCE
For all cut-offs between 50/20 (that is 50 per cent in the high
and 20 per cent in the low-pressure cylinders) and 80/50 and at all
speeds from 15 to 30 miles per hour, 80 to 160 revolutions per
minute, the water rate lies between 14.2 and 15.2 pounds per
indicated horse-power hour. Even at full gear with a cut-off 90/70,
the water rate is only 16.3 pounds at 15 miles per hour, and 16.6
pounds at 22.5 miles per hour.
Examination of the information available from published records
shows that the best water rate on record for an American locomotive
ranges from 15.5 to 19 pounds, these figures being obtained with
250 pound:-per square inch boiler pressure. The usual modern
locomotive with a boiler pressure of 200 pounds per square inch and
possible full stroke cut-off will usually be found to have a water
rate ranging from 17 to 27 pounds per indicated horse-power
hour.
It is evident that in Locomotive 60,000 the combination of
high-pressure and high expansion gives a high degree of engine
efficiency.
The ratio of expansion was computed by Heck’s method.
Owing to the high ratio of expansion obtained in the compound
cylinders of Locomotive 60,000, the pressures at the end of
expansion are less than would usually be obtained in single
expansion cylinders using steam of lower initial pressure. This is
a factor in increasing the cylinder efficiency. At the end of
expansion the steam is exhausted and loses pressure without doing
useful work. This represents a loss which can be reduced by a high
ratio of expansion which produces low pressures at the end of
expansion.
The proportion of power developed respectively by the high and
by the low-pressure cylinders, varies with the speed and cut-off.
At 200 revolutions per minute and a cut-off of 80/50 when
developing 4500 horse-power as above, the high-pressure cylinder
delivers 1080 horse-power or 24 per cent of the total, leaving an
average of 38 per cent for each of the low pressure cylinders. That
is, at this speed and cut-off, the high-pressure cylinder does
about one-third less work than each of the low-pressure cylinders.
If the speed of 200 revolutions per minute be maintained and the
cut-off shortened to 60/30 the indicated horsepower drops to 2880,
of which only 145 horse-power or 5 per cent is contributed by the
high-pressure cylinder. This combination of cut-off and speed does
not represent conditions likely to be met in actual service, as the
power developed is only slightly over one-half that of which the
engine is capable.
The cylinders were designed to give equal work up to
approximately 22 miles per hour, after which, as the tests verify,
the inside engine is relieved with increasing speed.
These tests are interesting in showing that a drawbar pull less
than the maximum capacity of Locomotive 60,000, can in many cases
be obtained more economically by throttling that by shortening the
cut-off. This is contrary to the generally accepted practice with
ordinary single expansion locomotives, but for Locomotive 60,000 is
borne out by experience in road tests. In actual service it is
usually better to use the throttle rather than the reverse lever
for minor reductions in tractive effort.
