The geared engine had not proved a success. It was unsatisfactory, as
well to its designer as to the railroad community. The problem of
utilizing more or all of the weight of the engine for adhesion
remained, in Mr. Baldwin's view, yet to be solved. The plan of
coupling four or six wheels had long before been adopted in England,
but on the short curves prevalent on American railroads, he felt that
something more was necessary. The wheels must not only be coupled, but
at the same time must be free to adapt themselves to a curve. These
two conditions were apparently incompatible, and to reconcile these
inconsistencies was the task which Mr. Baldwin set himself to
accomplish. He undertook it, too, at a time when his business had
fallen off greatly and he was involved in the most serious financial
embarrassments. The problem was constantly before him, and at length,
during a sleepless night, its solution flashed across his mind. The
plan so long sought for, and which, subsequently, more than any other
of his improvements or inventions, contributed to the foundation of
his fortune, was his well-known six-wheels-connected locomotive with
the four front drivers combined in a flexible truck. For this machine
Mr. Baldwin secured a patent, August 25, 1842. Its principal
characteristic features are now matters of history, but they deserve
here a brief mention. The engine was on six wheels, all connected as
drivers. The rear wheels were placed rigidly in the frames, usually
behind the fire-box, with inside bearings. The cylinders were
inclined, and with outside connections. The four remaining wheels had
inside journals running in boxes held by two wide and deep
wrought-iron beams, one on each side. These beams were unconnected,
and entirely independent of each other. The pedestals formed in them
were bored out cylindrically, and into them cylindrical boxes, as
patented by him in 1835, were fitted. The engine-frame on each side
was directly over the beam, and a spherical pin, running down from the
frame, bore in a socket in the beam midway between the two axles. It
will thus be seen that each side-beam independently could turn
horizontally or vertically under the spherical pin, and the
cylindrical boxes could also turn in the pedestals. Hence, in passing
a curve, the middle pair of drivers could move laterally in one
direction--say to the right--while the front pair could move in the
opposite direction, or to the left; the two axles all the while
remaining parallel to each other and to the rear driving-axle. The
operation of these beams was, therefore, like that of the
parallel-ruler. On a straight line the two beams and the two axles
formed a rectangle; on curves, a parallelogram, the angles varying
with the degree of curvature. The coupling-rods were made with
cylindrical brasses, thus forming ball-and-socket joints, to enable
them to accommodate themselves to the lateral movements of the wheels.
Colburn, in his "Locomotive Engineering," remarks of this arrangement
of rods as follows:
"Geometrically, no doubt, this combination of wheels could only
work properly around curves by a lengthening and shortening of
the rods which served to couple the principal pair of
driving-wheels with the hind truck-wheels. But if the
coupling-rods from the principal pair of driving-wheels be five
feet long, and if the beams of the truck-frame be four feet long
(the radius of curve described by the axle-boxes around the
spherical side bearings being two feet), then the total
corresponding lengthening of the coupling-rods, in order to allow
the hind truck-wheels to move one inch to one side, and the front
wheels of the truck one inch to the other side of their normal
position on a straight line, would be V[60^{2} + 1^{2}] - 60 + 24
- V[24^{2} - 1^{2}] = 0.0275 inch, or less than one thirty-second
of an inch. And if only one pair of driving-wheels were thus
coupled with a four-wheeled truck, the total wheel-base being
nine feet, the motion permitted by this slight elongation of the
coupling-rods (an elongation provided for by a trifling slackness
in the brasses) would enable three pairs of wheels to stand
without binding in a curve of only one hundred feet radius."
The first engine of the new plan was finished early in December, 1842,
being one of fourteen engines constructed in that year, and was sent
to the Georgia Railroad, on the order of Mr. J. Edgar Thomson, then
Chief Engineer and Superintendent of that line. It weighed twelve
tons, and drew, besides its own weight, two hundred and fifty tons up
a grade of thirty-six feet to the mile.
Other orders soon followed. The new machine was received generally
with great favor. The loads hauled by it exceeded anything so far
known in American railroad practice, and sagacious managers hailed it
as a means of largely reducing operating expenses. On the Central
Railroad of Georgia, one of these twelve-ton engines drew nineteen
eight-wheeled cars, with seven hundred and fifty bales of cotton, each
bale weighing four hundred and fifty pounds, over maximum grades of
thirty feet per mile, and the manager of the road declared that it
could readily take one thousand bales. On the Philadelphia and Reading
Railroad a similar engine of eighteen tons weight drew one hundred and
fifty loaded cars (total weight of cars and lading, one thousand one
hundred and thirty tons) from Schuylkill Haven to Philadelphia, at a
speed of seven miles per hour. The regular load was one hundred loaded
cars, which were hauled at a speed of from twelve to fifteen miles per
hour on a level.
The following extract from a letter, dated August 10, 1844, of Mr. G.
A. Nicolls, then Superintendent of that line, and still connected with
its management, gives the particulars of the performance of these
machines, and shows the estimation in which they were held:
"We have had two of these engines in operation for about four
weeks. Each engine weighs about forty thousand pounds with water
and fuel, equally distributed on six wheels, all of which are
coupled, thus gaining the whole adhesion of the engine's weight.
Their cylinders are fifteen by eighteen inches."
"The daily allotted load of each of these engines is one hundred
coal cars, each loaded with three and six-tenths tons of coal,
and weighing two and fifteen one-hundredths tons each, empty;
making a net weight of three hundred and sixty tons of coal
carried, and a gross weight of train of five hundred and
seventy-five tons, all of two thousand two hundred and forty
pounds."
"This train is hauled over the ninety-four miles of the road,
half of which is level, at the rate of twelve miles per hour; and
with it the engine is able to make fourteen to fifteen miles per
hour on a level."
"Were all the cars on the road of sufficient strength, and making
the trip by daylight, nearly one-half being now performed at
night, I have no doubt of these engines being quite equal to a
load of eight hundred tons gross, as their average daily
performance on any of the levels of our road, some of which are
eight miles long."
"In strength of make, quality of workmanship, finish, and
proportion of parts, I consider them equal to any, and superior
to most, freight engines I have seen. They are remarkably easy on
the rail, either in their vertical or horizontal action, from the
equalization of their weight, and the improved truck under the
forward part of the engine. This latter adapts itself to all the
curves of the road, including some of seven hundred and sixteen
feet radius in the main track, and moves with great ease around
our turning Y curves at Richmond, of about three hundred feet
radius.
"I consider these engines as near perfection, in the arrangement
of their parts, and their general efficiency, as the present
improvements in machinery and the locomotive engine will admit
of. They are saving us thirty per cent, in every trip, on the
former cost of motive or engine power."
But the flexible-beam truck also enabled Mr. Baldwin to meet the
demand for an engine with four drivers connected. Other builders were
making engines with four drivers and a four-wheeled truck, of the
present American standard type. To compete with this design, Mr.
Baldwin modified his six-wheels-connected engine by connecting only
two out of the three pairs of wheels as drivers, making the forward
wheels of smaller diameter as leading wheels, but combining them with
the front drivers in a flexible-beam truck. The first engine on this
plan was sent to the Erie and Kalamazoo Railroad, in October, 1843,
and gave great satisfaction. The Superintendent of the road was
enthusiastic in its praise, and wrote to Mr. Baldwin that he doubted
"if anything could be got up which would answer the business of the
road so well." One was also sent to the Utica and Schenectady Railroad
a few weeks later, of which the Superintendent remarked that "it
worked beautifully, and there were not wagons enough to give it a full
load." In this plan the leading wheels were usually made thirty-six
and the drivers fifty-four inches in diameter.
This machine of course came in competition with the eight-wheeled
engine having four drivers, and Mr. Baldwin claimed for his plan a
decided superiority. In each case about two-thirds of the total weight
was carried on the four drivers, and Mr. Baldwin maintained that his
engine, having only six instead of eight wheels, was simpler and more
effective.
At about this period Mr. Baldwin's attention was called by Mr. Levi
Bissell to an "Air Spring" which the latter had devised, and which it
was imagined was destined to be a cheap, effective, and perpetual
spring. The device consisted of a small cylinder placed above the
frame over the axle-box, and having a piston fitted air-tight into it.
The piston-rod was to bear on the axle-box, and the proper quantity of
air was to be pumped into the cylinder above the piston, and the
cylinder then hermetically closed. The piston had a leather packing
which was to be kept moist by some fluid (molasses was proposed)
previously introduced into the cylinder. Mr. Baldwin at first proposed
to equalize the weight between two pairs of drivers by connecting two
air-springs on each side by a pipe, the use of an equalizing beam
being covered by Messrs. Eastwick & Harrison's patent. The air-springs
were found, however, not to work practically, and were never applied.
It may be added that a model of an equalizing air-spring was exhibited
by Mr. Joseph Harrison, Jr., at the Franklin Institute, in 1838 or
1839.
With the introduction of the new machine, business began at once to
revive, and the tide of prosperity turned once more in Mr. Baldwin's
favor. Twelve engines were constructed in 1843, all but four of them
of the new pattern; twenty-two engines in 1844, all of the new
pattern; and twenty-seven in 1845. Three of this number were of the
old type, with one pair of drivers, but from that time forward the old
pattern with the single pair of drivers disappeared from the practice
of the establishment, save occasionally for exceptional purposes.
In 1842, the partnership with Mr. Vail was dissolved, and Mr. Asa
Whitney, who had been Superintendent of the Mohawk and Hudson
Railroad, became a partner with Mr. Baldwin, and the firm continued as
Baldwin & Whitney until 1846, when the latter withdrew to engage in
the manufacture of car-wheels, in which business he is still concerned
as senior member of the firm of A. Whitney & Sons, Philadelphia.
Mr. Whitney brought to the firm a railroad experience and thorough
business talent. He introduced a system in many details of the
management of the business, which Mr. Baldwin, whose mind was devoted
more exclusively to mechanical subjects, had failed to establish or
wholly ignored. The method at present in use in the establishment, of
giving to each class of locomotives a distinctive designation,
composed of a number and a letter, originated very shortly after Mr.
Whitney's connection with the business. For the purpose of
representing the different designs, sheets with engravings of
locomotives were employed. The sheet showing the engine with one pair
of drivers was marked B; that with two pairs, C; that with three, D;
and that with four, E. Taking its rise from this circumstance, it
became customary to designate as B engines those with one pair of
drivers; as C engines, those with two pairs; as D engines, those with
three pairs; and as E engines, those with four pairs. Shortly
afterwards, a number, indicating the weight in gross tons, was added.
Thus, the 12 D engine was one with three pairs of drivers, and
weighing twelve tons; the 12 C, an engine of same weight, but with
only four wheels connected. Substantially this system of designating
the several sizes and plans has been retained to the present time. The
figures, however, are no longer used to express the weight, but merely
to designate the class.
It will be observed that the classification as thus established began
with the B engines. The letter A was reserved for an engine intended
to run at very high speeds, and so designed that the driving-wheels
should make two revolutions for each reciprocation of the pistons.
This was to be accomplished by means of gearing. The general plan of
the engine was determined in Mr. Baldwin's mind, but was never carried
into execution.
The adoption of the plan of six-wheels-connected engines opened the
way at once to increasing their size. The weight being almost evenly
distributed on six points, heavier machines were admissible, the
weight on any one pair of drivers being little, if any, greater than
had been the practice with the old plan of engine having a single pair
of drivers; Hence engines of eighteen and twenty tons weight were
shortly introduced, and in 1844 three of twenty tons weight, with
cylinders sixteen and one-half inches diameter by eighteen inches
stroke, were constructed for the Western Railroad of Massachusetts,
and six, of eighteen tons weight, with cylinders fifteen by eighteen,
and drivers forty-six inches in diameter, were built for the
Philadelphia and Reading Railroad. It should be noted that three of
these latter engines had iron flues. This was the first instance in
which Mr. Baldwin had employed tubes of this material. The advantage
found to result from the use of iron tubes, apart from their less
cost, was that the tubes and boiler-shell, being of the same material,
expanded and contracted alike, while in the case of copper tubes the
expansion of the metal by heat varied from that of the boiler-shell,
and as a consequence there was greater liability to leakage at the
joints with the tube-sheets. The opinion prevailed largely at that
time that some advantage resulted in the evaporation of water, owing
to the superiority of copper as a conductor of heat. To determine this
question, an experiment was tried with two of the six engines referred
to above, one of which, the "Ontario," had copper flues, and another,
the "New England," iron flues. In other respects they were precisely
alike. The two engines were run from Richmond to Mount Carbon, August
27, 1844, each drawing a train of one hundred and one empty cars, and,
returning, from Mount Carbon to Richmond, on the following day, each
with one hundred loaded cars. The quantity of water evaporated and
wood consumed was noted, with the result shown in the following table:
------------------------------------------------------------------------
| UP TRIP, | DOWN TRIP, |
| AUG. 27, 1844. | AUG. 28, 1844. |
----------------------------+---------------------+----------+----------|
|"Ontario."| "New |"Ontario."| "New |
| | England."| | England."|
| (Copper | (Iron | (Copper | (Iron |
| Flues.) | Flues.) | Flues.) | Flues.) |
----------------------------+----------+----------+----------+----------|
Time, running | 9h. 7m. | 7h. 41m.| 10h. 44m.| 8h. 19m.|
" standing at stations. | 4h. 2m. | 3h. 7m.| 2h. 12m.| 3h. 8m.|
Cords of wood burned | 6.68 | 5.50 | 6.94 | 6. |
Cubic feet of water | | | | |
evaporated | 925.75 | 757.26 | 837.46 | 656.39 |
Ratio, cubic feet of water | | | | |
to a cord of wood | 138.57 | 137.68 | 120.67 | 109.39 |
------------------------------------------------------------------------
The conditions of the experiments not being absolutely the same in
each case, the results could not of course be accepted as entirely
accurate. They seemed to show, however, no considerable difference in
the evaporative efficacy of copper and iron tubes.
The period under consideration was marked also by the introduction of
the French & Baird stack, which proved at once to be one of the most
successful spark-arresters thus far employed, and which was for years
used almost exclusively wherever, as on the cotton-carrying railroads
of the South, a thoroughly effective spark-arrester was required. This
stack was introduced by Mr. Baird, then a foreman in the Works, who
purchased the patent-right of what had been known as the Grimes stack,
and combined with it some of the features of the stack made by Mr.
Richard French, then Master Mechanic of the Germantown Railroad,
together with certain improvements of his own. The cone over the
straight inside pipe was made with volute flanges on its under side,
which gave a rotary motion to the sparks. Around the cone was a casing
about six inches smaller in diameter than the outside stack. Apertures
were cut in the sides of this casing, through which the sparks in
their rotary motion were discharged and thus fell to the bottom of
the space between the straight inside pipe and the outside stack. The
opening in the top of the stack was fitted with a series of V-shaped
iron circles perforated with numerous holes, thus presenting an
enlarged area, through which the smoke escaped. The patent-right for
this stack was subsequently sold to Messrs. Radley & Hunter, and its
essential principle is still used in the Radley & Hunter stack as at
present made.
In 1845, Mr. Baldwin built three locomotives for the Royal Railroad
Committee of Wuertemberg. They were of fifteen tons weight, on six
wheels, four of them being sixty inches in diameter and coupled. The
front drivers were combined by the flexible beams into a truck with
the smaller leading wheels. The cylinders were inclined and outside,
and the connecting-rods took hold of a half-crank axle back of the
fire-box. It was specified that these engines should have the
link-motion which had shortly before been introduced in England by the
Stephensons. Mr. Baldwin accordingly applied a link of a peculiar
character to suit his own ideas of the device. The link was made
solid, and of a truncated V-section, and the block was grooved so as
to fit and slide on the outside of the link.
During the year 1845 another important feature in locomotive
construction--the cut-off valve--was added to Mr. Baldwin's practice.
Up to that time the valve-motion had been the two eccentrics, with the
single flat hook for each cylinder. Since 1841 Mr. Baldwin had
contemplated the addition of some device allowing the steam to be used
expansively, and he now added the "half-stroke cut-off." In this
device the steam-chest was separated by a horizontal plate into an
upper and a lower compartment. In the upper compartment, a valve,
worked by a separate eccentric, and having a single opening, admitted
steam through a port in this plate to the lower steam-chamber. The
valve-rod of the upper valve terminated in a notch or hook, which
engaged with the upper arm of its rock-shaft. When thus working, it
acted as a cut-off at a fixed part of the stroke, determined by the
setting of the eccentric. This was usually at half the stroke. When it
was desired to dispense with the cut-off and work steam for the full
stroke, the hook of the valve-rod was lifted from the pin on the upper
arm of the rock-shaft by a lever worked from the footboard, and the
valve-rod was held in a notched rest fastened to the side of the
boiler. This left the opening through the upper valve and the port in
the partition plate open for the free passage of steam throughout the
whole stroke. The first application of the half-stroke cut-off was
made on the engine "Champlain" (20 D), built for the Philadelphia and
Reading Railroad Company, in 1845. It at once became the practice to
apply the cut-off on all passenger engines, while the six- and
eight-wheels-connected freight engines were, with a few exceptions,
built for a time longer with the single valve admitting steam for the
full stroke.
After building, during the years 1843, 1844, and 1845, ten
four-wheels-connected engines on the plan above described, viz., six
wheels in all, the leading wheels and the front drivers being combined
into a truck by the flexible beams, Mr. Baldwin finally adopted the
present design of four drivers and a four-wheeled truck. Some of his
customers who were favorable to the latter plan had ordered such
machines of other builders, and Colonel Gadsden, President of the
South Carolina Railroad Company, called on him in 1845 to build for
that line some passenger engines of this pattern. He accordingly
bought the patent-right for this plan of engine of Mr. H. R. Campbell,
and for the equalizing beams used between the drivers, of Messrs.
Eastwick & Harrison, and delivered to the South Carolina Railroad
Company, in December, 1845, his first eight-wheeled engine with four
drivers and a four-wheeled truck. This machine had cylinders thirteen
and three-quarters by eighteen, and drivers sixty inches in diameter,
with the springs between them arranged as equalizers. Its weight was
fifteen tons. It had the half-crank axle, the cylinders being inside
the frame but outside the smoke-box. The inside-connected engine,
counterweighting being as yet unknown, was admitted to be steadier in
running, and hence more suitable for passenger service. With the
completion of the first eight-wheeled "C" engine, Mr. Baldwin's
feelings underwent a revulsion in favor of this plan, and his
partiality for it became as great as had been his antipathy before.
Commenting on the machine, he recorded himself as "more pleased with
its appearance and action than any engine he had turned out." In
addition to the three engines of this description for the South
Carolina Railroad Company, a duplicate was sent to the Camden and
Amboy Railroad Company, and a similar but lighter one to the
Wilmington and Baltimore Railroad Company, shortly afterwards. The
engine for the Camden and Amboy Railroad Company, and perhaps the
others, had the half-stroke cut-off.
From that time forward, all of his four-wheels-connected machines were
built on this plan, and the six-wheeled "C" engine was abandoned,
except in the case of one built for the Philadelphia, Germantown and
Norristown Railroad Company in 1846, and this was afterwards rebuilt
into a six-wheels-connected machine. Three methods of carrying out the
general design were, however, subsequently followed. At first the
half-crank was used; then horizontal cylinders inclosed in the
chimney-seat and working a full-crank-axle, which form of construction
had been practiced at the Lowell Works; and eventually, outside
cylinders with outside connections.
[Illustration: Fig. 8.--BALDWIN EIGHT-WHEELS-CONNECTED ENGINE, 1846.]