|Boston & Main 4017|
The key event in the development of the steam locomotive designs which brought North American railroads into 1950 was the introduction, about 1910, of a successful method of delivering high temperature superheated steam to the cylinders. (This was the "Schmidt" superheater, designed by Wilhelm Schmidt, 1859 - 1924. Schmidt was a German, generally associated with the Prussian State Railways, although the initial installation of his definitive superheater was in Belgium in 1901. In North America, the Locomotive Superheater Corporation, generally known as Elesco manufactured his device.)
To illustrate the importance of the superheater, one authority (Bruce)
stated that, for the same amount of fuel burnt, a superheated locomotive
would produce 25 to 30% more power than one of the same specifications
but retaining saturated steam. Although its introduction was not without
problems, the superheater was so vital an appliance that, by 1912, for all
practical purposes, all road locomotives were being built superheated,
and many roads were extensively retrofitting superheaters to existing
|Boston & Main 4021|
In any event, by 1916 the railroads had come to realize that there was a
requirement for speedier freight service. Partially, this was due to the
realization that there were potential cargoes, which might be developed
with better service. Perhaps it was because the opening of the Panama Canal
meant that a ship could leave New York, make stops on the way, and be in
San Francisco in about 21 days, and offer much better rates than could a
railroad, it behooved the roads to try to get their service moving a bit
faster. And, assuredly, after 1918, there was a distinct perception that,
at some point motor freight could be a competitor, at least for high value
|Boston & Albany 1411|
Some years ago in "Trains" there appeared an article in which the author
addressed the question of what was the reason why the Lima designed
H-10 class turned out to be such an outstanding design. The conclusion
reached in the article was that the secret was in the superheating.
The H-10 had 1700 square feet of superheater surface in contrast to the
1163 square feet of the H-7E, and the Lima design incorporated the type
"E" superheater, superior to that equipping the H-7. There were other
changes in basic specifications; the H-10 had slightly larger grate area,
and 28 x 30 cylinders instead of 27 x 30. (Actually, this was not an
improvement) The 'appliances" - booster, feed water heater and the like,
were extraneous to the superheater increase. (All of these developments
are covered brilliantly, and in great detail, by Eric Hirsimaki in his
1986 book, "Lima - the history.") It seems clear that the next step, the
prototype Berkshire was built with some sort of commitment from the New
York Central. The design was basically an enlargement, physically, of the
H-10, in so far as clearances, weights and similar items were involved.
However, there was an odd situation. We have mentioned that, by and large,
the railroads had, after the general introduction of superheating, been
willing to install locomotives best suited for slow freight operation. We
have also seen how the Pennsylvania did not follow this regressive design
policy. The New York Central also, in a different fashion, followed
motive power policies which provided for fast freight service. In 1910,
they purchased the first in a large series of 69 inch drivered Pacifics,
intended for fast freight service. (Other roads, the Erie and Lackawanna
for two, ordered similar freight 4-6-2s). And, in 1916 - 18, the NYC
installed 185 69-inch drivered freight 4-8-2s. (This was an amazing move;
4-8-2s were conceived as heavy, or "Mountain" passenger engines, and were
so regarded by the USRA.) The NYC had an extremely complex system of speed
limits, with all sorts of caveats concerning tonnage, train length, type
of locomotive, the actual tracks on which trains were operating. But,
one absolute rule was this: in either passenger or freight service, no
locomotive which did not have a four wheel leading truck, and drivers
of at least 69 inch diameter, was permitted to run at more than 50 mph.
In freight service, where the speed limit in 1925 was 60mph, this meant
that Limas A1A was going to be assigned to drag freight service, or, as
it worked out, assigned to one of the relatively few parts of the New York
Central system where main line grades were a problem, the Boston & Albany.
|Boston & Albany 1447|
The success of A1A on the B&A, and on its other road tests, lead to a
substantial amount of orders for Lima: in 1926-30 there were 55 units
ordered for the B&A; 49, plus A1A itself, for the Illinois Central; 25 for
the B&M. 25 for the MP. This was a substantial addition to the order book of
what was the smallest of the major locomotive builders in the United States.
Other builders participated; Alco built 5 for the MoPac's Texas subsidiary,
the International Great Northern, and 2 for the Toronto Hamilton & Buffalo,
built by Alco's Canadian manufacturing subsidiary, Montreal Locomotive.
These were identical in basic specifications to the Lima design. Alco also
built 12 similar 2-8-4s for the Chicago & North Western. The AT&SF
ordered 15 2-8-4s from Baldwin, differing not only in the omission of
limited cutoff but in having a more modern cylinder dimension, 27 x 32,
and a more realistic working pressure of 220 psi.
Limited cutoff was a concept, best exemplified by the Pennsylvania's
fleet of 2-10-0s, I-1s and sub classes. These locomotives had valve gear
designed to admit steam to the cylinders during only 50% of the stroke,
as opposed to the more normal 85%. The concept here was that this would
enable steam to expand fully, thus resulting in greater fuel economy.
To make this concept work, increased steam pressure was required to
achieve the desired starting tractive effort. Thus, PRR 2-10-2s of about
the same vintage as the I-1s had 205 psi, while the Decapods had 250 psi.
The Lima 2-8-4s had 60% cutoff, and, as originally designed, 230 psi.
This created marketing problem; the initial assignment of the Berkshires
on the B&A was to replace USRA light 2-10-2s and 2-6-6-2 Mallets in the
district between Selkirk and Springfield, MA. The 2-10-2s, class Z-1,
had a starting tractive effort of about 68,000 lbs, the Mallets, 63,000
working compound. The new locomotives had to show an at least an equal
starting to those they replaced. Thus, the A1A was built with 240 psi.
In all fairness, I should point out that limited cutoff was a feature of many highly successful designs; thus, what in my mind were the two best North American heavy fast freight locomotives, the Santa Fe 5001/5011 classes of 2-10-4, and the Norfolk & Western class A 2-6-6-4 had limited cutoffs of 67% and 75% respectively. These modest limits were, I believe, used to ensure acceptable factors of adhesion when starting without limiting the boiler pressure required to achieve high horsepower output at high freight train speeds.
However, the limited cutoff feature accentuated a severe drawback to the A1A
design; the higher boiler pressure required to accommodate limited cutoff,
plus the overly large cylinder dimension inherited from the H10, resulted
in extremely high piston thrust, which was difficult to counterbalance
adequately with a 63 inch diameter driver. It is interesting to note,
that, at the point when A1A locomotives were operating with the boiler
pressure having been reduced to 220 psi with the removal of limited cutoff,
they were still limited to 45 mph on the Boston & Albany, while 69 inch
drivered Mohawks were permitted a freight train speed of 50 mph. Even
more indicative of the Berkshires' capability for track damage was that,
on the River Division (West Shore), where the A1A were limited to 40 mph,
while all other types of 63 inch drivered freight power could operate at
50 mph. Another omission on the A1A was that off a combustion chamber;
this feature, which became part of just about every large road steam
locomotive built from the mid 1930s on, was regarded with disfavor by the
New York Central, on the grounds of higher maintenance costs. (Although
at the same time as the A1A class, and the J1 Hudsons, for that matter,
were being designed without combustion chambers, Alco was designing the
first of 300 L2 Mohawks, with combustion chambers.)
However, while the B&M and the B&A were still receiving 63 inch drivered
"Superpower" Berkshires, something different was being built at Alco's
Brooks works. This was a 70-inch drivered 2-8-4 being built for the Erie.
Ultimately, there were 105 of these locomotives built between 1927 and
1929; 25 from Alco, 25 from Lima, 35 from Baldwin and then the final 20
from Lima. Erie personnel did not design these locomotives, classes S1/4,
nor did the builders design them. Instead, a committee designed them.
|Pere Marquette 1206|
What the Advisory Mechanical Committee designed was a giant 2-8-4, with 70-inch drivers instead of the 63 inch ones of the A1A and the existing Erie Mikados. The significance of higher drive wheels is three fold; for one thing, the higher the driver, the lower the piston speed in relation to track speed. Thus, the 70-inch Erie drivers had a piston speed about 35% less than the 63-inch drivers of A1A. It is a given that, at equal track speeds, the lower the piston speeds the higher is the mean effective pressure in the cylinders, all other factors being equal, obviously. Secondly, the lower rotational speeds are beneficial to maintenance. Finally, the higher the driver diameter, the more area is available for counterbalancing.
A1A had a large boiler; the Erie Berkshires had a huge one. Grate area was
identical, 100 square feet; but the Erie (my statistics here are based on
Alco built 3300-3324) engines had 5669 square feet of evaporative heating
service against the 5210 square feet of A1A, and the Erie superheating
surface was 2448 square feet as opposed to 2211 square feet. It is important
to note that the impressive figures of the Erie design were related to the
less restrictive clearances and greater weight on drivers permitted by the
Erie over the restrictions imposed on Lima by the necessity to design to fit
NYC requirements. Thus, A1A had an outside boiler diameter of 94 inches,
while the Erie engines had 100 inch boilers. The weight on drivers for
the S1 was 276,000 lbs, that of A1A 246,200.The Erie did not employ a
|New York, Chicago & St. Louis 708|
These were extremely successful locomotives. With the exception of one major improvement, they remained unaltered until they began to leave the roster in the early 1950s. This was the rebuilding of most, if not all, of the Berkshires with cast one-piece underframes, including the cylinders, on the front half of the chassis. This was a major improvement in increasing availability and reducing maintenance costs.
From the Erie Berkshire, the Advisory Mechanical Committee developed the Chesapeake & Ohio class T-1 2-10-4. This design was based on a test of Erie 3377, a Baldwin, which for test purposes had its boiler pressure increased to 250psi and with additional weight on drivers. The T-1 design had 265psi, a combustion chamber, 69-inch drivers and 29 x 34 cylinders. (Originally, the locomotives came from Lima with 260 psi and 60% cutoff; the boiler pressure was increased, as above, and normal cutoff was used.)
The subsequent development history of the 2-8-4s is relatively simple.
Starting on the NKP in 1934, and on the Pere Marquette in 1937, two related
types of 2-8-4 were built. The earliest, for the Nickel Plate, was the
famous class S. This was a modified T-1, with the same 69-inch drivers,
245 psi and 25 x 34 cylinders. This design was replicated many times on
the NKP, and locomotives with the same basic specifications were purchased
by the Wheeling & Lake Erie, which, ultimately, wound up on the NKP roster
when the W&LE merged with the Nickel Plate. Under wartime circumstances,
ten identical locomotives were built for the Richmond, Fredericksburg and
Potomac, a line, which had relied on 77 inch drivered Baldwin 4-8-4s for
its freight and passenger trains.
|Wheeling & Lake Erie 6404|
|Chesapeake & Ohio 2754|
There was one final group of 2-8-4s built which some consider "Van Sweringen"
engines. These were built for the Louisville & Nashville, initially 14
locomotives by Baldwin in 1942, followed by 6 more in 1944 and a final 22
from Lima in 1949. The had two design differences from the NKP pattern;
they had 25 x 32 inch cylinders, but, because they operated with a maximum
steam pressure of 265 psi had about 1000 lbs greater starting te. There were
other differences, but also many similarities to the Van Sweringen designs.
Given the fact that, by the 1930s, large steam locomotives were constantly
running into weight and clearance restrictions, the amount of variety
which h a designer could put into a design of a given wheel arrangement
was highly limited, one can accept or reject the imitation of the Van
Sweringen pattern argument as one pleases.
There were three other classes of 2-8-4 built after 1934, which are included in the total of 611 North American Berkshires, starting in 1925 with A1A and ending with NKP 779 in 1949. (Incidentally, it should be remembered that the largest single group of 2-8-4s was the 646 "IS", for "Iosif Stalin" class of the former Soviet Union. These were much smaller than the run of the North American types above, and had 71-inch drivers for passenger service. In fact, in Europe all 2-8-4s were passenger engines; in Austria, Romania, Czechoslovakia and Norway, as well as Russia.) These were, in order of construction, 4 built by Lima in 1934, followed by 2 more in 1939, for the Detroit, Toledo and Ironton, a north-south line which ran against the grain of the country on its main line. These were about the same weight as the NKP/W&LE engines, but had a higher boiler pressure, 260psi, 63 inch drivers, but small 25 x 30 cylinders, thus keeping piston thrust within reasonable levels, They had almost 2000 lbs more starting tractive effort than the Van Sweringen Berkshires, and, more than A1A and its siblings, was a "Super Mikado". The next was the smallest 2-8-4, 5 units built in 1940 for the then Norfolk Southern. (This line subsequently became part of the Southern Railway, thus today being a component of todays Norfolk Southern) These were small locomotives, 334,000 lbs total engine weight, roughly 75 tons less than an Erie 2-8-4. They had 63-inch drivers, 23 1/2 x 30-inch cylinders (60% cutoff) and 250psi boilers. They had a starting tractive effort of 49,900 lbs, plus 11,000lbs from the booster.
The final design was the New York Central (Pittsburgh & Lake Erie) class A2a, built by Alco in 1948, and that builders last steam locomotive order. There were seven of these locomotives. To my mind, they represent Paul Keifer's concept of what a general purpose stream freight locomotive should have been. For the first time, the NYC permitted a 70,000lb axle loading. Thus, with good adhesion, this class had a starting te of 67,000. Since they would have been confined to the 50mph and under freights, they could have made use of a booster, which would have given them a starting te of about 80/81,000 lbs. Even without the booster, they were rated at 8000 tons on the admittedly water level route of the P&LE. They had a modest steam pressure of 230psi, but a boiler capacity equal to that of a NKP 2-8-4, and 25 x 32 cylinders.