After reading TRAINS and CLASSIC TRAINS for quite a while I am still perplexed as to the classification of steam locomotives. Could someone please define in layman terms what distinguishes each of the following locomotives:
Articulated -
Mallet -
Berkshire -
There are other steam locomotives, for sure, but these three classes are almost always mentioned. Your help in this matter will not go unappreciated.
Thank you.
Here’s a link http://www.spikesys.com/Trains/articuld.html explaining Mallets and articulated’s.
Same site different page describes the Whyte classification system for steam locomotives http://www.spikesys.com/Trains/wyte_sys.html
The Berkshire is a 2-8-4 wheel arrangement.
Enjoy
Paul
Not a bad link but Wiener also classified Shays and Heislers as articulated locomotives, although I will concede that Garratts, Fairlies, Mallets (both simple and compound) and Meyers will cover the majority of articulated and semi-articulated steam locomotives built.
By the way, what is the type name for 2-6-6-2, 2-6-6-4 and 0-10-2 wheel arrangements??
I guess I am just ignorant when it comes to steam. I went to those two links provided and while the information was interesting, it did NOT answer my question.
I was looking for a clear and concise definition of these locomotive types. The site given in these links assumed you knew what a mallet or articulated was. Their very brief explanations was hardly satisfactory.
Could you please be of more assistance. Thank you.
An articulated locomotive is equipped with two (or more) sets of driving wheels and their cylnders, at least one of the sets able to pivot with respect to the frame of the locomotive allowing it to negotiate sharper curves tahn if both sets of drivers were rigid. Each of the driver/cylinder sets is called an “engine,” BTW.
A Mallet is a subtype of articulated using a compound steam supply. What that means is that the steam is used twice. It is fed first into the high-pressure cylinders of the rear engine (most common arrangement) and then exhausted into the low-pressure cylinders (identifiable by being much larger in diameter) of the forward engine. Simple articulateds use the steam only once, and both their engines use high-pressure cylinders. Examples of Simple articulateds include the famous UP Big Boys (4-8-8-4) and Challengers (4-6-6-4); an example of the Mallet Articulated is the N&W Y-6 class (2-8-8-2). It should be noted that, among the articulated locomotives, you will find less standardization of type names, and the Whyte System deals poorly with them.
Lionel Wiener is a little more concise with his definitions:
An articulated locomotive is one in which the frames holding the driving wheels are able to pivot with respect to the frame of the locomotive. Examples would be Garratts, Shays and Heislers.
A semi-articulated locomotive is one in which one frame holding the driving wheels is able to pivot with respect to the frame of the locomotive while the other is rigidly attached to the frame of the locomotive. Prime example would be a Mallet.
Wiener classified locomotives with trailing truck boosters as temporarily articulated.
There were, AFAIK, no standard names associated with most articulated locomotives. IIRC, the Southern Pacific called 2-6-6-2 and 2-6-6-4 types “Articulated Prairies”.
The 0-10-2 was an extremely rare wheel arrangement. The only engines commerically built with this arrangement were built for the Union Railroad, and one often finds the arrangement called “Union Switcher”.
OTOH, the C&NW had a pair of Santa Fe types (2-10-2) from which the pilot trucks had been removed. These were used on the hump at the Proviso yard, and had their pilot trucks removed because they tended to derail on the hump.
Thanks for the clarification. There is still a bit of confusion since one lists a Mallet as a compound steam engine. While another says a Mallet only has one set of its drive wheels that pivot. Probably both definitions are true, depending on the particular locomotive.
Is this a correct assumption?
I also heard that the DM&IR was using 0-10-2´s on their ore trains…
These may well have been the former Union RR 0-10-2’s. As was true in the diesel era, the various US Steel roads were known to swap power among themselves, especially late in the steam era when much of the steam wound up on DM&IR.
Yes, The DM&IR did have 9 former Union RR 0-10-2’s. Missabe #601 - #609, ex Union #301 - #309. Missabe picked these locos up in 1949. As a side note Missabe #603 (Union #303) was returned to the Union RR for display in 1961, and I have heard that she displays Union RR markings on one side and DM&IR markings on the other side. Can anyone confrim this?
Dan
Joe,
The French locomotive designer Mallet, French pronunciation approximately MAL-LAY with equal emphasis on both syllables, created the first articulated locomotive that had the rear engine fixed beneath the boiler with high pressure cylinders and had the front engine hinged to get around sharp curves with low pressure (larger in diameter than the high pressure ones) cylinders using the steam exhausted from the rear engine. Early designs had the rear engine equipped with piston valves and the front with slide valves
The English pronounced his name roughly MAL-ley, the first syllable accented and rhyming with Salley.
The extra piping and plumbing needed to connect the rear engine to the front caused maintenance grief and many were converted from compound to simple articulateds with both engines receiving high pressure steam.
Mr. Vaulclain was a proponent of compound steam and used the principle on non-articulated engines; those with piston valves had a bulky looking triple cylinder set - valves, high pressure pistons, and low pressure pistons. Maintenance problems often resulted in these engines being converted to simple.
Art
Thanks for all the information. I believe I now know something about the types of steam locomotives, but,please, don’t test me.
One will notice that steam locomotive compounding experiments largely disappeared with the development of the superheater. The original point of compunds was to get more thermal efficiency from a steam engine. The superheater did a better job of this than compound arrangements.
However, compounding was was revived to reduce the weight of running gear. 4-10-2s and the 4-12-2 were all three-cylinder compounds with high pressure cylinders on the outside, and a high pressue cylinder cast into the locomotive frame. The center cylinder drove a rod connected to a crank on the main axle.
The N&W liked the mallet, and all their articulated engines were mallets.
That is correct. Mallets, unaltered, are by definition “compound” locomotives with two engines under the boiler. The engine closest to the cab was rigidly fixed to the frame and could not pivot relative to the boiler. The front engine, the one using steam scavenged from the rear high-pressure engine, could pivot, and its cylinders got the most out of the lower pressure (second hand) steam by exposing it to considerably larger surface areas on the associated pistons…a characteristic evinced by the noticeably larger cylinders.
Locomotives that had their engines elsewhere, i.e., not under the boiler, include the famous Beyer-Garratt locomotives. I believe that they were “simple” locomotives, if a bit odd, in that they sent high pressure steam directly to both engines. I saw one in use in the Andes Mountains of Peru in the early 1960’s…quite impressive.
Crandell,
Like this you mean? Double headed Garrat between Sydney and Newcastle NSW Australia. In service until 1973.
Thems was the days.[:p]
As all 3 cylinders received high pressure steam, these locos were not compounds. The earlier Vaulclain compunds had high pressure cylinders inside the frame which exhausted into low pressure cylinders outside the frame. The inside cylinder on 4-10-2’s and 4-12-2’s did have slightly smaller dimensions than the outer 2 and the exhaust was siameased with the exhaust from an outer cylinder, but the steam was not being used twice.
Triple expansion steam engines were very common in steam ships and Titanic had 2 triple expansion steam engines which exhausted into a steam turbine, so it used steam 4 times.
As is relatively well-known, there was only one triple-expansion steam locomotive in the United States: D&H 1403, which was a 4-8-0. Steam came from the boiler to a high-pressure cylinder under the engineer’s side of the cab, then exhausted to an intermediate-pressure cylinder under the fireman’s side, which then exhausted to a pair of low-pressure cylinder cylinders at the front in the usual location, which in turn exhausted up the stack. As can be imagined, it was incredibly efficient in its use of steam but was a maintenance nightmare.
The 60-series Garratts in New South Wales were the only 4-8-4+4-8-4 Garratts and were the largest Garratts ever built.
They certainly was! [:D] Yes, that is what I was talking about. I think the Federal Railway of Peru had two of them, and I cannot recall if they were 2-6-0-0-6-2, 4-6-0-0-6-4, or whatever. I recall that the engines were under tenders at opposite ends of the boiler, and that the whole valley thundered when one of them went by. ( I was about 10 at the time…a few leaves have passed under the bridge).