4-10-2 steam locomotives

[Anonymous]

Why was the 4-10-2 wheel arrangement so rare? The only US railroads to purchase them were UP and SP, both in 1925. And I don´t think that it was an unsuccessful locomotive, since it has been in service till about 1956. A 4 wheel truck allowed a bigger firebox and grate area, but SP´s 4-10-2´s could well compete with other Texas types, since their maximum tractive effort (with booster) was almost 97.000 Ibs, what is the proof that they really had a lot of steam power! And why there were only 3 cylinder 4-10-2´s built? Because of the trend in the 20ies? (Well, UP´s 4-10-2´s were converted later on into a 2 cylinder design, but that doesn´t count). UP named their 4-10-2´s Overland. SP named their 4-10-2´s Southern Pacific. But other names for the 4-10-2 design were also Super Mountain and Sierra. So why are there 2 further words for that wheel arrangement existing since there were only 2 roads which had such locos? I don´t believe that they were called like this in Brazil (as far as I know the only other country in the world which also had 4-10-2 types), because they speak portugese down there, so Super Mountain or Sierra (in portugese it´s Serra, without the i) would sound a little bit weird for them. Does anybody know the answer???

[nanaimo73]

What were these locomotives designed for ?
The 4 wheels up front suggest passenger power, but the 10 drivers suggest freight power to me.

The 97,000 lbs tractive effort is for starting, not really a measure of the ability to haul a train in a profitable manner.

From http://www.steamlocomotive.com/berkshire/

QUOTE: The development of the 2-8-4 wheel arrangement for steam locomotives was a result of an effort by the Lima Locomotive Works to improve on the speed and horse power of the USRA Mikado (2-8-2) locomotive, which was designed by the United States Railroad Administration during World War I. The USRA design had difficulty keeping up steam over long periods and often experienced wheel slippage.
Lima Locomotive Works' engineer William E. Woodward started with a New York Central Class H-7 "Mikado" type locomotive and added a larger firebox, creating an experimental Class H-10 "Mikado". He then went one step further and designed a locomotive with a 100 square foot firebox. This larger firebox required a four-wheel trailing truck to support it. The resulting locomotive was designated Class A-1, and it was the first 2-8-4.

This new 2-8-4 locomotive was sent to the Boston & Albany Railroad by Lima in the early spring of 1925 for test on that railroad. In several test runs over a division of the railroad that crossed the Berkshire Hills, the demonstration locomotive, which carried road number "1" hauled up to 2500 tons. The most dramatic test occurred on April 14, 1925. A Class H-10, 2-8-2 "Mikado" type steamed eastbound from the Selkirk Yard pulling a 46 car, 1691 ton, train. About 47 minutes later the Class A-1 demonstrator led a 54 car, 2296 ton, train up the same eastbound climb through the Berkshires. The demonstrator Class A-1 arrived at North Adams Junction ten minutes ahead of the Class H-10. Soon after these impressive tests the Boston & Albany ordered forty-five of these new locomotives, which quickly became known as "Berkshires".

I think they probably had a firebox to small for 10 drivers. Do you know how big it was ?

[jimrice4449]

The 3 cylinder 4-10-2 was the result of an Alco brain storm. They built a demonstrator (currently on display in a Philadelphia museum, I believe) Up and SP were both sufficientlt impressed to buy them The SP originaly intended them for psgr service over Donner Pass but the long wheelbase prsented track and engine maintainence problems and they wound up mostly in Arizona & New Mexico.
Purely as speculation I suspect that the heavier grades the UP used them on led to an insufficiency of steam for 3 cylinders and hence led to their conversion where SP's relatively level Sunset Route allowed the to run more on expansion.

[Anonymous]

I only know the measures of the SP 4-10-2´s: their grate area was 90 square feet, pretty much the same of the GS-4 4-8-4´s, which had 90,4 sq. ft. . But I don´t know the the dates of the UP engines. Other facts I know are that both engines had 63,5 inch drivers, and the SP engines had about 84.000 Ibs without booster and the UP engines 80.000 Ibs (they had no booster).

[Anonymous]

UP was looking for higher speeds with about the same tonnage rating as their 2-10-2's. They only bought 10 of them largely as an experiment and all but the first were built as oil burners. According to Kratville's Motive power of the UP, the first was delievered in 1925 and comparative tests with a 2-10-2 resulted in the ability to handle 20% more tons using 16% less fuel per 1000 gross ton miles. They were able to do this because the 3rd cylinder allowed the loco to be operated more efficiently at shorter cutofffs.. All 10 were assigned to the LA&SL division and were converted to 2 cylinders by the LA shops in 1942.

Impressed but not completely satisfied, UP did puchase 88 3 cylinder 4-12-2's between 1926 and 1930. These had 67" drivers, 97,000 lbs TE, and 4,300 hp. I suspect the 4 wheel lead truck might have been used on both types to keep axle loading down, since the 3rd cylinder and associated parts added a lot of weight. On both types the 3rd cylinder cranked the 2nd axle and the length and angle of the inside rod might have been a factor as well. However all UP locos built after the 4-10-2's had 4 wheel lead trucks.

[Leon Silverman]

The Philadelphia Museum housing the 4-10-2 is the Franklin Institute.

[M636C]

QUOTE: Originally posted by Leon Silverman

The Philadelphia Museum housing the 4-10-2 is the Franklin Institute.

But it was built just down the road at the Baldwin Eddystone plant, not by Alco, and it was a three cylinder compound, not a simple like all the Alcos. It had three separate valve gears, while the Alcos had Gresley-Holcroft Conjugated valve gear. But it IS a 4-10-2.

M636C

[PBenham]

Baldwin 60000 was supposed to be Baldwin's answer to American's 3-cylinder 4-10-2s and 4-12-2s both of which were built for UP and SP. But the depression did the concept in, as did the 72-75" drivered 4-8-4, with a 100 sq ft.Firebox! Alco, Baldwin and Lima all built these girls and they can be listed among the weapons that won WWII.