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Union Pacific 9000 Class 4-12-2's

  • Love the look of theses loco's,but i heard from somewhere a long time ago these were built using the boiler and god knows what else from older 3500 class 2-8-8-0 mallets!If true ,how on earth could you take an articulated loco and turn it into a rigid wheelbase loco.Wouldn't axle load and radius cause problems,amongst others i cant even think of.!!!  mick
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  • I can't speak for the origin of the 'makin's' of the 9000s, but I doubt that UP had 2-8-8-0 Mallets with 67" drivers.  The 4-12-2s were acquired to replace Mallets, to get the average freight train speed up.

    During the second decade of the 20th century the AT&SF dismantled some Mallets of questionable parentage and converted them into reasonably successful 2-cylinder simple locomotives.  I believe, but cannot prove, that the rear engines kept the (shortened) Mallet boilers and their original cylinders, while the front engines got new cylinders (of more reasonable proportions) and new boilers.

    A lot of weight issues can be addressed by tweaking the springing and equalization, and later locos could be riding on heavier rail (and thus have higher permissable axle loadings.)  As for curves, the writeup in Kalmbach's Cyclopedia - Volume 1, Steam Locomotives notes that one series had to be moved from the OSL to the UP's transcon main because of problems with the OSL's curves.  Another series (possibly those with blind #4 drivers) remained on the OSL until it was dieselized.

    Chuck

  • Thanks Chuck thats very informative! Your right about the drivers on the mallets-they were 57 inch.I'm guessing the AT&SF would have had to make and new rigid frame for the boiler etc to sit upon.Anywhere i can see pics of the AT&SF rebuilds?    mick
  • Only one type of 4-12-2 was built, the Union Pacific Railroad's 9000 class locomotives, 88 of which were built by ALCO between 1926 and 1930. These locomotives were used to increase the speed of freight trains in flat country, and were fairly successful, but were maintenance nightmares, largely because of their use of an inaccessible third cylinder driving a cranked second driving axle between the frames. There was no inaccessible valve gear to worry about, however. ALCO had obtained permission to use the so-called conjugated valve gear invented by Nigel Gresley. This system used two hinged rods connected to the outer cylinders to operate the inner cylinder. The 9000 class locomotives were the largest ever to use Gresley gear.

    Between 1934 and 1940 eight of the first fifteen locos had their Gresley gear removed and were converted to a "double Walschearts" valve gear which utilized a double eccentric (return) crank and second link on the right side (similar to the gear Baldwin used on its 3-cylinder experimental compound 4-10-2 #60000), which operated the valve for the inside cylinder. Union Pacific referred to this system as the "third link." The 4-12-2's constructed from 1928 utilized roller bearings in the Gresely lever bearings, thus none of these engines were converted. The pre-1928 engines not converted received the roller bearing levers in 1940, and no further conversions were made.

    During the design phase "blind" (flangeless) third and fourth axle were provided in order to improve curve handling, but the use of ALCO's lateral motion devices on the first and sixth axles (which allowed the axles to slide up to two inches to the side) made this unnecessary. They were the longest rigid frame locomotives in North America, and until 1934, the longest in the world. The trailing truck carried the same axle load as the drivers, which was unusual.

    There has been some debate as to whether the first driving axle of the 4-12-2 was cranked to provide clearance for the main rod connected to the second axle. It has been shown that there was no such crank on the first axle. Instead, the spacing between the first and second axles was increased by 18 inches to provide the necessary clearance.

    One example survives, at the Railway and Locomotive Historical Society's museum at the Los Angeles County Fairplex in Pomona, California.

    From Wikipedia

    Photo Sharing and Video Hosting at Photobucket All the best! Jan
  • Something that I have been curious about with UP's 9000 class, is normal side rod locomotives have the drivers "quartered" at 90 degrees so that the piston thrusts are evenly timed. Do the 9000's have their drivers set at 60 degrees ( I think my math is right on the 60 degrees), to keep the piston thrusts balanced? or how was the center cylinder timed/balanced in the valving sequence, if not?

       I know that on articulateds each engine set was independently quartered as if a separate engine, and that synchronizing between engines was not attempted, as they would go in and out of sync due to wheel slip, usually with the front engine set slipping more easily.

                                                                                Thanks for any info,

                                                                                              Doug

    May your flanges always stay BETWEEN the rails

  • As you suspected, the drivers are not quartered.  There was a major discussion about this on Yahoo Groups, Espee, message 54771.  Harry Meislahn actually meaured the crank location of Alton 3-cylinder 0-8-0 #12 in a museum. I believe his measurements were as follows:  if the fireman's side crank is at top dead center, the engineer's side crank leads it by 120 degrees and the center crank follows that by 114 degrees, allowing 126 degrees spacing to get back to the fireman's side crank.  The odd spacing is due to the center cylinder being slanted upwards several degrees.  There are some photos of his findings linked to the above site.
  •  sarges wrote:
    how on earth could you take an articulated loco and turn it into a rigid wheelbase loco.

    Lessee-- weren't the first RDG 3000-class 2-10-2s built using modified boilers from 2-8+8-0s? And you remember the RDG 4-8-4s used boilers from 2-8-0s. Re-using old boilers probably wasn't that uncommon-- wasn't it Worley that said SFe considered using ex-N&W 2-8+8-2 boilers to build 4-8-4s?

  • Felton,
       I found the following on web site: http://www.steamlocomotive.com/3cylinder/
    "I have been told that the designers had to keep the quartering at equal 120 degree angles partially for centrifugal mass balancing reasons. However, if the inside cylinder is inclined at say 7°, it would normally be necessary to set the cranks at 120°-127°-113° to preserve the torque distribution. Apparently, this was not necessary for the 9000s. The #2 driver has an enormous inside steel crank/counterbalance assembly that has to spin in concert with and balanced to the outside main rods. (One hundred and twenty degrees is the quartering angle listed in the book "Union Pacific Type, Volume 1" and confirmed by one of the co-authors, John Bush.) It is suspected that one of the reasons the Baldwin #60000 used a 90°-135°-135° configuration had to do with it being a compound locomotive, with the center cylinder receiving high-pressure boiler steam, and the outer cylinders receiving the low-pressure steam from the center cylinder. And according to John Bush, the locomotive had "a very interesting" outside valve gear design."

    The SP used 135 - 135 - 90 degree spacing with a cranked front axle, so I'm totally confused. 

    .
  •  sarges wrote:
    ...how on earth could you take an articulated loco and turn it into a rigid wheelbase loco... mick

    Actually, it's really not that hard to take boiler off an articulated chassis, and install it on a rigid chassis of sufficient length and strength.

    IIRC, the only place the boiler is actually connected to the chassis is at the cylinders.

    Dan

  • so I'm totally confused.

    Confused as to why the drawings haven't surfaced to put an end to this question.

    .
  •  BigJim wrote:
    I found the following on web site: http://www.steamlocomotive.com/3cylinder/
    "I have been told that the designers had to keep the quartering at equal 120 degree angles partially for centrifugal mass balancing reasons. However, if the inside cylinder is inclined at say 7°, it would normally be necessary to set the cranks at 120°-127°-113° to preserve the torque distribution. Apparently, this was not necessary for the 9000s."
    I'll bet the 4-12-2s were no different from other 3-cyl engines in that respect. If they used the Gresley-Holcroft gear with the usual lever proportions (2:1 and 1:1) then 120-127-113 would be pretty much mandatory (except that the actual tilt on the inside cylinder was a couple degrees more, as I recall).

     BigJim wrote:
    The SP used 135 - 135 - 90 degree spacing with a cranked front axle, so I'm totally confused.
    Who says they did?

  • I dont think these were built using mallets Seems to me trhey were a an order from the U.P. made from the frame up by baldwin and alco  I could be wrong  Kratvilles book  on motive power of the Union Pacific could prvide what  you are looking for 
    larry ackerman
  •  JanOlov wrote:
    [quoting from Wikipedia?]There has been some debate as to whether the first driving axle of the 4-12-2 was cranked to provide clearance for the main rod connected to the second axle. It has been shown that there was no such crank on the first axle.

    It seems the first and second driving axles were 88 inches apart and the inside rod was 113 inches long. If I remember right that the inside cylinder tilt was 9 1/2 degrees, and if we assume the axis of the center cylinder intersected the axis of the crank axle, then that leaves 10.45 inches between the centerline of the inside rod and the centerline of the first axle. So how fat is the rod, and what's the axle diameter?

    (We can't take it for granted that the inside cylinder axis intersects the axle axis. After all, the outside cylinders don't.)

  • The 9000s were built by Alco, and yes, the UP had 2-8-8-0, because in one this year's issues of the UPHS Streamliners had a picture of one of them. In fact some of them lasted in to hepler service. I'll go check and see...
    -Michael It's baaaacccckkkk!!!!!! www.youtube.com/user/wyomingrailfan
  • Better photo on Barnes & Noble April 2008 calendar.