The off-beat exhaust has always been a mystery. In all likelihood, when the center cylinder is inclined the crank axle is shifted an equal angle from the 120-degree position-- so it’s hard to say why the beat should be off. (Of course, not all 3-cyl engines had inclined center cylinders.)
Reading about English engines, you don’t see constant references to Gresley Pacifics sounding offbeat.
The middle cylinder had a different length of stroke than the outside cylinders, so this would have contributed to the off-beat rhythm.
Also–there is a lot of misinformation about the 4-12-2’s even quoted in usually fairly reputable online sources like www.steamlocomotive.com. For example, the middle cylinder on the UP 4-12-2’s was inclined at 9.5 degrees and not 8 degrees as often reported. (Kratville and Bush, UP Type, Vol. 1)
William Kratville and John Bush wrote two excellent books on the UP 4-12-2 that also include much information on the UP 4-10-2 (both as built and as later rebuilt). They are among the finest books ever written on any locomotive type, and are filled with lots of drawings and engineering data, and interviews with the men who designed, built, and maintained them.
Kratville and Bush discuss the offbeat exhaust. In addition to having a shorter stroke (31" versus 32" of the outside cylinders), they say the valve events were different–which also contributed to the offbeat sound.
The UP wanted much faster locomotives able to pull a much longer train much farther distances. Alco believed the 4-12-2 should be only a 35 mph standard operating speed locomotive. UP, as well documented by Kratville and Bush, had absolutely no intention of operating 4-12-2’s at 35 mph, but planned from the outset to operate at significantly higher speeds–regardless of what Alco’s recommendations were–they were trying to slash schedules and speed up trains as Santa Fe was already doing.
Additionally, the UP was facing a traffic crunch and somewhat rushed the testing period of the “demonstrator” 4-12-2, number 9000. The operating department was absolutely thrilled with the
Yes, the three cylinder locomotives had six chuffs per revolution. The third cylinder was connected to the second axle for most of the USA steam locomotives. The third cylinder was tilted up at an angle also but the outside two cylinders were horizontal to the rails. This did cause the exhaust from the third cylinder to be off beat and at speed, the roar runs together more than a two cylinder locomotive.
See the link below and click on the sound file. It is a Union Pacific 4-12-2 locomotive in 1954 and you can get the feel for the off beat sound.
That sound is not representative of a normal 4-12-2, but one in bad shape needing an overhaul. Refer to the discussion at www.steamlocomotive.com where it explains the Fogg recording of 9009 in 1954 is of a badly out-of-time 4-12-2. Toward the end of steam, maintenance of the middle cylinder suffered greatly as shop forces tended to “pass the buck” on down the line to the next shop. The resulting wear to bearings, drive boxes, etc. contributed to the out-of-sync sound.
So the exhausts would be slightly unequal-- but the timing would be unaffected.
They include a table showing how some engines had modified Gresley levers to shorten the travel of the center valve. But on the other engines, different valve events would just reflect the imperfection of the Gresley gear.
I do not know about the “modifications” to the Gresley gear (am still reading Volume 2), but 8 or 9 UP 4-12-2’s were converted to double Walschaerts motion on the right side, with the Gresley gear completely removed and the air pumps moved from the smokebox door to the side of the engine, resulting in the “bald faced nine” look.
According to www.steamlocomotive.com, some of the Gresley-equipped engines were not set-up correctly after major shopping by the UP maintenance forces, and for that reason would have been more “out of time” than others. Lubrication of the middle cylinder suffered because they didn’t want to crawl under and around the front axles to get to the crank on the second axle–and as a result, bearings, etc. got worn–further contributing to the “offbeat” sound. It’s more than just the different stroke length–but offbeat exhaust is also affected by the closer proximity of the exhaust passage from the third cylinder to the smokestack.
John
I see the cylinders on the SR 4-6-2s all drove the center axle, so that “most” is looking questionable. All? the 3-cyl LMS 4-6-0s used divided drive, and the SR 4-4-0s.
How about Germany and the rest of Europe-- did their 3-cyl engines have inclined center cylinders?
Dunno if they mention it in the text. They reproduce a UP table (in Vol 2, I think) giving dimensions for the Gresley levers; some engines have the usual 2:1 and 1:1 levers, but others don’t, the object presumably being to shorten the travel of the center valve without altering its phase.
.
While it might not be “correct,” from what I’ve read it was “normal.” The late Don Ball, Jr. always referred to the 9000s as sounding like a washing machine or a sewing machine. I seem to recall Jim Boyd mentioning that they had an offbeat sound as well. You don’t happen to know of any recordings of a “correct” sounding 9000, do you?
Chris–
It seems perhaps you are misunderstanding what I wrote above.
Refer to the link in the post below.
Respectfully submitted–
John
Edit: this link, 2/3 of the way down the page, under “Lopping” Exhaust:
http://www.steamlocomotive.com/4-12-2/
under ‘‘Lopping’’ Exhaust, abour 2/3 of the way down the page.
Working on that third cylinder was a maintenance nightmare, requiring access from under the loco. In Great Britian, where all the “labour” was grudgingly provided by government employees, this was not a problem, except when “labour” was on strike.
Hays
John -
I understood what you said…and read the article at Steam Locomotive.com. All I’m saying is that I’m guessing there were a lot of out-of-spec 9000s (more and more as the UP dieselized) out there and so the sound on the Fogg recording is probably pretty representative, even if it’s not what a well shopped 9000 should sound like. I’d just like to hear one that was “in spec” for comparison purposes.
Thanks,
Chris
Phew, now that’s what I call a sweeping statement.
Have you any experience, or sources, to back these observations up ?
Martin
Virtually every account I’ve ever read about the 9000s featured the “lopping” exhaust. The steamlocomotive.com article is the only place I’ve ever read that says they had “a very even 1-2-3, 1-2-3 beat.” Hence my curiosity to hear what a 9000 sounded like when it was “in spec.”
[quote user=“UP 4-12-2”]
The middle cylinder had a different length of stroke than the outside cylinders, so this would have contributed to the off-beat rhythm.
Also–there is a lot of misinformation about the 4-12-2’s even quoted in usually fairly reputable online sources like www.steamlocomotive.com. For example, the middle cylinder on the UP 4-12-2’s was inclined at 9.5 degrees and not 8 degrees as often reported. (Kratville and Bush, UP Type, Vol. 1)
William Kratville and John Bush wrote two excellent books on the UP 4-12-2 that also include much information on the UP 4-10-2 (both as built and as later rebuilt). They are among the finest books ever written on any locomotive type, and are filled with lots of drawings and engineering data, and interviews with the men who designed, built, and maintained them.
Kratville and Bush discuss the offbeat exhaust. In addition to having a shorter stroke (31" versus 32" of the outside cylinders), they say the valve events were different–which also contributed to the offbeat sound.
The UP wanted much faster locomotives able to pull a much longer train much farther distances. Alco believed the 4-12-2 should be only a 35 mph standard operating speed locomotive. UP, as well documented by Kratville and Bush, had absolutely no intention of operating 4-12-2’s at 35 mph, but planned from the outset to operate at significantly higher speeds–regardless of what Alco’s recommendations were–they were trying to slash schedules and speed up trains as Santa Fe was already doing.
Additionally, the UP was facing a traffic crunch and somewhat rushed the testing period of the “demonstrator” 4-12-2, number 9000. The operating department was absolutely thrilled with the dramatic cost savings and speed/tonnage increases of the 9000 relative to all previous motive po
From the Union Pacific Historical Society’s ‘‘Library’’ webpage, at - http://www.uphs.org/library/engines/ -
Vol I - ASIN: B0006EV8Y2 - was apparently published in 1990 - it appears to be available for about $220 to $370 from Amazon.com today.
Vol. II - ASIN: B000TXPA26 - was apparently published in 1995 - it appears to be available for about $65
Chris and Paul–
There allegedly are other recordings of the 4-12-2, including apparently another one on the same Howard Fogg album as the link above, but I’ve never heard them and do not know if they are available on cd.
I’ve found 3 dvd’s that have 4-12-2’s on them, but none have sound, and 2 of them only show a couple scenes with 4-12-2’s. The best dvd by far is Greg Scholl’s Union Pacific Steam Classics, Vol. 1, which includes several minutes of footage with plenty of runbys in Kansas and Nebraska (all with a tasteful music soundtrack as no sound is or was available at the time the video was being edited).
During the last 2 nights I searched through more than 100 pages devoted just to major changes during their service lives on the 4-12-2’s in the UP Type, Vol. 2, and the changes to the Gresley gear were mentioned only in passing. The final 25 engines which were built with complete one piece cast frames and integral cylinders had different middle cylinder valve events by 2 degrees than the previous 4 groups of 4-12-2’s–but the authors could find no solid evidence that definitively explained the reason(s) why. It is also unknown why 5078, 5080, and 5086 had their valve events changed to match the previous 4 groups of 4-12-2’s.
Of course, during the steam era, running changes and improvements were constant. Not all 88 engines ever received all the improvements.
Which brings me to the next point:
Paul, there were 88 UP 4-12-2’s and only 10 TOTAL 4-10-2’s. After rebuilding to 2-cylinder configuration during the 1940’s, they were renumbered into the higher end of the 2-10-2 number series as engines 5090 to 5099, and were generally considered comparable to a 2-10-2 in future assignments, etc.
The maximum horsepower of a 4-12-2 was nominally 4
1-2-3 1-2-3 1-2-3 sounds like a description of an uneven beat. Hard to figure what they meant.