The mention of the "Sweeney" stack on UP 4-2-6 2909 in a recent message thread on Trainorders made me realize that I only knew these large exhaust stacks merely by what I have heard among UP fans. So I did some research, and asked a couple experts. Once again, the information is incomplete, compared to what railfans and modelers think they know.

I know of at least one preserved UP locomotive with a Sweeney Nozzle, and that is OSL 2-8-2 2564 at the Orange Empire Railway Museum.

A check of Kratville's "Motive Power of the Union Pacific" found a brief mention on page 159, of the device by its real name, "Sweeney Nozzle," while discussing UP's 7000 class 4-8-2s. Gordon McCulloh also mentions the Sweeney Nozzle (and its associated Firebar grate) in his "A History of Union Pacific Steam" in his discussion of UP's 5000 class 2-10-2s. Back in 2006, in a comment to a Trainorders message thread, John Bush shared some brief information about the Sweeney Nozzle's place in UP's on-going efforts to reduce cinders from coal burning locomotives, and improve the draft of the entire system of firebox, smoke box, exhaust nozzles and exhaust stack.

But even after several different and varied online searches, not much shows up about the older Sweeney Nozzle itself, even in old newspapers and books published before 1923. And nothing shows up about UP's use of a similar design, once the patent (if there was one) apparently ran out in the early 1920s. There is likely some obscure published book or magazine article out there, but I don't have the resources to identify and use such source material. So I'm asking the folks here on RYPN.

Can anyone share a few comments about what railfans and modelers improperly know as UP's large and distinctive Sweeney stack? Where did it come from? Why was it used?

Here is what I have so far:

http://www.utahrails.net/up-steam-roste ... hp#sweeney

Don Strack

Here is what was published in June of 1899 concerning the "Sweney Nozzle"

J.J.G. Koopmans (PhD) references this material in his book "The Fire Burns Much Better".

Kent

No wonder that you could not find anymore info since his proper name is Don Sweney.
He was a student at the time and his patent is no 625.712 of 23rd May 1899 and it was
discussed in The Railroad Gazette 16th June 1899 page 426.
He is properly discussed in my Ph.D. thesis available from Camden.
As far as I remember he later was a V.P. at one of the larger railroads, might be U.P.
He died in 1943, I found his grave records.
As for recent applications, the Southern 401 has received one since the original double
blastpipe was inferior, according to Goss, and the Sweney allows for a central disc which is
perfect for finetuning in an oilfired locomotive.
King regards
Jos Koopmans

Thanks for the information about the book. I have ordered it.

Here is a link to the patent itself, courtesy of Google:

https://www.google.com/patents/US625712

From the Camden Miniature Steam Services web site: "the most authoritative book in print on steam locomotive exhausts. This second edition contains corrections, clarifications and amendments, many made in consultation with leading steam locomotive designers."

Does the book contain much information about the specific designs used on Union Pacific? I am interested in putting UP's research and testing in context with the rest of the industry.

Don Strack

Don- Here's a section on my web page about Southern 401. Info was provided by Jos and Kent McClure of the Monticello Railway Museum, operators of the locomotive:

http://www.trainweb.org/tusp/last30/monticello401.html

Might the UP 2-8-2 in Walla Walla have this nozzle? The stack looks huge. Also looks like this engine might be a good candidate for restoration if there ever was a local use for it.
http://steamlocomotive.info/vlocomotive.cfm?Display=1301

Alas, it does not. The reason is that it was/is extremely difficult to get anything from a
US library to Europe for copyright reasons. So whatever I have is from those publications that were available in European libraries. But Goss is properly treated as is the MMRA stack, the Illinois test a.s.o.

Interesting at the moment is that on trainorders.com Iwilton comments on the patent description. Regarding the diminished blast pressure claim of the patent the publication in the Railroad Gazette, see above, shows graphs supporting the claim. Please note that the Sweney is essentially a multi-orifice blastcap. As such its proper position is high in the smokebox as the distance to the throat of the chimney is properly related to the orifice dimension.
Kind regards
Jos Koopmans

Thanks for posting the information about back pressures. It appears that by March 1949, only a few locomotives still had either Sweeney nozzles, or Goodfellow nozzles.

I wonder how their new standard multi-jet nozzles performed on those locomotives that still had their large stacks.

I have wrapped all my research into a new web page:

http://www.utahrails.net/up/sweeney-stacks.php

As with any subject, there is always more to be learned.

Don Strack

Do you mind me commenting on your paper?
You quote the information sheet as "... increasing the size of the nozzles. As a result, the exhaust steam velocity increased,..." That cannot really be true, isn't it?
The 1930 annular ported nozzle is a development by G.W. Armstrong, "Improving draft efficiency" Railway Mechanical Engineer Sept 1930 p 499-502. It was tested on the N&W and is a development from elsewhere.
The use of the four-orifice blastcap is very probably the consequence of the research by Everett Young of Illinois University. The publication is on-line these days:
https://www.ideals.illinois.edu/handle/2142/4435
He proved in 1933 the equivalence between a single orifice with a stack of double length and a four-orifice version with proper stack of standard length. If it is realized that four half-scale models of the double length stack would eject their 1/4 of the total without any problem, the combination of the four stacks into a single large stack is then a logical one.
See Youngs fig. 16, 17 and 28 for proof. Young gives no theoretical explanation and the patent named is the technical design consequence.
The fact that orifices of larger area need wider stacks is logical. The ratio between steam and combustion products is about 1:2, so that 1 unit of steam momentum has to expel 3 units of the final mixture. Conservation of momentum tells us that the theoretical maximum velocity of the mixture cannot be larger than 1/3 of the steam velocity from the orifice. If the total of 3 times the steam at a velocity of 1/3 of the steam has to pass the throat of the stack it should be clear that that throat should have about 9 times the area of the orifice(s).
Both Armstrong and Young are treated in my book, you will find the details there.
Kind regards
Jos Koopmans

JJG Koopmans wrote:
>> Do you mind me commenting on your paper?
You quote the information sheet as "... increasing the size of the nozzles. As a result, the exhaust steam velocity increased,..." That cannot really be true, isn't it? <<

I removed that particular paragraph. It was quoted from another site.

I have uploaded several Union Pacific drawings that appear to cover UP's on-going efforts concerning nozzle and stack designs.

http://donstrack.smugmug.com/UtahRails/ ... d-Nozzles/

I have very little technical background when it comes to steam locomotives, and no engineering background. My intent is to discuss and illustrate the large exhaust stacks used by Union Pacific on its older, smaller steam locomotives. It appears that by time the first 800-class 4-8-4s and first 3900-class 4-6-6-4s came in 1937, and definitely by 1941 when the 4000-class 4-8-8-4s were delivered, UP had settled on what they called their "Multiple Jet" exhaust nozzle. The modifications UP applied to its steam locomotives in the 1930s and 1940s are well covered to my satisfaction in works by William Kratville and his co-authors, Harold Ranks and John Bush.

Don Strack