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UP 4-8-2 #7000-#7039

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UP 4-8-2 #7000-#7039
Posted by Lutz us-brass on Friday, April 7, 2023 4:08 AM

Is anyone positive if the Union Pacifics Mt-1 were originally equipped with stokers? William Kratville (p. 156 in "Motive Power") writes "emerged with Duplex stokers". ChatGPT (with unknown source): "The Union Pacific Railroad's 4-8-2 Mt-1 steam locomotives were not originally fitted with stokers from the factory". UtahRail.net also states "UP7000-7039 originally equipped without stokers".

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Posted by Steven Otte on Monday, April 10, 2023 8:36 AM

ChatGPT should not be considered a reliable source on the topic of... anything, really. Tests have shown it to be capable not only of inventing falsehoods, but of inventing false references to back up those falsehoods. For example... https://jonathanturley.org/2023/04/06/defamed-by-chatgpt-my-own-bizarre-experience-with-artificiality-of-artificial-intelligence/ 

--
Steven Otte, Model Railroader senior associate editor
sotte@kalmbach.com

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Posted by Overmod on Monday, April 10, 2023 10:00 AM

ChatGPT will almost certainly have scraped their 'information' from the UtahRails reference, which we can assume is one of the first that will come up if you search on 'Union Pacific MT-1 stokers' or whatever.

I suspect that the locomotives were subject to the ICC stoker requirement of the mid-Thirties related to locomotive weight.  Perhaps the UtahRails reference or something in Kratville discusses why Duplex was chosen, and if there are interesting mechanical details of the implementation.

As a rule, with both Wikipedia and any of the ChatGPT variants, use a strict policy akin to 'trust-but verify'... you should always back up anything 'asserted' by either with real, objective sources, before actually concluding anything or proceeding on what they have said.  With Wikipedia, be sure to read through the 'talk' page as very often there's information there that hasn't been properly included.

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Posted by timz on Monday, April 10, 2023 10:14 AM

This looks authoritative

https://babel.hathitrust.org/cgi/pt?id=njp.32101048912321&view=1up&seq=525

(lower right corner of the first page) 

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Posted by Overmod on Monday, April 10, 2023 11:28 AM

Duplex stoker clearly pictured on p.384.  So if the locomotives were 'recently delivered' without stokers they had them by press time for July 1922 publication.

(Unless of course it's an AI deepfake production... which I really, really doubt.)

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Posted by M636C on Monday, April 10, 2023 7:44 PM

Given the wide scope offered by the thread title, I wonder if I might widen the discussion to include valve gear.

The 7000s were built with Young Valve gear, which was not that widely applied. Looking at the description, I note that the 7000 had 9 inches of valve travel.

I don't think this amount of travel was usually available from Walschaerts gear, and since the 7000s (or some of them) were rebuilt with Walschaerts valve gear, was the valve travel shortened on conversion?

Peter

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Posted by timz on Tuesday, April 11, 2023 4:51 PM

I assume 9 inches was "available" from Walschaerts, but I guess people thought it was a bad idea. However, more than 9 inches on SFe's first 2-10-4:

https://babel.hathitrust.org/cgi/pt?id=mdp.39015013032902&view=1up&seq=711&size=150

Around 7-1/2 inches on all the later ones, tho.

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Posted by Overmod on Tuesday, April 11, 2023 9:36 PM

If I remember, the de Caso 232 U1 has Walschaerts with at least two of the cylinders having over 15" (!) valve travel.

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Posted by Lutz us-brass on Wednesday, April 12, 2023 12:37 AM

Thank you very much. That is really an authorative source describing the loco "as built"

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Posted by Lutz us-brass on Wednesday, April 12, 2023 12:38 AM

You're right, thanks.

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Posted by Overmod on Wednesday, April 12, 2023 12:01 PM

Some potentially interesting details:  these locomotives appear to have been built with 'oversquare' cylinders (29x28), and I have seen a picture of one which retained the Young valve gear, but had gotten a balancing 'beauty treatment' complete with disc (appears to be Boxpok) main.  There is evidence that these locomotives received cast engine beds and at that time the valve diameter was increased to 16" -- this may account for the lessening of valve travel due to the Walschaerts gear.

Apparently steamlocomotive.com thinks "many" of these engines got a parabolic nose and 'streamlining'.  I'm only aware of the one streamlined engine, 7002, which as protect power for Streamliners got the 100mph Timken rods and some other performance enhancements... the railroad went to 4-8-4s instead as the next generation of very-high-speed power, interestingly going to some pains to get 100mph capability without going either to thin-section rods or rod roller bearings.

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Posted by M636C on Thursday, April 13, 2023 2:20 AM

Overmod

If I remember, the de Caso 232 U1 has Walschaerts with at least two of the cylinders having over 15" (!) valve travel.

 

Quoting from Chapelon's "La Locomotive a Vapeur" (as translated to English)

"The Walschearts gear has exceptionally long travel, easpecially at short cut-offs, thus at 30% in both HP and LP cylinders, the travel is 142mm in the HP valves and 180mm in the LP, against 233 and 296 mm respectively in full gear at 75% cut-off."

296mm is 11.65 inches

The diameter of the LP valve is 422 mm (16.61 inches)

The 232U 1 had two sets of Walschearts valve gear with the inside (HP, although this isn't specifiied in the text) driven through rocking levers. Each cylinder has its own combination lever.

Apparently at starting, the LP cut-off was increased to 90% from the 75% specified above.

Peter

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Posted by M636C on Thursday, April 13, 2023 8:17 AM

timz

I assume 9 inches was "available" from Walschaerts, but I guess people thought it was a bad idea. However, more than 9 inches on SFe's first 2-10-4:

https://babel.hathitrust.org/cgi/pt?id=mdp.39015013032902&view=1up&seq=711&size=150

Around 7-1/2 inches on all the later ones, tho.

 

On page 126  of "the British Steam Locomotive" by O.S. Nock, figure 189 is a diagram of the valve gear of the Chinese 4-8-4, later class KF1.

To quote the text: "A further drawing (fig. 189) shows the layout of the valve and drive gear and the 2:1 lever extension of the valve rod used to provide a maximum travel in full gear of no less than 9 inches."

This arrangement had been removed from these locomotive post WWII, presumably with shorter valve travel. In 1988 (I think) I was able to visit Colonel Kenneth Cantlie at his home in London where we discussed the design of the KF1 locomotive which he had supervised. He said that this modification was neccesary to obtain such long valve travel, although long travel could also be obtained by using Baker valve gear.

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Posted by timz on Thursday, April 13, 2023 10:18 AM

Next question: what's the objection to 9-inch travel with Walschaerts? One article said the link should never be designed to swing thru more than 45 degrees. And the link can only be so long and still fit in the available space?

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Posted by Overmod on Thursday, April 13, 2023 10:46 AM

One approach to the issue of longer valve travel is to use a bell crank between the reach rod and the valve piston rod.  For long-lap long-travel valves this maintains reasonably fast port opening across the steam edges.

See also the variable-lead arrangement on the D&RGW 4-8-4s and 4-6-6-4s.

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Posted by Overmod on Thursday, April 13, 2023 10:51 AM

M636C
The diameter of the LP valve is 422 mm (16.61 inches)

Before the screaming starts, I believe these were Willoteaux fabricated valves, so both 'double' and lighter in mass.  I don't remember if the Carpenter translation has a cross-section that shows these, but if so, someone might scan it; I think Thierry Stora's site had a section on them.

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Posted by M636C on Thursday, April 20, 2023 9:10 PM

Overmod

 

 
M636C
The diameter of the LP valve is 422 mm (16.61 inches)

 

Before the screaming starts, I believe these were Willoteaux fabricated valves, so both 'double' and lighter in mass.  I don't remember if the Carpenter translation has a cross-section that shows these, but if so, someone might scan it; I think Thierry Stora's site had a section on them.

 

 

I've checked my translation of "La Locomotive a Vapeur" and I can find no details of Willowteaux valves apat from references to their fitting to certain locomotives. There isn't even a drawing of 232 U1, although there are drawings of the 232R and 232S types. This could be due to the fact that the 232R and 232S would have been included in the first edition of the book while the 232U appeared after that book had been published.

The main users of Willowteaux valves were the rebuilt Paris Orleans 3500 class Pacifics and the very similar "TP" Pacifics on the Etat Railway. While many were rebuilt with poppet valves for both high and low pressure cylinders (3700 series on the PO and 231D on the Etat), a number were rebuilt retaining the original HP cylinders and piston valves, but adding Willowteaux valves to the LP cylinders. This provided much greater cross sectional area for steam flow, and was a muh less costly solution to improving the power output of these locomotives. These were class 3800 on the PO and 231W on the Etat.

The actual valves replaced slide valves and were fitted outside the plate frames forward of the HP cylinders. While the poppet valve conversions had valve casings with square corners, Willowteaux conversions had casings with curved lower corners, possibly reflecting the outside diameter of the valve casings. This difference appeared on both PO and Etat locomotives. The Willowteaux vavles appeared to be generally similar in diameter to the HP cylinders, as was the case with 232U 1 although this was not readily visible as in the case of the rebuilt Pacifics.

Peter

 

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Posted by Overmod on Friday, April 21, 2023 9:45 AM

Willoteaux (note sp.) as I understand them have fabricated thin-section construction rather than a cast body between sealing rings.  The internal shape of the area that passes steam is curved and 'streamlined' to optimize port flow at high mass flow/LP pressure; in fact the valves I remember on 232 U1's LP side actually had two full valve bodies on a common actuated spindle, one for each end of a cylinder.

At one time I thought these were partially activated by rotation as well as excursion (which is something I used on the de Glehn 4-8-4s I 'designed' in my teens).  That would allow much faster 'porting' and 'unporting' than even a very long-lap valve with a straight steam edge restricted by valve-cylinder diameter could likely provide.  But there are no English-language sources that actually indicate the valves were anything other than a kind of merger of piston-valve and slide-valve practice in their function.

As I recall, there are sites on the Web that show these valves in section, but I don't have the time to confirm them and link here.  

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Posted by M636C on Thursday, April 27, 2023 8:34 AM

Overmod

Willoteaux (note sp.) as I understand them have fabricated thin-section construction rather than a cast body between sealing rings.  The internal shape of the area that passes steam is curved and 'streamlined' to optimize port flow at high mass flow/LP pressure; in fact the valves I remember on 232 U1's LP side actually had two full valve bodies on a common actuated spindle, one for each end of a cylinder.

At one time I thought these were partially activated by rotation as well as excursion (which is something I used on the de Glehn 4-8-4s I 'designed' in my teens).  That would allow much faster 'porting' and 'unporting' than even a very long-lap valve with a straight steam edge restricted by valve-cylinder diameter could likely provide.  But there are no English-language sources that actually indicate the valves were anything other than a kind of merger of piston-valve and slide-valve practice in their function.

As I recall, there are sites on the Web that show these valves in section, but I don't have the time to confirm them and link here.  

 

My apologies for mispelling Willoteaux.

I often add letters where a word is similar to a common English word.

I have trouble writing "Wabtec" without adding an "h" on the end.

However, I have found a diagram of Willoteaux valves.

Piston vs. Caprotti Valves 2 | Advanced Steam Traction (advanced-steam.org)

Just scroll down the page and a diagram of the proposed 152P design shows the twin Willoteaux valves for the single high pressure cylinder.. I guess that provides quadruple inlet and exhaust.

Having checked a number of French sources I've found the number of locomotives fitted with Willoteuax valves. Of 89 Paris Orleans 3500 series Pacifics, 15 were fitted with Willoteaux valves on the LP cylinders. All the others were fitted with Lentz poppet valves on both HP and LP cylinders. Of 283 Etat Pacifics, basically similar to the PO engines but with round top fireboxes instead of Belpaire, 22 were fitted with Willoteaux valves on the LP cylinders (of which two had  Willoteaux valves on the HP cylinders also.) Most had Lentz valves on the LP,, around 25 had Lentz valves on both the HP and LP and another 25 reached the SNCF in 1938 in original condition.

232U1 might be the only other locomotive with Willoteaux valves, since contrary to what was stated in the linked article, Chapelon indicates that 242A1 had twin Trick valves on the HP cylinder.

Peter

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Posted by Overmod on Thursday, April 27, 2023 12:22 PM

M636C
contrary to what was stated in the linked article, Chapelon indicates that 242A1 had twin Trick valves on the HP cylinder.

Bear in mind that "trick porting" is both a principle derived from a name (I think it was Richard Trick, but it has been a long time and only an incidental discovery) and a general principle involving multiple passages in a single slide or valve body.  It is quite possible that a reference would show trick-ported valves of fabricated and flow-streamlined construction -- good trick porting is all about improving steam flow, usually for high speed/short events, and often tied to the kind of mass flow that would have been required for unsuperheated steam...

I have seen longitudinal sections of 242 A1 and I suspect the valve construction would be readily seen in an appropriate section.  I am not good enough to tell conclusively from the available lateral section at the valves what the detail design actually is.

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Posted by M636C on Thursday, April 27, 2023 6:41 PM

I wasn't impressed by the clarity of the diagram, but it was almost certainly a section from a complete drawing of the 2-10-4 concerned.

I was amused by a reference to Trick ports on the New South Wales D58 class, where in an internal memo, the valves were described as the "Herr Trick" type to emphasise that it was a (German) person's name. I just use a capital letter.

Peter

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