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Comparing The Challengers

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Comparing The Challengers
Posted by II Phrogs on Friday, January 19, 2024 7:32 PM

    Hello all! I've had this question in my mind for quite some time, and after lurking on the forums for a turn I figured it's time to go ahead and ask it. I am curious as to how the 4-6-6-4 "Challengers" used by various roads compare to one another. While the Challengers of the Union Pacific seem to get their share of recognition, those used by other roads, the NP, WP, D&H, etc. Challengers seem to go forgotten. 

    How did these other 4-6-6-4's stack up to those of the UP, was there a clear "best" among them? How did the relatively poor quality coal used by the Northern Pacific impact their performance, and by extension did the conversion to oil for the SP&S locomotives give any advantage or boost to their performance? Were there any notably poor performers amonst the group? Any and all input/feedback would be much appreciated, if only to give some more recognition to these often overlooked (imho) locomotives!

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Posted by timz on Monday, January 22, 2024 10:41 AM

II Phrogs
was there a clear "best" among them?

Was there? Unlikely. Is there? No, no chance anyone now knows enough about them to even guess at which was "best" overall. Or worst.

Fans like to pronounce upon things like that, but none of them knows anything about what each engine cost to run. For all we know, an engine that looks bad to fans might have been low-maintenance, and fans have no way to find that out.

Likewise, us fans today can't compare legendary French compounds to American counterparts. We don't know how the costs would have compared.

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Posted by kgbw49 on Monday, January 22, 2024 12:54 PM

UP is best known for being the first to use them and therefore naming the type, and also used them on both freight and passenger trains.

UP owned 105 of the total of 252 4-6-6-4 types ever constructed.

Northern Pacific was next with 47 Challengers and Delaware & Hudson owned 40.

steamlocomotive.com has extensive comparative data.

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Posted by samfp1943 on Monday, January 22, 2024 9:01 PM

UP RR #3985 was a favorite of mine: I've been lucky enough to see it in operation on a number of occasions;l In Ks. Ok, Ar, and in Tn, Ky, and on its trip  East to run as Clinchfield 676 for Christmas season of '92-'93 (parts of which are available as You Tube Videos.)

 

Posters might find this linked site of interest.

https://www.trains.com/ctr/railroads/locomotives/most-successful-articulated-locomotive-the-4-6-6-4-challenger/

Article is of a TRAINS article; but the site carries Classic Trains advo.

"Most successful articulated locomotive: The 4-6-6-4 Challenger"

By Kevin P. Keefe | February 1, 2023.

"These mid-century brutes could move tonnage at up to 70 mph"

Listed article has manufacturing info, number built, and railroads that owned them. [ P.S.  That CRR #672 was  purchsed from D&H, and/or DRG&W]  #676 was to have been the last CRR# of its' 4-6-6-4's

FTA:"...The answer was the 4-6-6-4 Challenger, devised by Alco’s engineers and UP Chief Mechanical Officer Otto Jabelman and featuring an unusually high power-to-weight ratio thanks to its large 132-square-foot grate area, boiler pressure of 280 psi, and relatively small 21 x 32-inch cylinders. The two articulated engines together could muster 97,352 pounds of tractive force and were regularly called upon to operate at speeds up to 70 mph..."

 

"...The railroad introduced the 4-6-6-4 Challenger with an order for 15 engines in 1936, followed by four more orders 1937-1944, for a total of 105. All the Challengers featured most of the advances of the era, including one-piece cast frames and roller bearings on all axles. The use of 69-inch driving wheels made the Challenger truly a dual-service engine, suitable for use on passenger trains, notably the Portland Rose. Among the engines used in passenger service was No. 3976, painted in UP’s two-tone gray scheme with yellow striping and equipped with smoke deflectors...

 

A measure of the 4-6-6-4’s success is the fact that eight other railroads went on to acquire Challengers after the introduction of the type on UP. By comparison with UP’s 105 Challengers, the second-largest group was on Northern Pacific, 47 engines, acquired in three groups between 1936 and 1944. The NP engines were bigger and heavier than the UP versions, mostly because of the huge 152-square-foot fireboxes required for use of NP lineside supplies of lower-quality sub-bituminous coal. All the NP Challengers were later converted to oil...

Other railroaders fielding Challengers included the Clinchfield, with 12 engines, six of them acquired second-hand; Delaware & Hudson, with 40; Denver & Rio Grande, with 21, six of which went to the Clinchfield; Spokane, Portland & Seattle with eight, two of which later went to Great Northern; Western Maryland, with 12; and Western Pacific, with seven. Nearly all the Challengers were built by Alco, with the exception of Baldwin engines on D&RGW and WP...."

 

 

 

 


 

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Posted by BigJim on Tuesday, January 23, 2024 8:08 AM

Personally, I disagree with Mr. Keefe. I'm sure a lot of N&W fans do too!

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Posted by timz on Tuesday, January 23, 2024 10:26 AM

You're probably being too generous when you say there was something in that article to disagree with.

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Posted by Overmod on Tuesday, January 23, 2024 11:20 AM

timz
You're probably being too generous when you say there was something in that article to disagree with.

Isn't much question that the evolved 2-6-6-4s had significant advantages over Challengers (the only real 'superiority' being the supposed better guiding of an Adams-style four-wheel engine truck) and by the time of the Alleghenies the issue was beyond much rational 'disagreement'.

Not that I dislike Challengers, mind you.  The D&H engines in particular changed the whole game for D&H operations. 

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Posted by II Phrogs on Tuesday, January 23, 2024 12:25 PM

May I ask what advantages those might be? The only inherent disadvantage of the 4-6-6-4 when compared to the 2-6-6-4 that comes to mind (though I am not in any way an expert on the subject, hence my curiosity) is the shallow firebox of the Challengers, which extends over the rear drivers. While, at least in the case of the N&W A Class, the 2-6-6-4 seems to produce a fair bit more tractive effort, it also seems to have a surprisingly low adhesive factor, would that not balance things out in the end?

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Posted by timz on Tuesday, January 23, 2024 5:26 PM

II Phrogs
in the case of the N&W A Class, the 2-6-6-4 seems to produce a fair bit more tractive effort, it also seems to have a surprisingly low adhesive factor

Because it doesn't have that much more weight on drivers, you mean. Well, yes, can't pull hard without weight on drivers.

Saying "surprisingly low adhesive factor" is exactly the same as saying "surprisingly high calculated tractive effort". N&W thought they could get away with largish cylinders; maybe they assumed their engineers were good at coping with slipping. Maybe they were right -- none of us fans knows.

Incidentally, N&W's calculated tractive effort for the A might have been conservative. The A had limited cutoff (75% or so) so in its TE calculation N&W only assumed 77% mean effective pressure.

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Posted by Pneudyne on Tuesday, January 23, 2024 11:54 PM
 
Maybe look at the 4-6-6-4 vs. 2-6-6-4 comparison this way:
 
Start with the UP “big” Challenger of 1942 as a baseline.  Then design a 2-6-6-4 (or 2-6-6-6 if needs be) within the following constraints:
 

1.     The same driving axle load (67 500 lb)

2.     Lateral railhead forces (during curving and arising from restraint of yaw oscillation) no higher at any speed, recalculating the 4-6-6-4 for any lateral control improvements developed for the 2-6-6-4 case that could also be applied to the 4-6-6-4.

3.     No perceptible difference in whole locomotive and front engine unit stability at any speed,

4.     The same factor of adhesion.

 
What then would be the likely advantages conferred by the 2-6-6-4 (or 2-6-6-6), realizable in daily service?
 
(I don’t know the answer, by the way.)
 
 
 
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Posted by BigJim on Wednesday, January 24, 2024 8:12 AM

II Phrogs
While, at least in the case of the N&W A Class, the 2-6-6-4 seems to produce a fair bit more tractive effort, it also seems to have a surprisingly low adhesive factor, would that not balance things out in the end?


You only need to look at the performance of the Class A's hauling coal west and east to see that the factor of adhesion was not a problem. 

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Posted by II Phrogs on Wednesday, January 24, 2024 11:42 AM

BigJim

 

You only need to look at the performance of the Class A's hauling coal west and east to see that the factor of adhesion was not a problem. 

 

 

What of testing done on the Class A by other railroads  when tested (I believe it was the PRR, but feel free to correct me), where it was found quite wanting on grades in excess of 1%?

This is the exact reason I have always been a big fan of the Challengers (and why I wanted to know more about their differences across the various roads which used them!). They have always struck me as incredibly well balanced locomotives, being relatively fast and powerful, but not at the expense of adhesion to the rails. They were used by quite a number of railroads and as a result encountered a variety of running environments/conditions. On top of all this, they did it all using some of the poorest quality coal out there, unlike some locomotives which required a more pampered diet of only "top shelf" coal.

(unrelated, but I hope I included the quote correctly. I'm still getting used to using the forums and due to the wait time between submitting my reply and having it approved it's taking me some time to figure out the details.)

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Posted by pennytrains on Wednesday, January 24, 2024 7:53 PM

It'll a bit annoying but it goes away as soon as the moderators realize you're the real deal Wink

Big Smile  Same me, different spelling!  Big Smile

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Posted by timz on Wednesday, January 24, 2024 8:11 PM

II Phrogs
[N&W's 2-6+6-4] was found quite wanting on grades in excess of 1%?

How wanting? PRR tested the A, but none of us has any idea what tonnage it pulled on what PRR grades, or failed to pull. PRR decided not to bite, but none of us knows why.

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Posted by BigJim on Wednesday, January 24, 2024 9:25 PM

II Phrogs
What of testing done on the Class A by other railroads  when tested (I believe it was the PRR, but feel free to correct me), where it was found quite wanting on grades in excess of 1%?

No need for other RR's. Just listen to any of the actual recordings of the Class A's on the Blue Ridge grade, which by the way is in excess of 1%, and you will find that they are quite surefooted! Then, go find out what kind of tonnage they hauled on the way out of Williamson, WVa or Crewe, Va. I am sure that you will find that you need to do tons more researching before you go jumping to conclusions!

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Posted by kgbw49 on Friday, January 26, 2024 9:25 PM

Here is a picture of Challenger 3935 on Train 717 The Los Angeles Challenger in 1940.

https://www.railpictures.net/photo/850086/

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Posted by Flintlock76 on Saturday, January 27, 2024 9:57 AM

timz
How wanting? PRR tested the A, but none of us has any idea what tonnage it pulled on what PRR grades, or failed to pull. PRR decided not to bite, but none of us knows why.

I've said this before and I'll say it again.  I have no way of proving this but I suspect the PRR (with Baldwin looking over their shoulder) after testing an N&W Class A ( and Class J for that matter) didn't want to admit those "hillbillies" down in Roanoke were better at steam locomotive design than they were!  Laugh  

Corporate ego may not have played a role here but I wouldn't discount it entirely.  The PRR didn't call itself "The Standard Railroad Of The World" for nothing!  

Just a "might have been" to think about.  Post-WW2 and flush with money and not having bought any new steam locomotives since 1930 the Jersey Central was considering buying Challengers for their coal drags but not for long.  In the end they bought F3 diesels. 

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Posted by CSSHEGEWISCH on Saturday, January 27, 2024 10:00 AM

More proof of the lack of standardization in steam.

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Posted by Erik_Mag on Saturday, January 27, 2024 12:31 PM

Diesel locomotives can produce close to rated horsepower at any speed from the speed at which maximum continuous tractive effort to somewhere near maximum rated speed. Furthermore, by simply changing the gear ratio, a given locomotive mode can be set up for drag service or high speed service. Finally, diesel locomotives can be M.U.'ed so it is simple to lash up just the required number of units to haul a train. Fuel is pretty much the same for all RR's.

Steam locomotives are much less flexible, requiring different designs for flat land running versus mountain hauling, hauling long trains versus short trains, etc. Fuel could be high quality bituminous, lignite or bunker C, each requiring different firebox designs.

To be fair, lack of standardization in steam was driven by hard requirements as well as the whims of the various mechanical departments.

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Posted by BaltACD on Saturday, January 27, 2024 3:18 PM

Erik_Mag
Diesel locomotives can produce close to rated horsepower at any speed from the speed at which maximum continuous tractive effort to somewhere near maximum rated speed. Furthermore, by simply changing the gear ratio, a given locomotive mode can be set up for drag service or high speed service. Finally, diesel locomotives can be M.U.'ed so it is simple to lash up just the required number of units to haul a train. Fuel is pretty much the same for all RR's.

Steam locomotives are much less flexible, requiring different designs for flat land running versus mountain hauling, hauling long trains versus short trains, etc. Fuel could be high quality bituminous, lignite or bunker C, each requiring different firebox designs.

To be fair, lack of standardization in steam was driven by hard requirements as well as the whims of the various mechanical departments.

One overlooked area of the differences between steam and diesel.  Steam engines, besides containing the air compressors and the brake valve - did not factor into the braking equation for the train it was hauling.  Using he Independent brake would bring the brake shoes in contact with tires on the drivers.  The tires had been heated to create a shrink fit with the driver wheel when the tire cooled.  If too much Independent brake was used the tire(s) could expand from the heat and leave the driving wheel.

Diesel have the use of Dynamic Brakes to retard the movement of the train and thus the locomotives become a bigger factor in the braking of trains, especially in mountainous territory..

In steam days the Retainer Valves had to be manipulated by the crew to 'reatin' brake applications for a period of time while the trainline was being recharged after a brake application was released.  Setting the Retainers up or down was a manual fuction performed by the brakemen on a train.

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Posted by BigJim on Monday, January 29, 2024 9:04 AM

II Phrogs

May I ask what advantages those might be? The only inherent disadvantage of the 4-6-6-4 when compared to the 2-6-6-4 that comes to mind (though I am not in any way an expert on the subject, hence my curiosity) is the shallow firebox of the Challengers, which extends over the rear drivers. While, at least in the case of the N&W A Class, the 2-6-6-4 seems to produce a fair bit more tractive effort, it also seems to have a surprisingly low adhesive factor, would that not balance things out in the end?

I would suggest that you try to find and read a copy of Eugene L. Huddleston's book "The World's Greatest Steam locomotives". In this book Mr. Huddleston compares the "Allegheny", the Class A, and the Challenger. Plus, some other tid-bits!

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Posted by II Phrogs on Monday, January 29, 2024 2:50 PM

BigJim

I would suggest that you try to find and read a copy of Eugene L. Huddleston's book "The World's Greatest Steam locomotives". In this book Mr. Huddleston compares the "Allegheny", the Class A, and the Challenger. Plus, some other tid-bits!

 

Many thanks for the reading suggestion, I am ever on the prowl for a new book to expand my collection/knowledge and will certainly look into acquiring a copy of this one! Additonally thank you and others for the responses regarding the Class A 2-6-6-4's, I do hope I did not come off as disparaging these fantastic locomotives, I wish only to expand my understanding of these fascinating machines. 

If I may turn back to my initial question and request your and others knowledge on the subject, I have one standing question in regards to the Z-8 Challengers of the NP and SP&S. As I understand it, the SP&S challengers were converted to burn oil, however kept the gargantuan fireboxes of the original NP design. Would this conversion to oil have any appreciable impact on the performance of the locomotives? What differences might one expect going from burning the incredibly low quality coal used by the NP to burning oil? Any insight into this is greatly appreciated.

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Posted by kgbw49 on Monday, January 29, 2024 9:29 PM

Great Northern also owned two Z-6 oil-fired Challengers that were bought from subsidiary Spokane, Portland & Seattle that were numbered 4000 and 4001.

Eventually as it dieselized the Great Northern sold them back to SP&S.

But Great Northern is not typically though of as a Challenger owner but it was in the 4-6-6-4 club!

https://www.deviantart.com/avalanch11/art/Great-Northern-4-6-6-4-4000-Steam-Locomotive-996878578

 

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Posted by Conductor_Carl on Tuesday, January 30, 2024 12:29 PM

Comparing the different Challengers may be a bit hard as they are geographically far flung enough that their usage may vary, and what works for the Northern Pacific may not be applicable to the Delaware and Hudson.

I think that there are two ways that you could cut this to be interesting. 

1. Look at the usage of the UP challengers on the Rio Grande and Clinchfield. If they worked essentially just as well on all three roads then that is a lot of geographical distance and perhaps different usage covered by one loco type and would speak to a universal quality.

2. Compare the UP Challengers on the Rio Grande to the Rio Grande Challengers. This compares two the two different Challenger  different builders (ALCO and Baldwin) on essentially the same road and conditions. 

On a subject change, I feel like I have heard of the Western Maryland Challengers being a cut above. Something to the effect of them being higher horsepower than the others?

 

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Posted by BaltACD on Tuesday, January 30, 2024 2:36 PM

Conductor_Carl
...

On a subject change, I feel like I have heard of the Western Maryland Challengers being a cut above. Something to the effect of them being higher horsepower than the others?

Read in a book about the WM, the operating costs of their Challengers was such that the WM parked them several year BEFORE their equipment trusts expired - thus WM found it to their advantage to pay on the equipment trust without using the equipment that the trust was for.

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Posted by Conductor_Carl on Tuesday, January 30, 2024 5:50 PM

Well, that ain't good

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Posted by Pneudyne on Thursday, February 1, 2024 1:11 AM
 
Although there is likely insufficient operational and performance data to undertake a full comparison of the several Challenger types, at least a relatively simple dimensional comparison may be made.
 
The original UP Challengers of 1936 were built to a 65 000 lb axle loading limit, and had 386 000 lb on drivers.  The grate area was 108 ft² (a number inherited from the 4-12-2).  Boiler pressure was 255 lbf/in², cylinder dimensions were 22” x 32”, with 69 inch drivers.  Alco and UP may have been concerned about front engine stability at higher operating speeds.  So, although a conventional (two-plane) articulation joint was used, it was friction damped on its pitch axis.  The pilot truck also had pitch damping.  The choice of four-wheel pilot truck was part of this, although the total weight, coupled with the relatively modest weight on drivers imposed by the axle loading limit probably made the use of the four-wheel truck mandatory anyway.  Apparently, reduction of rail thrusts was one of UP’s objectives, and it was anyway accustomed to using four-wheel pilot trucks on its fast freight locomotives.  To put the UP Challenger adhesive weight into perspective, the N&W 2-6-6-4, as first built in 1936, had 430 000 lb on drivers, suggesting that it was built to an axle loading target or limit of 72 000 lb, more than 10% higher than the UP number.
 
The following NP Challenger was a derivative of the UP design, with a much larger (152 ft²) grate area to facilitate the burning of rosebud coal.  Thus, it was heavier, with an adhesive weight of 435 000 lb, suggesting a target axle loading of 72 500lb.  Perhaps to take advantage of this, the cylinder diameter went up to 23”.  Boiler pressure was 250 lbf/in².  It retained the same pitch damping arrangement as on the UP locomotive.  The longer firebox meant a longer engine wheelbase, 61’10” as compared with 59’11”.
 
The 1938 WP Challenger appeared to have been more-or-less the UP design with some detail changes, and somewhat heavier.  Adhesive weight was 416 000 lb.  Perhaps the axle loading target was 69 500 lb or thereabouts.  Cylinders were the “standard” 22” x 30”, with 70 inch drivers and a 265 lbf/in² boiler pressure.  Whether it had the pitch damping arrangement is unknown, but as a clone of the UP original it does seem likely.
 
The 1940 D&H Challenger was a modernization of the original UP design, retaining the same basic dimensions, including the 108 ft² grate area.  The driving axle load target was 68 000 lb, and the adhesive weight was 406 500 lb.  That was distributed asymmetrically, 201 000 lb on the rear and 205 500 lb on the front, this to provide nominally equal distribution on a 1.5% upgrade.  Boiler pressure was 285 lbf/in², and cylinders were 20½” x 32”.  These dimensions appear to reflect the D&H leaning towards higher-than-typical boiler pressures.  Mechanically, it had cast frames, something that the earlier Alco Challengers did not, but probably should have had.  Also, it had a single-plane articulation joint, which dispensed with the need for pitch axis damping.  This type of joint seems to have originated with the N&W 2-6-6-4 in 1936.  It might have been a GSC idea, something that took advantage of the extra strength of cast frames.
 
The second NP Challenger design in 1941 was a little longer than its original, with a total engine wheelbase of 62’2”.  The boiler had the same grate area as before, but was slightly longer.  Adhesive weight went up to 444 000 lb, suggesting an upward axle loading creep to 74 000 lb.  Cylinders were still 23” x 32”, but drivers were 70 inches (with slightly longer driving wheelbase) and boiler pressure was 260 lbf/in².  As far as I know, NP retained the two-plane articulation joint.  Whether it also retained the pitch axis damping is unknown
 
The 1942 Clinchfield Challenger was the D&H design with detail changes.  A 70 000 lb driving axle load allowed a 420 000 lb adhesive weight.  It reverted to the “standard” 22’ x 32” cylinder size with 265 lbf/in² boiler pressure.
 
But the 1942 UP “Big” Challenger was virtually a complete departure.  Rather it seemed to have been more-or-less a three-quarter sized edition of the Big Boy.  Grate area was 132 ft², boiler pressure was 280 lbf/in², cylinders were 21” x 32”, and drivers were still 69”.  The axle loading target was 67 500 lb (a number which UP appeared to have adopted with the original FEF), and adhesive weight was 404 000 lb.  They had cast frames and single-plane articulation joints.  Also they had the full Alco-Blunt system of lateral controls, as did the Big Boy, and which UP had adopted with the FEF-2 in 1939.
 
Baldwin’s first of two Challenger designs was in 1938 for the DRGW.  It had a 136.5 ft² grate area, 255 lbf/in² boiler pressure, 23” x 32” cylinders, 70” drivers and 438 000 lb adhesive weight, suggesting a 73 000 lb axle loading target.  It does appear that Baldwin was aiming at a somewhat larger locomotive overall than the baseline Alco design.  It did have cast frames, but with a conventional two-plane articulation joint.
 
Baldwin’s second Challenger design for WM in 1941 was somewhat smaller, broadly similar in size to the Alco baseline design.  Grate area was 118.8 ft², boiler pressure was 250 lbf/in², cylinders were 22” x 32”, and drivers were 69”.  Adhesive weight was 402 000 lb, suggesting an axle loading target of 67 000 lb.  It had cast frames with a conventional articulation joint.  It did have a different steam distribution system to the DRGW design, though.
 
Notwithstanding the variations indicated in the foregoing, all of the Challengers had one common dimension, namely 102 inches boiler maximum outside diameter (BMOD).
 
Note also that later batch builds of a given design sometimes had variations, particularly in respect of weight.
 
I should be wary of drawing too much from the above very simple comparison, which does not at all address the thermal aspects.  Nonetheless, on the basis of adhesive weights alone, it is not difficult to see a possible reason as to why DRGW preferred its own design over the UP “Big” design foisted upon it by the WPB.  Simply its own design would have been able to reliably start and accelerate a heavier load on the ruling grade.
 
UP does seem to have been more concerned about rail stress than most.  I suspect that the 67 500 lb axle loading that it allowed for its late steam designs, conservative relative to what other large roads were doing, did not reflect a lighter track and roadbed, but a concern as to what happened at higher sustained speeds, given that rail stresses increase as the square of the speed.  Its adoption of the Alco-Blunt lateral controls is another indicator.  Possibly the severe winter conditions to which most of its main line was exposed was another factor in its conservatism.
 
The original Alco UP Challenger was somewhat “shaped” by the fact that at least to a first approximation, it was an articulated derivative of the UP 4-12-2.  The latter was built to a nominal axle loading of 59 000 lb, although the trailing truck was over at 60 000 lb.  Thus, any likely derivative was almost certain to have an additional carrying axle.  The four-wheel pilot truck came into UP freight locomotive practice as a matter of necessity, with the 4-10-2.  This was intended to be as much like its 2-10-2 as possible, but the extra weight, and probably the extra overhang, of the three-cylinder assembly, necessitated a four-wheel pilot truck.  This was carried over to the 4-12-2, and apparently the UP found it advantageous in general.
 
 
 
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Posted by II Phrogs on Thursday, February 1, 2024 12:01 PM

Pneudyne
 

Just wanted to say thank you, this was both a highly informative and entertaining read and gives a good understanding of. the differencies and similarities between the various Challenger designs. 

If I am remembering correctly, I believe the D&RGW used a handful of the later Alco designed Challengers which were diverted from a UP order to make up for a shortage in motive power on the D&RGW during the war. To your knowledge, how did these UP Challengers fare in service on a different railroad? From what I've read the D&RGW wasn't particularly enamored with these locomotives. Was this due to any inherent flaw in their design, or was it more that the Challengers were delivered in lieu of the FT diesels that many roads were trying to get their hands on around this time? Is there any data or testimony on how these locomotives stacked up to the Baldwin 4-6-6-4's already in use on the D&RGW?

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Posted by Leo_Ames on Thursday, February 1, 2024 1:58 PM

I have no insight on how they were viewed by the line, but Trains reported at the time that the Rio Grande returned them to the War Assets Administration since they were surplus to their needs with the postwar traffic decline and they didn't want to purchase them.

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Posted by drgwcs on Thursday, February 1, 2024 8:35 PM

II Phrogs

 

 
Pneudyne
 

 

 

Just wanted to say thank you, this was both a highly informative and entertaining read and gives a good understanding of. the differencies and similarities between the various Challenger designs. 

If I am remembering correctly, I believe the D&RGW used a handful of the later Alco designed Challengers which were diverted from a UP order to make up for a shortage in motive power on the D&RGW during the war. To your knowledge, how did these UP Challengers fare in service on a different railroad? From what I've read the D&RGW wasn't particularly enamored with these locomotives. Was this due to any inherent flaw in their design, or was it more that the Challengers were delivered in lieu of the FT diesels that many roads were trying to get their hands on around this time? Is there any data or testimony on how these locomotives stacked up to the Baldwin 4-6-6-4's already in use on the D&RGW?

 

Rio Grande had originally wanted to order some additional Baldwin 4-6-6-4's. The war production board would not do so and diverted some from a UP order. The Alco UP design challengers diverted to the Rio Grande were on lease from the War Production Board. The Rio Grande crews did not like them. From what I remember reading (but I can't remember the source and was trying to find it) the crews found the pullling power lacking along with the ride qualities compared to the Baldwins. I am trying to remember but it seems like they may have had some issues with the centipede tenders. UP and Rio Grande approaced their usage of challengers a bit differently. UP tended to run higher speeds- Rio Grande slower and longer trains. After the war the Alcos were given back to the War Production board and would up beind sold to the Clinchfield.

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