Hi,
you asked:
"Was the UP Challenger a 100 % substitute for the UP 9000 class as concerns t.e.??"
This table may not answer all concerns about TE, however it shows, that basically 4-12-2's and 1936 built CSA 4-6-6-4 Challengers had similar tonnage ratings.
Heavy Challengers built after 1942 had some 100 tons higher ratings, reflecting their higher HP and better downhill capabilities. Example: Buford to Cheyenne is -1,55% grade, they could drift downhill with 1000tons (5100 vs 4100) more than the the 4-12-2.
So, the answer should be yes -edit- err no -equivalent -you name it
Tonnage ratings on the UP were usually only as high as a engine can start its trains on grades safetly from a full stop without stalling again.
Altough tonnage ratings were pretty similar between different classes, they certainly did achieve different road-speeds with their loads.
A wild guess of mine is, T1 and Santa-Fe Texas-Types and Q2-Duplexes would be rated quite similar like "Heavy Challengers".
Thank-you for your clarification, Juniatha. I believe I understand better what you mean. I guess I would want to know the numbers. What weight would each driver bear in each case, and what horsepower would each driver take prior to slipping at a given speed with a standardized weight comparison. I am out of my depth, naturally, but how do the factors of adhesion compare across drivers between the 9000 and the 3900's? What tractive effort can each locomotive apply to the drawbar at 0.01, 1, 4, 8, 15, 20, 30, and 45 mph on a measured length of track in the districts where they shared work?
If time is a factor, which of the two needed more frequent stops for replenishment after the typical tonnages each was meant to trail at the same speed had been moved 200 miles?
Crandell
Hi Crandell
My question really focuses on actual tonnage limit ratings for daily service on a given ramp section – you name it .
If we put aside all those extreme opinions offered in various articles in the past about alleged slipping problems with T-1 Duplex it was generally agreed that they were to a certain degree more sensitive at starting because of 2 x 4 coupled wheels drive sets instead of 1 x 8 . Now , my question is if that wasn’t likewise true with 2 x 6 instead of 1 x 12 coupled wheels ?
..
Hi California Zephir
Well , yes , the Challies could rise to some respectable speeds with a formidable revenue load , no doubt , also sneaked round corners more easily than the straight twelve coupled Nines – sure . Further , there were some problems with the middle drive in the 4-10-2 and 4-12-2 engines – actually quite the same problems that were encountered in Europe with three cylinder engines having separated drive axles for inside / outside cylinders . We could go on listing compromises in the Chally and the Nine , then I would likely get into how this and that could have been improved and what it would have enabled the engine to do – but that’s not the point .
What I would really like to know : were the simple expansion Mallets really fully up to pulling capacity of a straight twelve coupled engine of comparable size or were they a match rather for a big Texas type ?
In general : could a divided drive be directly compared ( per number of coupled wheel sets ) to a straight frame drive set or didn’t such an engine need a somewhat larger adhesion mass – either by having one more coupled axle or by higher mass per powered wheel set – to compensate for lesser surefootedness *because* of the divided drive sets ? In such a comparison , considering historic engines inevitably has historical variations in quality of design intervening – however let’s not allow those to blur the picture , let’s boil down to the principal question of what the effect of each configuration was – straight frame / articulated frames . Mind , in modern synchronous electrics as in diesel-electric engines , not just wheel sets of a power bogie but wheel sets of front to rear bogies are being electronically coupled to achieve maximum adhesion and minimize effects of slip spots !
Seeing the J-1 locos at work must have been impressive , thank you for showing the photos !
Hi Firelock
Yes , no half-measures : it’s in the name , this railroad was on the *up* not down *g* and is still around going strong .
Only , why on earth they introduced that longer wheel spacing first to second coupled axle when already they had opted for larger wheels on the twelve coupled as compared to the ten coupled predecessor I will never understand ! Well , sure , obvious reason was that middle drive to second coupled axle : to accommodate a longer drive rod . However , with just a little bit further slanting of center line of middle drive , the leading coupled axle could have been set at the same spacing as the others , saving at least some length in an already long coupled wheel base . (By the way – this 67” , 68” and 69” staggering of drive wheel diameters in the Nine , BB and CSA – all of it smaller than diameter reduction by wear : was it really worth it?)
Further , why did the Union Pacific insist on having the conical boiler section with the slope turned on top in the Nines instead of at the bottom as it was with the predecessor 4-10-2 – an arrangement that was for good reason applied later in 1950s / 60s fully welded combustion chamber boilers designed for high specific steaming rates ? UP didn’t continue that feature in their Challengers and later power .
However , that’s just one point each about the middle drive and the boiler arrangement , so let’s stop it here or else I will end up with a re-design proposal and that wouldn’t be fair in view of long time elapsed since these engines roamed the rails .
Hi BaltACD
Well , sure – however that’s not the question since the long wheel base didn’t interfere with tractive effort on a ramp – except for sharp curves where the flange to rail angle of the leading or first two coupled axles might cause a certain reduction of adhesion available to transmission of tractive effort due flange friction and contact point of wheel wandering away from polished spur on rail head – but that would apply to tight yard radii , on mainline radii of curves these aspects have but limited influence .
However taking into account detailed aspects of adhesion would lead astray from the basic question – see my second answer , second and third paragraph .
( Sorry I saw your posting appear only when I had sent mine , so I edited it to include this answer to you )
Regards
Juniatha
edit : trouble getting my formatting to appear as set – hopefully straightened now
But that long fixed wheel base of 6 driving axles limited where they could be operated.
Firelock76 I think CAZephyr pretty much said it all about the UP's 9000's, except for one thing: That loooong wheelbase was just so cool looking! Twelve drivers! Wow! No half-measures as far as UP was concerned!
I think CAZephyr pretty much said it all about the UP's 9000's, except for one thing: That loooong wheelbase was just so cool looking! Twelve drivers! Wow! No half-measures as far as UP was concerned!
Never too old to have a happy childhood!
selector Hi, Juniatha. I am unsure of your intent for the question's answer as you frame it, but apart from the match between the J1 and the UP Challengers, the nod generally goes to the other versions of the Challengers in terms of their overall speed with trailing tonnages. Their weight was more lightly distributed on the rails if I have it figured out correctly, so they were easier on the rails, and we all know they could use curvatures with shorter radius than could the all-flanged rigid 10-coupled Texas types. However, when we compare the work that any one pairing could do, there really isn't much difference between them when the mighty Bessemer & Lake Erie and the Santa Fe versions' tractive efforts at start and at speed are taken into account. Crandell
Hi, Juniatha. I am unsure of your intent for the question's answer as you frame it, but apart from the match between the J1 and the UP Challengers, the nod generally goes to the other versions of the Challengers in terms of their overall speed with trailing tonnages. Their weight was more lightly distributed on the rails if I have it figured out correctly, so they were easier on the rails, and we all know they could use curvatures with shorter radius than could the all-flanged rigid 10-coupled Texas types. However, when we compare the work that any one pairing could do, there really isn't much difference between them when the mighty Bessemer & Lake Erie and the Santa Fe versions' tractive efforts at start and at speed are taken into account.
I certainly agree with your information and would like to add some addtional thoughts.
The higher speed capability is certainly the main factor with the Challengers replacing the UP 4-12-2's, but maintenance was also a factor. The third cylinder with the associated valve gear was always a high maintenance type of design. By the time the first Challengers were built, the 9000 class had run for ten years and were already being rebuilt with disc main drivers and other upgrades to allow higher speeds for the Overland main line. One more factor was the long wheelbase and the problems of using them in certain areas with tight radius cuves. They ended up on the main line and the KP line, which could handle large steam.
Did the Challengers provide a 100% substitute, I would say no since the 4-12-2's were used until they were no longer needed. I am sure others might have different opinions but the Union Pacific continued to use them until very late in steam operations. The 9000 class were used on the Union Pacific for thirty years. By mid 1954, GP9's were coming on line and replacing all steam and the Challengers also. Steam maintenance was always labor extensive and the diesels eliminated the major water problems along with the extensive back shop maintenance.
The 9000 class continued to be used until late 1954 and early 1955 almost to the end of steam, but they were removed from service and the tenders used to build the fuel tanks for both versions of the 4500hp turbines. We have the first 9000 at Pomona Fair grounds for all of us to visit. Nice locomotive.
By the way, the J1 you mentioned is one of my favorite locomotives having watched them run many times in Illinois where I grew up. The pictures of a J1 are mine and they were a great locomotive.
CZ
just a thought :
Hi , all
… Shades of the Pennsy T-1 / NYC Niagara comparisons …
Had the UP Challenger really been a 100 % substitute for the UP 9000 class in daily traffic as concerns actual ( not formula ) starting t.e. and load capacity on ramps ? ( Side remark : the three cylinder arrangement was all but ideal in the 9000 class , further , just the 5th series had been built with cast steel locomotive bed . )
Or in general : could a simple expansion Mallet have started as sure footed in every-day service as a straight rigid frame engine of same number of coupled wheel sets and adhesion mass ?
Provided , it had enough piston thrust to develop the same indicated t.e. , didn't a big Texas type actually live up to practically same level of low speed ramp work as a 4-6-6-4 or 2-6-6-4 in spite of one less coupled wheel set , just because of better actual adhesion by its ten coupled rigid frame single drive set ? ( and I don’t mean by beefing up to the same adhesion mass by using higher engine mass per coupled wheel set )
Actual historical engine classes coming to mind are the PRR J-1 and Santa Fe 5011 class / the N&W A class and UP Jabelmann Challenger …
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