I've only been able to find stats for this class on one website. I know the O-8s did some dual purpose hauling, but did they really have 71" driving wheels? That sounds too big.
69" will do. # 3380 was an O-7 rebuilt to O-8 specifications. (Drury 2015, p. 181).
The article "The World's Greatest Mikado" from the January 1969 issue of Trains, states 69 inches for the O-7 and O-8 classes.
Did you get 71 inches from Steamlocomotive.com? There's a lot of inaccurate details at that resource, as to be expected for a site that attempts to cover as much as it does.
I don't know which is accurate, but the article I just read in Trains appears to be written by a source that's very familiar with the subject matter, so I'm inclined to believe they were 69".
Leo_Ames The article "The World's Greatest Mikado" from the January 1969 issue of Trains, states 69 inches for the O-7 and O-8 classes. Did you get 71 inches from Steamlocomotive.com? There's a lot of inaccurate details at that resource, as to be expected for a site that attempts to cover as much as it does. I don't know which is accurate, but the article I just read in Trains appears to be written by a source that's very familiar with the subject matter, so I'm inclined to believe they were 69".
69" sounds way more right to me. Thanks much. And yeah, that's where I got it. I guess I won't rely on that website so much in the future...
Don't get me wrong though, it's a great site. Just when it's trying to cover as broad a topic as North American steam locomotives, unfortunately errors are guaranteed to appear here and there.
Some of it is well off the mark though, so it's best to not take it as a definitive source but rather as a jumping off point to deeper research. Here's one such offender that has long annoyed me.
https://www.steamlocomotive.com/survivors/recent-losses.php
Union Pacific alone entered 1960 with 86 steam locomotives still officially on their roster, 50+ of which were scrapped in the end.
Toss in stuff like the NKP, N&W, Illinois Central, C&O, and so on and I imagine many hundreds of steamers have met the torch in the US since the 1950's ended. I imagine we're looking at 500+. Toss in Canada and Mexico and we're probably looking at thousands.
I actually posted the 71" in a post over on Classic Trains a couple of months ago, but yes, I got it in a fact-check on steamlocomotive.com and yes, I remembered it from many years ago as 69". I am not much of a GN fan so don't know if there might have been cheating up to a slightly larger pre-wear tire diameter as was done on some of the PRR J-1s (to 70") which is similarly confusing to document.
What is the real story on wheel diameter and intended locomotive service?
Generally, you need "high drivers" if you want speed. One reason for that is with piston valves, there is an RPM level where you get enough pressure loss in the admission and exhaust steam circuits that you lose power. Another reason is more room for the proper kind of balance weight distribution, cross balancing being an example?
So then, how did a Norfolk and Western J class run on test up to 100 MPH with 70 inch wheels?
Low drivers are said to be better for low-speed freight operation. So then, how did Golsdorf in Austria get by with a high-drivered mountain engine?
The formula for Super Power in "Big Boy -- Big Mistake" is a high-drivered locomotive, but the pioneer A1 Berkshire, was what, 63"? Anyway, if you put high drivers on a locomotive, it can pull OK up to the traction limit of whatever weight it has on drivers, but you need to put a big boiler on it so it doesn't run out of steam at speed, but then the locomotive is so heavy that you need to support substantial weight on the engine and trailing trucks, and then you have dead weight to carry around when climbing a grade?
But the ultimate speed of an engine is determined by the RPM where it self-limits power by the pressure drops in the steam circuits. Suppose you have a high-drivered engine and just put a placard in the cab, "You will run out of steam if you operate in full gear past 30 MPH"? Is there some reason you need to put low drivers on such an engine so the 30 MPH limit is automatically enforced by pressure drop in the steam circuit, or could you just train the crews that the locomotive has a speed limit past which it will run faster than the boiler can make steam?
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
The difference between 69" drivers and 70" drivers is pretty small. It accounts for aproximately an 4" difference in circumference, about a 1.5% difference at that diameter.
So in general terms, we could put the driver size of the O-8 in the same range as the NKP/C&O/PM 2-8-4 and the N&W J. And, all three classes have a similar weight on the drivers, all between 280,000# and 292,000#.
As for top speed, obviously the J has the advantage with the 4 wheel lead truck, but in terms of getting TE to the ground, the O-8 was just as effective as the J, and more powerful than the 2-8-4's.
The O-8 also had just as much grate area as the 2-8-4's
Suggesting that 2-8-4's are just bigger Mikado's and lighter track was the biggest justification for the 4 wheel trailing truck. And that drivers bigger than 63"/64" worked fine for pulling freight under the best most developed boilers.
I'm just a freelance model train guy, but I built five of these from Berks for my freelanced model railroad - picture taked before the paint shop:
And then there where these, baby brothers of the LIMA Berkshire, the DT&I 800 class Mikes - on 63" drivers, and smaller grates, but still pretty impressive:
http://steam.wesbarris.com/whyte/2-8-2/USA/photos/dti800-dickenson.jpg
It was this DT&I 800 class that inspired me to learn more about 2-8-4's vs the biggest 2-8-2's, coming to the conclusion that my freelanced LIMA Mikes with 69" drivers could have been built, even if only for roads with top notch trackwork.
Sheldon
Atlantic Central:
Way, cool!
ATLANTIC CENTRALAs for top speed, obviously the J has the advantage with the 4 wheel lead truck, but in terms of getting TE to the ground, the O-8 was just as effective as the J, and more powerful than the 2-8-4's. The O-8 also had just as much grate area as the 2-8-4's
There's a whole lot more to achieving high speed than putting a four-wheel pin-guided lead truck on a locomotive, and considerably more in the case of the N&W J class, which uses special balancing methods derived by Voyce Glaze (and which are applicable, with some care, to engines with good modern 2-wheel lead and trailing trucks).
A major reason for the two-wheel trailing truck on a Berk is weight distribution. Another is proper arrangement of the ashpan. These are relatively unimportant on a model railroad where the firebox structure is a molded plastic shell and the frame a 'casting of convenience' but in real life the combination of a good cast bed, a full set of circulators, and metallurgically-suitable material for high pressure on a locomotive with large grate area will be difficult to accommodate on a single axle that also guides and steers well.
(This is not to say that good modern high-power locomotives can't be developed on two-wheel trailing trucks -- they certainly could, and Richard Leonard among others has speculated that they are 'all that's necessary' for practical reciprocating power that is reasonably thermodynamically improved (e.g. with Snyder or other primary-air preheating and Cunningham circulators to chamber and legs) but this goes hand in hand with reducing required GA...)
Some of the early Berks in fact used an amusing truck that was designed to act either like a long Delta (with booster) or the American Arch articulated design with the weird inability to reverse corrected. The result could not get the rear axle to 'track' correctly with the correct action to center and steer the rear of the locomotive chassis (remember the booster required it to be fixed with respect to the frame) if any other axle(s) were present in conventional pedestals -- so for a couple of years the forward axle in the truck floated laterally as 'weight-bearing' only, supported by transverse hardened-steel rollers with only its own flanges for horizontal location and centering. (I don't know if this action was ever modeled...)
There's more to driver diameter than just 'larger is faster' and 'diameter speed', too. It pays to study Golsdorf's passenger 2-6-4 as in a number of respects the detail-design choices that seem so weird turn out to be instructive.
The choice of 68"-69" drivers in the '30s over 63" is largely an issue of sufficient room for in-plane balance installation in an otherwise strong-enough wheel center. Note that even as early as the conversions of the T&P 2-10-4s from dogs into reasonable road locomotives, adoption of lower rodwork inertia removed much of the 'problem' with that diameter; there was little augment issue with the P&LE A-2-As even at their 50mph road speed, and of course the ACE3000 used 58" nominal with Withuhn conjugated duplexing.
(I'm sure the issue with cast driver centers is going to come up at some point; remember that by far the fastest engine on 70" drivers did not use them even on the mains... while the ACL R-1s were a balance disaster even with them. And contrary to what I would have believed if not shown, the late Web-Spoke design became a functional replacement for cast centers on a number of roads, including NYC.
The difference between 69" and 70" is indeed small, and of course the diameter may decrease sustantially as the tires wear to design limit (in the case of the ACE3000, I recall this being 6" (or 3" radius) as they thought government single-wear wheel requirements would apply to them). The problem is that these wheels have flanges, and the spacing between axles in most reciprocating locomotives, in trying to reduce the rigid wheelbase without too many expen$ive lateral-motion cannon boxes, will have those flanges nearly touching behind the brake hangers. The Niagara was a special case, eith the frame spacing (and expensive Timken rod length) intentionally long enough for the 8" upsize when desired -- and at the time, 79" over 75" was enough of a no-brained that the change was promptly done. On the other hand I never saw even the shred of a proposal to put 79" drivers on a Mohawk, even though it might make 'design' sense a la Golsdorf to try, because 72" was already perfectly ample with correct balancing for any sustainable speed rationally expected of a 4-8-2 at its rated load.
Overmod ATLANTIC CENTRAL As for top speed, obviously the J has the advantage with the 4 wheel lead truck, but in terms of getting TE to the ground, the O-8 was just as effective as the J, and more powerful than the 2-8-4's. The O-8 also had just as much grate area as the 2-8-4's This is the stuff that happens when freelance model railroaders start doing steam design -- a bit like crayonistas revising London transit routes. There's a whole lot more to achieving high speed than putting a four-wheel pin-guided lead truck on a locomotive, and considerably more in the case of the N&W J class, which uses special balancing methods derived by Voyce Glaze (and which are applicable, with some care, to engines with good modern 2-wheel lead and trailing trucks). A major reason for the two-wheel trailing truck on a Berk is weight distribution. Another is proper arrangement of the ashpan. These are relatively unimportant on a model railroad where the firebox structure is a molded plastic shell and the frame a 'casting of convenience' but in real life the combination of a good cast bed, a full set of circulators, and metallurgically-suitable material for high pressure on a locomotive with large grate area will be difficult to accommodate on a single axle that also guides and steers well. (This is not to say that good modern high-power locomotives can't be developed on two-wheel trailing trucks -- they certainly could, and Richard Leonard among others has speculated that they are 'all that's necessary' for practical reciprocating power that is reasonably thermodynamically improved (e.g. with Snyder or other primary-air preheating and Cunningham circulators to chamber and legs) but this goes hand in hand with reducing required GA...) Some of the early Berks in fact used an amusing truck that was designed to act either like a long Delta (with booster) or the American Arch articulated design with the weird inability to reverse corrected. The result could not get the rear axle to 'track' correctly with the correct action to center and steer the rear of the locomotive chassis (remember the booster required it to be fixed with respect to the frame) if any other axle(s) were present in conventional pedestals -- so for a couple of years the forward axle in the truck floated laterally as 'weight-bearing' only, supported by transverse hardened-steel rollers with only its own flanges for horizontal location and centering. (I don't know if this action was ever modeled...) There's more to driver diameter than just 'larger is faster' and 'diameter speed', too. It pays to study Golsdorf's passenger 2-6-4 as in a number of respects the detail-design choices that seem so weird turn out to be instructive. The choice of 68"-69" drivers in the '30s over 63" is largely an issue of sufficient room for in-plane balance installation in an otherwise strong-enough wheel center. Note that even as early as the conversions of the T&P 2-10-4s from dogs into reasonable road locomotives, adoption of lower rodwork inertia removed much of the 'problem' with that diameter; there was little augment issue with the P&LE A-2-As even at their 50mph road speed, and of course the ACE3000 used 58" nominal with Withuhn conjugated duplexing. (I'm sure the issue with cast driver centers is going to come up at some point; remember that by far the fastest engine on 70" drivers did not use them even on the mains... while the ACL R-1s were a balance disaster even with them. And contrary to what I would have believed if not shown, the late Web-Spoke design became a functional replacement for cast centers on a number of roads, including NYC.
ATLANTIC CENTRAL As for top speed, obviously the J has the advantage with the 4 wheel lead truck, but in terms of getting TE to the ground, the O-8 was just as effective as the J, and more powerful than the 2-8-4's. The O-8 also had just as much grate area as the 2-8-4's
This is the stuff that happens when freelance model railroaders start doing steam design -- a bit like crayonistas revising London transit routes.
I understand all that, I was just trying to offer some thoughts without writing a book.
But the fact that the O-8 worked, deminstrates that more than one approach works, depending on the axle loads you can tollerate, the speeds you need, etc.
Maybe the main point I was trying to make got lost in there, it was about driver diameter. A Mikado with 69" or 70" drivers is really not that different from a Berk or Northern with that size drivers - the O-8 deminstrated this.
I seem to remember some story about the B&O considering or experimenting with the idea of larger drivers on a Mike as well?
And the NKP Berks were much lighter than the C&O versions, maybe they could have been suitably balanced on a single axle Delta, maybe not.
But, much as I know about real trains, I play with model trains for fun. So when I came up with this project years ago, I did at least some exploring of its plausiblity.
Based on the DT&I 800's and the O-8, I think LIMA could have built a 69" driver Mike similar to mine for a road willing to tollerate axle loads like the C&O had on a number of locos.
Possible/plausible, that's all.
ATLANTIC CENTRAL I understand all that, I was just trying to offer some thoughts without writing a book.
Someone beat you to it writing such a book.
David Wardale writes in "The Red Devil" of wanting to replace the 4-wheel trailing truck on the 25-Class with a 2-wheel trailing truck and tinkering with the equalization to put a bit more weight on the drivers. I have to search for that section, but I think he states that the added driver axle loading, beneficial to tractive effort, would have restricted the route availability of the modified locomotive that became the Red Devil 26-Class locomotive.
Paul Milenkovic ATLANTIC CENTRAL I understand all that, I was just trying to offer some thoughts without writing a book. Someone beat you to it writing such a book. David Wardale writes in "The Red Devil" of wanting to replace the 4-wheel trailing truck on the 25-Class with a 2-wheel trailing truck and tinkering with the equalization to put a bit more weight on the drivers. I have to search for that section, but I think he states that the added driver axle loading, beneficial to tractive effort, would have restricted the route availability of the modified locomotive that became the Red Devil 26-Class locomotive.
Well, I looked that up, it's interesting.
It is way outside my knowledge base because I have never followed trains outside Norh America to any degree.
It is an interesting idea, converting a Northern into a Mountain.
The B&O never had 2-8-4's or 4-8-4's, they were always happy with their fleet of 2-8-2's and 4-8-2's.
ATLANTIC CENTRALBut the fact that the O-8 worked, demonstrates that more than one approach works, depending on the axle loads you can tolerate, the speeds you need, etc.
Maybe the main point I was trying to make got lost in there, it was about driver diameter. A Mikado with 69" or 70" drivers is really not that different from a Berk or Northern with that size drivers - the O-8 demonstrated this.
For fun, look at Deem's version (in the '70s) of Chapelon's "North American" 2-10-4 of the latter 1940s This is not at all a large engine, comparable in size essentially to a Mike stretched by one driver pair with the two-axle trailer only for reducing axle load (as on the 242A1) and it is instructive how it makes enough steam for its three fairly commodious cylinders... and how the balance arrangement makes it less difficult for the two-wheel lead truck to do the necessary business without a Krauss-Helmholtz or similar arrangement.
Overmod ATLANTIC CENTRAL But the fact that the O-8 worked, demonstrates that more than one approach works, depending on the axle loads you can tolerate, the speeds you need, etc. This is very true, and one thing it points to is demonstrable fairly dramatically in English practice. A steam locomotive's indicated power is a function of its cylinders, rodwork geometry, and wheel diameter... whether those are on a 4-6-0 or 4-8-2 is circumstantial ... and the available TE then just a function of axle load. This avoids a major actual determinant of performance, economical long-term steam generation at lowest net cost, and it flirts with another, which is practical adhesion and slip recovery as usually bundled into a discussion of FA, but it explains why a relatively small and light 4-6-0 (say, a Castle or King class) can happily do the work of a much larger Pacific, on a comparable train, at comparable timing. And it's instructive to see the ways in which the feat requires special attention or care... Maybe the main point I was trying to make got lost in there, it was about driver diameter. A Mikado with 69" or 70" drivers is really not that different from a Berk or Northern with that size drivers - the O-8 demonstrated this. And from the standpoint of indicated performance this is again quite correct. Where I want you to start looking at the difference is in some of the early reported Berkshire testing vs. the excellent Lima/Woodard 8000 NYC H10 Mikado that preceded it, which has very similar constructional details. The advantages of the bigger boiler and chamber far outweigh the added weight, length, and cost to provide them on a locomotive optimized for long heavy service -- but if you are not needing the sustained high speed, then there is only the guiding advantage between a large Pacific and a proper Mikado... and that, we can agree, is relatively easily handled for a Mike just as it would be for a Berk if desired. For fun, look at Deem's version (in the '70s) of Chapelon's "North American" 2-10-4 of the latter 1940s This is not at all a large engine, comparable in size essentially to a Mike stretched by one driver pair with the two-axle trailer only for reducing axle load (as on the 242A1) and it is instructive how it makes enough steam for its three fairly commodious cylinders... and how the balance arrangement makes it less difficult for the two-wheel lead truck to do the necessary business without a Krauss-Helmholtz or similar arrangement.
ATLANTIC CENTRAL But the fact that the O-8 worked, demonstrates that more than one approach works, depending on the axle loads you can tolerate, the speeds you need, etc.
This is very true, and one thing it points to is demonstrable fairly dramatically in English practice. A steam locomotive's indicated power is a function of its cylinders, rodwork geometry, and wheel diameter... whether those are on a 4-6-0 or 4-8-2 is circumstantial ... and the available TE then just a function of axle load. This avoids a major actual determinant of performance, economical long-term steam generation at lowest net cost, and it flirts with another, which is practical adhesion and slip recovery as usually bundled into a discussion of FA, but it explains why a relatively small and light 4-6-0 (say, a Castle or King class) can happily do the work of a much larger Pacific, on a comparable train, at comparable timing. And it's instructive to see the ways in which the feat requires special attention or care...
And from the standpoint of indicated performance this is again quite correct. Where I want you to start looking at the difference is in some of the early reported Berkshire testing vs. the excellent Lima/Woodard 8000 NYC H10 Mikado that preceded it, which has very similar constructional details. The advantages of the bigger boiler and chamber far outweigh the added weight, length, and cost to provide them on a locomotive optimized for long heavy service -- but if you are not needing the sustained high speed, then there is only the guiding advantage between a large Pacific and a proper Mikado... and that, we can agree, is relatively easily handled for a Mike just as it would be for a Berk if desired.
When I did my research for my ATLANTIC CENTRAL LIMA Mikes, I did find and get partly into that early Berk testing and the H10.
In fact I considered mentioning the H10 in my earlier post. But, after getting the general feel for where the Berk came from, I simply shifted back to deciding if the Mike would have been plausible.
Since I already know everything about old houses , and I know a lot about trains, but not nearly what you know, I simply wanted my LIMA Mike to be possible.
There are after all, there only so many hours in the day, and I have a layout to build.
The ATLANTIC CENTRAL has a carefully thought out roster designed to appear plausible for its location and era.
Our primary rigid wheel base power is 2-8-0's, 2-8-2's, 4-6-2's and 4-8-2's.
There are few 2-10-2's, and 4-8-4's.
Larger power includes 2-6-6-2's, 2-8-8-0's, and 2-6-6-4's.
And then there are these new fangled Diesels.......
Here's the thing: a Lima Mike would be immensely possible, and it would have been possible to 'design' a good one, just not with a Berkshire firebox. (And not with an implied frame design assuming a four-wheel trailer, but that's less important in making a model more 'verisimilitudinous'...) That box is just a tad long and wide to be 'balanced' over a single axle which then needs leverage to the rear corners of the chassis -- badly, on a large-cylindered Mike -- to reduce 'waddle' and also reduce the overbalance needed.
One thing you could do on the Atlantic Central, although a little radical, is split the tender, and move the lead truck up as far forward as you can, as on some of the late JNR and Reichsbahn power. Then modify the radial buffer so that the tender actively helps guide the rear of the locomotive chassis, a bit as if there were a Jacobs bogie articulated there. In ll probability this would give you a water-bottom tender of NYC proportions, with very short cistern, 6-wheel Commonwealth truck front and 2-axle behind, like the arrangement on the smaller MILW A tenders, and a separate 4-axle A-tank (multiples if you want coast-to-coast style range). An advantage here is that a comparatively very short table will turn the engine, without recourse to exaggerated overhang like on the NYC PT pedestal tanks) and similarly there is less issue with stall length for high-horsepower steam. This was and is the solution for those otherwise-spectacular RENFE 4-8-4s that could never do much, just as the PRR V1 would never have done much, because the bunker and water capacity that would 'fit' only gives relatively short range before you have to stop.
Some of the detail changes are slight. Snyder preheaters are like the air-brake radiator 'bundle' of pipe, but arranged along the gap between mud ring and ashpan; they run on the same exhaust steam that goes to the FWH with a little turret tap up and a little trap down so they don't freeze. C&O testing of these reported produced over 10% efficiency gain (in the service the tests were run for) which is substantial.
Cunninghams tap circulation off a low point in the convection section, usually forward 'enough' from the throat connections to syphons or circulators. They pass this through a jet pump with no power moving parts, and then into ram's-horn manifolds that look similar to old Chevy 283 exhaust manifolds along the water legs. Here the pumped flow is directed into upward-facing fan nozzles inside the legs that greatly enhance upward flow in the sides of the radiant firebox. (There should be arrangements at the top to channel the upward flow, but Cunningham did not detail them). One thing this allows is thinner waterleg space for the same heat uptake, hence less mass than that added by the manifolds, and much of the advantage of an explicit forced-circulation boiler like a Lamont.
Agreed, the firebox is larger than it would have been. Only the very informed will notice that.
I did move the Delta trailing truck back to the correct bearing point at the end of the firebox, and added the beam detail.
It is after all just a little 1/87 scale toy.......
And the ACR Mikes exist in three sub classes, with variations in sand box/steam dome configuration, and rectanglular and Vanderbuilt tenders.
No pictures of the others right now......
Your kitbash 2-8-2 is not too far away from real life, albeit with higher drivers.
http://www.rrpicturearchives.net/showPicture.aspx?id=3882672
As to the original question, dirver diameter of the O-8 class was 69 inches. Source is 'Steam Locomotives of the Great Northern Railway' by Middleton and Priebe. It is THE definitave book on GN steam, at 544 pages.
This was published a few years ago by the Great Northern Railway Historical Society and sold out, mostly to members. Mr Middleton found a few books in his basement recently. They are for sale to all at original price at the Company Store. See gnrhs.org/store.
Mac McCulloch
It is a great book! I have a copy. I also like the chapter with the line drawings of GN steam proposed but never built. It is history, of course, and can't be changed, but one wonders what would have been built if the Great Depresssion had not taken hold. Of course one might say the diesel could have come on sooner, too, but GN had some interesting designs under study and the ability to build in-house.
Does that book go into what GN did with the UP steam turbines during the war years? That might have been the most significant of all the steam work they did...
One photo at Applyard (Wenatchee) Electric shop. One paragraph to the effect that in April of 1943, after having been rejected by UP and in the face of a severe power shortage, the two units, rated at 2500 HP each, made 14 round trips between Hillyard and Appleyard. 'Testing ended when the units suffered electrical failure and were returned to GE'.
This territory had a roughly ten mile long 1% grade westward from Fort Wright. Eastward there was a twently mile long 1% climb from Columbia River to Crater to get to the top of the Columbia Plateau and an up to .8 percent grade between Lamona and Bluestem of 20-25 miles. It was the steepest non-mountain subdivision on the GN main line.
Mac
Two of the GN considered-but-never-built that would have been something to see were:
A 2-8-8-4 with 69" drivers
A 4-4-4-6 with 8-wheel trucks on the tender
kgbw49A 4-4-4-6 with 8-wheel trucks on the tender
Mac, isn't the GNRHS store closed, with no indication when they will reopen?
A bit more data:
The 69"-drivered 2-8-8-4 was proposed by Baldwin. Tractive effort is 133,500 lbs with a factor of adhesion of 4.19. The drawing date is December 6, 1934.
Interestingly, while the GN never rostered a Yellowstone, they leased them from the DM&IR during the winter months for service on the Williston-Minot portion of the main line.
The 4-4-4-6 was proposed by ALCO on January 3, 1938.
It has 84" drivers, 68,000 lbs of tractive effort and a factor of ashesion of 4.10. Grate area is 127.5 square feet. The tender has 23,000 gallons of water and 5,000 gallons of oil riding on 8-wheel trucks. Length of the engine and tender over the coupler faces is 123 feet 11 7/8 inches. Weight on lead truck of 90,000 lbs., weight on drivers 280,000 lbs., and weight on trailing truck 170,000 lbs. Total heating surface 5,324 sf.
kgbw49The 69"-drivered 2-8-8-4 was proposed by Baldwin. Tractive effort is 133,500 lbs with a factor of adhesion of 4.19. The drawing date is December 6, 1934.
My guess is that the design used Baldwin's, rather than N&W's, contemporary hinge design, and lacked meaningful compliance 'yaw control' and damping on the lead truck. A combination of poorly-compensated horizontal augment and multiple-pendulum dynamics might have made a 'double Mikado' with likely GN cylinder dimensions on both engines an ... interesting ... experience at times.
If built as a Challenger chassis, with the forward engine firmly centered and a shallow firebox limiting equalization problems on vertical curves, this would have been a better design, and I doubt GN would highly object to the compromise in firing. Likewise any issue with the lead truck either on the O classes as built or this 2-8-8-4 double version should have been solved with more modern leading and trailing truck provision 'inside the state of the known art' in those years.
The 4-4-4-6 was proposed by ALCO on January 3, 1938. It has 84" drivers...
This does sound remarkably like ATSF's as described in Worley's 'Iron Horses of the Santa Fe Trail'. This would have had opposed cylinders a la B&O 5300, 19.5 x 26" cylinders (compare the stroke on the 3460 class if you wonder about anticipated top speed), 69,000lb nominal STE (with nominal 310 psi on more sensible 80" drivers) and what appears to be engine weight of 570,000lb 'wet'. Weight on drivers is unspecified but it would likely be no less that about the stated 4.1 FA -- conservative because of the known slipping, but arguably 'never high enough' to get rid of the true problems...
There are two different drawings of this ATSF engine (p.374 & p.379) the latter of which was drawn with a pedestal tender which is NOT something I think ATSF would have used on them. Interestingly there appears to be no recognition of the possibilities inherent in duplex drive as perceived by NYC: fitting a very large compound tender (with NYC's nominal 64t bunker and vestigial cistern, plus a large bidirectional A-tank) could have produced diesel-like unserviced range under potentially bad conditions...
Grate area is 127.5 square feet.
Length of the engine and tender over the coupler faces is 123 feet 11 7/8 inches.
Total heating surface 5,324 sf.
But where would GN prospectively use a locomotive of these characteristics?
Overmod Mac, isn't the GNRHS store closed, with no indication when they will reopen?
The GNRHS Company Store is open.
We changed software to a much better system this spring. Have had some members get confused because the new software does not ask for member number like the old one did. Members have to enter a code to get Member Discount, another change.
Due to Covid, we are shipping physical products about once per week. We have added electronic Reference Sheets. Customers get them almost instantly, and we do not have to mail them.
We are open!
kgbw49 A bit more data: The 69"-drivered 2-8-8-4 was proposed by Baldwin. Tractive effort is 133,500 lbs with a factor of adhesion of 4.19. The drawing date is December 6, 1934. Interestingly, while the GN never rostered a Yellowstone, they leased them from the DM&IR during the winter months for service on the Williston-Minot portion of the main line. The 4-4-4-6 was proposed by ALCO on January 3, 1938. It has 84" drivers, 68,000 lbs of tractive effort and a factor of ashesion of 4.10. Grate area is 127.5 square feet. The tender has 23,000 gallons of water and 5,000 gallons of oil riding on 8-wheel trucks. Length of the engine and tender over the coupler faces is 123 feet 11 7/8 inches. Weight on lead truck of 90,000 lbs., weight on drivers 280,000 lbs., and weight on trailing truck 170,000 lbs. Total heating surface 5,324 sf.
Setting aside the lowered traffic, revenue and operating income of the depression, and the fact that GN had several bond issues coming due in the 1930's, the GN already had engines very well suited to its real needs by 1930.
It had 30 R-1 and R-2 2-8-8-2 engines, the last built in 1930 at Hillyard. As built the R-2 was rated at 146,000# TE with 63" drivers. Weight on drivers was 592,000#. UP's 'Big Boys' were 4-8-8-4 with 136,375# TE and 540,000 pounds on the drivers. Big Boys were about 80,000# heavier in total engine weight and needed two extra axles to carry it. The R class was intended to work over the Rocky Mountains between Whitefish and Cut Bank or Havre. Ruling grade was 1% westward, and 1.8% eastward. They were built to get tonnage trains over the mountains, not to be speed demons. Why ever would GN go to a less capable engine?
For passenger service the GN had their 1929 built S-1 4-8-4 rated at 68,466# of TE on 73 inch drivers and their 1930 built S-2 rated at 58,300# of TE on 80 inch drivers. With the arrival of the S-2, the six S-1 engines were bumped to freight service. Alco's proposal looks like a lot of complication for not much gain. Also remember that the GN had a shorter, flatter route than did its main competetior, the NP. GN could beat the NP's time without having to push as hard as the NP did.
Yup, all good stuff, PNWRMNM. I still would have liked to see them built, just like the NYC C1a, a UP 4884-3, and one of the those GN 4-6-6-4 designs with the 73-inch drivers.
Never happened, but wouldn't they have been something.
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