I am not sure how these two engines could have had radically different main lengths. Please enlighten me.
When I get home (in the next couple of days) I'll check the drawings again. I may have been thinking of the combination of a slightly shorter rod and the larger diameter piston... But it did strike me that the two locomotives (shrouding apart) didn't look as similar as the dates and builder would suggest.
Peter
These are the only pictures I could find of an SP 4-6-2 with the Daylight treatment with the full skirting and paint still intact. My understanding from reading from my various SP Daylight trains and San Joaquin Division books is that the consists grew quickly and so Mountains quickly replaced the Pacifics, and eventually GS 4-8-4s replaced the Mountains.
The first one is a head-on shot with an 11 car consist:
https://www.railpictures.net/photo/284875/
Then this one in Berkeley:
https://pacificcoastrailroads.tumblr.com/image/122149735421
Firelock76, you are correct that this skyline casing actually sloped downward a bit from the middle of the boiler. On the Mountains and Northerns, the skyline casing sloped up from the cap towards the middle of the boiler and then somewhat flattened out to the very front of the locomotive.
https://i.pinimg.com/736x/dc/00/e5/dc00e5f0f000cff2c0bb0681f6bad3d7.jpg
M636CBut it did strike me that the two locomotives (shrouding apart) didn't look as similar as the dates and builder would suggest.
I had been proceeding on the assumption that these two designs were essentially similar, which I think was a serious mistake, and furthermore that they were both from 1938, which may be considerably more serious.
The E-4s are from before the era of the ACL R-1 debacle, which may indicate that their balancing reflected design assumptions including the AAR principles of 1934. This was precisely the reason I started looking at the relative dates.
Apparently the things needed to 'fix' the ACL R-1s were relatively slight: lower-mass crossheads and presumably pistons; tapered main rods; different centers in the main drivers (perhaps with angle-balancing pockets?). Despite having 12" valves and a relatively tiny superheater (1425' type A, which compares fairly dramatically with 1645' on the F-7 and a whopping 1884' on the E-4, both six-coupled locomotives) there are reliable accounts of the R-1s exceeding 100mph once their drivers no longer bounced destructively...
Now, we know that the C&NW was very attentive to improve the H class, rebuilding extensively both in the early 1940s and then again in 1947, producing certainly one of the best-ever 4-8-4s in the process. This clearly indicates to me that the 'tools and the talent' to fix any substantial speed issues with E-4s were there, along with the organizational willingness to spend the money where the use justified it.
It is my opinion, which may or not be backed up by documentation, that the E-4s were considered orphaned power not long after their construction, and were used more to 'run off some of the investment' while waiting for diesel replacement rather than rebuilt as appropriate to achieve the performance inherent in their design. While that is a shame from a pure steam-enthusiast's view, I would have to defer to C&NW's people if that were their decision, as they demonstrated extraordinary competence in understanding how to improve older power.
As to the E-4, that's simply an amplified version of what I stated earlier. It was not a wise investment. The Hs were used primarily in fast freight on the Overland Route.
I have to ask, did those skyline casings have anything to do with smoke lifting? They seem like otherwise useless applications of sheet metal otherwise.
Flintlock76, in Robert J. Church's book "Those Daylight 4-8-4's: The Story of Southern Pacific GS Class Locomotives", it references that the skyline casing helped with smoke lifting. There is a "scoop" structure at the stack that lifts air as the locomotive moves, and then apparently the air flow created by the skyline casing keeps the smoke above the cab.
Class GS-1 was not built with skyline casing. That class was pretty much an extended SP Mountain with a larger firebox. The GS-1 locomotives were largely assigned to Texas during their service lives.
Skyline casing started with the first Daylight Northerns class GS-2. Lima had a hand in the development of these locomotives. They had the same driver diameter of the GS-1 but improved performance to handle the expedited schedule.
GS-3 upped the driver diameter to 80 inches and increased the boiler pressure.
GS-4 added the vestibule cab and dual headlight setup that we all know so well on 4449.
The smokelifting setup must have been effective because they retrofitted it to Mountains and the handful of Daylight Pacifics, and evening had it on the AC-9 2-8-8-4 locomotives.
kgbw49Flintlock76, in Robert J. Church's book "Those Daylight 4-8-4's: The Story of Southern Pacific GS Class Locomotives", it references that the skyline casing helped with smoke lifting. There is a "scoop" structure at the stack that lifts air as the locomotive moves, and then apparently the air flow created by the skyline casing keeps the smoke above the cab.
There was an extensive discussion of 'smoke lifting' a few months ago, kicked off by discussion of the 1931 Canadian (NRC) research into using aerodynamic flow to 'lift smoke' (this would eventually produce the smoke-deflector designs used in Germany and on a variety of North American roads founded on very different principles). That thread included a link both to the original NRC studies and to some of the subsequent research and discussion involving them (for example, Garth Wilson's 2008 essay for the Oxford Design History Society). Someone with better access than I may be able to find that thread; my Googling with the usual terms is not pulling it up.
It's a fundamentally-attractive idea that some of the frontal air resistance of the locomotive could be used to 'lift' smoke not being ejected by the induced draft ... this coming as the combination of better valve-gear design and front ends with low back pressure produced less and less violent ejection of combustion gas.
The problem is that the usual problem with 'smoke' is that it rolls back and along the boiler and then either into the cab (as on the PRR T1s) or down one side or the other obscuring the view from the cab. And this is not anything that a skyline casing will have more than momentary influence over. The same is true for the various arrangements to induce air lifting with scoops or air jets (one of them carefully designed by me as a young teen, unaware as yet of just how wrong the idea was)... or for that matter with carefully-shaped parabolic noses
The issue is not with frontal or 'bluff' resistance at all, but with induced vacuum and wave turbulence down the length of the boiler behind the initial flow shock and airflow around the front of the locomotive. And this is what the elephant-ear designs (including Witte) propose to do, and what you see them do when modeled in a wind tunnel. We had a thread a decade ago on this.
One of the problems is that, like a hurricane, the exhaust gas plume is not a 'thing' but a process. Airflow in front of the stack, louvers, jets or ducts behind: these things temporarily lift the gas. But it promptly flows down into the long region of reduced vacuum along the boiler side rather than 'staying up' where it was supposedly put.
A useful exercise, I think, is to review the various discussions of front-end experimentation and smoke lifting in the Kratville books on UP engines. He does not know (apparently any more than most of the UP guys did) exactly why something works or doesn't ... but it isn't difficult to put the picture together from the stories. UP was notorious in the late '30s for designing a locomotive (one of the multiple-stack 800s, perhaps a tinkered FEF-2?) that had so little effective ejection from low-back-pressure exhaust at over 80mph that it could not maintain enough fire for steam demand even net of the more efficient use of the expansion in the steam mass flow -- someone with access to the text can quote this more specifically. Now, it will be clear that for a fairly long range of speed before that point is reached, the gas will NOT be exiting the stack with consistent lifting, and unsurprisingly larger and larger 'ears' will be needed to spoil the vacuum effect or create effective lifting turbulence and flow. On the other hand, it will probably not be surprising that on a Big Boy, without these issues, there's no particular distinctive benefit from ears, and aside from some desultory testing you don't see them.
All this begs a significant question being asked here: why did SP spend such a long time implementing skyline casings if they aren't supposed to work? There are some interesting approaches including a full duct running most of the length of the boiler with vertical 'vents' further back that might have been intended to relieve low pressure directly over the boiler centerline on the presumption that the smoke would track there at high speed. Whether this would work 'sufficiently' in practice is interesting to contemplate... and perhaps not quite as carefully assessed in practice as advocated in design.
Thank you gentleman, good information!
I had to ask because, to me at least, the esthetic look of the locomotive is ruined by the removal of the side-skirting, the skirting does a good job of balancing the look of the skyline casing, if good looks is all they were after. Skyline casing alone makes the look of the locomotive weird, if not downright ugly, to me at least. Others may differ and that's OK.
Anyway, I was curious why they'd remove one and not the other as well.
Flintlock76Anyway, I was curious why they'd remove one and not the other as well.
Relatively less involved with access to things under the skyline casing than with skirts.
Both in Britain and North America there was some flirtation with 'streamstyling' the stack (see the as-built B&M Pacifics Lima built in 1934 as a good example) but you don't see it catch on either for 'function' or aesthetics.
Some pictures and captions in Thoroughbreds about how the casing in the Dreyfuss designs could start losing panels. There are design patents for the styles applied to UP 2906 and 7002; these look much better in the drawings and overhead views than they did from the ground. I suspect that some careful perusal of 'later' online images or the Quadrant Press book on streamlined steam will show how different railroads addressed the concerns with skyline casings.
Let me repeat a point that I think I made in the "NRC" thread: one of the things involved in Green's research was the specific problem of smoke when approaching station stops, something that might have been of particular relevance to some operations in Canada (e.g. that recently described for Edmonton-Calgary where there were relatively many stops separated by up-to-90mph running.) Here you get the whammy of presumably high firing level going in a short time to very little steam mass flow through the front end, almost a prescription for black smoke right at the time you don't want it, drifting worse and worse as the engine slows to enter stations. A mechanical device using slipstream to address some of this issue at 'zero operating cost' compared to the costs of adequate 'drifting steam' would logically be attractive...
What is a skyline casing? If I look at a photo of a Daylight Pacific, where should I focus my attention?
Look at the skyline of the locomotive from the nose back to the cab. It encases everything that is on top the boiler.
Of course, there are necessary openings for such as the smokestack and everything else that needs access to the open air.
Johnny
Lithonia OperatorIf I look at a photo of a Daylight Pacific, where should I focus my attention?
Here's a good shot by Gene Deimling of one of the three P-10s that had been 'streamlined' in the full Daylight colors and skirts in 1941. Here it is in the '50s, very dirty, but showing in a 3/4 view most of the relevant details of the 'skyline casing'
Note the air horn tucked up behind the little Witte-esque elephant earlets that flank the stack. I believe a similar construction produces the Frankenstein-monster-like 'forehead' on the MT-1 casing treatment. You can see the panels in the casing and how they likely wrap around the various things on top of the boiler
http://espee.railfan.net/nonindex/steam-01/2485_sp-steam-p10-gene_deimling.jpg
Very nice, Overmod. I doubt that the train number boards caused much turbulence.
The curved fairing to the base of the funnel duct is not as clear as in the other photos but is still there...
The theory of the skyline casing is that it removes sources of turbulence due to the irregular size and shape of the domes and other projections, particularly in crosswinds.
In New Zealand they decided to just put up the sides of the skyline casing on the 1939 J class 4-8-2 leaving the top open. I'm told that the cinders collected in the open duct and ended up in the cab. It was at least easy to remove which happened quickly....
In the attached photo, I assume that is an olive green streamlined car between the combine and the articulated pair. Is that photo at Sacramento?
M636CIn New Zealand they decided to just put up the sides of the skyline casing on the 1939 J class 4-8-2 leaving the top open. I'm told that the cinders collected in the open duct and ended up in the cab. It was at least easy to remove which happened quickly....
Stewart also noted the fun involved with the 'streamlined' recessed headlight on the K-class 4-8-4s as built, the 'well' for which was another 'mahvelous' magnet for cinders and soot. I wish I had my copy of 'When Steam was King' handy as he had quite a command of the language and used it there nearly as effectively as he did regarding six-cylinder simple Garratts...
I'm back home and have the book I referred to earlier handy.
It is Dampflokomotiven in den USA 1825 -1950 Band 2 by Heinrich Buchmann published by Birkhauser in 1978. I bought it in Amsterdam in 1991 at a marked down price but had to carry it back to Australia via the UK and USA. I should have bought Stefan Tzerbatich's book on U Boats (also in German) but it wasn't marked down...
The F-7 appears on page 107 and the E-4 on page 108.
The two locomotives have the same overall wheelbase, the same coupled wheelbase and the same boiler pitch.
On the E-4 the distance between the trailing truck axle and the leading coupled axle is 66" and on the F-7 it is 74". The E-4 cylinders are located 1' closer to the driving wheels relative to the truck, both trucks being 88' wheelbase.
So the cylinders are 9" closer to the main drivers on the E-4 than on the F-7.
Sadly the main rod length of the F-7 isn't specified but it is 124" on the E-4. On page 109, there is a drawing of the ACL R-1 which also had a 124" main rod.
But despite all the similarities, the two 4-6-4 look as though the designers never spoke to eachother.
The E-4 grate is (roundly) 13' by 7'. The F-7 grate is (roundly) 12' by 8'.
The F-7 has a 44.5" combustion chamber (with its own thermic syphon) but that on the E-4 might be about 24". The F-7 boiler is 18'10.75" between tubeplates while the E-4 is 19' exactly.
Partly due to the longer and narrower grate, the E-4 has a longer wheelbase trailing truck, 84" compared to 64" on the F-7.
I happy to believe that balancing of driving wheels changed between the two designs, but I don't believe that ideas on boiler design changed in the same period.
The book has a number of other similar diagrams, ATSF 3460, NYC J3a, NYC L3b UP 800 and so on.
But its main feature is builder's photos of many types from about 1925 to 1948.
The author has a soft spot for SP AC-9s. There is a full page scene early in the book and four photos alongside the obligatory builder's photo.
Worth buying if the price is low enough. I might look for volume 1...
The Lark, the Shasta Daylight and the Cascade were all streamlined trains that ran along the West coast. These trains ran from Oakland north to Portland Oregon.
The Guide shows that the Lark was an overnight train between Los Angeles and San Francisco, with cars for Oakland. It did not run north of Oakland.
M636CI'm happy to believe that balancing of driving wheels changed between the two designs, but I don't believe that ideas on boiler design changed in the same period.
I think it is the application of different thoughts about best-practice boiler design that apply here.
i have not looked with careful enough analysis at this yet, but the steamlocomotive.com stats for these two show a relatively large disparity in heating surface for what nominally seem small differences in firebox shape and nominal grate area.
I have been proceeding on the assumption that the 'issues' with E-4 speed are related to valves/passages and to balancing -- not to an inability to make steam above a certain required mass flow, or amount of available draft. I suspect at least some of the data to determine whether this is so would be in the detailed AAR test records ... if those are accessible to one of us.
The Lark had two-tone gray colors with off-white stripes in the same general pattern as the red and orange Daylight paint pattern.
Gil Reid painted a great picture of the Lark coming out of the Santa Susana Pass tunnels pulled by GS-4 4454 that he titled "Gray Plus Orange and Red". I have the print framed and hanging above one of my fireplaces.
You can see the print (and order one if you wish) here:
http://gilreid.com/product/gray-plus-orange-and-red/
I have this one hanging in my office, as I (as others do, too, I am sure) often feel like that Hudson working all out pulling the train of passengers along for the ride:
http://gilreid.com/product/79-mph/
And for you T-1 5550 fans, Gil Reid did this one about "120 mph plus":
http://gilreid.com/product/1948-prr-t1-5536120mph-plus-unsigned-unnumbered/
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