sandiego I worked in the engineering department for both the Union Pacific and Chicago and North Western railroads and designed and laid out in the field many track layouts. We never used spirals on industry, yard, or other non-main trackage; low-speed main line (10 MPH) curves didn't get spirals either. In addition, we didn't use any superelevation on those types of curves. If track speed required it we would lay out main line curves with spirals on both ends of the curve; the rest of the curve was a normal circular curve with constant radius (unless a compound curve was needed because of topography or other obstacles). Kurt Hayek
I worked in the engineering department for both the Union Pacific and Chicago and North Western railroads and designed and laid out in the field many track layouts. We never used spirals on industry, yard, or other non-main trackage; low-speed main line (10 MPH) curves didn't get spirals either. In addition, we didn't use any superelevation on those types of curves.
If track speed required it we would lay out main line curves with spirals on both ends of the curve; the rest of the curve was a normal circular curve with constant radius (unless a compound curve was needed because of topography or other obstacles).
Kurt Hayek
Kurt, thanks for the info. If I can ask, what size turnouts did you generally use in yards? and what radius curve might have been typical?
Sheldon
It's interesting that there are a couple of very different semantic meanings for the phrase 'nominal rebuild' -- and we've been using them.
To me, a 'nominal' rebuild or repair is one that's called that, but there is comparatively little actual rebuilding or repair involved... it is more a change 'in name only'. (Like the semantics in the phrase 'nominal charge')
In your version, the new structure is so completely different that to call it a 'rebuild' (as with some famous examples of diesel locomotives in the '60s) rather than a new locomotive that happens to share some parts with an older predecessor starts to look like Jason's ship or grandfather's axe if we call it 'rebuilt'. This too is true.
What I suspect is that this is tax-related, much as the Frisco 2-8-2 rebuilds of the late '40s were. It isn't the sort of rebuilding represented by the Reading 4-8-4s, where the structure of the older locomotive was substantially retained to save money, and the resulting locomotive didn't share 'historical class' or common service consideration with the older locomotive...
(Incidentally, were you ever successful in contacting a civil engineer or equivalent who had actually supervised or bossed either a passenger wye or yard-trackage job that involved transitions or easements in practice? We've heard from someone reasonably expert in industrial siding work, and from AREA/AREMA text references, but I still agree with you that it would be nice if someone who KNOWS from experience would chime in here.)
Overmod 7j43k The minimum radius for a Great Northern N-2 (2-8-8-0) was 522'. For an N-3, it was 359'. This was far from a 'nominal' rebuilding -- among the changes was installation of cast-steel beds with driving-axle roller bearings. As I think one of the very logical consequences of this would be lateral-motion device installation, I suspect the reason for the indicated difference would be substantially associated...
7j43k The minimum radius for a Great Northern N-2 (2-8-8-0) was 522'. For an N-3, it was 359'.
This was far from a 'nominal' rebuilding -- among the changes was installation of cast-steel beds with driving-axle roller bearings. As I think one of the very logical consequences of this would be lateral-motion device installation, I suspect the reason for the indicated difference would be substantially associated...
nominal: in name only
"far from a 'nominal' rebuilding" would then be a true rebuilding.
I think I will stay with the concept of "in name only", since the only parts reused from the N-2's were journals (non-roller bearing), axles, driving wheel centers, sandboxes, turbo generators and some lesser items.
However, the two classes were quite similar in overall dimensions. Which is why I found the large difference in minimum radii especially interesting.
There may or may not have been lateral-motion devices on the N-3's. I doubt there were on the N-2's. Don't forget that many locomotives also used the simple concept of increased clearances for axle side motion.
There are a couple of GN enthusiasts in these forums who I suspect can discuss the rather spectacular N-3s in detail, including whether their fancy nickel-steel boilers suffered the way many contemporary design efforts did.
7j43kThe minimum radius for a Great Northern N-2 (2-8-8-0) was 522'. For an N-3, it was 359'.
Overmod 7j43k Note that the rigid wheelbase for 8444 (844) is longer than for a Big Boy. Is that including the effect of the lateral-motion devices on driver axles? That's not to say that you're wrong in absolute terms, just that the actual 'rigid' wheelbase is considerably less than the driver wheelbase as determined by pedestal spacing in the bed and driver diameter...
7j43k Note that the rigid wheelbase for 8444 (844) is longer than for a Big Boy.
Is that including the effect of the lateral-motion devices on driver axles? That's not to say that you're wrong in absolute terms, just that the actual 'rigid' wheelbase is considerably less than the driver wheelbase as determined by pedestal spacing in the bed and driver diameter...
It doesn't include that effect.
I suspect the principal determinant of Big Boy minimum radius is more in the permissible 'throw' of the steam-pipe arrangement to the forward engine and to the potential interference of the forward engine's rear drivers and rigging with the back engine's cylinder structure.
Maybe.
The minimum radius for a Great Northern N-2 (2-8-8-0) was 522'. For an N-3, it was 359'. Considering that the N-3's were nominal rebuilds of N-2's, I expect the reason for the difference was anything BUT things like length of rigid wheelbase.
Ed
7j43kNote that the rigid wheelbase for 8444 (844) is longer than for a Big Boy.
I believe the Big Boy will make it around a 288' radius curve.
Outsailing86 most RR curves are around 2000-3000 feet, the minimum curve is around 550/600 for a 6 axle diesel. 4 axles can go tighter, but they usually limit to the 6 axle, although you might see an industry need to be switched by a 4 axle.
most RR curves are around 2000-3000 feet, the minimum curve is around 550/600 for a 6 axle diesel. 4 axles can go tighter, but they usually limit to the 6 axle, although you might see an industry need to be switched by a 4 axle.
From George R. Cockle's "Union Pacific 1977-1980":
For an SD45, minimum radius is 261' without train, 341' with train.
For a DD40AX, minimum radius is 363' with train.
For a GP38-2, minimum radius is 305' with train.
For an SW10, minimum radius is 105' without train.
in steam engine days there was a lot of gauge widening done to help in the curves. All sorts of tables... but the practice is generally gone now. There was some concern when the big boy started running about curves. in those causes they go out and excessively grease the curve.
From the same book:
For 8444 and 3985, maximum curvature is 290' (unstated whether with or without train)
Note that the rigid wheelbase for 8444 (844) is longer than for a Big Boy.
My reading and study of railroad curvature and easements suggests that easements and superelevation are not automatically linked to each other.
Clearly you might not want superelevation without an easement, but surely with fixed axles and tapered wheels that depend on wheel taper to steer them around corners, easements are benefit even at slow or moderate speeds without superelevation.
This seems more than obvious if you understand how the rigid axle wheel set gets around the curve without dragging one wheel.
The Chicago IC/CN Amtrak trains do it too. look up the saluki and illini
regarding spirals (RR term for easements). Yes, this is a calculation based on super elevation and imbalance (that's covered in the honors course). New construction, I'm sure they are putting some spiral into the curve. An existing track? Hard to say... never know what they were up to. when rails are replaced for being worn out, they are generally replaced as is, where is. some tidbits to consider:
railroad spirals are different than highway spirals. But consulting engineers usually have highway curves preprogrammed, compared to RR spirals calculating by hand. We don't need to talk about the younger workforce today, but you know which route they are taking...
easements in Model Railroads is to make the train look more realistic. Out on the mainline, the spiral is there to runoff the elevation along with begin steering the train. most RR curves are around 2000-3000 feet, the minimum curve is around 550/600 for a 6 axle diesel. 4 axles can go tighter, but they usually limit to the 6 axle, although you might see an industry need to be switched by a 4 axle. in steam engine days there was a lot of gauge widening done to help in the curves. All sorts of tables... but the practice is generally gone now. There was some concern when the big boy started running about curves. in those causes they go out and excessively grease the curve.
So the Union Station diagram posted in this thread has some dimensions on it, and I printed it out and applied some drafting tools to the drawing.
Sure, we don't really know how accurate the drawing is.
But the drawing suggests that most of the many slip switches are #7's and that the sharpest radius in the wye is about 400' and that there may be small easements on the wye tracks.
At the terminal end, the wye turnouts are wyes, which seem to also measure about 8 degree frog angles (#7) which would make their effective diverging routes #14 turnouts with a closure radius of 1,480' and an even larger subsitution radius.
That seems like a pretty good easement into a 400' radius curve.
Just doing the math as was suggested........
Clearly there would not be superelevation in complex passenger terminal or yard trackage.
And easements would be short. On passenger wyes, at worst an easement likely exists by virture of the turnout having a frog number and subsitution radius that is effectively larger than the expected 350'-400' or so radius of the wye or similar trackage.
Even a #8 turnout has a substitution radius of 800' and a closure radius of 465'. Seems unlikely turnouts would be much smaller than that.
But even a #6 has a substitution radius of 400' and the points by the nature of their design would provide a small easement.
So then, when you get to the end of the frog, you have turn that angle into the desired minimum radius - basic geometry would suggest small easements based on what we know about turnout design.
I thought I made it clear enough in my earlier comments that these would not be be long easements, or they may be parabolic curves with a pretty small minimum radius point.
Looking at aerial photos today, the Camden Yards wye sure looks to be complex curves with easements on both ends but with longer easements on the north (station) leg.
I'm sure every situation is different as I have suggested several times and there is no way to know how EVERY yard or passenger terminal was built 70-100 years ago.
I'm just suggesting that this trackage is not like a straight piece of snap track connected to an 18" radius piece, not that it has 300' long sprial easements like the mainline, again unless space and conditions allowed for or took advantage of a parabloic curve.
If I build a model wye with #6 Atlas Custom Line turnouts, and 36" radius curves (which I am about to do soon), it has easements just because the turnouts have a closure rail radius of 40" or more and a substitution radius of about 67".
Even if the prototype built a wye that small (I think an 85' passenger car could just barely swing a 261' radius curve and/or #6 turnouts?), that would represent a significant easement just by virture of the turnout geometry - enter the turnout at 485' effective radius, transition to 261' radius.
gregc the datasheets said that all curves are "eased", even in yards. they described the length of the easement in terms of the amount of superelevation that must be transitioned. on a mainline curve, the amount of superelevation depends on the radius of the curve and the speed. a slower speed curve would require less superelevation and a shorter easement than a higher speed curve of equal radius. it seems there would be very little superelevation on yard trackage.
the datasheets said that all curves are "eased", even in yards.
they described the length of the easement in terms of the amount of superelevation that must be transitioned.
on a mainline curve, the amount of superelevation depends on the radius of the curve and the speed. a slower speed curve would require less superelevation and a shorter easement than a higher speed curve of equal radius.
it seems there would be very little superelevation on yard trackage.
I would think that most modelers with some familiarity of prototype practices would take for granted such factors as easements and superelevation on curves, especially as these factors relate to speed.
Rich
Alton Junction
7j43kI know that most mainline curves were eased. I am wondering how far that concept extended into yard trackage.
the NMRA Legacy Datasheets on Properties of Curves and Easements provided a lot information that i found interesting. (thanks Sheldon)
they described the length of the easement in terms of the amount of superelevation that must be transitioned. on a mainline curve, the amount of superelevation depends on the radius of the curve and the speed. a slower speed curve would require less superelevation and a shorter easement than a higher speed curve of equal radius.
clearly there is minimal easement thru a turnout.
it seems there would be very little superelevation on yard trackage. i didn't read any discussion on how long easements were on yard trackage.
the datasheets described methods including the bent ruler and tangents (graphical) for determining easements.
greg - Philadelphia & Reading / Reading
gregci'm questioning whether they are reversed with passengers on board?
Greg, while not "real" railroads...
On both the TENNESSEE VALLEY RAILROAD MUSEUM, and the DURANGO AND SILVERTON NARROW GAUGE tourist railroads the passenger trains are turned on wyes with all of the passengers on board.
I am so happy on tourist trains.
-Kevin
Living the dream.
My first Amtrak journey was on the National Limited in 1971 from Kansas City to St. Louis. Being the consummate "railfan" I was occupying the "dutch door" of one of the cars as we approached St. Louis Union Station.
We pulled beyond the station "Leg" then the three E units shoved the train back into the platform area. All passengers were still on board. I vividly recall the scissors action between the cars as we negotiated some of the most complex trackage I've ever witnessed.
The striking plate of the diaphragm of the car ahead of me was fully one-half covering of the opening on my car. Of course this had been going on for years, even in the days of full-width diaphragms.
Union_Station_St_Louis_diagram by Edmund, on Flickr
Superelevation? Not likely with the high concentration of crossings, slip switches and crossovers in the plant.
Later that night I departed St. Louis aboard the Abraham Lincoln, still carrying a heavyweight diner .
GMnO_Diner-1075 by Edmund, on Flickr
Another "fond" memory there was the thick-as-creosote coffee loaded with chicory
https://web.engr.uky.edu/~jrose/RailwayIntro/Modules/Module%206%20Railway%20Alignment%20Design%20and%20Geometry%20REES%202010.pdf
Another handy reference for industrial trackage:
https://www.up.com/cs/groups/public/@uprr/@customers/@industrialdevelopment/@operationsspecs/@specifications/documents/up_pdf_nativedocs/pdf_up_std_exhibit_a3.pdf
"Somewhere" at one time I came across diagrams of IIRC, some of the Baltimore dock trackage. It included track radius information. I don't recall seeing any easements used in that application.
— and from the NS:
http://www.nscorp.com/content/dam/nscorp/industrial-development/track-design-information/04_Industrial_Track_Design.pdf
Spirals and superelevation Spiral curves and/or superelevation shall only be required where the speed of operation so dictates. Designs for lead tracks one mile or longer will be evaluated by the Company on an individual basis to determine if spirals and superelevation are required.
Near me is the PRR's Whiskey Island ore dock which features four, parallel "baloon" tracks making a complete "U" trun. No easements were used on these either.
Good Luck, Ed
richhotrain wrote: "Backing fully loaded passenger trains into a stub end track passenger station through the use of a wye was commonplace back in the day."
It's still done today.
Passenger trains Northbound on the Springfield line from New Haven curve to the right into Springfield station on one side of "the wye", do their work, and then back out to the Sweeney building, then head north across the diamond (CSX/B&A), to the old B&M Connecticut river line.
Coming south, they pull across the diamond, then back into Springfield, do the station work, then pull around the wye leg to head south.
Overmod 7j43k I think it's fine to have opinions, but what I'm after is info from someone who KNOWS. Ed, PM users mudchicken and diningcar, who are likely to KNOW this firsthand or else directly know someone who does. I would have sent this via PM myself if it worked on my accessible devices. And I will delete this once Ed indicates he's read it.
7j43k I think it's fine to have opinions, but what I'm after is info from someone who KNOWS.
Ed, PM users mudchicken and diningcar, who are likely to KNOW this firsthand or else directly know someone who does.
I would have sent this via PM myself if it worked on my accessible devices. And I will delete this once Ed indicates he's read it.
Thanks, got it.
I MAY just drop the same question over at Trains. But it looks like I've got my answer.
gregc but i understand that Ed's question is simply about avoiding a jolt to passengers due to an abrupt change is curvature, if passengers are aboard. i also wonder when/if that curved trackage would have any superelevation
but i understand that Ed's question is simply about avoiding a jolt to passengers due to an abrupt change is curvature, if passengers are aboard. i also wonder when/if that curved trackage would have any superelevation
I was wondering where the passengers-in-the-cars thing came from.
No. My question has nothing to do with passenger comfort. At the speeds they're going, I don't see an easement making a significant difference.
I wrote:
"An eased curve at very slow speeds will create less offset between cars, and lesser sideways forces. That may or may not be something that is desired in any particular place."
I suppose one could read that as a concern for passenger comfort. But I was wondering about stress and loading on the equipment. Just as I do for MY passenger cars (without passengers).
Amount of superelevation is directly connected to speed of equipment. I doubt anyone would bother for something like 5 MPH. I do wonder what it would be, though.
To me, it is strange that an engineering decision would be that spiral easements are not indicated on curves negotiated by cars. Automobiles, by their nature, can only negotiate a change of path on eased curves (maybe not "spiral", but I'm not a mathematician). It's the path they take as the steering wheel is turned, thus shortening the radius continuously. When exiting the curve, the reverse happens: the radius expands continuously as the steering wheel is returned to the 'zero' position.
gregc i can't read the image you posted. i haven't seen any of your explanations. i don't see why easements for modeling purposes would follow railroad practice that need to balance curvature, superelevation and centripedal force for a specific track speed.
i can't read the image you posted.
i haven't seen any of your explanations. i don't see why easements for modeling purposes would follow railroad practice that need to balance curvature, superelevation and centripedal force for a specific track speed.
Can't read it on your tiny phone screen? I can see it just fine on my desktop.....
On the NMRA site, in the members section.
NMRA Legancy Data Sheet D3b.3 page 4
gregc ATLANTIC CENTRAL I would bet most wye tracks are/were layed out this way as well as a great many curves in general. this is for modeling purpose. see ndbprr's description for prototype mainline easements -- at speed to avoid flange contact. ndbprr Easements and super elevation are used on mainline tracks to ease trains into and through curves at speed. but i understand that Ed's question is simply about avoiding a jolt to passengers due to an abrupt change is curvature, if passengers are aboard. i also wonder when/if that curved trackage would have any superelevation
ATLANTIC CENTRAL I would bet most wye tracks are/were layed out this way as well as a great many curves in general.
this is for modeling purpose.
see ndbprr's description for prototype mainline easements -- at speed to avoid flange contact.
ndbprr Easements and super elevation are used on mainline tracks to ease trains into and through curves at speed.
No one understands any better than myself about curves, easements and working toward zero flange contact. I have been explainng that concept on here for more than a decade.
But the method outlined above comes from railroad civil engineering and is used on the prototype.
But of course you want proof.
I'm done.
ATLANTIC CENTRALI would bet most wye tracks are/were layed out this way as well as a great many curves in general.
ndbprrEasements and super elevation are used on mainline tracks to ease trains into and through curves at speed.
gregc 7j43k Los Angeles does. does that answer your question?
7j43k Los Angeles does.
does that answer your question?
It's a start (but see Dave's comments above).
It will be filled out a lot better when you answer YOUR question about how many stations have eased wyes.
Los Angeles Union does not look to me to be on a main track. It is on the tail of the wye (two of the three wye tracks are ONLY there to serve the station). The station is less than half a mile from the wye.
Or, put another way, there's no way a train is going to go through those curves at mainline speeds.
I suspect that's true for the majority of stations on the tail of a wye (as opposed to ones AT the wye).
The bottom half of this page explains how to layout curves that change direction less than 90 degrees as a continous easement in and back out.
I would bet most wye tracks are/were layed out this way as well as a great many curves in general.
gregcso how many of the wyes with station platforms have easements?
My guess is most, because most wyes with station platforms are typically also main tracks and main track curves would have easements.
But really this has nothing to do with the original question, which was about wyes used to turn equipment, which are probably not the same wyes as those with platforms.
Dave H. Painted side goes up. My website : wnbranch.com
richhotrain gregc so how many of the wyes with station platforms have easements? Best guess: all of them. The better question is: how many passenger stations had platforms on the tail end of a wye? A lot of wyes used by passenger trains were located on the mainline before the station as opposed to at the station. Rich
gregc so how many of the wyes with station platforms have easements?
so how many of the wyes with station platforms have easements?
Best guess: all of them.
The better question is: how many passenger stations had platforms on the tail end of a wye?
A lot of wyes used by passenger trains were located on the mainline before the station as opposed to at the station.
The east is/was full of those as well, like Point of Rocks, MD, Perryville, MD and many, many more.
Harpers Ferry the passenger platforms are on a curve, and back in the day extended out onto the bridge over the Potomac.