On the whole, is it always better to have as flat a grade as possible? For example, is it better to have a 1/2% grade for 2 miles, or a 1% grade for 1 mile on a freight rail line?
Thanks to Chris / CopCarSS for my avatar.
Murphy,
It is generally desirable to have the lowest possible ruling grade. The ruling grade is the steepest a train and power combination will encounter subject to two conditions. One, the grade has to be longer than the train. Two, it excludes helper territory.
The condition of starting with all of the train on the grade is the most difficult for both locomotives and draft gears. In practice most ruling grades have a slow speed begining, or are several miles long.
Think of DC motored diesels with minimum continuous speeds and associated maximum amperage limits. The amp limits can safely be exceeded for a few minutes, but if the railroad makes a habit of exceeding the amp limit, they will find themselves repairing an inordinate number of traction motors and suffering too many trains stalling on the ruling grade due to motors failing at the most inconvenient times.
In the context of your question as asked, with today's trains it is probably 6 of one and half a dozen of the other. Assuming no speed restriction at the bottom, the 1% is short enough to be a "momentum grade", that is capable of being taken by using the momentum of the train to carry it much of the way up the grade. You did not tell us what the ruling grade on the line segment is, but a one mile 1% grade is unlikely to be the ruling grade. A ten mile long 1% grade could well be the ruling grade.
You did not ask, but long uniform grades are preferable to short up and short down grades in succession. These undulating grades are difficult to impossible to control slack action on. The rear end is constantly running in or running out due to the action of gravity on the rear end of the train. Think of a succession of 1500-2000 foot long up and down grades of 1% and running a 6000-8000 foot train over them. Back in the day, the guys in the caboose sat down and hung on while traversing such territory.
Mac
Murphy Siding On the whole, is it always better to have as flat a grade as possible? For example, is it better to have a 1/2% grade for 2 miles, or a 1% grade for 1 mile on a freight rail line?
That's better! at least some of us older folks with poor vision can see it!
Two further comments on Mac's excellent explanation:
- Paul North.
Paul_D_North_Jr The originally proposed Pennsylvania Railroad alignment would have had a steady moderate grade from Harrisburg to the summit just west of Altoona (I forget the exact percentage, but this article says 0.852%: http://en.wikipedia.org/wiki/Horseshoe_Curve_(Pennsylvania)#Construction ). However (following quote is from Wikipedia, but it tracks the Barnard, Roberts & Co. book on this subject): "The line was surveyed by J. Edgar Thomson, who had built the Georgia Railroad. His operating experience led him to lay out not a line with a steady grade all the way to Harrisburg to the summit of the mountains, but rather a nearly water-level line from Harrisburg to Altoona, where a steeper grade (but still less than that of the B&O) began for a comparatively short assault on the mountains. This arrangement concentrated the problems of a mountain railroad in one area.." (from: http://en.wikipedia.org/wiki/Pennsylvania_Railroad#Main_Line , 5th paragraph)
The wikepedia quote that Paul provided is completely incorrect as to the location of the bottom of Charles L. Schlatter's east slope 0.85% survey of 1839. The base was actually near Alexandria, many miles from Harrisburg. See Charles R. Roberts, Triumph I, page 68.
Both Schlatter and Thomson located the summit tunnel at virtually the same place and at the same elevation. Schlatter gave the Canal Commissioners what they demanded, a low grade line. Thomson, knowing that the preponderance of the tonnage would be eastward, and desiring to minimize side hill cuts, fills, and curvature basically doubled the grade to an average of about 1.7%, which more than halved its length.
As built, the grade is roughly 11 miles long. Given the projected, and realized, traffic pattern, Thomson made an economic choice to build a cheap line and concentrate his helper territory to the 11 miles between Altoona and the summit.
Further previous post.
It is about 150 miles from Harrisburg to the summit. From Harrisburg to Altoona the ruling grade is .4%. Thomson's choice was 125 miles at .4% plus 30 miles at .85% or 140 miles at .4% plus 11 miles at 1.7%. First cost of the low grade route would have been higher. It would have required more curves and probably taken longer to build. The longer distance at .85% than I previously figured is due to the fact that the route as built climbs at .4% so the difference is .45% or 23.5 feet per mile. The distances are for illustrative purposes only, I did not figure them closely. The .4% ruling grade does not extend for the entire distance between Harrisburg and Altoona.
Mac & Paul- Thanks for the input. It kind of clears up some of those things I wonder, when I see a rail line, and wonder why the heck they built it that way. I never thought about the ruling grade being loner than the train itself. There is a branch line near me, that is probably from the 1880's. It goes up and down, following the prairie. The last few years, BNSF has started moving unit grain trains from an elevator at the end of the line. Running a mile long grainer run the roller coaster built for 4-4-0 with a dozen cars must be like a carnival ride.
samfp1943 Murphy Siding On the whole, is it always better to have as flat a grade as possible? For example, is it better to have a 1/2% grade for 2 miles, or a 1% grade for 1 mile on a freight rail line? That's better! at least some of us older folks with poor vision can see it!
The reason(s) rail lines were built the way they were in the 19th and first half of 20th century(s) were primarily due to the constraints of money, plus construction techniques and equipment.limited what could be done.
The comments about undulating grades and resulting slack action were not that significant until speeds were increased and trains became longer and heavier. Currently, and for the past 50 years, the emphasis has been to construct, or reconstruct, rail lines to minimize slack action since locomotive power is a much more flexible than in the steam age.
The Santa Fe 44 mile line change in the Arizona mountains between Williams and Crookton was completed in December 1960. Westward decending gradient from Williams Jct. is a continous 1.00 % for 31 miles where it then encounters an acending gradient of 0.88 %. A 10,000 foot verticle curve was constructed which resulted in a rate of change in the sag of 0.018. This is one reason the BNSF Transcon is so very efficient in modern operations with 10,000 foot or greater length of trains.
Murphy Siding samfp1943 Murphy Siding On the whole, is it always better to have as flat a grade as possible? For example, is it better to have a 1/2% grade for 2 miles, or a 1% grade for 1 mile on a freight rail line? That's better! at least some of us older folks with poor vision can see it! During the summer months, I write a long, weekly, blog sort of thing about car racing at a local racetrack. I finally figured out, that if I printed it in a little bigger font size, I could see it better to proof read. Some clown always complains that it's too hard for him to read with the big font. I tell him to try reading small font with progressive bifocals.
The why do you post is such a small font here?
Semper Vaporo
Pkgs.
Incidentally, I wish that Kalmbach had a larger default font.
Johnny
Semper Vaporo Murphy Siding samfp1943 Murphy Siding On the whole, is it always better to have as flat a grade as possible? For example, is it better to have a 1/2% grade for 2 miles, or a 1% grade for 1 mile on a freight rail line? That's better! at least some of us older folks with poor vision can see it! During the summer months, I write a long, weekly, blog sort of thing about car racing at a local racetrack. I finally figured out, that if I printed it in a little bigger font size, I could see it better to proof read. Some clown always complains that it's too hard for him to read with the big font. I tell him to try reading small font with progressive bifocals. The why do you post is such a small font here?
I always set the size to 3 (12pt), which proves pretty readable, I think. Of course, I also change the font and color, but that's another story.
As to grades - we have a couple on our line to deal with - Purgatory and Big Moose. Purgatory is shorter but slightly steeper, with some variations (that slight increase near the top will get you on slick rail!). Big Moose hill is about five solid miles of 1%+, but with the curves (there is very little tangent track on the hill) it would probably be compensated higher. I believe the Central used helpers there on occasion, at least in steam days. I know it, too can be a real challenge.
Speaking of vertical curves:
The grade is around 1% on both approaches...
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Seems to me the default font size is #3 (12pt). Somehow on your system that has been changed to font size #1 (8pt). I have searched all over the various "settings" features of the web site interface that I can get to and I cannot find any place wherein one can alter that setting.
I am wondering if there is some method of when posting a message the system remembers the last font set by the user. I am going to try an experiment here of setting the font to something other than #3 (12pt) and then post and see if it remembers it for the next posting.
This is in font size #1 (8pt)... and now to click the "Post" button.
And I return to the default font size of #3 (12pt) so it does not remember it on my system.
I might suggest that you clear the cookies in your system just in case that is where the default is altered, though I have no idea how your system would have changed it and stored it in a cookie. Please note, that it is difficult with the usual tools available to the general user to clear just one cookie or just those associated with one web site, and many web sites remember passwords and whether the user was logged-in or out when they last left the site, so if you clear all the cookies on your system, you might have to remember what your passwords were for each of the sites that you are used to just going to and finding you are already logged in.
Another possibility is that if you were to clear your browser's cache it might correct the situation. How to do that depends on which brand and revision of browser you are using).
Thanks for the advice, but, I'm not computer literate. .
Murphy, I have to remember to make the changes before I begin a reply, or else highlight what I have written and then make the changes. I change the font first (I prefer Times New Roman), and then change the size to 4 (14 point). This size is much easier for me to read than the 12 point. Just click on the font and choose the typeface you like, and click on the size, and choose one that you can read easily.
I haven't asked for help from a grandchild yet, but, every now and then, a daughter helps me.
Murphy Siding Thanks for the advice, but, I'm not computer literate. .
Semper,
If all else fails hit control+. That will increase the whole page and make small type more readable.
Norm
PNWRMNMThink of a succession of 1500-2000 foot long up and down grades of 1% and running a 6000-8000 foot train over them. Back in the day, the guys in the caboose sat down and hung on while traversing such territory.
Just take a little air and use some throttle.
Oh, wait, the big roads discourage that, all dynamics these days.
We have a line that resembles a roller coaster. Lots of ups and downs, momentum grades, built prior to the Civil War. Sometimes we go with 2 tons-hp, and get the trains in. On the biggest hill, a long enough train will have the rear end pushing a bit as the head end is going up. Otherwise, speed drops quite a bit with say a 40-60 car train (30 mph down to 15-20). 80-plus cars and the rear end helps push.
Mike WSOR engineer | HO scale since 1988 | Visit our club www.WCGandyDancers.com
I've got two grade separation projects less than 3 miles apart where the rubber-tired bubbas want the railroad to drop 12-16 feet to accommodate road overpasses on a 35 mph branch and make up the depressions with 2% grades where ruling grade currently is 1.25%. The bubbas no savvy why I have a low opinion of their idea. (should I put up a ticket booth?)
MC, if you have explained the facts of life to the bubbas, perhaps they prefer the tales that little boys tell one another. Tell them that you can do it if they will pay for several miles of new grade so that the railroad will not need two helper districts--or if they will pay for the helpers. Have you suggested that they build a couple of flyovers on their road?
Deggesty MC, if you have explained the facts of life to the bubbas, perhaps they prefer the tales that little boys tell one another. Tell them that you can do it if they will pay for several miles of new grade so that the railroad will not need two helper districts--or if they will pay for the helpers. Have you suggested that they build a couple of flyovers on their road?
The 300 lb gorilla is now introduced to the 800 lb gorilla in the room.
If the ruling grade is dependent, somewhat, on the length of trains on the line, does that mean that the ruling grades are updates, as typical train lengths have increased?
Murphy Siding If the ruling grade is dependent, somewhat, on the length of trains on the line, does that mean that the ruling grades are updates, as typical train lengths have increased?
I suspect not, at least in the mountains. Those grades are typically controlled in large part by the terrain. Away from the mountains, I suspect many ruling grades have been reduced by either line relocation or regrading. For example, in the 1880's Jim Hill's Manitoba reduced the 1% ruling grades it inherited from the St. Paul & Pacific from 1% to .4% on its Minnesota main lines.
Many of today's main lines are the results of years of "fixing" cheaply built lines.
Does Norris mean, by his last question, that the term 'ruling grade' is not fixed on a given district for a given railroad over time? It seems power and other capabilities, lengths of trains arising, and perhaps one or two other factors can render what was at one time 'the' ruling grade no longer the ruling grade by definition.
I read here, explained I think by RWMN five years ago or so, that the term at one time meant the steepest grade in a district that could be handled by the typical consist on a timetable trailing the typical head-end power. So, if one particular grade was all the typical lone Mikado could negotiate with a timetabled freight of a given trailing tonnage, that was the ruling grade. Steeper grades in that district were helper grades. Or something like that...
-Crandell
selector Does Norris mean, by his last question, that the term 'ruling grade' is not fixed on a given district for a given railroad over time? It seems power and other capabilities, lengths of trains arising, and perhaps one or two other factors can render what was at one time 'the' ruling grade no longer the ruling grade by definition. I read here, explained I think by RWMN five years ago or so, that the term at one time meant the steepest grade in a district that could be handled by the typical consist on a timetable trailing the typical head-end power. So, if one particular grade was all the typical lone Mikado could negotiate with a timetabled freight of a given trailing tonnage, that was the ruling grade. Steeper grades in that district were helper grades. Or something like that... -Crandell
Ruling grade is the maximum grade on a particular route or line segment. On CSX's I-95 corridor between Florida and New Jersey - The Baltimore Belt line between Camden Station and Bayview Yard is the ruling grade. CSX's intent is not to provide helpers to move trains over this Eastward grade, however, if a train stalls the necessary actions will be taken to get it moving again.
Sand Patch, both Eastward and Westward, is the ruling grade between Cumberland and Chicago. While some trains can be consisted to cover these grades without helper, there are helpers that are used for both tonnage and train length (stringlining is a real possibility if there is too much trailing tonnage being pulled around the curvature in the grade) considerations. For shorter line segments within these routes there are other ruling grades for those specific line segment, ie between New Castle, PA and Willard, OH the ruling grade is at Akron, OH - both East & West - while the grade is relatively short, it is enough to stall a train - short trains more so than long ones - as the long trains can use the downslope of one side of the grade to assist the train on the upslope from the bottom of the grade. Short, heavy trains end up with all the tonnage of the train on the upslope with no assistance from downslope gravity.
Never too old to have a happy childhood!
For the seven largest Class 1's It would appear with the diversity of power available there would be little concern for what was once a 'ruling grade'.
There are really no typical train sizes and weights on the 200 - 300 mile subdivisions between crew change locations. So the power distributors are allocating power for the trains based upon a run through of several subdivisions with the option of adding or removing power, as may be dictated, at locations where power is being serviced.
Secondary lines may have to be treated it differently.
selectorthe term 'ruling grade' is not fixed on a given district for a given railroad over time?
BaltACD [snipped - PDN] . . . the ruling grade is at Akron, OH - both East & West - while the grade is relatively short, it is enough to stall a train - short trains more so than long ones - as the long trains can use the downslope of one side of the grade to assist the train on the upslope from the bottom of the grade. Short, heavy trains end up with all the tonnage of the train on the upslope with no assistance from downslope gravity.
This discussion has been mostly about freight trains, but I should point out that one notable advantage of the high power-to-weight ratio of the TGV/ HSR trains is that comparatively steep grades don't faze them. I understand the French will go up to the 3 to 4% range to minimize earthwork costs and especially to avoid the much longer distances that would be required to achieve a lower grade %, for the same vertical ascent.
Which leads into a great article on this subject, one of the more thoughtful and stimulating ones by the recently deceased Robert A. LeMassena:
"Shorter plus steeper equals faster plus cheaper - accent is now on speed, not tonnage" by LeMassena, Robert A., from Trains, August 1970, pgs. 44 - 46 (Magazine Index 'keywords': Line location )
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