Hi!
Before I get into my question, let me say I've been a certified train nut since the early '50s. I've been a Trains (and all the MR mags) subscriber for many, many years, and have been a member of the ATSF and IC historical societies for 20 plus years. I am familiar with mechanics, physics, and basic engineering. My point in all this is to establish that I am not a "newbie" and have a head full of railroad related knowledge.
All that being said, this one question has bugged me for years...........
Remember when you ran a long American Flyer or Lionel train that had heavy cars in the front and rear and light ones - like an empty gon or flat - in the middle? How many times did those light cars get pulled off the tracks? Obviously their light weight could not keep them upright as they were pulled somewhat sideways by the heavier cars further up/down the curved track.
The obvious question is, why doesn't this happen on the prototype? I've seen a lot of long 80 - 110 car freights with MTs in the center and they sure don't seem to have any problems getting from point A to point B.
As I write this, I'm thinking that perhaps the prototype curves are just way to gentle as compared to model trains (of course they are for the most part), and that just may be the answer. And then again, maybe the prototype does have this problem and sets up their trains appropriately when circumventing sharp curved tracks.
Of course, maybe the prototype does experience derailments from this, and they are not publicized or a rarity....
Anybody out their know about this????
Thanks!!!
Mobilman44
ENJOY !
Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central
Well, there was a long thread a while ago about how engineers can or cannot refuse a train, and one point that came up was that trains with empties in front are unsafe.
My guess is real trains don't go around hairpin bends like out models....imagine a freight train on subway-like curves!
"stringlined" is the term you are looking for...and it does happen in the real world.
I think that a part of the reason why you see this happen far more often on people's basement layouts than in real world operations, has to do with the skill and knowledge of a professional engineer, versus your typical transformer jockey in the homelands.
I also suspect that the proportional weight of an "empty" compared to a typical load in the real world is not as featherweight as is the case with that empty gondola car from Lionel.
Stringlining is the right word and it does happen in the real world. Page 52 of Feb 2004 Trains has a photo of a Santa Fe train on its side. The cars shown are auto racks and it was on a 10 degree curve west on Summit on Cajon Pass.
Details are all explained much better than I can.
rrnut282 wrote:I have an NS Employee Timetable that's just a couple of years old. In it, there is a limit for trainling tonnage behind MT flats, etc., for every mainline covered. Sometimes the limits are different depending upon the direction travelled.
....as well as whether the train is going up a grade or down, has dynamics or not, etc..
Distributed Power alleviates the 'stringline' problem to some degree; however, it is still important that the engineer have the necessary train-handling skills for the particular terrain. In addition (as mentioned above) the blocking of a train is very important, as well as the ratio of long cars (65+') to short ones (50' or less) including their position and grouping in the train.
There is only so much length a train can (safely) be for every section of track. On a dead-straight, flat track, the length and tonnage would be mostly dictated by available power as well as the maximum stress level of the knuckle/drawbar assembly. On very curvy and/or hilly track, a shorter train would be mandated.
UP also has train makeup rules concerning weight distribution on the train (last quarter of the train can't consist of more than a third of the weight, IIRC), and about long cars next to short cars (one or the other can be pulled off on curves). You're also right that a tinplate railroad's curves are considerably sharper than anything you'll find in prototype railroading.
Certain types of prototype cars are probably more prone to stringline derailments than others--empty centerbeam flats immediately spring to mind here.
Carl
Railroader Emeritus (practiced railroading for 46 years--and in 2010 I finally got it right!)
CAACSCOCOM--I don't want to behave improperly, so I just won't behave at all. (SM)
....I can't say for sure but right here in Muncie during the last few years we've seen the NS Triple Crown pulled off {on a long sweeping curve, inside}, twice. Most likely due to several conditions of train operations and the curve and grade it was negotiating.
Quentin
Many factors contribute to stringling a train, first would be tight curves, and usually high draft forces, the opposite can hapen to where high buff forces push the train off to the outside of the curve. I recall a derailment in Denver, CO where the engineer used too much independent brake to stop and a car derailed and when he went to pull on them he stringlined the train into the river.
An empty car weighs from 30-40 tons, so weight does play a factor in helping keep the cars on the rail, also most railroads have restrictions on empty cars in a train, on the BNSF it would be no empties in the head 10 cars, where you would find the highest buff and draft forces. also As was said eariler no more than 1/3 the weight of the train can be in the rear 1/4 of the train. Engineers get a wheel(train list) at the start of their trip and an important part of pre-trip plannign is finding the empties and loads and where they are located and what measures need to be taken to alleviate any problems.
The major difference between models and real life, curves are not as sharp and weight is significant even for empties. Also, the railroads dont run trains 70 mph everywhere, only where it can be safely done. Sharp curves have speed restrictions, most modelers run at a constant speed wether runnign straight track or curve track.
silicon212 wrote:It's called 'stringlining' and it has happened on tight radius curves on a mainline. 1991 in Dunsmuir, CA. on the SP rings a bell - a tank got pulled off the rails and into the Sacramento River, killing fish and causing environmental issues. It escapes me, but I believe it was a tank of sodium hydroxide (lye). IIRC, the derailment happened because the engineer was using too much power through the curve.
It was metam sodium.
One thing that nobody has brought up is that the curves on layouts almost always have a considerably smaller scale radius than the radius of curves on real railroads. The trains may be to scale, but the track layout are not.
"No soup for you!" - Yev Kassem (from Seinfeld)
Hey at least I got the sodium part right!
Anyways, you are correct. Model layouts are typically 3-4 times tighter in the radius than most of the tight radius rail that's on any mainline.
Good Morning!
Thanks folks! It looks like my question really does apply to the real world - as the situation does happen and is addressed in employee manuals and trainmen's considerations.
After reading your postings, it confirms that the weight difference between an empty Lionel car versus heavier cars is typically more proportionally than the prototypes, and of course you have very trained, highly skilled folks at the throttle - who are under the very real pressure that a derailment - from any cause - is a major event. And of course in our model world we often push the limits (train speed, length, make-up, etc.) and a derailment is a fairly simple thing and almost always allows us a "do-over".
Thanks again, you all are great!!!!!
Timber Head Eastern Railroad "THE Railroad Through the Sierras"
ericsp wrote: silicon212 wrote:It's called 'stringlining' and it has happened on tight radius curves on a mainline. 1991 in Dunsmuir, CA. on the SP rings a bell - a tank got pulled off the rails and into the Sacramento River, killing fish and causing environmental issues. It escapes me, but I believe it was a tank of sodium hydroxide (lye). IIRC, the derailment happened because the engineer was using too much power through the curve.It was metam sodium.One thing that nobody has brought up is that the curves on layouts almost always have a considerably smaller scale radius than the radius of curves on real railroads. The trains may be to scale, but the track layout are not.
I was reading last night about how Great Northern had to limit the speed mainline trains could use when entering a passing track thru the curved leg of a turnout to 35 MPH because of the tightness of the curvature....and this was a No.20 turnout, about three times less sharp than a typical model railroader's no. 6 mainline turnouts!!
IIRC in John Armstrong's books he says that in HO a "broad" 33" radius curve would translate to the sharpest real mainline curve you would see, but it would be restricted to about 20 MPH.
Ishmael refers to a very good example of this sort of thing.
It wasn't for nothing that ATSF spent $ millions back in 1972 to alter the routing at Summit on Cajon Pass in California. The actual grade was not reduced any significant amount, but the curves approaching the top of the pass were made much gentler, and thus much less likely to see long empty flats and autoracks spread on the ground.
(In the days of 40' freight cars, it must not have been such an issue, at least at that location.)
I've only been a member of this forum for less than a year and have no experience with real railroading. But I am continually amazed at the complexity of this industry and have a new found respect for those who work daily, on what at times, can be a very dangerous occupation.
This ol-timer appreciates the work you guys do and I learn something new almost everyday.
Wayne
Modeling HO Freelance Logging Railroad.
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