Are all rails the same height regardless of weight? If not, how is the transition made from light to heavy rail at, say, at an interchange?
In the US, 155-lb rail is 8 inches tall and there must be lots of rail in use that’s 6 inches or less. In the past joint bars were cast with the necessary shape to fit two sizes together, with the heads matching and the bases not. Guess now they often taper a rail to join the two sections?
No, height increases as weight increases in general.
Most common, or traditional way to deal with different rail weight at a joint is “comp bars”, more formally compromise bars. For example 112-90 which have significantly different heights.
Mac
I have a table several pages long listing all of the rail sizes in common use, from 12 pound per yard mine cart rail up to some 175 pound/yard stuff rolled to support bridge cranes. Almost all vary slightly in height, even different sections of identical weight.
I have seen homemade transition bars fabricated by welding the cut ends of a pair of different size bars together. I have also seen transition bars that were obviously cast to match two specific rail sizes. Nowadays, I would expect most transition joints to be the site of thermite welds.
Chuck
If you Google “Railroad Compromise Bars” you’ll be able to find phtographs that will give you a general idea of what these can look like (as well as a few good drink recipes…just kidding!).
Arouund here CSX is bringing in a speciality rail about 12 feet long. For sidings near here used 141 - 112 transition rail for the connections. Field welded transition to 141 rail across all rebuilt siding crossings. 112 side just bolted to 112 siding rail as a mix of both welded and stick rail… Note transition rails are marked with weight values.
Assume that if siding rail is replaced with 141# will cut out transition rail and weld new rail to crossing 141#. That way do not have to dig up crossing to install new rail and can reuse transition rail.
Not mentioned yet is that if there is a significant difference (usually 1/8"+) in the width of the rail head with regard to the webs of the rails being joined, then compromise joint bars often come in “hands” - as in “left-hand” and “right hand”. So there can be 4 different bars in the track at each such transition, none of which is (theoretically) interchangeable (oh, what fun !). See these webpages for how to tell the difference (note that there are 2 slightly different methods - the one illustrated here; or, by standing in the track and facing the joint - the one with the heavier rail on the right is the RH joint, and so on - results are the same):
http://harmersteel.com/catalog/track-tools-accessories/compromise-joints-insulated-joint-bars/
http://www.caltrain.com/assets/_engineering/engineering-standards-2/Drawings/2000s/SD-2233.pdf
EDIT TO ADD: Also, some railroads/ specifications limit the amount of change in rail height to about 1" at each compromise joint, so that there’s not too abrupt of a transition in the relative strengths/ stiffness/ flexibility and hence load / stress concentrations there, etc. Thus, more compromise joints are needed where there’s a large change in rail section, at least a rail-length apart.
For example, to go from a 90 lb. ARA-Type B (“RB”) rail (5-17/64" high, practicallly 5-1/4") to 115 RE (6-5/8" high, which is 1-3/8" higher), you’d need another ‘intermediate’ rail section to accomplish that transition in accordance with the specs. Just to choose one, a couple pieces of 100 RE (6" high) rail would work just fine - then the ‘steps’ up are 3/4" from the 90
“Compromise rail”, in addition to the compromise joints, and the compromise weld methods.
Me, I like a good solid forged compromise joint bar - heavier/ stronger than a standard joint, and I can’t recall ever seeing a broken one that was well-made and in well-maintained track.
- Paul North.
Quoting Paul North: “So there can be 4 different bars in the track at each such transition, none of which is (theoretically) interchangeable (oh, what fun !).”
Paul, your exclamation reminded of a line from a nineteen thirties’ song, “The Merry Go Round Broke Down”–“Oh, what fun, oh wonderful time, finding love for only a dime!”–the singer and the girl fell in love, for five cents apiece when the merry go round they were riding broke down.
Back to the topic. The description of insulation now used in joints made me think of the insulation that I used to see between rail ends; it looked like layers of composition cardboard; is that what was used years ago?
Oh, how we need spel Czech! I thought I had caught the errors, and just did catch another one before posting.
Thanks to everyone for the info. Strange how this kind of thing is never mentioned
in the fan magazines.
I would hope that well-maintained track would mean that they quickly replace anything before it breaks, so if you saw a broken anything it would mean whatever you were seeing wasn’t well-maintained 
And you railroad chauvinists haven’t mentioned the compromise joints we jolly trolley boys see in the, admittedly dissapearing as time goes by, places where streetcars transition between street girder rail and off-street regular rail.
And everyone, even if they don’t realize it, knows the tune to that song.
At least, they do if they’re old enough to remember the Looney Tunes cartoons.
[(-D][(-D][(-D][Y]
Chuck
Well, kind of back on topic - it was compromise joints, etc. - now we’ve veered off to insulated joints. Nevertheless . . .
It was more of a fiber (or fibre) material, harder and tougher than composition carbdboard - what you were seeing is insulation that had been in track, weathered and worn, for too long, and as a result “broken down”. We used to order it (and I often got the assignment to pick it up, since it was in my territory at the time) from NVF in Yorklyn, Delaware. I just looked it up, and NVF stands for National Vulcanized Fibre, and I suppose that’s what it was. You might better understand the chemistry of that than me - see:
http://www.mfgpages.com/company/NVF-Co-in-DELAWARE-USA-5476810/
http://www.nvf.com/forbon/forbon.htm
- Paul North.
All correct in normal practice. Avoiding having to work in the crossing saves lots of time and hassle for the rail gang - they’re not really set up for that much slower and more intricate operation. Plus, in the meantime the crossing and track has the advantage of the huge strength and stiffness of the 141 RE, which will make it last that much longer.
141 RE is 7-7/16" high, 112 RE is 6-5/8" high, so the difference in height is 13/16" - OK.
See, for example: http://www.icrr.net/rails.htm
http://www.akrailroad.com/products/tee-rail-section-data
The Moment of Inertia (strength) of the 141 RE is 100.44 in.^4, as compared to about 65.6 in.^4 for the 112 RE. So, for about 26 % more steel (112 ==> 141), there’s a strength gain of about 53% (65.6 ==> 100.4), or over 2x what a straight-line increase would be (53%/ 26% = 2.04). That’s why the heavier/ larger rails are so worthwhile - if you can afford them on a $/ track-foot basis !
http://harmersteel.com/catalog/tee-rails/141-lbyd-arema-rail/
Paul, I hope this wll not be considered off topic, but what difference is there in the web thickness?
“Well-maintained” in this context means fairly heavy (current standards) rail, good ties, and clean, well-tamped ballast, such that there’s not a lot of motion - “pumping” of the track - when a train goes over it.
Nothing in my posts excludes compromise joints to girder rails. [swg] I installed and inspected quite a few of them in the Penn’s Landing/ southern Delaware Avenue portion of Philadelphia when that street and track (Phila. Belt Line RR) was rebuilt in the 1970’s; also some in the SEPTA trolley lines - Media (Route 101), and Sharon Hill (Route 102); and most interestingly, in the Philadelphia Navy Ship Yard (PNSY) - mainly for their giant gantry/ portal cranes that ran in paving on the dock next to the ship for vehicle traffic, so that the cranes would also be able to reach and service the ships.
Some links to girder rail info (which can be hard to come by):
http://www.atlantictrack.com/MRT_Brochure.pdf - Page 7 of 20
Generally not much difference, not as much as you might expect. For structural reasons related to the wheel load of the railcars, shear (or vertical load) carrying capacity from the wheel to the nearest ties needs to be similar for all rail weights.
Here, the web of the 112 RE is 19/32" thick at its thinnest, while the 141 RE is 11/16" = 22/32". Hence the difference is 3/32", so the 141 RE is only about 16% more than the 112 RE (19 ==> 22), while the 141 RE is overall 26% larger by weight and cross-sectional area.
Thus, the web thickness has increased by only about 2/3 (16% ==> 26%) of what we would expect by considering just the general increase in size of the 141 RE over the 112 RE.
- Paul North.
I figured my coment would be explained for the forum. There is a cartoon in which Daffy Duck actually sings the song, though I do not remember the title. I heard it while working for one of the local channels here 40+ years ago during our afternoon kiddie shows. I still like the old pre-sixties WB cartoons, especially the ones that worked around classical music.
Of course, who could argue with the cultural and artistic achievements of Spongebob?
Off-topic notwithstanding, this has proven to be a very interesting thread. Of course, any time I run across “moment of inertia” I know I’m in an interesting thread and am tempted to dig out my Solids book, wherever it is hidden, or wonder if my Solids prof is still breathing.
Deggesty
Paul, I hope this wll not be considered off topic, but what difference is there in the web thickness?
[REVISED TO CORRECT AND CLARIFY THIS PORTION OF MY PREVIOUS POST ABOVE] Generally not much difference, not as much as you might expect. For structural reasons (properties of shapes), the shear (or vertical load) carrying capacity from the rail car wheel to the nearest ties is almost all in the web portion (only) of the rail. However, as the rails get taller/ higher for the heavier wheel loads, so does the web - that’s pretty much where most of the increase in the height of the rail comes from. So the web area kind of increases automatically, and with just a little bit of thickening, then has enough increased area and strength to carry the heavier wheel loads in shear.
[Rest of previous post is still valid.]
- Paul North.