What kind of standards exist for certain weight rails? Given 136-lb rail, what kind of traffic can run over it, and at what speed?
Also, what dictates the choice of rail weight? What not use heavier or lighter rails?
RJ, the specifications for rails are very detailed, and include detailed specs for the chemical make up of the steel used in rolling the rail, and every detail of the cross-section at all points on the rail. AREMA (American Railway Engineering and Maintenance of Way Assoc.) is the Professional Association which publishes recommended practice for all relevant parts of the railway, like the IEEE does for Electrical Engineering. AREMA has a committee that sets the standards for Rails, and for example a 136RE rail is rolled to an AREMA 136-lb Rail standard. Back in the 60’s and earlier many railroads had their own favorite crossections, so for example a Pennsy 133 lb rail and a UP rail of the same weight would not be identical. Before the Schism Railroad Engineers were members of ASCE (American Society of Civil Engineers), and a committee of ASCE set the standards.
The foot of the rail serves to anchor the rail to the ties and helps to prevent the rail from being rolled over by forces from the locomotives and railcars. The web functions as a micro or mini-bridge spanning the ties, a taller web section makes the rail stiffer and spreads the load of a train over more ties, ballast and roadbed. The head is the portion that the wheels roll on, its thickness determines how much can be worn away by the wheels rolling over it before the rail must be replaced. So the Railroad Engineer looks at the amount traffic the Operating Department wants to run over the track in a given time frame, consults his budget given to him by the cheap bastards in the financial department, uses up his vocabulary of 4 lettered words, and orders the best rails he can afford, using a mixture of “premium” rails on the tightest curves, a
The weight of the rail has surprisingly little to do with track speed. Guilford found that out the hard way when they tried to limit speeds on Amtrak’s Downeaster service.
More important to speed are other standards on the roadbed: gauge, cross-level, number of ties per pre-determined distance, ballast, etc.
Watch the track next time a train goes over it–the rail will bend under the weight of the locomotives and cars, with the passage of individual axles over a given spot. This is true to varying degrees regardless of the weight of the car and its contents, and the weight of the rail. Of course, the bending is less with lighter cars, or heavier rail. The bending of the rail is expected, and is harmless in itself. But the more the rail bends like this, the more damage it will cause to the spikes, anchors, and plates that hold it to the ties–which will make the ties less capable of keeping the track in gauge.
So lighter rail probably wouldn’t withstand the pounding of heavy loadings as long. Rail heavier than 136-pound? Many main lines are being relaid with 141-pound (or better). Heavier still? The added weight is harder to transport and work with, and, of course, costlier–maybe justifiable down the road, but probably not soon.
Wait until Mudchicken weighs in on this thread–and when he does, accept his answer as authoritative. (I see Mr. Beaulieu came on and got off while I was dreaming about this–his reply isn’t bad, either!)
136lb rail means it weighs 136 lbs per foot, does it not? If the TGV rail weighs 60 kg per meter, that works out to be about 40 lbs per foot. That would be very light rail. Is 60kg per meter correct?
No finance types here [(-D]
Thanks for sharing, I found it very interesting and informative.
Enjoy
Paul
In a word rj, NO. 136 lb rail means 136 lbs per yard. When you convert to lbs per meter( isn’t this a stretch?) there’s very little difference.
I think you are referring to the UIC-60 rail section, a very common standard section in Europe, western Asia, and the Middle East. It’s nominally equivalent to a 115-lb. section in the U.S. but there are some differences.
S. Hadid
To add to beaulieu’s precise answers. Within reason any traffic can run over virtually any weight rail from 90 lb. upward at virtually any speed, if high maintenance costs and increased derailment risk are not a concern. The FRA sets safety standards for track, e.g., Class 3 is limited to 40 mph freight, but these standards do not concern themselves with the weight of rail. It is more economical to hold the FRA standards for higher track speed classifications by using heavier rail (115 lb. or heavier), but it is not mandatory. In fact the ride quality of the heavier sections (above 115 lb.) is often not very good because the rail is much stiffer.
For heavy axle loads – 263K cars and better – or high million gross ton traffic density (say, over 40 MGT/year) our practice is to always use 6" base rail, which is 133, 136, or 141 lb. rail. The 5-1/2" base rail, such as 115-lb., has issues with heavy axle loads and does not last very well. It’s OK for yard tracks and sidings but even in sidings I’d rather have the 6" base rail.
The major decision with rail weight is the amount of traffic (million gross tons), the axle load, the cost of maintenance, and last but hardly least, the loss of revenue that occurs every time rail is changed out, transposed, or ground. Bigger is always better from the operating department’s perspective, and if the money is there, from the engineering department as well. But we do lay some 115 lb. – and we even will lay some second-hand 90 lb. CWR this year, in yards – in places where traffic is light and budget is tight.
There are certain sections that come under the category "th
The 60kg per metre is correct, the US measurements are per yard, not per foot. So 136lb rail weighs 44 lbs per lineal foot.