Height and weight of rails question

[tstage]

Is it fairly prototypical to always have a mainline higher than the siding? On one particular stretch of highway close to home, their are 2 main line tracks and one siding that run parallel with the road. The siding is in front and is noticably a foot or so lower than the other two tracks. Would that also be true as the mainline travels through a yard.

The reason for asking. I was at a train show a couple of weekends ago and was looking at a module layout that one of the local clubs had set up. As I was looking at the yard area, I noticed that the yard itself was graded lower than the main running through it, and that the turnout and subsequent track leading into the yard area was graded down into the yard. Would this be normal and prototypical in a real yard situation. If so, why?

Also, why is it common practice to run lighter weight (90-lb.) rail in yards, sidings, and branchline than on the main. It seems to me that you would want a heavier weight (e.g. 132-lb.) rail in the yard to handle the static weight of all the cars and locomotives. Key word: Seems to me

Anyhow, sorry for showing my ignorance here but I had to ask. Thanks for your responses. [:)]

Tom

[TomDiehl]

To answer the first question, yes, that is prototypical. Over the years, the ballast under the mainline would be cleaned or refreshed (new ballast added) which would slowly build up the area under the track(s). A mainline would also be built to heavier construction than a siding, with a better foundation under it than a siding, where trains move very slowly. Another reason the main would be higher than the siding.

Mainlines are laid with heavier rail because the pounding of the train moving over it is more of a concern because of dynamic forces than the static weight of cars sitting on a siding or spur.

[dehusman]

Rail is cascaded down to lower service. Old mainline rail is put into sidings and yards. On the mainline you have a lot more dynamic load, the flexing as the train moves over the rail. In a yard or sidign where the speed limits is generally less than 20 mph that load is much less. It really doesn't take that big a rail to handle the static load of the car. Its the dynamic load and the ability to support the train if the ties under it are bad that becomes important.

Dave H.

[nbrodar]

There is also the money aspect. Rail and ballast cost money. You put the best stuff on the mains, where the railroads make the money. The mains tend to be higher, so they drain better, and can better support the dyamnic load of moving equipment.

[HoosierDaddy]

I've also heard that sidings and yards are lower than the main so that gravity helps to keep a loose car from rolling up onto the main.

HD

[Anonymous]

So, if higher mains and lower and lower grade yards are prototypical, what weight rails would be used in the various eras?

If we're now using 130 lb. on the mains and 90 lb. on the yards, how about the 50s? and the 30s? and the 1890s?

Was there something like a "standard" rail weight for the Class 1 mains?

From there, do standard manufactured rails, say for HO and N compare?

SMS

[Anonymous]

There's no real standard per se. The PRR used 155LB Rail on Horseshoe Curve way back in the 1920's, which is heavier rail than what's in common use.

Some stuff laid even in the early years of this century was as light as 55lb. It all depended on the cost and expected needs of the line.

[Anonymous]

I work a location to the south of Crewe fairly regularly...
There is a spur that has been shortened by adding buffer stops (bumping post)... the in-use side has been renewed in the last five years or so... the out of use side has components with the date 1903 cast in them. This spur hasn't been OOU for so long.
... and it is a major location.

[Anonymous]

Dynamic loads are higher than static loads, because of the sudden loading, plus the acceleration or G forces of the cars and locos must be resisted by the rail. Also, a heavier rail will deflect less and the mainline will require less frequent maintenance. A big factor when one considers the costs of closing the line. I often visit Medicine Hat, which is a crew change station on Canadian Pacific. The transcontinental mainline on either side of town is 136 lbs continuous welded rail. The mainline in front of the station where trains travel 5 to 10 mph is 110 lbs jointed rail. Keeping yards and siding lower than mainline does help to prevent a slow roll away from getting on mainline, but derails do so more reliably