A railroad question

If you want to replace one gauge of railroad tracks with another what usually makes the most sense, ripping them out and replacing them with new rails or building another right beside it and then abandoning the old one or is there some other method of doing so I am not aware of? The assumption is that in most cases the tracks are used fairly heavily. Also, if this is important, the old tracks are pretty worn out while the new ones come straight from the factory.
 

Saphroneth

Banned
My guess is that, if you're downsizing, you can just move the rails closer together in a pinch - though that will also mean a shorter distance between stops and hence you'll need to rework the support structure.
Upsizing is probably too hard to do without wholesale replacement of at least the sleepers, and doing the whole line is probably easier.
 
My guess is that, if you're downsizing, you can just move the rails closer together in a pinch - though that will also mean a shorter distance between stops and hence you'll need to rework the support structure.
Upsizing is probably too hard to do without wholesale replacement of at least the sleepers, and doing the whole line is probably easier.


Definitely upsizing the length, so basically you are combining a bunch of short lines to a make one major line. The scenario is that some Northern railroads by up a bunch of small Southern ones and want to replace the old track with the standard gauge. In areas where the track wasn't all torn out by Sherman's troops how did they replace them OTL?
 

Saphroneth

Banned
Definitely upsizing the length, so basically you are combining a bunch of short lines to a make one major line. The scenario is that some Northern railroads by up a bunch of small Southern ones and want to replace the old track with the standard gauge. In areas where the track wasn't all torn out by Sherman's troops how did they replace them OTL?
I mean changing the gauge. Length you've got no real choice but to add more track.
 
I mean changing the gauge. Length you've got no real choice but to add more track.

What I am saying is if shortline A connects to town B while another shortline connects that town to town C which connects to town D at the other end and another shortline connects that to town E. A big railroad company buys all those shortline railroads but they all have different gauges. How do you replace all that track? Do you rip out and replace or do you just lay new track beside it and abandon the old ones?
 

Saphroneth

Banned
What I am saying is if shortline A connects to town B while another shortline connects that town to town C which connects to town D at the other end and another shortline connects that to town E. A big railroad company buys all those shortline railroads but they all have different gauges. How do you replace all that track? Do you rip out and replace or do you just lay new track beside it and abandon the old ones?
Oh, I see.

Honestly they're likely to just remove the old rails. It's not a great deal of extra effort, and arguably it's easier than preparing another stretch of ground (i.e. expanding cuttings, levelling off drops, carting in the bed and so on.)
 
It depends.

On a lot of things.

1) downsizing gauge is, as said above, trivial. Just move the rails closer.

2) upsizing gauge. That's where things get interesting. Constraints you have to worry about
a) width of roadbed, sleepers etc. This may depend on how generous/overengineered the original was. If it was only just adequate, you've got major work to do. If it was 'normal', and the gauge isn't going up much, you might get away with simply moving rails, and increasing roadbed size and sleepers as a maintenance operation over the years. If you're increasing the gauge a lot, it's going to be more difficult
b) curves, etc. One of the major reasons for going with smaller gauges is that you can have sharper curves. If you're upsizing gauge, there will be many places where you have to build new road bed with shallower curves.
c) loading gauge. Physical size of equipment, and the space allocated around it. In particular, tunnels and underpasses will need to be replaced, almost certainly. Which is going to be 'fun'.
d) weight. Presumably your wider gauge will carry larger cars with larger loads. Is the road bed up to the increased traffic? More to the point, are the bridges your train's crossing strong enough.


Short answer. A quick and dirty widening of the track, running trains slowly (due to too sharp curves) and underloaded you might get away with. But upgrading the line would almost certainly take a lot of work to get it to full potential.


In particular, upgrading narrow gauge track would be a nightmare. Narrow gauge is usually chosen because it's running through mountains, river valleys, etc., with lots of twists and curves. If you want to run standard gauge through the same territory you might be better off resurveying and building a totally new line.
 
It depends.

On a lot of things.

1) downsizing gauge is, as said above, trivial. Just move the rails closer.

2) upsizing gauge. That's where things get interesting. Constraints you have to worry about
a) width of roadbed, sleepers etc. This may depend on how generous/overengineered the original was. If it was only just adequate, you've got major work to do. If it was 'normal', and the gauge isn't going up much, you might get away with simply moving rails, and increasing roadbed size and sleepers as a maintenance operation over the years. If you're increasing the gauge a lot, it's going to be more difficult
b) curves, etc. One of the major reasons for going with smaller gauges is that you can have sharper curves. If you're upsizing gauge, there will be many places where you have to build new road bed with shallower curves.
c) loading gauge. Physical size of equipment, and the space allocated around it. In particular, tunnels and underpasses will need to be replaced, almost certainly. Which is going to be 'fun'.
d) weight. Presumably your wider gauge will carry larger cars with larger loads. Is the road bed up to the increased traffic? More to the point, are the bridges your train's crossing strong enough.


Short answer. A quick and dirty widening of the track, running trains slowly (due to too sharp curves) and underloaded you might get away with. But upgrading the line would almost certainly take a lot of work to get it to full potential.


In particular, upgrading narrow gauge track would be a nightmare. Narrow gauge is usually chosen because it's running through mountains, river valleys, etc., with lots of twists and curves. If you want to run standard gauge through the same territory you might be better off resurveying and building a totally new line.


So building another set of tracks very close to it would be the way to go if you want to standardize the whole thing? Basically it is mainly to hook up the Cotton South with Tennessee and West Virginia and from there places further north.
 
So, one size does not fit all--might two?

Going for just the one standard will almost certainly mean abandonment of many roads completely, from the above discussion of reasons for installation of smaller gauges in the first place.

Or--since it would seem enterprises don't choose gauges at random or only on petty whims but for good reasons, the rationalizers might decide that one gauge does not actually fit all, and accept some of the penalty of operating with more than one.

Say, wherever small gauge has been adopted simply because the original line was put in by people whose main operations were in small gauge country but they extended beyond that into regions where large gauge works, those lines get replaced.

But once we reach the territory where small gauge makes more sense, the masterminds choose which of perhaps several used is best to standardize on--perhaps the smallest makes the most sense since it works, if inefficiently, everywhere, or perhaps a medium size dominates in laid trackage and the places where the gauge is smaller can take this medium though not full size.

So they wind up replacing much of the small gauge with another small gauge, but not having to do all of it since some is already the size they settle on, and so they have in the end two gauges, standard for reasonably flat lands and a smaller mountain standard for the rough country, and they adopt various schemes whereby they maximize the utility and minimize the costs of maintaining both.

For instance, using three rails one can run the smaller gauge cars on the larger gauge right of way. They might adopt ingenious tricks like developing cargo cars that slide sideways from small gauge bases to large gauge ones, thus enabling cargoes to run all the way from mountain depots to St Louis or Chicago without being reloaded--to be sure the cars running on the big lines will be undersized, so it is a question of which inefficiency is more important to avoid--reloading, or underusing the capacity of the big lines.

A certain amount of variation in gauges would indeed turn out to be mere whim or caprice, with different investors at different times being convinced that one or another was the way to go. The standardizers will have some work cut out for them. My guess is that if they do come around to the idea that they are going to have to maintain two or perhaps three standards, depending on local conditions, that they would invent technical means to streamline the transition of either cargo or car bodies from one set of bogies to another, and thus while widening one line, they can run a temporary third rail down the new track, and devise means to route through traffic running temporarily on the old stock around the construction zone. Or at worst, construct a moving pair of terminals, one on the remaining end of the old line rolling up it toward its final end, and another on the new line just behind the newest construction, and use some kind of inefficient but effective means to port cargo and passengers through or around the construction zone between the old and new lines. Eventually the project reaches the last meter of old line, builds up the last of the old stations to the new standard and the old rolling stock is junked.

Sometimes they'd be lowering gauge though, and then as said by others above the reconstruction is easy, and they can just lay in a closer third rail to be used by their narrow-gauge stock eventually while running the old medium stock through until the third rail is fully installed.

I suppose the way to do this is to send tracking experts on expeditions down each existing line they acquire, with a keen eye out for the most constraining turns or inclinations, tunnels and bridges and so on, and when they come to these to evaluate the largest gauge (from the list of the existing ones) that passage could handle without major rerouting. Then estimate the cost of upgrading to standard up to the first point that standard is too large for, plus the cost of switching over to the largest gauge that passage could take, and when they've got all their data collated at HQ, figure out which existing smaller gauge could accommodate all the stretches between such choke points at the lowest overall cost--factoring in avoiding regauging wherever possible, the possibility of major reworking enabling a larger gauge, the higher price of going up gauge versus down gauge set against the greater efficiency of higher gauge where it is possible. It would be quite a bureaucratic undertaking to be sure! They might have to decide to either continue some spur operations on very small gauges at some loss of profit or shut some of those stretches down completely--or put them up at auction, with a promise to provide terminal service transferring goods onto their lines if some third party will undertake to operate a spur.

Ideally they wind up with just two gauges, with a minimum of transfer points.
 
When US southern lines were narrowed from the common 5' gauge to the predominant northern gauge of 4' 9"*, one rail was moved in the 3 inches necessary to accomplish the change. Some preliminary work was done by removing some old spikes and pre-setting many new ones. A good overview of the project and preparations:
http://southern.railfan.net/ties/1966/66-8/gauge.html


*4' 8.5" came later but was so minor at the time as to require no special project, just done during normal rail renewals)
 
When US southern lines were narrowed from the common 5' gauge to the predominant northern gauge of 4' 9"*, one rail was moved in the 3 inches necessary to accomplish the change. Some preliminary work was done by removing some old spikes and pre-setting many new ones. A good overview of the project and preparations:
http://southern.railfan.net/ties/1966/66-8/gauge.html


*4' 8.5" came later but was so minor at the time as to require no special project, just done during normal rail renewals)

Just what I needed, thanks.
 
Narrow, dual gauge, and standard

Since southern rails were often a broader gauge, it was an easy fix for the track. Narrowing the gauge of cars or diesel locomotives is also fairly easy. Steam locomotives, on the other hand, often can't be narrowed, as all sorts of hardware is between the wheels.

If a particular line came through the war mostly intact, dual gauging that line might make sense, so you can keep using its locomotives. A whole train would seldom be mixed gauge, although sometimes idler cars (cars that carry nothing, but are intended to make things fit) would have special couplers to allow, for example, a standard gauge loco to pull broad gauge cars. Turn the flat, and now your broad gauge loco can pull standard gauge cars.

Of course, dual gauge means more complex trackwork, and slow speeds over switches, but it's been used a lot over time. Mostly, it's used at interchange points, but sometimes large stretches of track will be dual gauged.

Very narrow gauged line is usually that way for a very good reason, and best left that way.
 
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