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Comment by jabl | Hacker News Reader

In 1886 the USA switched the rail gauge of the southern states to standard gauge. Most of the work was done over two days.

http://southern.railfan.net/ties/1966/66-8/gauge.html

Obviously doing this today would be a much more complicated affair, considering the much higher speeds and weights of contemporary trains.

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This is a lot easier to do with wooden sleepers than with concrete ones. You can drive new nails into wooden sleepers almost at will, so you can keep the sleepers in place and "just" move one rail to a different position. Concrete sleepers have pre-fabricated holes for the indicated gauge, which means replacing them.

German soldiers re-gauged Soviet railways on a very short notice too when Barbarossa started.

Building a machine, if it doesn't exist, to rapidly make small holes in concrete shouldn't be hard.

It is not just holes. I didn't want to analyze the entire problem in full, but FIY, this is how a concrete sleeper looks like:

https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.dayaen...

As you can see, the entire shape of the sleeper is adapted to the expected distance between rails.

In contrast, a wooden sleeper is just a straight log with no pre-made bumps for rails.

Most of the work was not done over two days, it says they did a bunch of prep work before the two days to minimize the downtime, and besides being done within two years they didn't specify how long the prep work.

As the Finns will presumably not permit Russia to do prep work on the rails in advance of their invasion, they'll have to do all that prep work after the invasion. The article doesn't say how long that two years of prep would actually take if needed ASAP, but if it would take a month then the Finns would have a huge boon.

If you want to, you can do it fairly fast. The decades plan is nonsense. It cannot take decades to change tracks, especially since the size of the rail network is quite small.

The decades are planning so the process happens fast. There is a lot that needs to happen correctly to do this fast.

I could personally switch a track guage - but it would be multiple days per km of track switched, if you trained me on how to do this I could do it much faster (I have no idea how much faster, but faster). Train a lot of people like me and it is faster. Or you could buy machines.

We also need to switch all the train wheels, again, not hard - but not something an untrained person can do quickly.

Most likely a large part of the process is finding other railroads around the world that have the needed equipment that will let them borrow it for a few months (most of which time spent in shipping not using the machines.) there are a lot of railroads with old machines they keep for emergency use that can be pressed into use. There are railroads thinking about buying a new machine that would make the order now (with the options Finland needs) if Finland contributes on the understanding Finland gets it for a few months...

Toronto has 83 km of TTC-gauge streetcar track. 99% of it is set in concrete. This would take a little longer than 2 days.

If you want to nitpick about some corner case, go ahead.

I have this feeling that Finland's railway tracks are not set in concrete at street level ;)

But they are set into prefabricated concrete sleepers, which cannot be modified to a new track gauge and instead need to be swapped out completely. Whereas during the US gauge change, the railways used wooden sleepers, with the rails fastened simply with nails hammered into the sleepers, so it was simply a matter of pulling out the nails and hammering them in again at the new track gauge.

There are machines these days that change sleepers automatically. I do not know if they do gauge conversion, but changing track (meaning replacing old one) and sleepers nowadays is fully automated.

I imagine running a machine in reverse, removing the track and changing sleepers and one moving forward at the same time installing the new track only. Or have one remove the old sleepers and track and and another one installing new sleepers and track (imagine building new track kind of operation).

Yes, those kind of track relaying machines exist, and they could most likely be adapted to work for the gauge change (one end of the machine would have to be set up for broad gauge and the other end for standard gauge), but they still manage only a few kilometres of track per day, and they're comparatively rare and expensive – basically there are only enough of them around for the amount of track relaying required during routine maintenance.

So repeats of the famous 19th century gauge change by converting large swathes of the network in just a few days (thousands of miles of track as in the US in 1886, or even just the 177 miles west of Exeter in the UK in 1892) remain rather unlikely.

There are metal sleepers that sit on a concrete pad. The challenging part is the rail is encased in concrete that enables drivers to drive over the tracks.

Getting to the sleepers would take weeks of jackhammering plus more time to repour the concrete.

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