[theshrike79]

The difference between Finnish and Russian gauge is 4mm

IIRC the diff to European standard is closer to 10cm, still doable but a hurdle compared to just driving a trainload of troops to the middle of Helsinki it's a bit harder

[T-A]

First sentence from the article: The Finnish government has announced the conversion of its rail network from Russian gauge (1,524 mm) to European standard (1,435 mm).

1524 - 1435 = 89

https://en.wikipedia.org/wiki/5_ft_and_1520_mm_gauge_railway...

https://en.wikipedia.org/wiki/Standard-gauge_railway

[ta1243]

So "closer to 10cm" then

Clearly not "doable", without guage changing bogies.

[eqvinox]

The really annoying thing is that it's too close for "simple" dual gauge rails (e.g. 1435 + 1000); 1435 + 1524 is possible and in fact exists (e.g. the one single SE-FI railway bridge that exists is dual guage: https://openrailwaymap.org/?style=gauge&lat=65.8273204537081...), but AFAIK it's expensive because the mounts interfere and need to be quite custom.

[ta1243]

That bridge is 4-rail, not 3-rail

https://en.wikipedia.org/wiki/Torne_River_Railway_Bridge#/me...

Even if you were to 4-rail every line, you'd potentially run into loading gauge issues (you would have to offset the current centre of the bogies, go too far one way and you collide with platforms, too far the other way and you collide with oncoming trains)

[eqvinox]

Bleh, but kinda confirms my point too. I do think there are some 3-rail setups in other border regions though? I should check… then again it doesn't matter that much if it's 3 or 4.

As for the loading gauge, yes, of course. On the plus side, this is Finland, most of the lines is in the middle of nowhere and single track even. Maybe the best option for them is to just build 1435 in parallel whereever possible, and just merge where not otherwise practical (bridges, tunnels, populated areas & stations). I don't even think it's that infeasible considering Finland's layout. I'd wager there are only a handful of specific locations that need expensive work.

[dotancohen]

  > The difference between Finnish and Russian gauge is 4mm

What is the acceptable tolerance? It doesn't sound like a huge engineering effort to design a boogie compatible with both without requiring switching.

[CapitalistCartr]

Train tracks are normally not precise to within 4mm anyway, and wheels are wide enough to tolerate that.

[iggldiggl]

> Train tracks are normally not precise to within 4mm anyway

Yes they are. Of course practical tolerances including allowances for wear and there are large enough that things can be made to work, but in terms of nominal construction tolerances for example, 4 mm can easily eat up all your construction tolerances or even exceed them.

[sidewndr46]

I obviously don't have a in depth knowledge of Finnish rail, but have you ever looked at rail in the US? I can show you tracks with completely missing ties. Tracks that move vertically by a foot when the train goes over them. Tracks that visually snake all over the place. The difference is made by slowing down the train. Derailment at 3 mph rarely matters. The biggest risk is the conductor doesn't know it happened & continues to drag the car along the tracks

[iggldiggl]

Sure, but even in the US that infrastructure state is usually only found on minor branch lines (shortlines), not on the main lines.

[orthoxerox]

There used to be a St.Pete-Helsinki high-speed train before the war, Allegro. It was built with bogies for a 1522mm gauge.

[anticensor]

Yes, the acceptable tolerance is -4mm+7mm.

[iggldiggl]

Where? Finland specifically, or elsewhere? Both my local tram system in Germany as well as DB as the national infrastructure operator in Germany have construction tolerances of only +/- 2 mm. Maintenance tolerances on the other hand can be quite a bit larger, at least in the plus direction (on the order of 15/20/25 mm).

[lazide]

Sure, but thats Germans. I'm surprised it isn't specc'd in 10ths.

[anticensor]

They should've specced 1435mm±410µm, with no broadening at curves.

[theshrike79]

I just wish the Germans would be as accurate with their train schedules as they are with their rail gauge tolerances :D