Alternate universe: Would HS2 be built?

[Haydn1971]

Something you have to remember is that trains rarely take un-cambered corners at high speed. So there relative instability is not that important.

There are high degrees of lateral force on cambered track too... Whilst these things might be running at up to 85mph - is that on track geometry akin to the British network or is that just on long straight sections or sections with very large radii. I remain unconvinced of this idea, purely because it's not been rolled out in Europe where networks have more in common with the UK - by chance maybe ? I doubt it

 

[NotATrainspott]

Speaking of cambered curves, the massively increased height would mean the horizontal clearance necessary under all conditions would have to increase. Going around corners, the increase would be even greater. That may then mean you have to rebuild horizontally as well, at which point the entire exercise is basically pointless. In a world where we've ended up rebuilding the entire rail network, it really wouldn't be beyond the wit of man to ensure that any classic trains running on these lines were fitted with steps or ramps so that they could call at rebuilt UIC platforms.

 

[HSTEd]

There are high degrees of lateral force on cambered track too... Whilst these things might be running at up to 85mph - is that on track geometry akin to the British network or is that just on long straight sections or sections with very large radii.

These speeds would be on relatively straight parts of track - but by European standards the quality of the track in question is extremely low and the ride very poor. So the top of the train is bouncing around like crazy as it rolls.

I remain unconvinced of this idea, purely because it's not been rolled out in Europe where networks have more in common with the UK - by chance maybe ? I doubt it

Double stack hasn't appeared in Europe because train capacities in Europe are limited by weight thanks to our old fashioned couplings - this makes increasing train weight using double stacks rather pointless since it just makes the train length allowable shorter.
Also since they already have double deck trains there is no reason for a larger loading gauge for passenger purposes.

Speaking of cambered curves, the massively increased height would mean the horizontal clearance necessary under all conditions would have to increase. Going around corners, the increase would be even greater. That may then mean you have to rebuild horizontally as well, at which point the entire exercise is basically pointless.

It is difficult to think of a track geometry where trains at high speed would end up on two lines that would have impinging envelopes and not already be violating signal protection.

Parallel lines going around a corner will have the trains sticking out further horizontally but the envelopes associated with the trains still won't overlap.

In a world where we've ended up rebuilding the entire rail network, it really wouldn't be beyond the wit of man to ensure that any classic trains running on these lines were fitted with steps or ramps so that they could call at rebuilt UIC platforms.

But we wouldn't be rebuilding the entire rail network.
Even with the most optimistic traffic assumptions only a small fraction of the trackage would be cleared to this enormous gauge.
Certainly a very large fraction of the rolling stock would still be of conventional size.
Which means you are proposing a total replacement of all rolling stock with classic compatibles to avoid adopting taller trains. Whilst still conducting an enormous reconstruction.

There is little reason to believe there are very large problems in stability with building a medium or high speed train with 5.595m height.

EDIT:

A check around indicates that the full width part of the British loading gauge begins at 3'6" (~1.06cm) above the railhead.
So to be conservative we add 1.06m to the 4.32m height which gives us 5.38 metres.
Unfortunately I haven't been able to find a cross section of a TGV Duplex with the wheels on.

But I think 5.595m is going to be sufficiently stable for up to 140mph running at the very least.
The top of a double deck train does not weigh that much - thanks to aluminium construction and the like.
The equipment that would be underslung in this high clearance design is rather heavy however and thus we could expect a relatively low centre of gravity and thus the platform would be relatively stable.

 

[SpacePhoenix]

With the conversion to double-deckers being ruled out, how much track could be electrified with overhead (or 3rd rail replaced with overhead)?

 

[DownSouth]

These speeds would be on relatively straight parts of track - but by European standards the quality of the track in question is extremely low and the ride very poor. So the top of the train is bouncing around like crazy as it rolls.

Not for the tracks which actually carry stack trains. If they ever let it get to the point where the upper container is bouncing around (and the federal regulator does keep an eye on this, including sending 'shipments' which are actually containers loaded with motion logging instrumentation) they cannot keep running stack trains until they fix their tracks.

You must be thinking of the secondary routes owned by Class I Railroads or the shortlines owned by Class III Railroads, where there are no high speed passenger trains and the freight tonnage is lower. Low quality track and train order working is fine for those routes, they present great ways of ensuring that freight is not priced off the rails and onto the roads.


When it comes to curves, a route with stack trains is no different to any other route - you can build the track to the standard needed for the relevant traffic to travel at the desired speed, or set the speed according to the standard of the track and the dynamics of the relevant traffic. In Australia - where the maximum speed for the interstate freight network is 115 km/h (about 75 mph) - there are plenty of curves which stack trains can take at full speed.

 

[AM9]

Not for the tracks which actually carry stack trains. If they ever let it get to the point where the upper container is bouncing around (and the federal regulator does keep an eye on this, including sending 'shipments' which are actually containers loaded with motion logging instrumentation) they cannot keep running stack trains until they fix their tracks.

You must be thinking of the secondary routes owned by Class I Railroads or the shortlines owned by Class III Railroads, where there are no high speed passenger trains and the freight tonnage is lower. Low quality track and train order working is fine for those routes, they present great ways of ensuring that freight is not priced off the rails and onto the roads.


When it comes to curves, a route with stack trains is no different to any other route - you can build the track to the standard needed for the relevant traffic to travel at the desired speed, or set the speed according to the standard of the track and the dynamics of the relevant traffic. In Australia - where the maximum speed for the interstate freight network is 115 km/h (about 75 mph) - there are plenty of curves which stack trains can take at full speed.

So what happens when train with a very high CoG goes slow or even stops on a super-elevated curve?

 

[GRALISTAIR]

Probably worrying for nothing, but that seems like a lot of weight, up high on a comparatively narrow base.

So what happens when train with a very high CoG goes slow or even stops on a super-elevated curve?

OK I think the question I was going to ask has been answered. It is a while since I have done mechanics and resolved forces and all that good stuff - but is this whole conversation about worries regarding keeping the centre of gravity as low as possible or am I being too simplistic?

 

[najaB]

OK I think the question I was going to ask has been answered. It is a while since I have done mechanics and resolved forces and all that good stuff - but is this whole conversation about worries regarding keeping the centre of gravity as low as possible or am I being too simplistic?

It is indeed. Also, about keeping it within the track width.