[whinvik]

Wow I though 300 Kph was some kind of physical limit. I mean every high speed train in the world used to max out at 300.

Now it feels like it was just lack of competition. Maybe now other countries will start producing lines and trains capable of 400 Kph and hopefully its not a China only thing going forward.

[gregoriol]

There is show and there is reality: French TGV achieved 574,8 km/h in 2007 for show, but it was under specific conditions, not in real world conditions.

While it is technically proven that it is possible to do 400+km/h on rail, it's not practical: maintenance, wear, noise, turns, embranchement, and overall cost, ... many considerations that are probably less important for Chinese railway now, which needs some "show".

[litbear2022]

You should update your data; in 2013, China's high-speed rail reached 605 km/h on experimental lines. The CR450 is scheduled to enter commercial service in 2026.

[whinvik]

Sorry if I wasn't clear but was not talking about demo runs. There are plenty of those. Was more meaning operational speeds having a limit.

[jmyeet]

Like pretty much everything else, it's an optimization problem rather than a physical limit.

So running a train at 350kph is more expensive than 300kph, both in per-distance and pre-unit time terms. But if you can run more services that way then sufficient demand might make it economical. Also, if it's too slow, people may choose flying instead.

Maglev can go even faster but those have never been made economical, really. It's much more complicated and expensive.

It's a bit like how commercial planes have actually gotten slower. 747s used to fly closer to Mach 0.9. Now most commercial planes fly at around Mach 0.8. There are physical problems flying between Mach 0.8 and 1.2 but sometimes that doesn't matter so the best private planes top out at about Mach 0.93. Even then they rarely fly that fast.

[bob1029]

In the case of private jets, the Mach figure is mostly a proxy for other performance metrics.

Flying an aircraft at max cruise can save a lot of time on longer flights, but it's also substantially more expensive.

[bluGill]

300kph is the limit because aerodynamics make that about the best compromise on the effeciency cury. higher speeds are completely possibly - but air planes running with much less atmospheric drag start to become the better option.

of course the above is all about compromise and you can emphasize whatever numbers you want to get different results.

Edit: it is often a good idea to have everything capable of faster speeds - say 350km/h. You don't normally want to use those speeds, but if a train gets delayed (as happens) you can use that extra speed to make up time. Just don't let this become a normal thing.

[Pet_Ant]

What about if they added “wings” to trains? That could generate some lift reducing the effective weight is my shower thought.

No idea how much the wings would add versus the lift help.

[NuclearPM]

The friction is almost entirely from drag/air resistance, not from the resistance of the rails.

[bluGill]

the losses from weight are linear with speed - at high speed completely dwarfed by losses from pushing air out of the way which is quadradic with speed.

the wings on race cars are poited down - they increase weight to keep the car on the ground at the expense of more drag, which they overcome with a bigger engine (and more fuel use)

[Kuinox]

The French TGV managed to reach 574km/h, so 300km/h is not an hard limit. https://www.youtube.com/watch?v=EOdATLzRGHc