Quite remarkable. Too ahead of its time? Wonder why it never got revisited
Modern technology might be able to turn the car couplings into something that can actively manage their tilt relative to each other, thus allowing them to propagate the balance beyond a single gyro car, but there's a lot of PID-controller-type [1] math that would go into determining if this was even possible with real, physical objects trying to control things the size and mass of train cars in a train track environment. The computations are probably not that difficult in 2024 but trying to actually deliver the correct forces in a timely manner may be difficult if not impossible. There aren't always solutions, or practical solutions, to the PID equations in the real world.
Plus, I'm sitting here imagining the size of the electric motors we're trying to torque the cars against each other with and it's hard not to say that we're better off just having two tracks and putting those motors on the wheel themselves. (Which then collapses to having a locomotive setup like we have now.) In the "power/control/price" triangle we're basically forced to take the max on power and control, so these are going to be ferociously expensive if they can be built at all.
And there's some bad failure cases that I just don't know that you can mitigate. Having 30 minutes after power loss to evacuate passengers is generally going to be enough, but cargo can't be evacuated on that timeline. And that's not the only failure case. A seized gyro is going to be catastrophic and even a single one could take the whole train down, even with that PID control system (which is going to be a stretch even without also having to build in buffers for failed gyros).
The fact that a 2-track-train can just sit there for extended periods of time with no power is one of those advantages you don't even think about until you try to take it away.
Guy was a genius though. It's basically an analog computer that keeps itself upright that you can ride. The final design is amazing with its judo-esque approach to using physics against itself. But I don't think it can be scaled up much beyond "neat tourist attraction". I'd ride one as a tourist attraction, though.
[1]: https://en.wikipedia.org/wiki/Proportional%E2%80%93integral%...
Indeed, the more I think on it the more difficult the edge cases seem, I hadn't even gotten to the power out thing, although from thinking on the spinning cube conversations in this thread[1], I had thought about magnets as a failsafe mechanism, but at that point....
"The fact that a 2-track-train can just sit there for extended periods of time with no power is one of those advantages you don't even think about until you try to take it away." <- This heh.
Another problem is that the system is reactive, meaning that there is a lot of shaking and balancing that is quite unacceptable - think about drinking a cup of tea in such a wobbly train even on straight lines, while on curves it's not staying horizontal by design.
Yet another problem is that it can't share the current infrastructure without major switch changes while sharing the infrastructure the other way around is impossible.
And in the end all of this effort for trying to fix a problem that doesn't really exist, at least not in Europe where most of the rail infrastructure was already built 100 years ago.
Worth noting that modern tilting trains do this quite successfully (on two rails!), in order to run faster on tracks with tight curves. By “leaning in” to curves, you make the ride more comfortable, not less.
Tilting trains are used extensively on the UK’s West Coast Main Line, for example.
That is the intention, but many people report discomfort due to the non-ideal adjustments, at least for the tilting trains in germany.
I commute 50 mins each way on a Pendolino in the UK (into and out of London) and find that if I'm doing work on my laptop, or responding to emails on my phone as the train tilts I feel uncomfortable and dizzy.
The "slow" Desiro trains that don't tilt take 2 minutes longer to get into London, because whilst their top speed is 15Mph lower they accelerate faster.
Interestingly, I don't get motion sickness in VR, which is the opposite problem (movement visually, none in reality).
Thought to be so, because there's a mismatch been visual and inner ear inputs. That is: you can see you're going around a corner, but you don't feel it. Resulting in motion sickness. Since all people have different tolerances of motion sickness, it's impossible to have a "correct" amount.
Almost all systems compromise between zero and full compensation, but passenger comfort is just one of many factors, and not the most significant. The discomfort on German tilting trains is probably because they are too close to "ideal".
One of the issues with the German tilting trains is that they try to compensate up to 8° without track knowledge (BR 612) thus the first carriage (the one after that less so) swinging abruptly to compensate when entering or exiting a curve. Not sure how the class 390s solve that problem.
I would love to see some data - I assumed this was a solved problem, but I wouldn't be too surprised if the tolerances were revised to fit the problem.
I forgot to mention the 'interesting' part of this problem: that the effects are measured cumulatively. That is, against passenger journey length. Drivers and other staff are not considered as far as I know!
Clever engineering without a necessary, defensible, competitive business advantage usually becomes either a hobby or an art project.
It could be interesting with it's own infrastructure, though my first thought is that it might be better suited to tunnels, being able to maximize use of the tunnel profile.
Modern trains do that too. https://en.wikipedia.org/wiki/Advanced_Passenger_Train eventually led to https://en.wikipedia.org/wiki/Avelia_Liberty, which is being deployed for Acela in the US.