Tilting trains

[rebmcr]

The tilt on the Shanghai Maglev which runs from Pudong Airport is something different to experience. With a top speed of 430kmh (approx 270mph) the journey doesn't take long enough to feel sick.

That's superelevation, not tilt.

 

[306024]

That's superelevation, not tilt.

That's a relief, now I know we were merely superelevating round bends I feel much better.

 

[Blamethrower]

That's a relief, now I know we were merely superelevating round bends I feel much better.

Tilt is where the train itself moves.

Cant is where the track is tilted (like at Rugby where the track is canted AND the train tilts)

I wouldn't have called Shanghai maglev as "tilting" either though, the train stays where it is on the track, it's the track that "tilts".

Although a quick look at dictionary.com may help

 

[edwin_m]

From personal experience, it wasn't just tanked up journalists who felt sick on the APT.

APT attempted to compensate fully for lateral acceleration, so passengers would feel as if they were on straight track but looking out of the window would show they were on a curve. The resulting sense of disorientation was thought to be one reason for feeling sick. The way round this was to modify the systems to compensate only partly, so passengers still felt some pull to the side on a curve. This seems to have solved the sickness problem and also has the benefit that less tilt is needed so the train can have a larger cross-section and feel less cramped.

 

[jayiscupid]

That's a relief, now I know we were merely superelevating round bends I feel much better.

I'm not sure what Shanghai Maglev you were riding but on all the times I've ridden it (20+) it's always been smooth and even at max speed (431km/h) the cant of the track is not noticeable.
You can't feel it even if you ride in the cab (Even though you can see the track cant).

 

[hulabaloo]

APT attempted to compensate fully for lateral acceleration, so passengers would feel as if they were on straight track but looking out of the window would show they were on a curve. The resulting sense of disorientation was thought to be one reason for feeling sick. The way round this was to modify the systems to compensate only partly, so passengers still felt some pull to the side on a curve. This seems to have solved the sickness problem and also has the benefit that less tilt is needed so the train can have a larger cross-section and feel less cramped.

Sounds about right - an account I heard from the infamous press run was that everyone was fine when the train left in the dark, and it was only after sunrise people began to feel queasy.

Of course, the Pendilinos have counteracted this problem by making the windows smaller and harder to see out of

 

[306024]

Tilt is where the train itself moves.

Cant is where the track is tilted (like at Rugby where the track is canted AND the train tilts)

I wouldn't have called Shanghai maglev as "tilting" either though, the train stays where it is on the track, it's the track that "tilts".

Although a quick look at dictionary.com may help

A quick look at dictionary.com did help, it confirmed I don't understand the point you're trying to make . To my simple mind if the train doesn't tilt (or lean if you prefer) with the track (or magnetic field) it shoots off at a tangent with unfortunate consequences. I suspect we may be playing a game of semantics.

I'm not sure what Shanghai Maglev you were riding but on all the times I've ridden it (20+) it's always been smooth and even at max speed (431km/h) the cant of the track is not noticeable.
You can't feel it even if you ride in the cab (Even though you can see the track cant).

I didn't know there was a choice . Quite agree it was smooth and went round the bends effortlessly, for which I am rather grateful.

 

[rebmcr]

A quick look at dictionary.com did help, it confirmed I don't understand the point you're trying to make . To my simple mind if the train doesn't tilt (or lean if you prefer) with the track (or magnetic field) it shoots off at a tangent with unfortunate consequences. I suspect we may be playing a game of semantics.

Tilting is only about passenger comfort, it's never about derailment safety.

Cant, a.k.a. Superelevation, is about both but can be hard to balance when trains of different speeds use the same curve (freight, intercity, stopper etc).

 

[edwin_m]

Tilting is only about passenger comfort, it's never about derailment safety.

Cant, a.k.a. Superelevation, is about both but can be hard to balance when trains of different speeds use the same curve (freight, intercity, stopper etc).

Agreed. If a train went fast enough round a tight enough curve it would overturn, but the speed limits round curves are set much lower than that to avoid passengers being thrown around inside the train. Either superelevation (=cant) or tilt will increase both the comfortable and the safe curving speeds. Tilt will increase the comfortable speed but not the maximum safe speed, but even with maximum tilt the comfortable speed remains well below the safe maximum speed.

 

[Philip Elliott]

Tilt will increase the comfortable speed but not the maximum safe speed

It will increase the maximum safe speed by moving the centre of gravity of the train towards the inside curve although the effect is small. Where you can see the effect more prominently is with motorcyclists.

 

[edwin_m]

It will increase the maximum safe speed by moving the centre of gravity of the train towards the inside curve although the effect is small. Where you can see the effect more prominently is with motorcyclists.

Active tilt (as used in the UK) is designed to rotate the coach body about its centre of gravity, so the effect will be very small indeed. Passive tilt relies on the centre of gravity moving outwards on curves, so will make the overturning risk worse.

It is essential that a motorcyclist leans inwards on curves, because (looking from the front and ignoring gyroscopic effects) there is only one point of contact with the ground and if the net force at this point of contact doesn't pass through the centre of gravity the bike and rider will topple over. The skill of riding a cycle or motorcycle includes instinctively correcting for this imbalance.

This isn't so with a train or a car, because when viewed similarly there are forces through both the left and the right wheels. Hence toppling won't occur until the lateral acceleration is enough to rotate the vehicle about the outer wheels so the inner ones lift off the road/track.

 

[najaB]

That is basically correct. Was there a question on the back of it?

 

[absolutelymilk]

How much maintenance does the TASS system require? After HS2, would it be worth the effort to keep the system running for the intercity trains that remain? (as there will be fewer and they will have more stops so less 125mph running)

(The economic case for HS2 shows around 6 or 7 intercity trains out of Euston per hour post HS2)

 

[najaB]

How much maintenance does the TASS system require?

Very little. Basically they just need to reinstate the balises after sleepers are replaced.

 

[rebmcr]

How much maintenance does the TASS system require? After HS2, would it be worth the effort to keep the system running for the intercity trains that remain? (as there will be fewer and they will have more stops so less 125mph running)

(The economic case for HS2 shows around 6 or 7 intercity trains out of Euston per hour post HS2)

TASS balises are the same model as ETCS balises. They could simply be used for that as well.

 

[Skie]

How is tilt failure handled? (Assuming that the train isn't in its vertical position, that is—then I presume they just continue with it isolated at normal line speed?)

Was on a train where this happened and it was quite severe. We were in a corner and tilted normally one moment and the next the train had levelled itself out and the emergency brake was on. The act of being levelled out so quickly was a bit rough and the 390's ability to drop the anchor is quite impressive! There was certainly plenty of leaning around like a bad sci-fi show

After 10 minutes of standing still we were back underway, though with tilt disabled and speed reduced as a result.

 

[cjmillsnun]

Was on a train where this happened and it was quite severe. We were in a corner and tilted normally one moment and the next the train had levelled itself out and the emergency brake was on. The act of being levelled out so quickly was a bit rough and the 390's ability to drop the anchor is quite impressive! There was certainly plenty of leaning around like a bad sci-fi show

After 10 minutes of standing still we were back underway, though with tilt disabled and speed reduced as a result.

I knew that the default mode of tilt failure was to return to the neutral position, but I didn't know they anchored up as well. I suppose that is so that a driver can do an inspection and clarify that everything is in the neutral position and the train is in gauge.