APT vs Pendolino Tilt Mechanisms / Sickness

[CharlieSpotted]

Having watched a program about the APT recently, I've been trying to work something out that's been bugging me. It's clear the APT made people nauseous (actually physically sick?) and the Pendo doesn't generally have this effect. What's the key difference between the mechanisms that means that the Pendolino's tilt doesn't make people ill?

 

[JohnMcL7]

The problem was fixed on the APT as well, the sickness was caused by the carriage tilting perfectly which meant when the train was tilted people could see visually they were at an angle but they couldn't feel it at all. The solution was for the train not quite to tilt perfectly so people could feel some sensation of going round the corner to match what they were seeing.

The APT-P was sadly before my time but it seemed to have suffered badly from a lot of negative publicity including the belief it made people ill, latterly it apparently went into regular service with few issues which given the complexity of the train is very impressive. I felt they were a bit harsh on the APT-P on the recent channel 5 documentary making it out to be completely worthless while the HST had been so much better.

 

[CharlieSpotted]

Interesting... what do you mean by "tilting perfectly" though? Too smooth? Did they therefore make the motion a bit more rough? Something like that?

 

[Domh245]

The "perfect tilt" meant that the tilt entirely compensated for the forces experienced by going around the corners, so you couldn't feel that the train was tilting or going around the corners which made people queasy when they could see it. To fix it, they made it tilt less and therefore not 100% compensate for the forces experienced.

 

[JohnMcL7]

Interesting... what do you mean by "tilting perfectly" though? Too smooth? Did they therefore make the motion a bit more rough? Something like that?

If the carriage tilted the correct amount for the radius of the curve, passengers in the carriage would feel the same as if the carriage was flat and it would mean a drink on a table would be level. The problem was when the carriage was fully tilted passengers could see that was the case and would be seeing the sky out one window and the ground out the other however they would feel like they were still level. It's the opposite to car sickness where you're focused on a book which is static but your body can feel it's moving.

The solution was for the carriage to tilt slightly less than was required so people could get a feel of being tilted and even though it was only a very small effect, much less than the carriage was actually tilted it was enough to match what people were seeing and didn't feel ill.

 

[Old Hill Bank]

The APT tilted to 12 degrees which was to much, Pendos only do 8 Degrees.

 

[bastien]

There's probably another, more simple explanation: Hyperbole.

 

[43096]

There's probably another, more simple explanation: Hyperbole.

And another one: alcohol taken on by the press before/on the press trip. Private Eye's "Lunchtime O'Booze" was probably there...

 

[James James]

Or there's the original explanation of compensation being too perfect, which is what the science confirms:
https://www.ncbi.nlm.nih.gov/pubmed/10052584

Further interesting research suggests that better synchronization could let you achive perfect tilt without sickness:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3205836/

 

[daikilo]

There's probably another, more simple explanation: Hyperbole.

By tilting "perfectly", what the passenger feels is a downward pressure a bit like an aircraft taking off. With the Pendo there is mostly downward pressure but also some lateral which the human brain (ear?) seems to cope better with.

Today, I guess the average new passenger doesn't know that the Pendos actually tilt. I think some don't even realise that the track does on most higher speed curves as well!

 

[GrimShady]

APT-P was a fantastic bit of kit!

What annoys me about how it's presented in the media is a failure when in actually fact the issues were fixed with the train being in service for a year or two after. Also the business case changed for the WCML.

Intercity 225 is heavily based on APT and in actual fact is not much different from the planned APT-S fleet, even MK4 was deisgned to tilt!

Intercity 225 has been an excellent and successful train over the last 30 years let down by poor coach interiors in its first 15 years of operation.

 

[zn1]

My old dear who is now in her early 70s hates the pendolinos - she is always complaining of motion sickness when travelling on them, but then she recently travelled on the Voyagers and didnt get any motion sickness, i had no answer for her, so what does one tell her ? why on electric tilt she gets motion sickness but on DEMU Tilt she doesnt ??

she always goes north from MKC - she has yet to experience the fun south of MKC,

 

[507 001]

My old dear who is now in her early 70s hates the pendolinos - she is always complaining of motion sickness when travelling on them, but then she recently travelled on the Voyagers and didnt get any motion sickness, i had no answer for her, so what does one tell her ? why on electric tilt she gets motion sickness but on DEMU Tilt she doesnt ??

she always goes north from MKC - she has yet to experience the fun south of MKC,

Voyagers don’t tilt to the same angle as pendolinos.

 

[Domh245]

The Voyagers tilt even less than the Pendolinos (6° vs 8°), although I wonder if there is also anything to do with other factors like the larger windows?

 

[alangla]

I vaguely remember seeing a film of the APT press runs where a BR engineer put a coffee jar on its side through some curves and the jar hardly moved. On a Pendolino it would move a bit, a Voyager more so. On an HST it would be flying across the coach. I think the lack of movement is the"perfect" tilt.

Edit to add - having been on a Pendolino with failed tilt, the difference in movement of stuff on the tables is remarkable - even with the speed restrictions that tilt failure imposes

 

[The_Engineer]

I also recall that APT has what is called reactive tilt, so on entering a curve there's a lag before tilt kicks in and corrects the forces. Tilt on the WCML is achieved by the train detecting balises just before the curve which, with a speed calculation, allows tilt to come in right at the start of the curve. In other word the trains "anticipates" the curve. It was thought this made a big difference in the prevention of nausea.

 

[James James]

I also recall that APT has what is called reactive tilt, so on entering a curve there's a lag before tilt kicks in and corrects the forces. Tilt on the WCML is achieved by the train detecting balises just before the curve which, with a speed calculation, allows tilt to come in right at the start of the curve. In other word the trains "anticipates" the curve. It was thought this made a big difference in the prevention of nausea.

The second research paper I linked to above goes into a fair bit of detail on reactive vs predictive tilt. I haven't heard of the SBB bothering to upgrade their ICN's (the trains that were used for the study) from reactive to predictive tilt though...

 

[Bevan Price]

I recall that "feeling sick" was reported after the first press run of APT - but some people thought that sickness might have been due to consumption of too much ethanol by some of the media people.....

 

[Mikey C]

My old dear who is now in her early 70s hates the pendolinos - she is always complaining of motion sickness when travelling on them, but then she recently travelled on the Voyagers and didnt get any motion sickness, i had no answer for her, so what does one tell her ? why on electric tilt she gets motion sickness but on DEMU Tilt she doesnt ??

she always goes north from MKC - she has yet to experience the fun south of MKC,

Were those VTWC Voyagers, as they're the only ones which tilt, the Cross Country ones don't

 

[strimmer]

I traveled from Euston to Preston on the APT on 24th August 1984, along with my two sons. None of us felt sick at all, nor did anybody else in the coach we were in.

 

[Roast Veg]

Don't forget that sometimes the psychological effect of motion sickness can be extremely strong. I suffer from fairly chronic motion sickness and the thought of some events can trigger a response without even experiencing them. If somebody were to come to the conclusion that the train made them unwell, it might stay that way indefinitely even if the source of the sickness were actually removed...

 

[The_Engineer]

I traveled from Euston to Preston on the APT on 24th August 1984, along with my two sons. None of us felt sick at all, nor did anybody else in the coach we were in.

It does vary from person to person. And alcohol intake didn't help on the press run.....

 

[ericlesley]

Didn't British rail sell their research and patents to fiat? So the pendilino is essentially an improvement of the ATP

 

[CharlieSpotted]

I'd like to thank everyone for your replies. I knew there would be some knowledgeable folks here!

 

[nuneatonmark]

Didn't British rail sell their research and patents to fiat? So the pendilino is essentially an improvement of the ATP

Yes, another brilliant British invention sold on the cheap so someone else could make money out of it. The government of the time should have been shot. Just think of all the jobs we could have had in this country and the foundation for a world leading train design and manufacturing company that would have been.

 

[dgl]

Yes, another brilliant British invention sold on the cheap so someone else could make money out of it. The government of the time should have been shot. Just think of all the jobs we could have had in this country and the foundation for a world leading train design and manufacturing company that would have been.

Remember though that FIAT already had developed the original Pendolino before acquiring any technology from BR.

 

[sprinterguy]

The APT tilted to 12 degrees which was to much, Pendos only do 8 Degrees.

The APT-P trains tilted to a maximum of 9 degrees. The APT-E had passive provision for up to 12 degrees of tilt within the loading gauge designed into the profile of the bodyshell and the capability of the tilt system, but was also limited to 9 in main line testing.

 

[edwin_m]

Remember though that FIAT already had developed the original Pendolino before acquiring any technology from BR.

The original Pendolino, and the tilting Talgos and I think the LRC in Canada also, used a passive tilt system. Basically the train is suspended from a pivot high up and swings outwards like a pendulum in response to the centrifugal forces. This has the obvious disadvantage that the pivot and its supports intrude into what would otherwise be passenger service. The lower parts of the train swinging outward probably mean it would have to be even narrower in this area to clear British platforms (and hence have a big gap when stopped at those platforms). The move outward of the centre of gravity also increases the risk of overturning on curves, but this may be insignificant relative to other factors that limit curving speed.

The APT and the current Pendolino use an active tilt system where the body is actually rotated around an axis which roughly coincides with the centre of gravity, which therefore does not move much. This can apply tilt more accurately and quickly than a passive system and the body narrowing higher up is less of a constraint on the interior or the stepping distances.

 

[DarloRich]

The APT is one of the big what if's - I also wonder if the problems with the ride were as bad as were suggested ( the problems with the project seem clear!)

Yes, another brilliant British invention sold on the cheap so someone else could make money out of it. The government of the time should have been shot. Just think of all the jobs we could have had in this country and the foundation for a world leading train design and manufacturing company that would have been.

I am fairly certain that might be a bit of an overreaction. I suspect this will have been done by the Thatcher government of the mid 80's. Now selling this technology on the cheap might be a bad thing. I suspect people could think of worse things they did.

 

[boxy321]

There are people that get sea sick on the canal. For them a Chiltern class 168 is there. We'll stick to the quick stuff.