Tilting trains

[GJEdmunds]

How do the Pendolino trains know when to tilt, and by how much, and to which side - I'm assuming it is all automatic?

 

[LNW-GW Joint]

How do the Pendolino trains know when to tilt, and by how much, and to which side - I'm assuming it is all automatic?

Using TASS - Tilt Authorisation and Speed Supervision.
There are balises in the track which have the information you describe (also how far to the next balise, and what the permissible speed is).
The on-board kit reads that and reacts accordingly, with displays in the cab for the driver.
The faster tilt speeds are known as Enhanced Permissible Speeds (EPS) which is indicated on trackside speed boards (eg 110/125 EPS).
A train without tilt enabled and working is limited to 110mph on the WCML.
TASS is a form of Automatic Train Protection (ATP).

The same system is used in the Voyagers (221s), but their tilt capability is a bit less (6 degrees max rather than 8) so there are occasionally differential speeds applied.
eg through the reverse curves at Weedon the line speed is 100mph for non-tilting trains (eg LM's 350s), 110mph for 221s and 120mph for 390s.
The balises have to convey all that information to the train and the driver.

We can't use uncontrolled "tilt at will" in the UK, unlike on the continent, because our structures gauge and track separation are too restricted.
Nevertheless, I think the WCML is the highest-performing tilt-equipped line in the world (in terms of speed/distance run with tilt enabled).
I can't think of another 400-mile line run mostly at 125mph with tilt operational throughout.
Most other lines have a lower top speed (eg the Czech Pendolinos tilt, but still within a line maximum of 160kph).
The Italy-Switzerland Pendolinos are rather similar, and the ICN trains on faster domestic Swiss routes only tilt for short stretches.

 

[najaB]

How do the Pendolino trains know when to tilt, and by how much, and to which side - I'm assuming it is all automatic?

There is a system called TASS (Tilt Authorisation and Speed Supervision) that uses fixed balises in the four-foot to let the train know that it is 'allowed' to tilt. The leading car has a device that measures the lateral force as the train goes into a corner and determines how much tilt is required to counter it and sends the commands to the tilt mechanism to tilt (up to the amount that TASS has authorised).

That is why tilting trains cannot operate in tilt mode on non-equipped tracks.

 

[cambsy]

The Pendolino and Super Voyagers use a system called TASS, which stands for Tilt Authorisation and Speed Supervision, which uses metal yellow balise between the track about 2km apart to tell the train when it can tilt and what speed it permitted to do, its read by a transponder on the leading coach, the train can go maximum 3mph over the permitted speed before the brakes are activated, so top speed is 128 mph, the tilt works using gyroscopes and accelerometers, which computers use to determine level of tilt, there is built in safety systems for tilt failure etc,so it can't go out of gauge, and tilt is switched on and off for sections where tilt is not allowed, the maximum degree of tilt is 9 degrees for Pendolino which gives them a higher tilt speed and why they are more cramped inside, and 6 degrees for Super Voyager which gives lower tilt speed.

 

[GJEdmunds]

Thanks very much for the info - now I understand - thats completely answered my question.

 

[najaB]

Oh, it's also worth adding that the system used in Voyagers and Pendolinos isn't intended to counter 100% of the cornering force as that induces motion sickness in most people.

 

[Class 170101]

That is why tilting trains cannot operate in tilt mode on non-equipped tracks.

But can of course run conventially without tilt.

eg Pendolinos running between Manchester and Preston / Liverpool via Eccles
or Voyagers between Wolverhampton and Crewe via Shrewsbury.

 

[edwin_m]

I don't think TASS actually supplies information to the train about how tight the curve is and how much it should tilt. I believe TASS gives the train permission to tilt and authorises maximum speed when tilt is operative or inoperative, but once this happens on-board sensors are used to work out when and how much to tilt.

 

[najaB]

I don't think TASS actually supplies information to the train about how tight the curve is and how much it should tilt.

Nobody has said that it does.

 

[gsnedders]

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?)

 

[najaB]

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?)

Depends on what you mean by 'tilt failure'. If you mean if the train is in the neutral position and unable to tilt, then yes it will run at normal line speed. If it were to fail such that it was tilted from vertical and unable to return to neutral then it would have to come out of service as soon as possible, since the train will likely be out of gauge.

 

[axlecounter]

Nobody has said that it does.

Well, LNW-GW Joint in the first answer did. And now I'm confused. Do balises carry tilting specific informations like degrees or only informations about when to tilt ("in 123 meters to the left") or maybe just an authorisation (yes/no).
And if the latter, how is this tilting system different from those used in other european countries?

 

[najaB]

Well, LNW-GW Joint in the first answer did. And now I'm confused. Do balises carry tilting specific informations like degrees or only informations about when to tilt ("in 123 meters to the left") or maybe just an authorisation (yes/no).

It contains the information that LNW-GW Joint said it does: permissible speed, distance to next balise and tilt authorisation. Certainly it doesn't contain any information about the track geometry - the train works out how much tilt and in what direction using on-board sensors.

 

[hulabaloo]

Do the trains "pre-empt" the curves and tilt going into them? I saw a documentary many moons ago about this system being developed, and that proactive rather than reactive tilting stopped the feeling of motion sickness.

 

[najaB]

Do the trains "pre-empt" the curves and tilt going into them?

No. The lead vehicle senses the curve and reacts accordingly. That is why the ride in the first carriage is sometimes more 'lively'.

 

[61653 HTAFC]

Oh, it's also worth adding that the system used in Voyagers and Pendolinos isn't intended to counter 100% of the cornering force as that induces motion sickness in most people.

Being tanked up on free booze from the buffet car doesn't help with motion sickness either! :roll:

 

[cjmillsnun]

Being tanked up on free booze from the buffet car doesn't help with motion sickness either! :roll:

Indeed. But that would never stop journos from berating things without valid reason now would it

 

[najaB]

Being tanked up on free booze from the buffet car doesn't help with motion sickness either! :roll:

Indeed. But that would never stop journos from berating things without valid reason now would it

Ah, now I get the reference... Damn that ATP was a sweet-looking train!

 

[thenorthern]

When the tilt system does fail then they do indeed lock it out of service. Bearing in mind that with the 11 car Pendolinos each coach has 2 bogies with a tilt hydraulic rams on each side (11x2x2=44) so it can be quite common for it to fail. I have been on one before which has failed and at the start of the journey and way of fixing it was to simply turn the electrics on and off again.

Its important to note a well that contrary to popular belief a large amount of the Virgin Trains Routes don't have TASS equipment including all of the North Wales Coast Line, Blackpool Branch Line, Shrewsbury Branch and I think the Edinburgh spur from Carstairs.

 

[HSTEd]

How did the beacon system for the ATP work?

I imagine it was rather different to TASS given that ERTMS had not been invented at the time.

 

[najaB]

...and I think the Edinburgh spur from Carstairs.

That is correct, no EPS speeds from Carstairs to Edinburgh.

 

[LNW-GW Joint]

Its important to note a well that contrary to popular belief a large amount of the Virgin Trains Routes don't have TASS equipment including all of the North Wales Coast Line, Blackpool Branch Line, Shrewsbury Branch and I think the Edinburgh spur from Carstairs.

Also not on the slow lines, nor Northampton loop or any other diversion route.
Only on a tiny stretch between Carstairs and Glasgow near Motherwell.
I think TASS only reaches Cheadle Hulme towards Manchester (and not at all Crewe-Cheadle Hulme).
Not much after Runcorn towards Liverpool, nor most of the Birmingham International-Wolverhampton loop.
Nor between Acton Grange and Wigan on the main line, either, which seems the oddest omission.

 

[najaB]

Nor between Acton Grange and Wigan on the main line, either, which seems the oddest omission.

The Sectional Appendix says that TASS is fitted throughout - is it fitted but no EPS speeds or is the SA wrong?

 

[LNW-GW Joint]

The Sectional Appendix says that TASS is fitted throughout - is it fitted but no EPS speeds or is the SA wrong?

No EPS, I meant. Even through the sharp curves at Dallam (80), Winwick (80)and Golborne (90).
There's also no EPS through Kilsby Tunnel (PSR 110mph), for air pressure reasons I think.

 

[najaB]

No EPS, I meant. Even through the sharp curves at Dallam (80), Winwick (80)and Golborne (90).

That is a bit odd - you'd think you could get an extra 5-10mph through those.

 

[sprinterguy]

How did the beacon system for the ATP work?

I imagine it was rather different to TASS given that ERTMS had not been invented at the time.

If you are referring to the Advanced Passenger Train, then maximum permissible speeds were communicated to the driver by means of a basic form of in-cab signalling, known as C-APT, which used track mounted transponders located at one kilometre intervals. This page has further detail, contemporary with the introduction of the Prototype trains:

http://www.apt-p.com/aptcapt.htm
The men who drive the APT will also drive conventional trains over the same routes, yet APT is allowed to exceed existing speed limits by a substantial margin. To prevent confusion, the higher limits are displayed automatically in the APT cab. This advisory system (C-APT) leaves the driver firmly in control of the train, but gives him a digital advance warning on his desk of the higher APT speed limits.

On the track, beacons, called transponders, store permanent speed limit information in coded form. Sealed in glassfibre re-inforced cases the transponders, containing electronics and a loop aerial, are waterproof and need no external power supply.

The transponders are powered by a radio beam transmitted by a loop aerial under the front of the train. A coded message (the message is 80 bits long) is re-transmitted by the transponder and fed to the train-bourne processor unit. Micro-processor circuits check the validity of the code and display the approaching speed limit to the driver.

When the train approaches a speed restriction the display changes to the new limit at the appropriate braking distance. An audible warning sounds which the driver must acknowledge, otherwise the brakes are applied automatically.

The driver selects a suitable braking rate to bring the train down to the new limit displayed. At the start of the speed restriction an indicator light on his desk is briefly illuminated, while at the end he receives a short warning sound to alert him to the higher speed.

C-APT has to fail safe so transponders are bolted to the sleepers at intervals of 1km or less, if the equipment fails to detect a transponder after 1km, the display goes blank and an audible warning is initiated which must be acknowledged by the driver. With a blank display the driver reverts to conventional line speeds.

To eliminate the risk of wrong speed limits being displayed, all the train-borne equipment, except for the display, is duplicated, while the electronic system has an inbuilt self-checking routine.

A secondary use of C-APT is to close air intakes when approaching tunnels to prevent ear discomfort to passengers.

Electronic sensors informed the APT-P trains of when and how much to tilt, not unlike the Pendolinos, although originally the APT-P trains were fitted with a duplex system, so that two parallel sets of machinery and sensors were located at the end of each coach in case of failure of one set and informed the tilt movements of the carriage they were attached to. This however caused late and jerky tilt responses, so the system was modified so that the tilt activating sensor was relocated to the carriage in front: This removed the redundancy in the system as there were insufficient spare electrical connections between carriages for both sets of sensors to be relocated, making the tilt system more susceptible to failures.

 

[axlecounter]

It contains the information that LNW-GW Joint said it does: permissible speed, distance to next balise and tilt authorisation. Certainly it doesn't contain any information about the track geometry - the train works out how much tilt and in what direction using on-board sensors.

He said

There are balises in the track which have the information you describe

as an answer to

How do the Pendolino trains know when to tilt, and by how much, and to which side

hence my doubts.

 

[LNW-GW Joint]

He said
hence my doubts.

I didn't describe the balise capability very well, sorry.
The balise doesn't do track geometry or tilt actuation, and the on-board system works it all out from other sensors.

Just one clarification: the tilt on the 390s is electrically actuated, like the Swiss ICN (which uses a similar SIG bogie).
This is distinct from the hydraulic actuation of other Pendolinos and the Bombardier 221 Voyagers.

TASS itself is an Alstom design even though also fitted to 221s.

 

[306024]

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.

 

[D1009]

Being tanked up on free booze from the buffet car doesn't help with motion sickness either! :roll:

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