Track geometry measurements

[zbang]

(Splitting this to a new thread)

What would a TGV measure? (I'm just spitballing here, there must be more.)

cant between wheels of a single axle, might use a measurement-only wheelset & axle

gauge separation

rail head width (each)

rail head profile (prob. captured by a pair of cameras on each rail)

rail curve (horiz. & vert.) over a specific distance (each)

discontinuities in the rail head  (e.g. joints)

speed over the track being measured / distance traveled / clock time

My assumption is that the sensors/etc are not directly attached to the frame of the vehicle, but rather to a controlled frame that attempts to separate the vehicle movements from the measurements. That's a different system but AFAIK fairly well understood. Might not be necessary if there enough measurements to correct for the rail anomalies (will have to think about that).

It's possible that some of the measurements could be derived from video images. And the entire system would have to account for things like points.

I'm not looking at the data analysis part, only what measurements to take, although it's likely the data would be both short and long averaged to separate overall geometry from smaller anomalies.

I'm also not looking above the track, so tunnel clearances etc aren't covered.

How does that look?

[class411]

I've no idea how it's actually done, nor exactly what they measure, but one interesting point to consider is that whereas for many decades, the only way to perform this task would have been with mechanical sensors and paper plotter output, in the last 15 - 20 years, advances in electronics and computers have been such that the task could now be performed with an array of laser distance measuring devices (pointing at the rails) feeding a computer that could generate visualisations of the data produced in many useful ways.

Whether that has happened yet is, or course, another matter.

[zbang]

Unless a new TGV has been designed in the last 5 years, laser scanning isn't that likely, OTOH some rail system out there has probably done it as well as Sperry Rail Services.

[tut]

Unless I'm much mistaken:

TGV is Train à Grande Vitesse, that is high-speed train, the French high-speed rail service.

TRV is Track Recording Vehicle which I'm sure you mean to refer to. That is the 1973 Stock vehicle which does the actual track recording as part of the Track Recording Train (TRT), which consists of the said 1973 Stock Track Recording Vehicle and a 1960 Stock Driving Motor at each end.

[zbang]

Track Geometry Vehicle (perhaps it's a new machine to replace the TRV), I'm writing generically about what needs to be measured, not what anyone calls the embodiment.

TGV was also a software company in the 1990/2000s.

[brigham]

And ITV is the Spanish MOT, but I'm sure British television can cope with that.

[class411]

May 21, 2024 21:09:07 GMT zbang said:

Track Geometry Vehicle (perhaps it's a new machine to replace the TRV), I'm writing generically about what needs to be measured, not what anyone calls the embodiment.

TGV was also a software company in the 1990/2000s.

There has been a problem with the re-use of TLA's (Three Letter Acronyms*) for many years.

There have been attempts to move to ETLA's (Extended Three Letter Acronyms) for some time, but without much success.


[PEDANT]
* Actually, usually, initialisms.
[/PEDANT]

[gefw]

Would be interesting to hear what Network Rail measure using their "Yellow Banana" (which I think is quite modern) and how this fits with their track monitoring, works planning & Assurance arrangements.

Hopefully LUL will still retain the basic "live" remote condition monitoring of ride quality (as per ATMS).
Will the noise levels start to be measured as well?
At some stage "AVI runs" were used on the central line for track monitoring ( to help understand reported problems?)
Does anyone think the arrangements for ultrasonic rail testing will change?
Note it is probably best to measure much of the track geometry under the load of the train wheels. (to pick up voiding under sleepers, loose chair bolts etc)

[d7666]

May 22, 2024 8:36:10 GMT class411 said:

May 21, 2024 21:09:07 GMT zbang said:

Track Geometry Vehicle (perhaps it's a new machine to replace the TRV), I'm writing generically about what needs to be measured, not what anyone calls the embodiment.

TGV was also a software company in the 1990/2000s.

There has been a problem with the re-use of TLA's (Three Letter Acronyms*) for many years.

There have been attempts to move to ETLA's (Extended Three Letter Acronyms) for some time, but without much success.


[PEDANT]
* Actually, usually, initialisms.
[/PEDANT]

< bigger pedant >

Surely here TLA means Three Letter Abbreviation ?

TLA abbreviation - here TGV uses the first letters of Track Geometry Vehicle

TLA acronym - does not always use first letters merely three letters taken from the three words


< / bigger pedant >

Anyway. Agreeing with 'tut' , TGV = Train à Grande Vitesse . We all know that surely

[brigham]

An ACRONYM is a WORD made of the initial letters. You can SAY IT.

FIAT is an acronym. BMW is not.

TARDIS and LASER were the ones I remember from childhood. MASER and IRASER came later.

If you are going to call ANY abbreviation an Acronym, you will soon need a new word for an ACTUAL Acronym.

[Chris M]

Any further discussion of linguistics needs to move to a new thread so we can get back to discussing track geometry in this one