All main line trains with air bag suspension (so in practical terms we are talking at all current main line EMU) have load cells in their suspension in order to maintain constant height, failed suspension warnings, and excessive overload. Deflated air bags, or overloaded hence low air bags, may cause the train to go out of it's approved kinetic envelope = "out of gauge" in plain English.
For example Thameslink 319s right from new would not motor if the suspension load cell detected overload and I'm pretty sure that principle applied to everything from Pep type EMU onwards. 319s were already set low on their suspensions (i.e. lower than 321 et al contemporaries) for clearance reasons in the tunnel section, so not overloading a 319 was somewhat critical.
Obviously the older units it was some electro mechanical analogue set up - but anyway for external train loading it is a means to tap into that data and transmit it and have it interpreted into a usable form for broadcast to customers.
It is not load sensing or load measurement that is new - but transmitting and communication of that data into something meaningful. Which takes quite a lot of comms and apps coding effort.
Keeping with Thameslink, 700s have had on board car by car loading indicated in the internal PIS displays since Day One. And they work too. Whether any of that will ever make it's way into stations public information I have no idea.
Last Edit: Jan 5, 2023 13:08:47 GMT by goldenarrow: Quote removed
... out of it's approved kinetic envelope = "out of gauge" in plain English ...
"Out of it's approved kinetic envelope" sounds as if it's too hot or cold, or travelling too fast (or backwards).
"Out of gauge is difficult: My first guess would have been that it referred to track that was too wide or narrow (virtually impossible given the way sleepers and fixings work I would imagine [but I'm probably wrong]). However, as from context, it clearly applies to a train, I would initially have thought that it meant that the wheels were exceeding a lateral margin of spacing error. From further context however, it seems that trains and their environment have a vertical gauge as well as a horizontal.
But I don't think either qualifies as plain English.
This is a problem that often occurs with technical subjects when, attempting to describe one thing, you end up having to describe a whole series of others for your explanations to make sense.
Gauge can refer to at least three things: 1. Track gauge - the width between the rails 2. Loading gauge - the maximum dimensions a vehicle can be to fit platforms, bridges, tunnels, etc. 3. Structure gauge - the minimum dimensions lineside structures need to be so as not to foul trains
The kinetic envelope is basically loading gauge but taking account of the movement of the vehicle at operating speed (due to bounce, sway, tilt, etc) rather than static measurements.
Post by theblackferret on Jan 5, 2023 11:59:15 GMT
Thanks to one and all for the technical explanations.
I wonder if anyone can set out what the various people symbols indicate(is red next,or does it go further to purple or black if it's standing room only?). Is there an equivalent for lightly-loaded trains ie half a green person or equivalent for completely empty?
If they wish to trial it further, audio accompaniment would be useful to assist visually-impaired passengers.
And if you call me brother now,forgive me if I enquire, just according to whose plan?-Leonard Cohen Story Of Isaac We don't want to save the world, we want to kill the human race-The Meteors Teenagers From Outer Space
As I was reading it I realised that I should have been well aware of the vertical element to 'gauge', because, centuries ago, when I had a model railway, there was always a model of a structure to ensure that wagons did not exceed the vertical loading gauge in the Triang catalogue. (Presumably they just left a safety margin for kinetic elements.)
"out of gauge" is the industry wide common term for anything not conforming to LOADING gauge. At least, common term on main line. It even has official use in train classifications, and Rule Book, and so on.
In context here of a train with air suspension, a train may be "in gauge" (within the loading gauge at any specific location) when suspension working but "out of gauge" (exceeding ditto) when deflated because the body is now in the wrong place. Classic examples of this are trains with deflated suspensions can run normally on plain open line but not pass platforms at anything except dead slow.
So air suspension must have a means of being detected, to stop a train from getting into a problem. Next step to crude detection is measurement, and thence communications to indication.
Kinematic envelope is the slightly bigger than physical size dimensions of the train that allows for all movement at all speeds but with sufficient space beyond to never touch a physical structure. Kinematic just means motion of a body.
At the back of my mind, when Sarah Siddons went to Portsmouth c.1984 or so, there were no loading gauge issues on main line but ISTR kinematic envelope somewhere but I've had 40 years to forget since then. It only needs a door handle or the like protruding.
Off topic, way before 442s were deployed normally on the Brighton line, SEG took one there on a railtour. The exceedingly thorough person who cleared the train issued an instruction that due to a potential kinematic envelope infringement, our 442 was not permitted to pass another442in Balcombe tunnel because in the worse case combination two could come into contact; it was never really going to happen since another 442 was not really going to be there, but the instruction had to be issued.
LU must have similar concepts but i've no idea if they formally use different terminology.