How feasible would it be for trains to have 'wheels on rails' sensors ?

[choochoochoo]

Given planes have 'weight on wheels' sensors, how feasible would it be for trains to have 'wheels on rails' sensors ?

 

[cats_five]

....but given planes have 'weight on wheels' sensors...

Planes leave the ground as a normal part of their lives...

 

[choochoochoo]

Planes leave the ground as a normal part of their lives...

But it wouldn’t be a very normal part of their life for the landing gear to be allowed to retract whilst on the ground.

 

[a_c_skinner]

It ought to be practical to devise sensors that tell the driver to stop and examine if there is sustained and hugely excessive vibrations in any vehicle in the train, certainly in passenger stock which has (the potential for) complex comms between vehicles. Not as a quick cheap retrofit but aeroplanes do tell their pilots about the engines vibrating.

 

[choochoochoo]

Might be a bit naive in my understanding of how electricity and track circuits operate, but if track circuits are completed by wheels on an axle touching the rails, could a sensor be placed on that axle to detect when its completing a track circuit and thus send an alert if it might have derailed and is no longer completing a track circuit ?

 

[Cherry_Picker]

Yes, but then you just have another thing with a sensor on it that throws up more faults than it's worth.

 

[Kentish RYS]

Might be a bit naive in my understanding of how electricity and track circuits operate, but if track circuits are completed by wheels on an axle touching the rails, could a sensor be placed on that axle to detect when its completing a track circuit and thus send an alert if it might have derailed and is no longer completing a track circuit ?

No, because not all the railway is track circuited. A lot is Axle Counters (they detect the electromagnetic field of a passing wheel flange, but do one side therefore counting axles, on the entrance and exit of a track section). Also a lot is non continuous train detection or tablets/token/radio tokens or Signaller looking out the box window for a tail light (or using a tail light camera or train crew using train arrived complete plunger). Ive probably forgotten something in that quick list of the many ways the GB Mainline network knows where trains are. Also different track circuit types use very different frequencies or voltages and traction return on the Mainline goes through the axles. It probably isn't impossible to have a comparison list to work out if it is a track circuits not traction return but would be very expensive and not worth it for the little benefit (low derailment rialsk and %of Network that is not Track Circuited

 

[43096]

Might be a bit naive in my understanding of how electricity and track circuits operate, but if track circuits are completed by wheels on an axle touching the rails, could a sensor be placed on that axle to detect when its completing a track circuit and thus send an alert if it might have derailed and is no longer completing a track circuit ?

Track circuits are fail safe i.e. the wheels/axle break the circuit.

 

[D365]

It ought to be practical to devise sensors that tell the driver to stop and examine if there is sustained and hugely excessive vibrations in any vehicle in the train, certainly in passenger stock which has (the potential for) complex comms between vehicles.

It's temperature sensing, rather than vibration, but onboard "hot axle box detection" systems have been fitted to some new build fleets.

 

[a_c_skinner]

It's temperature sensing, rather than vibration, but onboard "hot axle box detection" systems have been fitted to some new build fleets.

Didn't know that and the level of vibration when an axle derails is so sustained and so marked it shouldn't be difficult to make such a system that isn't hugely costly and doesn't produce too many false alarms.

 

[Peter Mugridge]

Track circuits are fail safe i.e. the wheels/axle break the circuit.

Surely, though, for that to detect a derailment the entire train needs to be off the rails, as a single bogie still on would still provide the short circuit?
By that point, it would be blindingly obvious to all on board that it was off the road anyway.

 

[Nicholas Lewis]

It ought to be practical to devise sensors that tell the driver to stop and examine if there is sustained and hugely excessive vibrations in any vehicle in the train, certainly in passenger stock which has (the potential for) complex comms between vehicles. Not as a quick cheap retrofit but aeroplanes do tell their pilots about the engines vibrating.

The bogies are naturally subjected to high g forces in all directions that are damped by suspension so any sensor has to be able to distinguish between normal and chaotic behaviour and that probablys means processing power on each coach. Given how unusual it is is it really worthwhile retrofitting a solution.

 

[AlterEgo]

But it wouldn’t be a very normal part of their life for the landing gear to be allowed to retract whilst on the ground.

That's not what a weight on wheels sensor is for.

 

[a_c_skinner]

The bogies are naturally subjected to high g forces in all directions that are damped by suspension so any sensor has to be able to distinguish between normal and chaotic behaviour and that probablys means processing power on each coach. Given how unusual it is is it really worthwhile retrofitting a solution.

I've never been in a derailed vehicle but from the descriptions of passengers who have the magnitude and character of the vibration is completely different to normal service, hugely different. So different that it really ought to be an easy proposition to detect. Yes it would need processing power, everything does and it would need comms to relay the answer, and yes we don't have that many derailments so I doubt retrofitting would be worthwhile but it seems an obvious refinement.

 

[HSTEd]

The US Federal Railroad Administration backed electronically controlled pneumatic (ECP) braking standard supports vibration sensors, axle temperature sensors and a great deal else besides.

But fitment would cost a few thousand dollars per freight vehicle and the freight operators won't want to spend it.

 

[choochoochoo]

That's not what a weight on wheels sensor is for.

I understood it's part of a air/ground logic system that involves preventing/enabling certain functions on the the ground. Preventing gear retraction being one of them. Thrust reverser/ground spoiler deployment being prevented in air being another.

 

[AlterEgo]

I understood it's part of a air/ground logic system that involves preventing/enabling certain functions on the the ground. Preventing gear retraction being one of them. Thrust reverser/ground spoiler deployment being prevented in air being another.

Of course. Sorry, I'd misread the context of your post!

 

[Acathater]

Presumably you could fit load cells into the bogies which measured the intensity of vertical movement and also the frequency of that movement, registering an alarm when "out of range"
Removing background noise, especially on old track, might be a problem though - as also may be reliability given the constant vibration