What do these boxes do?

[sutty]

Took ages to find a photo of one of these.

The yellow box between the rails. They seem to have an "open" end and a closed end. I thought axle counters but couldn't do a Google images match for one?

 

[RPM]

It is an AWS magnet. (Automatic Warning System).
http://en.wikipedia.org/wiki/Automatic_Warning_System

 

[dysonsphere]

It is an AWS magnet. (Automatic Warning System).
http://en.wikipedia.org/wiki/Automatic_Warning_System

Damm beat me to it.

 

[edwin_m]

An axle counter head is always positioned just on the inner side of a rail. It looks like a small box fixed to the rail, sometimes with two protruding mushroom-like objects.

 

[sutty]

Thanks, all

Is there any rhyme or reason for which end is open and which end is closed?

 

[LowLevel]

It's not so much an open end and a closed end. It's based on the direction of travel.

The yellow bit is the magnet, the grey metal bit is the ramp. The ramp is the bit that's hit first, so depending on which trains travel, depends on which end the ramp is on the magnet. If trains can travel both ways on the line in question, both ends will have a ramp.

There's 2 types of magnet - all AWS setups have what is known as the 'per-magnet' - this is designed to sound a warning horn in the driving cab. It is a magnet that is always operating.

If the magnet is associated with a signal that can show green, for example, and therefore needs to be able to sound the clear 'ding' in the driving cab, it will have a second magnet called an electromagnet - this is energised only when the signal is green and feeds accordingly to the AWS receiver on the train so you get a ding rather than a buzzing.

I've probably not explained this brilliantly as it's rather hard to do in text form over the internet but I hope you get the idea.

 

[MarkyT]

The 'open' sloped ramp part is installed on the approach side to help protect the important and expensive magnets from damage, by deflecting anything that might be hanging from the underside of a train, dragging along the sleepers. There is a ramp on either side if the line is bidirectional.

 

[SpacePhoenix]

It's not so much an open end and a closed end. It's based on the direction of travel.

The yellow bit is the magnet, the grey metal bit is the ramp. The ramp is the bit that's hit first, so depending on which trains travel, depends on which end the ramp is on the magnet. If trains can travel both ways on the line in question, both ends will have a ramp.

There's 2 types of magnet - all AWS setups have what is known as the 'per-magnet' - this is designed to sound a warning horn in the driving cab. It is a magnet that is always operating.

If the magnet is associated with a signal that can show green, for example, and therefore needs to be able to sound the clear 'ding' in the driving cab, it will have a second magnet called an electromagnet - this is energised only when the signal is green and feeds accordingly to the AWS receiver on the train so you get a ding rather than a buzzing.

I've probably not explained this brilliantly as it's rather hard to do in text form over the internet but I hope you get the idea.

This Wikipedia article might help explain it better to the OP.

 

[edwin_m]

The yellow bit is the magnet, the grey metal bit is the ramp. The ramp is the bit that's hit first, so depending on which trains travel, depends on which end the ramp is on the magnet. If trains can travel both ways on the line in question, both ends will have a ramp.

Just to be clear, there is normally no physical contact between the AWS equipment and the train - the train passes over and detects the magnetism from the magnets. As someone else has suggested, the ramp is to reduce the risk of damage should anything be hanging down from the train.

The Great Western Railway invented the first AWS-type system in around 1905, where a ramp on the track would lift up a shoe fitted underneath the train. If the signal was clear there was an electrical voltage on the ramp which would prevent the brakes applying on the train. This system was superseded by the magnetic AWS system and finally disappeared in the 1970s.

 

[LowLevel]

I know, I just couldn't think of a better way to put it at the time - 'travel over'is probably the way forward!

 

[TDK]

There are 2 magnets under that box, one is a fixed magnet that will indicate a warning to the driver that either the signal is not green or they are approaching an ESR/TSR/PSR (only have the one magnet by the way) and an electro magnet that is only energised when a signal is green so therefore give a driver a clear signal.

 

[MarkyT]

There are 2 magnets under that box, one is a fixed magnet that will indicate a warning to the driver that either the signal is not green or they are approaching an ESR/TSR/PSR (only have the one magnet by the way) and an electro magnet that is only energised when a signal is green so therefore give a driver a clear signal.

The permanent and electro magnets are in separate boxes, as shown here: http://en.wikipedia.org/wiki/File:BR_AWS_inductor_1.JPG
This is an interesting installation as it has ramps at both ends suggesting the line is bidirectional. The permanent magnet is on the right and is the standard un-supressed type. With no additional electromagnet for movements in the left to right direction it suggests there is a fixed red or yellow signal for that direction to the right of the AWS installation, or only shunt movements occur in that direction.

Suppresed permanents are larger with a cable termination box:
http://commons.wikimedia.org/wiki/File:BR_AWS_inductor_3.jpg
(note the steel plate over the permanent inductor, out of use pending commissioning)

Standard magnets are yellow for use on unelectrified and OHLE lines. On DC 3rd rail lines green painted units are used with higher field strength.

 

[Tomnick]

...or a cancelling indicator, as would often be found on single lines where there's not really the justification to suppress the AWS for moves in the 'other' direction.

 

[sutty]

Thanks, all for your detailed responses. It was the ramp that made me curious, good to gain an understanding. Cheers.