AWS Related question

[waterboo]

Evening guys, i wish to present a couple of questions that have befuddled me for the longest time.....

1. When the AWS sunflower and respective alarm sounds, how long does the driver have to cancel the alarm before the emergency break action is applied?

2. There is also an alarm if i remember. It goes off after a period where the driver has not adjusted the traction brake controller for a period of time. Again, how long does the driver have to cancel this alarm?

Many thanks.

 

[skyblue]

Aws alarm is 3 seconds I believe and the other one you are thinking of is the vigilance alarm where it is 6 seconds. Though I am sure there are others on here that can give you a more detailed answer

 

[A-driver]

Aws alarm is 3 seconds I believe and the other one you are thinking of is the vigilance alarm where it is 6 seconds. Though I am sure there are others on here that can give you a more detailed answer

Pretty much spot on. I have never tried to see how long you get exactly except with the vigilance on preps but I believe it's specifically something silly like 2.7 seconds for AWS and closer to 7 secs for the vigilance. AWS on HSTs is apparently shorter.

 

[waterboo]

Cheers guys, that is way more shorter than I imagined.

 

[codesam]

Cheers guys, that is way more shorter than I imagined.

It's longer than I would have assumed. At 90Mph a train would travel >100m in 3 seconds.

 

[Juniper Driver]

It's longer than I would have assumed. At 90Mph a train would travel >100m in 3 seconds.

Yeah but it would stop pretty sharpish once the Emergency Brake came on.

 

[#1 driver]

1. When the AWS sunflower and respective alarm sounds, how long does the driver have to cancel the alarm before the emergency break action is applied?

technical point , sunflower shows you have stopped a brake application .
so you will get the tone and indicator goes black , the yellow indication is displayed after you've hit the button .

 

[Llama]

...and released it again.

 

[ac6000cw]

technical point , sunflower shows you have stopped a brake application .
so you will get the tone and indicator goes black , the yellow indication is displayed after you've hit the button .

Yes, the 'sunflower' is the important reminder that you've passed a signal at caution and acknowledged the AWS warning.

 

[westcoaster]

technical point , sunflower shows you have stopped a brake application .
so you will get the tone and indicator goes black , the yellow indication is displayed after you've hit the button .

umm, surely the sunflower showing shows you gone over a supressed magnet, wether tjis is for a signal, or portable aws magnet.

 

[cjmillsnun]

umm, surely the sunflower showing shows you gone over a supressed magnet, wether tjis is for a signal, or portable aws magnet.

No, it's to show that you have cancelled the AWS horn after going over a suppressed magnet.

See http://www.rgsonline.co.uk/Railway_...ng/Railway Group Standards/GERT8075 Iss 1.pdf

P18 onwards

 

[Beveridges]

The vigilance device goes off if you don't touch the Brake or Power for 40 seconds.

 

[Beveridges]

Not all trains have vigilance fitted, class 142's, 150/1's and 156's for instance. Better without it than with it IMO.

 

[Tomnick]

A suppressed magnet surely has no effect on the 'sunflower' indication and causes no audible indication? That's exactly why magnets are, where appropriate, suppressed for movements in the other direction!

 

[ac6000cw]

Table 7 of of that RGS document details the permanent/electromagnet magnet combinations.

If the associated signal is capable of displaying green (clear), then effectively the train equipment is 'armed' by the permanent magnet, and (if green) disarmed immediately afterwards by the adjacent electromagnet. If the signal aspect is not green the electromagnet is not energised and the warning horn/emergency brake application sequence occurs (unless cancelled by the driver).

Simple, effective and fail-safe (but having the Achilles Heel that frequent warnings e.g. produced by trains closely following each other running on yellow/double yellows, can cause automatic, subconscious AWS warning cancellation by drivers - one reason why the Southern Region of BR was reluctant to install it initially).

 

[cjmillsnun]

A suppressed magnet surely has no effect on the 'sunflower' indication and causes no audible indication? That's exactly why magnets are, where appropriate, suppressed for movements in the other direction!

It's the electromagnet that is suppressed in normal operation if there is a clear (green) signal aspect.

 

[GB]

It's longer than I would have assumed. At 90Mph a train would travel >100m in 3 seconds.

How long did you initially think it was? Its not really practical to have the warning any less then 2-3 seconds without getting emergency brake applications every where.

On another note, the warning is only 2 seconds on the German Class 66's that GBRf have.

 

[Railsigns]

It's the electromagnet that is suppressed in normal operation if there is a clear (green) signal aspect.

Not so. An electro-magnet is never suppressed; it's either energised or de-energised.

Only a permanent magnet may be suppressed. Suppressing a permanent magnet effectively makes it invisible to any passing train while the suppressing coil is energised.

 

[ac6000cw]

It's the electromagnet that is suppressed in normal operation if there is a clear (green) signal aspect.

No - the electromagnet is energised if the signal is clear.

In some situations it is necessary/desirable to suppress the magnetic field from the permanent magnet - so that the train equipment doesn't detect anything.

Having a 'south pole - north pole' sequence (for clear) is not the same as 'no pole' (in the suppressed case). The 'south pole - north pole' sequence is a positive clear indication, the other is 'do nothing, retain the current state'.

 

[edwin_m]

With hindsight it's a shame the AWS wasn't put on (say) the left hand sleeper end with the receiver on the left hand side of the cab in the direction of travel. That would have avoided any need to suppress magnets for wrong-direction movements. Whereas APC magnets are mounted on the sleeper ends but are bi-directional so fitted to both sides!

 

[tom1681]

With hindsight it's a shame the AWS wasn't put on (say) the left hand sleeper end with the receiver on the left hand side of the cab in the direction of travel. That would have avoided any need to suppress magnets for wrong-direction movements.

Unfortunately some units (eg. 153) and probably most locos only have one receiver which is used whichever way there are going...

 

[O L Leigh]

Er, no. There will be one receiver under each cab.

O L Leigh

 

[Llama]

Actually 153s do only have an AWS receiver under #1 cab.
TPWS receiver at each end though.

 

[O L Leigh]

Really...? What is the rationale behind that?

I shall have a look underneath one the next chance I get to verify that, if I may.

O L Leigh

 

[455driver]

Definitely only one receiver on a 153, located at the no1 end (the big/original cab end).

153s only have one GSMR unit as well, although they do (obviously) have a head unit in each cab, if you retain registration at one end it will appear in the other end when you set up.

 

[edwin_m]

I believe some locos also have one shared AWS receiver, and this may be the reason AWS was put on the centerline of the track in the first place. But these days having it on the sleeper ends would save a lot of complication trackside at the cost of a few extra receivers on trains.

 

[Pacerpilot]

Definitely only one receiver on a 153, located at the no1 end (the big/original cab end).

And the beauty of this set up.....should you bring the train to a stand over a magnet (for the uninitiated, they are rather awkwardly situated in some places) you cant cancel the warning, nor can you key in the opposite end and the move the unit. Its EBS up, out of service and return to depot. Bridgend has a Class 153 specific stop marker installed on the down side for this very reason.

 

[scotraildriver]

Class 67 has only 1 receiver. Can be a pest when shunting near magnets cause you're never sure when the AWS will go off. And as someone else said if you get stuck on a magnet you need a push. Calling for an assisting loco because you are stuck on a magnet doesn't go down well...........

 

[Llama]

And the beauty of this set up.....should you bring the train to a stand over a magnet (for the uninitiated, they are rather awkwardly situated in some places) you cant cancel the warning, nor can you key in the opposite end and the move the unit. Its EBS up, out of service and return to depot. Bridgend has a Class 153 specific stop marker installed on the down side for this very reason.

Personally I would isolate the AWS flag rather than EBS, that might let you move it.
[/pedant]

 

[Pacerpilot]

Glad some one picked up on my traction refresher