323 Brake question.

[365 Networker]

I was watching a dvd of cross city trains back in the 1990s and noticed that on the earliest clips, when braking the 323s sound was slightly different. The difference compared to today was that when coming to a stand the initial pulsing which is always heard when accelerating can be herd again just as the train stops. These days the motors cut out before this can happen. Does anyone know why this change was made? Could it have been to do with reliability?

Video showing this sound.

323 old brake1.mp4

drive.google.com

 

[hexagon789]

I was watching a dvd of cross city trains back in the 1990s and noticed that on the earliest clips, when braking the 323s sound was slightly different. The difference compared to today was that when coming to a stand the initial pulsing which is always heard when accelerating can be herd again just as the train stops. These days the motors cut out before this can happen. Does anyone know why this change was made? Could it have been to do with reliability?

Video showing this sound.

323 old brake1.mp4

drive.google.com

Change from the original Gate Turn-Off Thyristor to the current Insulated-Gate Bipolar Transitor traction package?

 

[365 Networker]

Change from the original Gate Turn-Off Thyristor to the current Insulated-Gate Bipolar Transitor traction package?

I believe that happened around 2016 - the braking sound appears to have changed not long after they were introduced - mid 1995 possibly.

 

[hexagon789]

I believe that happened around 2016 - the braking sound appears to have changed not long after they were introduced - mid 1995 possibly.

Fair enough.

Second guess - change to the dynamic brake to friction brake changeover speed and the fade-out rate?

 

[365 Networker]

Fair enough.

Second guess - change to the dynamic brake to friction brake changeover speed and the fade-out rate?

That could be it. If that is the reason, I wonder why it was changed.

 

[43096]

Change from the original Gate Turn-Off Thyristor to the current Insulated-Gate Bipolar Transitor traction package?

My understanding is that the IGBT kit mimics the old GTOs, using the same frequencies in order to make acceptance easier. Consequently the sets still sound the same now as when they had GTOs.

 

[LowLevel]

If you listen to this video from 2010 it sounds like the noise is still there when the second unit stops. I'm going for the traction package change in 2015 which did make a difference to the sound they made.

EDIT - Though to be fair I think you're right that the final hum is a bit different.

 

[tomuk]

If you listen to this video from 2010 it sounds like the noise is still there when the second unit stops. I'm going for the traction package change in 2015 which did make a difference to the sound they made.

EDIT - Though to be fair I think you're right that the final hum is a bit different.

To retain their existing safety case the replacement IGBT traction package intentionally switches at the same rates as the old GTOs. Therefore there shouldn't be any difference in sound. Noting however that the traction packs are of different construction GTO were Freon cooled the IGBTs water/methanol cooled.

Any differences you hear in videos is probably due to whether the unit is using regen braking or straight air. To use regen not only has the 323 need to be working fully but the OHL also needs to be receptive.

 

[365 Networker]

If you listen to this video from 2010 it sounds like the noise is still there when the second unit stops. I'm going for the traction package change in 2015 which did make a difference to the sound they made.

EDIT - Though to be fair I think you're right that the final hum is a bit different.

I forgot to add to the original post that between 2014 and November 2016(after the traction upgrade) the motors would cut out completely at around 5 mph, although only on the London midland units. This also happened on all 323s between 1995 and 1998.
2016 video:-

1995 video:-

After 2016, the London Midland units reverted back to how they were in the 2010 video.

 

[hexagon789]

My understanding is that the IGBT kit mimics the old GTOs, using the same frequencies in order to make acceptance easier. Consequently the sets still sound the same now as when they had GTOs.

I noticed that, but wasn't sure about how it would affect the sound.

In which case, I go back to my second theory - it's the switchover from regen/rheo braking to friction happening at different speeds for whatever reason.

 

[boiledbeans2]

If you listen to this video from 2010 it sounds like the noise is still there when the second unit stops. I'm going for the traction package change in 2015 which did make a difference to the sound they made.

EDIT - Though to be fair I think you're right that the final hum is a bit different.

As you mentioned, yes there is a difference in the final hum.

In the OP's video, there is a longer drawn out final hum, but in the 2010 video in your post, the longer final hum is missing, even though the motors are still emitting sound down to zero speed.

I checked my own videos recorded in 2021, and they sound like the 2010 video.

Would it also be down to driving technique? E.g. in the OP's video, the driver reduced the brakes right before standstill, leading to a longer hum?

 

[tomuk]

Would it also be down to driving technique? E.g. in the OP's video, the driver reduced the brakes right before standstill, leading to a longer hum?

Quite possibly in these days of defensive driving platforms are approached with a lot more caution. I don't think the old practice of reaching the platform ramp and slamming on the anchors is still appreciated.

 

[bramling]

As you mentioned, yes there is a difference in the final hum.

In the OP's video, there is a longer drawn out final hum, but in the 2010 video in your post, the longer final hum is missing, even though the motors are still emitting sound down to zero speed.

I checked my own videos recorded in 2021, and they sound like the 2010 video.

Would it also be down to driving technique? E.g. in the OP's video, the driver reduced the brakes right before standstill, leading to a longer hum?

There’s certainly the potential for different driver techniques to have some effect, in particular whether the driver manages to throw the brake completely off in the couple of seconds before the final stop (as is good practice, albeit quite rare), though by this time one would expect the train to be braking on friction as the rheo will fade out at the last moment.

An interesting question, and would be interested to know the answer.

 

[hexagon789]

Quite possibly in these days of defensive driving platforms are approached with a lot more caution. I don't think the old practice of reaching the platform ramp and slamming on the anchors is still appreciated.

That was never the approved technique!

With a 3-step brake it was:

At braking point - select Step 3
Once speed is significantly reduced (often in vicinity of entering platform) - select Step 2
Just before stopping mark - select Step 1 to give smooth stop.

I.e. easing off progressively approaching the stopping mark

If anything the modern method seems to be approach station in too light an application and then slam it all in when they suddenly realise they aren't going to stop at the right place

 

[bramling]

That was never the approved technique!

With a 3-step brake it was:

At braking point - select Step 3
Once speed is significantly reduced (often in vicinity of entering platform) - select Step 2
Just before stopping mark - select Step 1 to give smooth stop.

I.e. easing off progressively approaching the stopping mark

If anything the modern method seems to be approach station in too light an application and then slam it all in when they suddenly realise they aren't going to stop at the right place

The worst are those who will use step 2 for a few seconds, coast for a couple of seconds, then step 2 again, then repeat this numerous times before throwing everything in for the final stop. So annoying!

 

[hexagon789]

The worst are those who will use step 2 for a few seconds, coast for a couple of seconds, then step 2 again, then repeat this numerous times before throwing everything in for the final stop. So annoying!

Or Step 1-release-step 1-release

Rinse and repeat a dozen-odd times

Coast

Near stopping mark

Full service

*Crunch* and stop in a heap

 

[365 Networker]

The worst are those who will use step 2 for a few seconds, coast for a couple of seconds, then step 2 again, then repeat this numerous times before throwing everything in for the final stop. So annoying!

Or Step 1-release-step 1-release

Rinse and repeat a dozen-odd times

Coast

Near stopping mark

Full service

*Crunch* and stop in a heap

I completely agree. In my opinion, the best technique used was step 2 initial and then step 1 when approaching the stopping point - 365 drivers used to be quite good at that. The braking standards seemed to deteriorate from about 2014 - what annoys me most is when a driver crawls into an 8 car platform at 20Mph and then slams on the brakes right at the last second.

 

[507 001]

Northern’s 323s seem to vary from unit to unit as to whether they’ll regen/rheo down to a stand. Sometimes they will change mid journey, presumably due to a change in railhead conditions. In this scenario the final stop is usually much rougher.

The differences in the units caught on video is probably just coincidence.

 

[boiledbeans2]

If anything the modern method seems to be approach station in too light an application and then slam it all in when they suddenly realise they aren't going to stop at the right place

Not specific to 323s, but this is what happens a lot on LU nowadays. I experience this a lot on the manually driven Bakerloo and Piccaddlly line trains - using the emergency brake at the last second. It is obvious because you hear a sudden venting of air.

Anyway, back to topic. So as the modern method is full brakes at the last second, it may be possible that the newer videos don't have the longer hum as the train decelerates faster with full brakes. But the OP's video has a gentler brake application in the last second so has a longer hum.

If anyone is a 323 driver here, maybe you could try braking differently at the stations to see if it sounds different!

 

[D365]

Not specific to 323s, but this is what happens a lot on LU nowadays. I experience this a lot on the manually driven Bakerloo and Piccaddlly line trains - using the emergency brake at the last second. It is obvious because you hear a sudden venting of air.

Emergency isn’t recoverable, so I think you’re seeing a full service brake.

 

[365 Networker]

using the emergency brake at the last second. It is obvious because you hear a sudden venting of air.

Emergency isn’t recoverable, so I think you’re seeing a full service brake.

That's most likely the Westinghouse or auto brake - both will make a loud air venting sound when released.

 

[hexagon789]

Not specific to 323s, but this is what happens a lot on LU nowadays. I experience this a lot on the manually driven Bakerloo and Piccaddlly line trains - using the emergency brake at the last second. It is obvious because you hear a sudden venting of air.

Sounds like using the auto air brake on those stocks, it's direct release only. You can only graduate the application.

I completely agree. In my opinion, the best technique used was step 2 initial and then step 1 when approaching the stopping point - 365 drivers used to be quite good at that. The braking standards seemed to deteriorate from about 2014 - what annoys me most is when a driver crawls into an 8 car platform at 20Mph and then slams on the brakes right at the last second.

Yep, get that last technique here too.

Then by contrast a few years ago I had a driver come steaming into the station at I estimate just over 30mph in a 156, give it everything, ease off to 2, then 1, feather a release and we stopped just about as smoothly as you can on a 156 bang on the mark.

 

[bramling]

Not specific to 323s, but this is what happens a lot on LU nowadays. I experience this a lot on the manually driven Bakerloo and Piccaddlly line trains - using the emergency brake at the last second. It is obvious because you hear a sudden venting of air.

You won't be getting that on the Picc, as their trains don't have the Westinghouse brake. On the Bakerloo it's always been fairly common for drivers to momentarily drop the handle to assist the train to stop, whilst to some extent this may be poor driving, but it's also to some extent because the 72 stock is - and always has been - rather unpredictable on the braking front. They've been absent from the Northern Line for over two decades now, yet old hand drivers can *still* be heard moaning (fondly or otherwise) about them, they will say that on a 59 stock it would either be a good train or a bad one but consistently so, but 72 stock could change massively from one brake application to the next. Despite the 72 stock having a reputation as a rather poor train, they are set to achieve 50 years in service, and may well reach 60.

In most circumstances a stop with brakes fully released should be possible, even on a gradient, but it's comparatively rare, and doesn't seem to be something that people are trained to do. It's always pleasing to be on a train where the driver does it well.

 

[boiledbeans2]

You won't be getting that on the Picc, as their trains don't have the Westinghouse brake. On the Bakerloo it's always been fairly common for drivers to momentarily drop the handle to assist the train to stop[...]

Emergency isn’t recoverable, so I think you’re seeing a full service brake.

Many thanks for the corrections. Yes, what I meant is the releasing of the handle. Isn't that equivalent to emergency brake as it's releasing the deadman's handle?

Often I stand at the front of the platform while waiting for the train to arrive, so I see the last few seconds of the driver's braking technique and it sometimes involves releasing the handle, along with the big air venting sound.

What do you mean by "Emergency isn't recoverable"? I suppose it just takes a longer time for the air to recharge?

== Doublepost prevention - post automatically merged: 1 Jul 2022 ==

[...] they will say that on a 59 stock it would either be a good train or a bad one but consistently so, but 72 stock could change massively from one brake application to the next. Despite the 72 stock having a reputation as a rather poor train, they are set to achieve 50 years in service, and may well reach 60. [...]

I would assume the 72 braking system design to be very similar to the 67 stock? So the conclusion is that a computer can drive better than a human? (*ducks and runs*)

 

[bramling]

Many thanks for the corrections. Yes, what I meant is the releasing of the handle. Isn't that equivalent to emergency brake as it's releasing the deadman's handle?

Not necessarily. The 72 stock is designed so that the handle can be released in Rheo 1 & Hold below a certain speed without triggering a deadman activation. I forget what that speed is, but it's certainly well into single figures. In theory this allows the driver to drop the handle in Rheo 1 & Hold and have their fingers ready on the door buttons - needless to say this practice is frowned upon, but nonetheless remains extremely common. Dropping the handle at slightly higher speed will of course give an emergency brake application, but if only dropped momentarily then it gives a bit of extra braking, and this is what is commonly seen & heard on the 72 stock. Again, not really regarded as good practice at all, but at times necessary on trains whose braking is notoriously erratic.

I would assume the 72 braking system design to be very similar to the 67 stock? So the conclusion is that a computer can drive better than a human? (*ducks and runs*)

Yes the 72 stock is essentially the same as the 67 stock. But the Victoria Line's ATO also ran into issues at times, so it was very common in 67 stock days for drivers to give a bit of Westinghouse to assist the train to stop, especially with the need to line up to monitors.

 

[D365]

What do you mean by "Emergency isn't recoverable"? I suppose it just takes a longer time for the air to recharge?

Exactly that - driver can’t release the brakes immediately after an emergency application.

 

[bramling]

Exactly that - driver can’t release the brakes immediately after an emergency application.

This doesn’t apply on LU, although if we’re talking about final stops then the train will have probably stopped anyway. What the driver can’t do is partially release a Westinghouse application.

 

[365 Networker]

I've managed to find some more recent videos of this sound:-

Skip to around 3:55.

Skip to around 38:15

Interestingly the motors only make the sound occasionally - possibly when the brakes are applied harder.

 

[Liam L]

Interestingly the motors only make the sound occasionally - possibly when the brakes are applied harder.

The only time I really hear that noise is when the brakes are applied abit harder