Seemingly poor breaking performance in Flirts, IETs and possibly other classes in poor rail adhesion conditions

[Fen Enthusiast]

I can recall a conversation I had with a group of other rail enthusiasts a couple of years back about the braking performance of Hitachi IETs and Flirts. Basically, it was about 755’s which I had recently used commuting home from work frequently slipping when breaking in poor adhesion conditions and feeling like being in an earthquake and about IETs struggling to stop or possibly even overshooting platforms in poor adhesion conditions. I can definitely recall the mention of that "they can't scrub their breaks". If someone could explain that to me as I don’t know what "scrubbing breaks" is I'd be grateful. Anyway, thinking back to that conversation, it occurred to me that Flirts and IETs are the only new trains I know of that struggle or seemingly struggle with breaking in low adhesion rail conditions. Living in East Anglia, I've often travelled on ElectroStars, TurboStars, Sprinters, class 755 Flirts and the recently retired class 317’s, but asides from the infrequent instances of it happening on ElectroStars, I can never really recall instances of other classes having trouble with wheel slip whilst breaking in low rail adhesion conditions. Is it a more newer train problem with poor breaking performance during poor rail adhesion conditions or is it more of a "break scrubbing" issues or other things resulting in this? I'd be very grateful for some more light to be shed on this thanks.

 

[jopsuk]

been a long standing issue (long before the current gen- 158s had problems) with disc braked stock that if there's contamination on the wheels the lack of a tread brake means there's nothing to remove it- with 158s this more caused track circuit detection failures until modifications (a brush I think?) were made, so for a while some units were formed with a 156 car and a 158 car.

As for no wheel slip on 317s? Really? Definitely been on many a 317 in damp conditions struggling to pull away.

 

[northernbelle]

I can recall a conversation I had with a group of other rail enthusiasts a couple of years back about the braking performance of Hitachi IETs and Flirts. Basically, it was about 755’s which I had recently used commuting home from work frequently slipping when breaking in poor adhesion conditions and feeling like being in an earthquake and about IETs struggling to stop or possibly even overshooting platforms in poor adhesion conditions. I can definitely recall the mention of that "they can't scrub their breaks". If someone could explain that to me as I don’t know what "scrubbing breaks" is I'd be grateful. Anyway, thinking back to that conversation, it occurred to me that Flirts and IETs are the only new trains I know of that struggle or seemingly struggle with breaking in low adhesion rail conditions. Living in East Anglia, I've often travelled on ElectroStars, TurboStars, Sprinters, class 755 Flirts and the recently retired class 317’s, but asides from the infrequent instances of it happening on ElectroStars, I can never really recall instances of other classes having trouble with wheel slip whilst breaking in low rail adhesion conditions. Is it a more newer train problem with poor breaking performance during poor rail adhesion conditions or is it more of a "break scrubbing" issues or other things resulting in this? I'd be very grateful for some more light to be shed on this thanks.

While their wheelslip protection might be more 'active' than older types, the braking performance of modern types is generally far superior to that of the older designs they've replaced.

 

[TheEdge]

I drive 745s and 755s and drove the GA legacy rural fleet and the EMT 158s.

Whoever told you FLIRTs have poor braking performance is talking absolute rubbish. Their actual performance during low adhesion is barely different from that in normal conditions. Although we still do defensive driving in autumn you could drive pretty much exactly the same in the depths of autumn as at the height of summer and not really have an issue. The reason they shudder in low adhesion is because they have a fantastic wheel slip prevention (WSP) system and that shuddering is it kicking in when they really start to loose it and the unit swaps over from its regen brake to its actual physical disc brakes. The dancing the in cab display is doing as the WSP is basically performing cadence braking is quite impressive. As to "they can't scrub their brakes", they can, they have had brake scrubbers installed since day 1.

As to the old stuff not slipping, they really did. At any time between October and February there were certain locations you just had to crawl into if you actually wanted to stop. And getting the things started was a nightmare at times. I once had a 156 repeatedly roll backwards while in notch 7 trying to go forwards, it was a common method used to try and clean the rail under the driven wheels to try and give them clean rail.

 

[Mowgli]

I drive 745s and 755s and drove the GA legacy rural fleet and the EMT 158s.

Whoever told you FLIRTs have poor braking performance is talking absolute rubbish. Their actual performance during low adhesion is barely different from that in normal conditions. Although we still do defensive driving in autumn you could drive pretty much exactly the same in the depths of autumn as at the height of summer and not really have an issue. The reason they shudder in low adhesion is because they have a fantastic wheel slip prevention (WSP) system and that shuddering is it kicking in when they really start to loose it and the unit swaps over from its regen brake to its actual physical disc brakes. The dancing the in cab display is doing as the WSP is basically performing cadence braking is quite impressive. As to "they can't scrub their brakes", they can, they have had brake scrubbers installed since day 1.

As to the old stuff not slipping, they really did. At any time between October and February there were certain locations you just had to crawl into if you actually wanted to stop. And getting the things started was a nightmare at times. I once had a 156 repeatedly roll backwards while in notch 7 trying to go forwards, it was a common method used to try and clean the rail under the driven wheels to try and give them clean rail.

I can vouch for all this. They can sound absolutely dreadful when all the WSP and scrubbers are working hard which can disconcert the passengers (and sometimes the driver!) but they do the business well.
Another bonus on the Stadlers if sliding is the ability to stick in the emergency brake and take it off again without the train grinding to a halt - none of this breaking train wire 4 or whatever it was with the old stock - and having to wait for it to reset before starting off again.

 

[dan4291]

I can vouch for all this. They can sound absolutely dreadful when all the WSP and scrubbers are working hard which can disconcert the passengers (and sometimes the driver!) but they do the business well.
Another bonus on the Stadlers if sliding is the ability to stick in the emergency brake and take it off again without the train grinding to a halt - none of this breaking train wire 4 or whatever it was with the old stock - and having to wait for it to reset before starting off again.

IETs are the same, you can put the brake in emergency and take it out again without having to wait.

 

[Ken H]

My car makes a horrid noise when i do an emergency stop and its struggling not to skid. Is the noise you get from a train struggling to grip the same sort of kit.