Class 175 retarders

[Philip]

Is the dynamic brake/retarder still giving problems on the units? I know it was isolated a few years back, as it was temporarily by FNW not long after they entered service. I haven't been on them much, has the system been reinstated on any of them?

Why does this braking system cause problems on the Coradias? It's the same on the 180s...

 

[Bletchleyite]

Because despite having a nice passenger interior, the design and build from a mechanical point of view (and build quality point of view) is utterly terrible?

The units *should* have been the ultimate evolution of the bombproof Class 156 (which I expect to last as long as or longer than the venerable Met-Camm Class 101s) but unfortunately were nothing of the sort.

I *half* recall the retarders may be back on now, but I'm not sure, I might be thinking of the Class 185 which has a similar device.

The Juniper EMUs are/were similarly rubbish - it just seems to be a quality issue at Alstom at the time.

 

[Great_Western]

The 175's are one of the most infuriating units on the network, from a passenger point of view they are excellent. Staff seem to like them and I assume drivers do to. But their meachanical failings and interior cleanliness completely let them down. I am pretty sure if W&B were to give them a big overhaul, they would be giving SWT 159's a run for the best units of that type.

 

[Philip]

I've read that the initial problem which caused it to be temporarily isolated not long after they entered service was down to the cooler group not coping well with the sudden surge of hot transmission oil, when the brake was applied. Apparently it caused the thermostat to go haywire and this automatically shut down the engines. But the retarder was reinstated not long after and was certainly still being used into ATW/TPE days, so I'm assuming the problem was sorted.

Is it a similar problem that caused Alstom to isolate it again a few years back? It seems odd (assuming it's still out of use) that with it being a 100mph DMU, the system isn't being used. Is the design so flawed so that it is beyond rectifying? How do the brake pads cope?

 

[najaB]

How do the brake pads cope?

I would expect that the brake pads were specced to be suitable for use 100% of the time, with the retarder system providing extra stopping power. In a similar way to how airliners aren't allowed to include thrust-reversers in their stopping distance calculations.

 

[Bletchleyite]

I would expect that the brake pads were specced to be suitable for use 100% of the time, with the retarder system providing extra stopping power. In a similar way to how airliners aren't allowed to include thrust-reversers in their stopping distance calculations.

IIRC they aren't the originals, a different type were fitted when the retarders went out of use (which are very noisy in use).

 

[Bletchleyite]

The 175's are one of the most infuriating units on the network, from a passenger point of view they are excellent. Staff seem to like them and I assume drivers do to. But their meachanical failings and interior cleanliness completely let them down. I am pretty sure if W&B were to give them a big overhaul, they would be giving SWT 159's a run for the best units of that type.

They are getting *very* tatty - I agree it's time for a full interior rebuild, including possibly new seats.

 

[Bornin1980s]

^Are the existing seats not hard enough?!

 

[Bletchleyite]

^Are the existing seats not hard enough?!

I actually quite like them, but they are *very* tatty, worn and damaged, so it may be cheaper to simply replace them than to refurbish to as-new condition.

 

[Murph]

I would expect that the brake pads were specced to be suitable for use 100% of the time, with the retarder system providing extra stopping power. In a similar way to how airliners aren't allowed to include thrust-reversers in their stopping distance calculations.

In the case of airliners, the brakes only have to be able to do a full unassisted stop from V1 once, with a resulting fire that remains small enough to tolerate a 5 minute response time from the fire service. They are very much designed around engine and air brakes also being used in normal circumstances. A maximum application brakes-only stop from V1 on a modern large airliner will very likely require replacement of all tyres and brake pads, possibly wheels and bogies as well (depending on how quickly the fire is extinguished).

The certification does require that they can safely do a brakes-only stop, but does not require that the aircraft is still fit for service afterwards.

 

[najaB]

The certification does require that they can safely do a brakes-only stop, but does not require that the aircraft is still fit for service afterwards.

You are confusing the maximum energy certification test which is much as you described (you left out the fact that it requires the brake pads to be in the most worn legally allowed condition), and day-to-day operations which is what I'm talking about.

Landing field length calculations are made assuming a wet surface and no reverse thrust - it's a bonus if it works, not a requirement to stay alive.

 

[edwin_m]

I would expect that the brake pads were specced to be suitable for use 100% of the time, with the retarder system providing extra stopping power. In a similar way to how airliners aren't allowed to include thrust-reversers in their stopping distance calculations.

I don't think the retarders provide extra deceleration, as the total deceleration is limited by wheel-rail adhesion. I imagine they were provided to reduce brake pad wear, and if they are isolated the friction brakes are designed to meet the full braking load indefinitely - but the pads will need replacing more often. Changing brake pads is a significant cost for operators, especially if it determines the interval the train has to come into workshops. There were also some bits in the press last week saying that brake dust (including from trains) is a significant cause of particulate pollution.

 

[Philip]

IIRC they aren't the originals, a different type were fitted when the retarders went out of use (which are very noisy in use).

I don't think the retarder itself was noisy on 175s, from what I remember most of the noise came from the engine revving up to incredibly high revs, I'm assuming to drive the cooling fan?

I find the 185 retarder quite impressive to hear when it's used in a tunnel. Cowburn Tunnel is a good example when they brake for the speed restriction, heading east. The engine doesn't rev hard but the noise from the fan vanes creates a wind-tunnel sound effect.

 

[Bletchleyite]

I don't think the retarder itself was noisy on 175s, from what I remember most of the noise came from the engine revving up to incredibly high revs, I'm assuming to drive the cooling fan?

No, I meant the braking using the pads was noisy.

How do the retarders work? I did always wonder why the engine revs up.

 

[Philip]

No, I meant the braking using the pads was noisy.

How do the retarders work? I did always wonder why the engine revs up.

I think when the brake is applied the kinetic energy is converted to heat and through the heat exchanger it heats up the transmission oil which acts as a viscous drag force in the transmission and ultimately slows the axles and thus the train. From what I've read the initial problem on the 175s was poor design around the oil cooler group, which couldn't cope with the sudden influx of very hot oil. The engines would then shut down automatically because of the thermostat. Apparently another issue was cracked pipework because of the cooling issues. Like I say that was the initial problem when first launched, I don't know why it isn't being used now.

 

[najaB]

I don't think the retarders provide extra deceleration, as the total deceleration is limited by wheel-rail adhesion.

Badly worded on my part. 'Supplemental' would've been a better word than extra - energy dissipated by the retarder doesn't need to be dissipated by the brake pads.

 

[tom1649]

I actually quite like them, but they are *very* tatty, worn and damaged, so it may be cheaper to simply replace them than to refurbish to as-new condition.

Replace them with ironing boards you mean? No thank you. Sorry, that was off topic.

 

[craigybagel]

They're still isolated on the entire fleet and have been for many years. They seem to cope just fine - it's rare you'll hear any funny noises coming from the brakes (unlike when Northern had their sister 180 units which used to squeak something terrible when stopping) and from personal experience of the emergency brakes in action they'll stop pretty well if you need them to (although the drivers would know more about that than me).

As to everything else with them - I may be tempting fate here somewhat but given I spend about 80% of my working life on them, I've found them to be exceptionally reliable. Yes the toilets are temperamental and lock themselves out too easily, yes the air-conditioning switches from Baltic to Mediterranean depending on which part of the carriage you're in and yes they are starting to look a bit tired inside, but I've also only had one failure on them in 3 and a half years of working them, and even that was a fairly trivial issue that whilst it required the unit to be taken out of service, it was a very quick fix. The gremlins that were there in the past have been ironed out and Chester have done a very good job with them. I'd take one over a 158 any day....

 

[Philip]

They're still isolated on the entire fleet and have been for many years. They seem to cope just fine - it's rare you'll hear any funny noises coming from the brakes (unlike when Northern had their sister 180 units which used to squeak something terrible when stopping) and from personal experience of the emergency brakes in action they'll stop pretty well if you need them to (although the drivers would know more about that than me).

As to everything else with them - I may be tempting fate here somewhat but given I spend about 80% of my working life on them, I've found them to be exceptionally reliable. Yes the toilets are temperamental and lock themselves out too easily, yes the air-conditioning switches from Baltic to Mediterranean depending on which part of the carriage you're in and yes they are starting to look a bit tired inside, but I've also only had one failure on them in 3 and a half years of working them, and even that was a fairly trivial issue that whilst it required the unit to be taken out of service, it was a very quick fix. The gremlins that were there in the past have been ironed out and Chester have done a very good job with them. I'd take one over a 158 any day....

Was it the strip down/refurb they had at Longsight around 2011 that sorted out the problems?

 

[craigybagel]

Was it the strip down/refurb they had at Longsight around 2011 that sorted out the problems?

No idea, before my time

 

[sk688]

Why do Alstom products suffer from such quality issues, in all their Post Privatisation Stock?

The 175s have this problem
The 180s were so unreliable that they were returned by FGW
The 458s were terrible with leaky roofs and shocking reliability upon introduction
The 334s entered service two years late, and have had to be completely rebuilt despite being just 10-15 years old

Alstom aren't a poor manufacturer, the 390s are quite good, and the Northern and Jubilee line trains are excellent ( Northern units are bombproof, the Jubilee ones have one of the best Traction Motor sounds of any train, and are similarly reliable )

So what is it, that has made their Cordia / Juniper family so poor?

 

[craigybagel]

Why do Alstom products suffer from such quality issues, in all their Post Privatisation Stock?

The 175s have this problem
The 180s were so unreliable that they were returned by FGW
The 458s were terrible with leaky roofs and shocking reliability upon introduction
The 334s entered service two years late, and have had to be completely rebuilt despite being just 10-15 years old

Alstom aren't a poor manufacturer, the 390s are quite good, and the Northern and Jubilee line trains are excellent ( Northern units are bombproof, the Jubilee ones have one of the best Traction Motor sounds of any train, and are similarly reliable )

So what is it, that has made their Cordia / Juniper family so poor?

The 390s went through a whole load of testing at Old Dalby before they entered service, that might be the difference? Of the other fleets, the 175s are doing great, the 458s were until they got reformed and rebuilt (but i believe that again their reliability is on the up right now?), I've not heard of much issues with the 334s of late and the 180s, whilst still somewhat notorious, have had to suffer from so much shuffling around and being split between franchises. I reckon if they were all focused on one depot with one company and they got the care and attention the other fleets got things might be better.

Sadly though, it did also seem to kill off Alsthom in this country.

 

[cjmillsnun]

The 390s went through a whole load of testing at Old Dalby before they entered service, that might be the difference? Of the other fleets, the 175s are doing great, the 458s were until they got reformed and rebuilt (but i believe that again their reliability is on the up right now?), I've not heard of much issues with the 334s of late and the 180s, whilst still somewhat notorious, have had to suffer from so much shuffling around and being split between franchises. I reckon if they were all focused on one depot with one company and they got the care and attention the other fleets got things might be better.

Sadly though, it did also seem to kill off Alsthom in this country.

The 458s were pretty terrible when first introduced. SWT nearly ditched them completely due to major reliability issues. They did improve but like other Alstom products were awful on introduction.

 

[craigybagel]

The 458s were pretty terrible when first introduced. SWT nearly ditched them completely due to major reliability issues. They did improve but like other Alstom products were awful on introduction.

This is true for the first few years alright, but apparently just before they were mixed with the 460s they were doing very well.

 

[LowLevel]

The 390s went through a whole load of testing at Old Dalby before they entered service, that might be the difference? Of the other fleets, the 175s are doing great, the 458s were until they got reformed and rebuilt (but i believe that again their reliability is on the up right now?), I've not heard of much issues with the 334s of late and the 180s, whilst still somewhat notorious, have had to suffer from so much shuffling around and being split between franchises. I reckon if they were all focused on one depot with one company and they got the care and attention the other fleets got things might be better.

Sadly though, it did also seem to kill off Alsthom in this country.

The 175s are doing far from great - a number of vehicles have recently spent time out of traffic because the solebars were so badly corroded they were dangerous. Not good on less than 20 year old trains!!

 

[craigybagel]

The 175s are doing far from great - a number of vehicles have recently spent time out of traffic because the solebars were so badly corroded they were dangerous. Not good on less than 20 year old trains!!

Good point, I'd actually managed to forget about that one Maybe I'd tried to block out the painful memories of that time, work wasn't much fun. I still maintain though that on a day to day basis they're pretty good. Put it this way - given a choice from any thing in our fleet to work my last train home in the 9th hour of my 10 hour shift I'll always pick a 175.

 

[LowLevel]

Don't get me wrong - I think they're lovely trains - like a modern DMU version of a HST - just a shame they suffer with build quality problems!