Class 175 and 185 dynamic braking

[Philip]

Just asking is the hydro-dynamic brake working again on any 175s or is it still isolated on them all after 2 years? If it's still isolated is it likely to be re-activated anytime soon?

Why do 185s not seem to have any problems with the hydro-dynamic brake compared to the very similar system on Coradias which has been so problematic?

 

[anthony263]

didnt know the class 175's had any dynamic braking

 

[185]

First Transpennine Express, despite using a plie of taxpayers money to have Hydrodynamic Brakes fitted, isolated all of them with 18 month of purchase. The HD Brake rocker switches are all locked in the 'Off' position.

 

[Pacerpilot]

The Hydrodynamic Retarder is permanently isolated on all 175s and there are no plans to reactivate it,

 

[Lampshade]

175s, 180s and 185s all have them isolated.

 

[Philip]

First Transpennine Express, despite using a plie of taxpayers money to have Hydrodynamic Brakes fitted, isolated all of them with 18 month of purchase. The HD Brake rocker switches are all locked in the 'Off' position.

Unless I'm thinking of something different, I've heard it on 185s within the last week? I mean when the engine revs up to slow the train down. On the 175s it's quite loud and noticeable, depending on which part of the carriage you're sitting in - but as said I've not heard it on these since about mid-2009.

 

[185]

HD Brake engages - Engine Revs up - uses fuel - costs more money - less yachts for the shareholders.

That's the way they think

 

[Lampshade]

What on Earth was the point in them then? hock::?

Don't Northern's 180s get through a set of brake pads every fortnight? Surely having the hydrodynamic brake working would save costs there.

 

[driver9000]

As far as I was aware only one or two 185s had the HD brake isolated for a trial into brake pad wear. A couple of years ago the fleet had the HD brake isolated during the autumn leaf fall but then reinstated once leaf fall had finished.

The 180s had the HD brake isolated by FGW as it was the cause of the fires in the early days of their lives. Isolating the HD brake was cheaper and simpler than finding a cure. The 175s under FNW all used the HD brake and continued to do so into TPE days, I'm not sure what the situation is with them under ATW.

 

[Erniescooper]

The only problem with hydrodynamic brake is that it dumps a lot of heat into the cooler group in a very short space of time through the transmission oil cooler, the cooler group sometimes struggles with this and either overheats the engine or transmission. The 175 had its cooler group refurbished recently with a new design of radiator which at the moment is proving very reliable and the plan is to do a trial re-introduction of hydro brake in the next few months.

 

[Flying Snail]

HD Brake engages - Engine Revs up - uses fuel - costs more money - less yachts for the shareholders.

That's the way they think

The engine will rev but it won't burn any fuel. It should be the same as all modern EFI engines, the fuel injectors are cut off as no fuel burn is necessary to keep the engine moving.

 

[No Fault Found]

The Hull Trains 180's are having larger transmission oil heat exchangers fitted in an effort to keep the oil temperatures down to enable reinstatement of the H-brake. A trial test was carried out recently on a modified vehicle with the H-brake back in but i am not sure of the outcome.

It will still take the proposed modified cooler groups from Covrad to keep the coolant temperatures down.

And they are very keen to get the H-brake reinstated as the cost of the brake pads is horrendous

 

[Goldfish62]

Sort of related,the SET Networkers had their rheostatic braking switched off about 10 years ago due to, apparently, cooling problems. The re-engineered Hitachi ones had it switched back on as it was said the cooling problems had been overcome. However, it appears to have been switched off again in recent weeks. What's going on here?

Why do UK railways seem to have so many problems with rheostatic braking when it's been a virtually universal feature for several decades elsewhere in Europe (and on LU)?

 

[O L Leigh]

The engine will rev but it won't burn any fuel. It should be the same as all modern EFI engines, the fuel injectors are cut off as no fuel burn is necessary to keep the engine moving.

No, it's not the same as engine braking in a car. If it was you would be entirely correct in saying that it uses (virtually) no fuel. The hydrodynamic brake acts on the driven wheels by engaging an impellor in the fluid coupling (I think). It is the resistance to the impellor provided by the transmission fluid that provides the braking effort. At this stage the engine is completely disconnected from the drivetrain.

However, as has already been mentioned, this generates a lot of additional heat that has to be dissipated (the kinetic energy of the train HAS to be converted into some other sort of energy, otherwise the system doesn't work). This is done by cycling the hydraulic fluid through the transmission oil cooler. It is the demands on the cooling system generated by this sudden additional heat that causes the engines to rev up while braking. I'm not sure of the precise reason for this, whether the engine is required to force the fluid through the cooling group more quickly or if it's responding to an additional electrical load such as cooling fans, but the net result is that the train uses more fuel per trip than it would if it relied on it's friction brake alone.

O L Leigh

 

[mbonwick]

Smaller loading gauge? Meaning everything has to be crammed in, leading to poor airflow over radiators/heat exchangers perhaps?

 

[Lampshade]

Why do UK railways seem to have so many problems with rheostatic braking when it's been a virtually universal feature for several decades elsewhere in Europe (and on LU)?

Lack of understanding of it? No TOC has had the patience to persevere with it for any great length? Only Alstom have really pioneered it in this country the classes it was fitted to were hardly beacons of reliability?

I'd be interested to know the result of the reactivation of the HD brake for Hull Trains.

 

[O L Leigh]

mbonwick: Perhaps. The best place for them would probably be on the roof so they are in a clear airflow, away from other hot things and not getting caked in grime. Then again, I'm sure there are other very good reasons why they aren't up there.

O L Leigh

 

[Goldfish62]

Lack of understanding of it? No TOC has had the patience to persevere with it for any great length?

Possibly, but then BR were never really into it either, right up to the late '80s.

 

[O L Leigh]

Was just having a look at Wiki. Interestingly the Voith T211r transmission used in all Pacer and Sprinter classes has a retarder, so these units too could have used a hydrodynamic brake.

O L Leigh

 

[Erniescooper]

The engine revs up because it supplies brake force through the transmission to slow the train down, the Brake Control Unit and Voith Turbo Control blend braking between friction and H-brake to make sure of the correct rate of decelaration and not to overspeed the engine.

 

[Flying Snail]

Sort of related,the SET Networkers had their rheostatic braking switched off about 10 years ago due to, apparently, cooling problems. The re-engineered Hitachi ones had it switched back on as it was said the cooling problems had been overcome. However, it appears to have been switched off again in recent weeks. What's going on here?

Why do UK railways seem to have so many problems with rheostatic braking when it's been a virtually universal feature for several decades elsewhere in Europe (and on LU)?

Rheostatic braking is a completely different technology, it uses the traction motors to generate electricity which is then converted into heat through resistor banks. It has been used for a long time in the UK, including all the AC electric classes.

The units in question have hydraulic transmissions not electric.

The engine revs up because it supplies brake force through the transmission to slow the train down, the Brake Control Unit and Voith Turbo Control blend braking between friction and H-brake to make sure of the correct rate of decelaration and not to overspeed the engine.

That is at odds with O L Leigh's description which suggests that the engine is not used at all to provide resistance through the transmission while braking.

To be fair I assumed that what you posted was the case as it is a common setup with similar transmisssions in other applications that I am familiar with but O L Leigh may well be correct.

 

[O L Leigh]

That is at odds with O L Leigh's description which suggests that the engine is not used at all to provide resistance through the transmission while braking.

To be fair I assumed that what you posted was the case as it is a common setup with similar transmisssions in other applications that I am familiar with but O L Leigh may well be correct.

I claim no special knowledge. I was just trying to clarify that the H brake was different from engine braking because the retardation comes from the viscosity of the transmission fluid rather than the compression in the engine.

O L Leigh

 

[No Fault Found]

I am under the impression that the engine revs up to speed the oil pump up that is in the transmission and solenoid valves are opened inside the transmission to give an opposing force to the drive couplings.

I know for certain there is no electronic communication between the cooler group and engine to speed the engine up for extra cooling, this is all done through the cooler group's triple pump.

The other main problem with the H-brake is that the immense pressure going through the hoses to the transmission heat exchanger under braking. I believe in the thousands of psi. These hoses kept blowing and throwing hot oil onto the turbo, hence the fires.

 

[Erniescooper]

You've got me doubting myself now, it's a very long time since I went near a working H-brake so you could very well be right.
The 175 transmission hoses have a jacket on them so if they get holed there won't be any oil spray.

 

[Goldfish62]

Rheostatic braking is a completely different technology, it uses the traction motors to generate electricity which is then converted into heat through resistor banks. It has been used for a long time in the UK, including all the AC electric classes.

The units in question have hydraulic transmissions not electric.

I am indeed fully aware of all that - my point was that it was another non-friction braking system that had been switched off. It may have been used on the AC classes, but certainly not widespread on EMUs. It was introduced by BR on the 3xx classes in the mid-70's then promptly abandoned for the Mk3 based EMUs. It has only come back into widespread use on EMUs in the last decade.Compare that with LU introducing it in the 1960s and continental railways using it even before that.

 

[Eng274]

mbonwick: Perhaps. The best place for them would probably be on the roof so they are in a clear airflow, away from other hot things and not getting caked in grime. Then again, I'm sure there are other very good reasons why they aren't up there.

O L Leigh

The improved airflow would definitely be welcomed to cool the hydraulic fluid. I think the main reason of having all the engine/transmission/cooling gear together is to have less piping between all those components. A line ferrying hot hydraulic fluid to a roof-based heat exchanger would necessitate a stronger pump to circulate it up a 3m incline, hence a higher demand on the engine. A longer line between heat exchanger and transmission may also require more hydraulic fluid to occupy the increased cooling system volume - or very narrow diameter circulatory pipes. (Bigger volume may be beneficial, but overall fluid consumption will go through the roof..excuse the pun)

Rheostatic systems get away with being roof-based because the converted kinetic->electric energy can be carried through a comparatively light cable. They are not without their own flaws though, in Autumn months was there not some instances of tree foliage catching fire after becoming jammed in the resistor banks?

[Haven't got the hang of multi-quoting just yet] - I wasn't aware the Voith T211r had an integral retarder, I always assumed early Sprinter / Express classes relied solely on tread / disc braking respectively?

 

[O L Leigh]

I wasn't aware the Voith T211r had an integral retarder, I always assumed early Sprinter / Express classes relied solely on tread / disc braking respectively?

Admittedly my source was Wikipedia's page about Voith, so it could be wrong.

However, putting that to one side, it would certainly seem that the T211r had hydrostatic braking capabilities. But if the retarders were fitted they weren't used or if they weren't fitted they were certainly available.

O L Leigh

 

[No Fault Found]

The improved airflow would definitely be welcomed to cool the hydraulic fluid. I think the main reason of having all the engine/transmission/cooling gear together is to have less piping between all those components. A line ferrying hot hydraulic fluid to a roof-based heat exchanger would necessitate a stronger pump to circulate it up a 3m incline, hence a higher demand on the engine. A longer line between heat exchanger and transmission may also require more hydraulic fluid to occupy the increased cooling system volume - or very narrow diameter circulatory pipes. (Bigger volume may be beneficial, but overall fluid consumption will go through the roof..excuse the pun)

It's not the heat exchanger that would need to be roof based, it is the water jacket radiators. The heat exchanger transfers the heat from the oil to the coolant (very little to air). The problem with the system is that the extra high oil temperature boils the coolant, via the heat exchanger, and the cooler group cannot bring the temperature of the coolant back down quickly enough.

All of the modules are underslung as that is the only place for them and they are all individually hung on metalastik mounts so they move independently of eachother. Otherwise solid pipes could be used to transfer the oil which would not split but they need a small flexible section which is where they are prone to failure.

 

[millemille]

I am indeed fully aware of all that - my point was that it was another non-friction braking system that had been switched off. It may have been used on the AC classes, but certainly not widespread on EMUs. It was introduced by BR on the 3xx classes in the mid-70's then promptly abandoned for the Mk3 based EMUs. It has only come back into widespread use on EMUs in the last decade.Compare that with LU introducing it in the 1960s and continental railways using it even before that.

The rheo brake on all 3 classes of DC Networkers was never intentionally switched off fleet wide for long periods.

There were occasional fleet wide isolations for safety reasons relating to traction/braking software issues but the general lack of working rheo braking was purely down to reliability/spares/manpower issues.

Dropping a rheo grid or changing a blower motor is a pretty big job when the available down time for un-planned maintenance is limited, and the very nature of the diagrams and routes on the South Eastern means that the grids, even when working properly, tend to overheat quickly and the rheo drops out and the train reverts to full friction braking, so the brake pad life savings didn't necessarily exist and weren't a driver for getting the reho working fleet wide.

You sure you're not getting rheostatic and regenerative braking confused?

Regen was isolated from day one due to infrastructure problems.

 

[Philip]

So looking at the posts in this topic, take it the 185 H-D brake is still fully operational with no plans to isolate it and the 175 system could soon be working again at least on a trial basis?

Do Northern/Newton Heath plan to re-activate the system on their 180s like Hull Trains are doing?