GWR Class 800

[D365]

The flickering lights remind me of watching GT cars in The FIA WEC.

The reason behind that effect on camera has been explained before. The Class 68 locomotives also appear to do a similar thing.

 

[jon0844]

Found this video today.

It sounds very Velaro-esque!

https://youtu.be/icKAdriYD1k

Why so many cables between each coach? Looks rather messy - as well as possible places for future problems with dodgy/worn connections?

 

[najaB]

Why so many cables between each coach? Looks rather messy - as well as possible places for future problems with dodgy/worn connections?

Normal brake lines and control cables, plus a HV bus cable running the length of the train.

 

[J-2739]

Why so many cables between each coach? Looks rather messy - as well as possible places for future problems with dodgy/worn connections?

Japanese inspiration

 

[Domh245]

Why so many cables between each coach? Looks rather messy - as well as possible places for future problems with dodgy/worn connections?

On most trains these are 'hidden' around the level of the coupling. Hitachi have used the higher up approach on the 395s before these, so I guess it is there standard system. I guess it gives easier access for maintenance.

 

[jon0844]

On most trains these are 'hidden' around the level of the coupling. Hitachi have used the higher up approach on the 395s before these, so I guess it is there standard system. I guess it gives easier access for maintenance.

Ah, thanks.

 

[jimm]

They are new, so will need some wear and tear. Although I must admit, that's EXACTLY what they said about the 180's and look at them now... Please god no.

I've no idea who 'they' were but they obviously didn't know much about the sintered disc brake pads used on the 180s.

The 800s are presumably equipped with Knorr-Bremse's sintered brake pads, so you will get a similar sound from them.

 

[TheKnightWho]

I've no idea who 'they' were but they obviously didn't know much about the sintered disc brake pads used on the 180s.

The 800s are presumably equipped with Knorr-Bremse's sintered brake pads, so you will get a similar sound from them.

Will the screeching disappear over time?

 

[D365]

Will the screeching disappear over time?

No it won't. If you want to know more about the design then there's a brochure here by Knorr-Bremse.

 

[fgwrich]

On most trains these are 'hidden' around the level of the coupling. Hitachi have used the higher up approach on the 395s before these, so I guess it is there standard system. I guess it gives easier access for maintenance.

Those trunks of 24 cables are one of Siemens 'Desiro' downfalls, and one they've worked to address on the Desiro City with the Flyby Wiring set up instead.

The Bombardier 22X and Alstom Pendolino family has a similar set ups st the end of each vehicle with all the extra wiring. However, Hitach's does seem more excessive than the others.

 

[TRAX]

Will the screeching disappear over time?

If they're like all the other trains equipped with these, yes.

 

[Dave1987]

Whats with the screeching brakes?

I would have expected them to have regen brakes.

 

[ainsworth74]

I would have expected them to have regen brakes.

They do. I was under the impression that all trains use their disk brakes at low speed and coming to a stand (and staying there) even when they are fitted with regen?

 

[D365]

They do. I was under the impression that all trains use their disk brakes at low speed and coming to a stand (and staying there) even when they are fitted with regen?

Yeah that's right, the braking effect of a dynamic braking system diminishes significantly below 10-12mph and therefore air braking takes over at that speed. Blended braking therefore reduces wear on the air brakes - DEMUs and EMUs which do not regenerate disperse the waste energy as heat through roof-mounted rheostat grids.

 

[Dave1987]

They do. I was under the impression that all trains use their disk brakes at low speed and coming to a stand (and staying there) even when they are fitted with regen?

Not the EMU's I drive. The regens stay braking until below around 5mph. It's not a criticism until the usual suspects pounce, I would just expect the regen brakes to be active until a very slow speed. That squealing is certainly happening at speeds where I would have thought the regens would be doing the braking. Maybe they aren't certified to use the regens yet.

 

[D365]

Not the EMU's I drive. The regens stay braking until below around 5mph. It's not a criticism until the usual suspects pounce, I would just expect the regen brakes to be active until a very slow speed. That squealing is certainly happening at speeds where I would have thought the regens would be doing the braking. Maybe they aren't certified to use the regens yet.

It probably depends on the effectiveness of the motor gearing at lower speeds, seeing as these are geared for 140mph I don't imagine that they will behave in the same way as a 75/100mph suburban unit. I don't think that a unit would be allowed out without dynamic braking in operation though as that would put too much wear on the air brakes - on a modern EMU/DEMU they're not designed for braking from high speeds in day-to-day service.

 

[Dave1987]

It probably depends on the effectiveness of the motor gearing at lower speeds, seeing as these are geared for 140mph I don't imagine that they will behave in the same way as a 75/100mph suburban unit. I don't think that a unit would be allowed out without dynamic braking in operation though as that would put too much wear on the air brakes - on a modern EMU/DEMU they're not designed for braking from high speeds in day-to-day service.

Hmmm I sorry but I don't agree. I've driven trains where the regens have been purposefully isolated because of a fault and the air/disc brakes act fully to compensate and it's been in service all day with no issues. The regens are better but the air brakes are certainly designed to brake the train from full speed to a stand in service all day, else you would have to fail a train simply because of a fault with a traction motor.. It obviously just means the discs and pads have higher wear.

 

[D365]

Sorry, I should have been a bit more specific. Maybe the air brakes are designed for it, but braking from higher speeds will mean that the brake pads are worn quicker which makes it obviously more expensive.

 

[Dave1987]

Sorry, I should have been a bit more specific. Maybe the air brakes are designed for it, but braking from higher speeds will mean that the brake pads are worn quicker which makes it obviously more expensive.

Ow indeed and regens are very very good brakes. You can really tell when you are on the conventional air/disc brakes compared to the regens. I'm just surprised they are on the air/disc brakes from such a high speed unless the regens aren't operational yet or the brakes squeal even when just rubbing.

Again this is not a criticism just an observation before I'm pounced on.

 

[D365]

And I didn't see that you mentioned the higher wear in your own posting. The difference might just be due to the motor gearing, as you will rarely hear (for example) any braking squeal on an Electrostar.

 

[Bletchleyite]

Do the 800s have roof-mounted resistor banks to be able to use regen off the wires, like Voyagers do? If not, this may be why. They're mostly running on diesel at the minute.

 

[D365]

Do the 800s have roof-mounted resistor banks to be able to use regen off the wires, like Voyagers do?

According to this infographic, they do ("Brake Resistor" supplied by Telema of Italy). Don't forget that if the unit isn't able to put the regenerated electricity back into the OHL supply then it will automatically switch to rheostatic braking.

 

[coppercapped]

I was told, though I cannot confirm it, that the squealing of some brakes is due to the differences in pad material. The 'squealing' brake pads are made of sintered metal particles whilst the others are a form of bonded resin + additives.

Quite a lot of continental brakes squeal as well.

 

[D1009]

Not the EMU's I drive. The regens stay braking until below around 5mph. It's not a criticism until the usual suspects pounce, I would just expect the regen brakes to be active until a very slow speed. That squealing is certainly happening at speeds where I would have thought the regens would be doing the braking. Maybe they aren't certified to use the regens yet.

This isn't a subject in which I have much expertise, but I associate regen brakes with EMUs, i.e. to put current back into the OHLE, but with a bi-mode on diesel, the energy must do something else. Is there any difference between the modes?

 

[najaB]

This isn't a subject in which I have much expertise, but I associate regen brakes with EMUs, i.e. to put current back into the OHLE, but with a bi-mode on diesel, the energy must do something else.

As posted above, it heats resistor banks on the roof.

 

[D1009]

As posted above, it heats resistor banks on the roof.

So to my question, that's a no then?

 

[najaB]

So to my question, that's a no then?

Well, heating resistors is doing something. If you meant something useful, that's a different matter.

 

[Goldfish62]

I was told, though I cannot confirm it, that the squealing of some brakes is due to the differences in pad material. The 'squealing' brake pads are made of sintered metal particles whilst the others are a form of bonded resin + additives.

Quite a lot of continental brakes squeal as well.

All TGVs including Eurostar Class 373, Corail stock and much else run by SNCF.

 

[D365]

So to my question, that's a no then?

If you want the simplest possible answer: a Class 80x will normally dissipate electricity generated by dynamic braking through the resistor grids. If it is running under OHLE it may automatically put this electricity back into the overheads but the onboard systems will control this automatically.

 

[D1009]

If you want the simplest possible answer: a Class 80x will normally dissipate electricity generated by dynamic braking through the resistor grids. If it is running under OHLE it may automatically put this electricity back into the overheads but the onboard systems will control this automatically.

I was simply trying to ask whether running in electric mode would make any difference to the screeching brakes or to the speeds below which the dynamic brakes did not operate.