Greater Anglia Bombardier Aventras (Class 720): Technical discussion and introduction

absolutelymilk

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There doesn't seem to be a thread about these units so thought I would create one.

Do we know anything about the acceleration/power characteristics of these trains yet?

Note: This thread is about the technical aspects of the units and their introduction, not about the seats!
 
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59CosG95

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There doesn't seem to be a thread about these units so thought I would create one.

Do we know anything about the acceleration/power characteristics of these trains yet?
Seems unlikely, given that the only Aventras built are the Class 345s (and 710s, of which the first has only just emerged), and the FLIRTs haven't even been built yet.

The tech specs are available though; the GA Aventras (Class 720s; 720/1 for the 10-car, 720-5 for the 5-car) are both 100mph max, as are the FLIRTs (745/0 for the 90 + mk3 replacements, 745/1 for the 379 replacements, 755/3 for the 3-car bi-modes, 755/4 for the 4-car bi-modes). The FLIRTs are designed with Stadler's "FLIRT 200" front end, so it may be the case that, given linespeed upgrades on the GEML in future, the 745s may be able to run at 125mph (200 km/h).

What this might have on the effect of rates of acceleration, I don't yet know.
The 345 bogies are (as 9-car units) arranged thus: 2-Bo + Bo-2 + Bo-Bo + Bo-2 + 2-2 + 2-Bo + Bo-Bo + 2-Bo + Bo-2; 10 powered axles per train, giving an acceleration of up to 1 m/s^2.
Assuming that the Class 720s are arranged in a similar fashion for an equivalent set of coaches, the acceleration should be broadly similar.
 

Alfie1014

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Interesting comment in this month’s Modern Railways about the new 10 car Aventras for GA in that for maintenance at Ilford they will have to be split into 2 x 5 cars to fit in the new shed and will have to do this to 1 unit a night! Well that’s never going to be a risk to performance is it?

And if that’s the case why not just go for all 5 cars?
 

Wivenswold

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Could it be possible that there are special connectors between coaches 5 and 6 that make it a quicker job? You'll be able to tell from my lack of tech-speak, that this is not an area of expertise for me.
 

eastdyke

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Could it be possible that there are special connectors between coaches 5 and 6 that make it a quicker job? You'll be able to tell from my lack of tech-speak, that this is not an area of expertise for me.
mmmmm ........ special connectors ........ that come apart quickly?
 

Domh245

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mmmmm ........ special connectors ........ that come apart quickly?

Presumably some sort of automatic coupler, as opposed to a bar coupler or such.

I think that the S stock on the Underground have got such an arrangement that allows reasonably easy splitting of the two half sets, but I may well be wrong
 

dp21

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Presumably some sort of automatic coupler, as opposed to a bar coupler or such.

I think that the S stock on the Underground have got such an arrangement that allows reasonably easy splitting of the two half sets, but I may well be wrong

You're correct. I've seen the designs and they have autocouplers including rear-facing cameras and some form of headlight so that when propelling there is maximum visibility. "In theory" all it takes is some connectors in the gangway to be disengaged, hit uncouple and bobs your uncle.

If they started messing around with jumpers and all that nonsense it would just be carnage.

Obviously it's not ideal but unfortunately that's the decision that's been made. At least the majority (89) of the units are 5 cars I suppose...
 

edwin_m

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You're correct. I've seen the designs and they have autocouplers including rear-facing cameras and some form of headlight so that when propelling there is maximum visibility. "In theory" all it takes is some connectors in the gangway to be disengaged, hit uncouple and bobs your uncle.
Presumably also some kind of door to close off the gangway (is it full width on these units?). Shunting controls too? I guess blunt-end-first moves would only be allowed within the depot.
 

Domh245

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Presumably also some kind of door to close off the gangway (is it full width on these units?). Shunting controls too? I guess blunt-end-first moves would only be allowed within the depot.

As it'd only be for depot work, they can probably get away with just using a frame that clips on to the handrails like that used on the S stock, or tarpaulin for weatherproofing when outside. I would also expect that there will be shutters at points along the train for fire management, which could probably also be used.
 

dp21

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Thank you dp21. That's the technical answer I was grasping for so badly.

You are quite welcome.

Presumably also some kind of door to close off the gangway (is it full width on these units?). Shunting controls too? I guess blunt-end-first moves would only be allowed within the depot.

As it'd only be for depot work, they can probably get away with just using a frame that clips on to the handrails like that used on the S stock, or tarpaulin for weatherproofing when outside. I would also expect that there will be shutters at points along the train for fire management, which could probably also be used.

With regards these two posts I'm not 100% sure. The moves would only be done on depot and I believe shunt controls have been sacrificed in favour of propelling from the driving end but under tightly controlled circumstances hence the lights and the cameras etc. Given that's been BT's approach in the past I'd expect to see something similar but it's anyone's guess at the minute.

There's some sort of bulkhead between the two halves even on the 7-car 345s isn't there?

I believe so but I'm hoping someone more enlightened can help with that.
 

edwin_m

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The 700s also have some kind of closeable bulkhead on some of the gangways. I presume it is indeed a fire barrier but putting one in the right place would also provide weatherproofing and prevent the crew falling out if the unit is split on depot. I imagine putting a tarpaulin over a gangway under 25kV would be an unacceptable hazard.
 

Dstock7080

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I think that the S stock on the Underground have got such an arrangement that allows reasonably easy splitting of the two half sets, but I may well be wrong

You're correct. I've seen the designs and they have autocouplers including rear-facing cameras and some form of headlight so that when propelling there is maximum visibility. "In theory" all it takes is some connectors in the gangway to be disengaged, hit uncouple and bobs your uncle.
S Stock do not have auto-couplers between any cars. There are no headlights or cameras either.

S Stock cannot be divided except within a depot and all cars have the same bar-coupling.
 

dp21

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My comment was with regards the 720 design, not the S-stock however I appreciate the correction.
 

hwl

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Seems unlikely, given that the only Aventras built are the Class 345s (and 710s, of which the first has only just emerged), and the FLIRTs haven't even been built yet.

The tech specs are available though; the GA Aventras (Class 720s; 720/1 for the 10-car, 720-5 for the 5-car) are both 100mph max, as are the FLIRTs (745/0 for the 90 + mk3 replacements, 745/1 for the 379 replacements, 755/3 for the 3-car bi-modes, 755/4 for the 4-car bi-modes). The FLIRTs are designed with Stadler's "FLIRT 200" front end, so it may be the case that, given linespeed upgrades on the GEML in future, the 745s may be able to run at 125mph (200 km/h).

What this might have on the effect of rates of acceleration, I don't yet know.
The 345 bogies are (as 9-car units) arranged thus: 2-Bo + Bo-2 + Bo-Bo + Bo-2 + 2-2 + 2-Bo + Bo-Bo + 2-Bo + Bo-2; 10 powered axles per train, giving an acceleration of up to 1 m/s^2.
Assuming that the Class 720s are arranged in a similar fashion for an equivalent set of coaches, the acceleration should be broadly similar.
720s
10car:
2-2 + 2-Bo + Bo-Bo + 2-Bo + Bo-2 + 2-2 + 2-Bo + Bo-Bo + 2-Bo + Bo-2
5car:
2-2 + 2-Bo + Bo-Bo + 2-Bo + Bo-2

Note that the 10cars are electrically and controlwise 2x 5 car units (but not mirror image or identical interiors or cabs).
50% powered axles.
 

59CosG95

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720s
10car:
2-2 + 2-Bo + Bo-Bo + 2-Bo + Bo-2 + 2-2 + 2-Bo + Bo-Bo + 2-Bo + Bo-2
5car:
2-2 + 2-Bo + Bo-Bo + 2-Bo + Bo-2

Note that the 10cars are electrically and controlwise 2x 5 car units (but not mirror image or identical interiors or cabs).
50% powered axles.
Ahhh, thanks very much @hwl, given that 56% of the 345s' axles are powered, the acceleration on the 720s shouldn't be that far behind.
 

HLE

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It’s the railway. Not much is done on time.
 

delticdave

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Do we know if the 720's will be used on the Southminster branch?
The peak services to / from Liv. St. won't be a problem, ('cos at least one of the existing services
is usually a 12-car 321 set), but since most of the service runs from either of the bay platforms at Wickford,
are said platforms long enough for a 5-car 720?
 

Alfie1014

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Nope, the bays according to the Anglia Sectional Appendix are around 110m, whereas a 5 car 720 is 122m. There is virtually no room at the country end to move the points and extend the platforms out as there is an under bridge which would have to be widened. You could demolish one or other of the station buildings at London to extend though or terminate in one of the through platforms and run London services through the other. Though with 4tph each way that could be a recipe for delays!
 

samuelmorris

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Ah of course I was looking at the branch stations, forgot about Wickford itself. It's a tricky one but they must have thought of this when specifying 120m long units. Unless of course they intend to run Southminster services direct from somewhere else (e.g. Shenfield in the off-peak, London in the peak). I haven't heard of any such plans though?
 

Wivenswold

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Isn't there a "wired" siding London side of Wickford that's long enough?

Personally think they'll end up with a small fleet of 321s or 360s for branch lines. Based on nothing but gut feeling.
 

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