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Class 701 'Aventra' trains for South Western Railway: progress updates

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OneTrackMinded

OneTrackMinded

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hwl said:
That is a maximum acceleration rate, the acceleration rate is non linear and varies with speed (two separate V^2 components involved in the non-linearity). The shape of the whole curve across the relevant speed range is what matters not the gradient of the steepest bit of the curve alone and the aventra curves is slightly flatter than others so while the peak value may not be as high the average is better.

With well designed modern 3phase traction motors & traction electronics and decent number of motored axles, gearing makes very little difference for max 75mph with gearing optimised for 75mph or 100mph and the excellent Aventra traction motor cooling really helps here.
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That's very interesting, thanks for the insight.
 
SEtrains

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Energy

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hwl said:
With well designed modern 3phase traction motors & traction electronics and decent number of motored axles, gearing makes very little difference for max 75mph with gearing optimised for 75mph or 100mph and the excellent Aventra traction motor cooling really helps here.
Click to expand...
The Aventras are quite unique in their external blower cooling for motors.

Powered axles is an interesting point, the Aventras have 1 powered axle per bogey but consequently have most (4/5 typically) bogeys motored. The 745s manage excellent acceleration despite only 8 motored axles, each with 600kw motors.
 
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hwl

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Energy said:
The Aventras are quite unique in their external blower cooling for motors.
Click to expand...
External blowers are effectively universal for locomotives so not that unusual overall just for EMUs, a big step for low speed cooling and ensuring effective cooling across the entire motor speed range.
Energy said:
Powered axles is an interesting point, the Aventras have 1 powered axle per bogey
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No, Aventras have zero or two power axles per bogie never 1, Voyagers and meridian have 1 and Electrostars have 0, 1 or 2 depending on which class number of vehicles per unit.

The 5car 701s have 8 motored axles (4 bogies) - 40% and the 10car 16 motored axles (8 bogies).
710 have 2 motored axles per car (1 bogie), 50% (so 8/10 for 4/5car)
720 & 730 have 10 motored axles (50%) with 0 motor bogies (1car),1 (3cars) or 2 (1 car) motor bogies per car
345 have 20 of 36 axles motored (55.5%) with 0 (1car),1 (6cars) or 2 (2 car) motor bogies per car
Energy said:
but consequently have most (4/5 typically) bogeys motored. The 745s manage excellent acceleration despite only 8 motored axles, each with 600kw motors.
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Efficient deceleration is not the mirror image of good acceleration where you have to assume much lower effective adhesion
 
OneTrackMinded

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hwl said:
The 5car 701s have 8 motored axles (4 bogies) - 40% and the 10car 16 motored axles (8 bogies).
Click to expand...
I wonder why the decision was made for the 701s to have the lowest percentage of motored axles considering they perform similar duties to the 710s (commuter and metro) which have 50%? Obviously not something necessarily isolated to the DC thing considering 710s are dual voltage
 
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hwl

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OneTrackMinded said:
I wonder why the decision was made for the 701s to have the lowest percentage of motored axles considering they perform similar duties to the 710s (commuter and metro) which have 50%? Obviously not something necessarily isolated to the DC thing considering 710s are dual voltage
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701s are multiples of 5 car only not 4 or 5car with the option to easily lengthened to 5 required for the 710s, hence 1 motor bogie per vehicle makes the 710s more easily scalable. And more motors make sense with AC if 710s were DC only then it would be less likely to have 50%. The weight reduction makes performance the difference smaller.
 
OneTrackMinded

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hwl said:
701s are multiples of 5 car only not 4 or 5car with the option to easily lengthened to 5 required for the 710s, hence 1 motor bogie per vehicle makes the 710s more easily scalable. And more motors make sense with AC if 710s were DC only then it would be less likely to have 50%. The weight reduction makes performance the difference smaller.
Click to expand...
Forgot about the weight reduction. Out of interest, how much power output does each motored axle have?
 
OneTrackMinded

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hwl said:
265kW max.

Desiro and Electrostar 250kW
Desiro City 200kW
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Desiro Cities like the 707 must have more powered axles to achieve the higher max acceleration of 0.85m/s/^2 then if they're only 200kW and the 701 is 265kW at 0.7/m/s^2 max acceleration
 
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hwl

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OneTrackMinded said:
Desiro Cities like the 707 must have more powered axles to achieve the higher max acceleration of 0.85m/s/^2 then if they're only 200kW and the 701 is 265kW at 0.7/m/s^2 max acceleration
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No 707s are 8 axles (40%) like 5 car 701.
717 are 12axles (50%). 700s are all 50%.

Siemens just put a higher peak max acceleration rather on the spec sheet. Cheekily the 0.85 may not be on DC! The assumptions behind those rates are stated and they may not be directly comparable.

In reality 701s and 707s have a lot of software adjustment of performance to deal with variation in third rail voltage and available current than Electrostar or Desiro so in reality reading too much in to hardware differences is possible.
 
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Energy

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hwl said:
No, Aventras have zero or two power axles per bogie never 1, Voyagers and meridian have 1 and Electrostars have 0, 1 or 2 depending on which class number of vehicles per unit.

The 5car 701s have 8 motored axles (4 bogies) - 40% and the 10car 16 motored axles (8 bogies).
710 have 2 motored axles per car (1 bogie), 50% (so 8/10 for 4/5car)
720 & 730 have 10 motored axles (50%) with 0 motor bogies (1car),1 (3cars) or 2 (1 car) motor bogies per car
345 have 20 of 36 axles motored (55.5%) with 0 (1car),1 (6cars) or 2 (2 car) motor bogies per car
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Interesting, I'm surprised Bombardier managed two motors on a lightweight bogey.

Though looking at the SF7000 it manages 2 motors per bogie, no idea why I thought it was only 1 per bogie on Aventra (the Flexx Eco doesn't have many photos online).

Meanwhile, Hitachi is comparatively poor with outside frame bogeys on the 385s and 80Xs despite having the same or lower-powered motors.

I'd imagine that the 345s have an interesting transformer and traction converter setup with their length.
hwl said:
Efficient deceleration is not the mirror image of good acceleration where you have to assume much lower effective adhesion
Click to expand...
Fair enough, I guess for Stadler it's less of a priority on intercity and (slower) regional routes.
 
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norbitonflyer

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SEtrains said:
I’ve noticed that 701 043 has been used the most on the public class 701 services. Is there any reason why this is?
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Indeed. Don't know of any reason unless it's because it has the commemorative logo on it.
swr-arterio-train-07.jpg


028 -3 outings
037 - 5 outings
039 - 8 outings (+1 cancelled because of disruption at Wraysbury)
043 - 13 outings (including today)
 
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hwl

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Energy said:
Interesting, I'm surprised Bombardier managed two motors on a lightweight bogey.
Click to expand...
Removing the cooling fan from the shaft and having external (to the bogie) cooling shortens the rotor shaft (and hence external motor) length and allows wheel mounted disc brakes on internal frame bogie the motored axles which Siemens can't do and to use tread brakes instead and Hitachi use outside frame motor bogies to have disc brake on motored axles.
Energy said:
Though looking at the SF7000 it manages 2 motors per bogey, no idea why I thought it was only 1 per bogey on Aventra (the Flexx Eco doesn't have many photos online). Meanwhile, Hitachi is comparatively poor with outside frame bogeys on the 385s and 80Xs despite having the same or lower-powered motors.

I'd imagine that the 345s have an interesting transformer and traction converter setup with their length.
Click to expand...
All Aventras have "interesting" set ups compared to traditional ways. Each traction electronics box has 4 or 6 traction inverters (1 per motor) which feed bogies on multiple vehicles. Siemens and Hitachi still mostly do the traditional traction electronics box and motors on the same vehicle which results in a mix of heavy and light vehicles.
Leading axles traditional suffer from lower adhesion, hence Bombardier's Aventra thinking makes not motoring leading bogies on units easier.
Energy said:
Fair enough, I guess for Stadler it's less of a priority on intercity and (slower) regional routes.
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Exactly but Stadler are used to 15kV 16 2/3Hz supplies that often struggle with regen, so regen thinking isn't near the top of their list, more at the "after thoughts" end.
 
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Energy

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hwl said:
Exactly but Stadler are used to 15kV 16 2/3Hz supplies that often struggle with regen, so regen thinking isn't near the top of their list, more at the "after thoughts" end.
Click to expand...
FLIRTs also tend to be quite short and they have fewer bogies, a 4-car electric-only FLIRT with only the end bogeys powered is still 40% as the rest are jacobs bogies. The 745s are unusual for having a lot of normal bogies and their length.

The high-power motors make up for the high axle weight though as you said they'll still struggle for regen.
hwl said:
Removing the cooling fan from the shaft and having external (to the bogie) cooling shortens the rotor shaft (and hence external motor) length and allows wheel mounted disc brakes on internal frame bogie the motored axles which Siemens can't do and to use tread brakes instead and Hitachi use outside frame motor bogies to have disc brake on motored axles.
Click to expand...
I presume its still forced air but using ducts from the body to the motors?
hwl said:
All Aventras have "interesting" set ups compared to traditional ways. Each traction electronics box has 4 or 6 traction inverters (1 per motor) which feed bogies on multiple vehicles. Siemens and Hitachi still mostly do the traditional traction electronics box and motors on the same vehicle which results in a mix of heavy and light vehicles.
Leading axles traditional suffer from lower adhesion, hence Bombardier's Aventra thinking makes not motoring leading bogies on units easier.
Click to expand...
Interesting, thanks for the detail.
 
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hwl

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Energy said:
FLIRTs also tend to be quite short and they have fewer bogies, a 4-car electric-only FLIRT with only the end bogeys powered is still 40% as the rest are jacobs bogies. The 745s are unusual for having a lot of normal bogies and their length.
Click to expand...

Less than 40% on an equivalent basis
Energy said:
The high-power motors make up for the high axle weight though as you said they'll still struggle for regen.
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High axle load is bad for track access charges...

The weight isn't massive compared to a locomotive axle load so fingers crossed you get good adhesion, the Siemens / Bombardier strategy is quite good at mitigating against poor adhesion. ;)
Energy said:
I presume its still forced air but using ducts from the body to the motors?
Click to expand...
Yes, flexible concertina type bellows as used on locomotives for 7+ decades. You can spot the motor bogies from the presence of a small radial duct fan unit a few feet inboard of the bogie on the under carriage (sometime with an air compressor mounted next to it so it is only visible from one side)
Energy said:
Interesting, thanks for the detail.
Click to expand...
 
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43OO4

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Just out of curiosity, what SR EMU designation are we giving these? :p

I propose 5AVN/10TRA, though I've seen 5FKD/10FKD too :lol:
 
GW43125

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RTT reports 043 out today, but 037 has just flown past me at Clapham on its way back to Wimbledon Park.
 
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