Why does the 357 accelerate almost 2x as fast as every other electrostar?

[Railperf]

The top speed of the 2009 stock on the Victoria line is 50mph.

Yes, so i reckon either Victoria or Jubille are quicker to 50mph than an S7/S8. In open air the Jubilee stock is very quick indeed.

 

[SolomonSouth]

Yes, so i reckon either Victoria or Jubille are quicker to 50mph than an S7/S8. In open air the Jubilee stock is very quick indeed.

Yeah I have heard 1996 stock are about 45 secs to 50. Decent for a DC train, but a 375/376 would be slightly faster and a 465/0 could match that. A 465/9 would significantly outrun it - I've had 0-50 in 37 secs from a 465/9. 465907 I think the unit was. Greenhithe towards Dartford.
Not sure on 0-50 for 444/450/707 units but the 700 is around 41 secs to 50, so I'm assuming those 3 are all pretty similar.

 

[Railperf]

Yeah I have heard 1996 stock are about 45 secs to 50. Decent for a DC train, but a 375/376 would be slightly faster and a 465/0 could match that. A 465/9 would significantly outrun it - I've had 0-50 in 37 secs from a 465/9. 465907 I think the unit was. Greenhithe towards Dartford.
Not sure on 0-50 for 444/450/707 units but the 700 is around 41 secs to 50, so I'm assuming those 3 are all pretty similar.

Jubilee stock is very fast off the mark but acceleration tails off after 22mph : 0-20mph in 7 sec, 0-30mph in 12.8 sec, 0-40mph in 22.4 sec, 0-50mph in 38.7 sec, 0-54mph in 48.9 sec

== Doublepost prevention - post automatically merged: 17 May 2021 ==

Yeah I have heard 1996 stock are about 45 secs to 50. Decent for a DC train, but a 375/376 would be slightly faster and a 465/0 could match that. A 465/9 would significantly outrun it - I've had 0-50 in 37 secs from a 465/9. 465907 I think the unit was. Greenhithe towards Dartford.
Not sure on 0-50 for 444/450/707 units but the 700 is around 41 secs to 50, so I'm assuming those 3 are all pretty similar.

Ac v DC Comparison - similar gradients:

Class 700 AC up 1 in 200 Fom rest to 1.6 miles - 1 min 43 secs @ 85.8mph
Class 700DC up 1 in 264 from rest to 1,6 miles - 2 min 2 sec @ 69.6mph
Class 700 AC down 1 in 176 rest to 1.6 mil;es 1 min 36s @ 94.9mph

 

[SolomonSouth]

Jubilee stock is very fast off the mark but acceleration tails off after 22mph : 0-20mph in 7 sec, 0-30mph in 12.8 sec, 0-40mph in 22.4 sec, 0-50mph in 38.7 sec, 0-54mph in 48.9 sec

== Doublepost prevention - post automatically merged: 17 May 2021 ==

0-54 in 48.9 sec is very good, but judging by the acceleration rate at 50mph, it would take over 60 secs to 60. Decent for a DC unit but a 375/376 would likely scoff at that taking 60 secs to 60, and a 465/9 and 378 likely as well.

Ac v DC Comparison - similar gradients:

Class 700 AC up 1 in 200 Fom rest to 1.6 miles - 1 min 43 secs @ 85.8mph
Class 700DC up 1 in 264 from rest to 1,6 miles - 2 min 2 sec @ 69.6mph
Class 700 AC down 1 in 176 rest to 1.6 mil;es 1 min 36s @ 94.9mph

Interesting. 700 on DC is indeed very slow, confirming my suspicions. 700 on AC is a lot faster than the 319 for sure but dare I say.... the 700 accelerates worse above 50mph than a 377 or 387.
Bottom line is for a new AC unit the 700 is incredibly sluggish - IETs, 345, 331, 710, 720, 379, 357, 360, 350, 380, 395, 755s (both diesel and electric), 745, and 323 are all quicker off the mark say 0-30 mph than a 700. I'd say most of the units listed are quicker to 60mph as well.
Even a renatus 321 is a similar pace according to the eversholt graph here: https://eversholtrail.co.uk/fleet/321-renatus/ it gets 50 secs to 60. Also a 365 AFAIK was about/just over 50 secs to 60 but not sure of 0-100 time for a 365 I think it tapers after 80mph....

 

[Railperf]

No, the 700's can reach 100mph in under 2 minutes - quicker than 377/387s.

Tube stock is designed for very quick platform departure, hence the incredible acceleration to 25mph. Short distances between stations mean that speeds over 50mph are not necessary, and the additional time/energy needed to reach 60mph saves only a few seconds at most on each station to station section.
But in a drag race between - say Jubillee line stock - and the mainline stock, is that the tube stock would seriously leave the others standing at the very startto around 30-35mph, then your 345's etc would start reeling it back in!

== Doublepost prevention - post automatically merged: 18 May 2021 ==

0-54 in 48.9 sec is very good, but judging by the acceleration rate at 50mph, it would take over 60 secs to 60. Decent for a DC unit but a 375/376 would likely scoff at that taking 60 secs to 60, and a 465/9 and 378 likely as well.

Interesting. 700 on DC is indeed very slow, confirming my suspicions. 700 on AC is a lot faster than the 319 for sure but dare I say.... the 700 accelerates worse above 50mph than a 377 or 387.
Bottom line is for a new AC unit the 700 is incredibly sluggish - IETs, 345, 331, 710, 720, 379, 357, 360, 350, 380, 395, 755s (both diesel and electric), 745, and 323 are all quicker off the mark say 0-30 mph than a 700. I'd say most of the units listed are quicker to 60mph as well.
Even a renatus 321 is a similar pace according to the eversholt graph here: https://eversholtrail.co.uk/fleet/321-renatus/ it gets 50 secs to 60. Also a 365 AFAIK was about/just over 50 secs to 60 but not sure of 0-100 time for a 365 I think it tapers after 80mph....

The Renatus units are a fair bit quicker than standard 321's but still not in a Class 360/379/700 league.
Never mind the 745's and 720's
The problem is that they are still only 4 motored axles, and i'm not sure that the installed traction power is that much higher than standard - even if the traction electronics have been upgraded. Probably the AC traction motors are more efficient, and deliver a slight improvement - that's all.

 

[SolomonSouth]

No, the 700's can reach 100mph in under 2 minutes - quicker than 377/387s.

Tube stock is designed for very quick platform departure, hence the incredible acceleration to 25mph. Short distances between stations mean that speeds over 50mph are not necessary, and the additional time/energy needed to reach 60mph saves only a few seconds at most on each station to station section.
But in a drag race between - say Jubillee line stock - and the mainline stock, is that the tube stock would seriously leave the others standing at the very startto around 30-35mph, then your 345's etc would start reeling it back in!

== Doublepost prevention - post automatically merged: 18 May 2021 ==


The Renatus units are a fair bit quicker than standard 321's but still not in a Class 360/379/700 league.
Never mind the 745's and 720's
The problem is that they are still only 4 motored axles, and i'm not sure that the installed traction power is that much higher than standard - even if the traction electronics have been upgraded. Probably the AC traction motors are more efficient, and deliver a slight improvement - that's all.

Oh did 321s used to have DC traction equipment? It got them to 60 in around 70 seconds AFAIK. Renatus seem about 50 seconds I've heard from eversholt, about 20 secs quicker than the standard 321 then according to that, but I feel 50 seconds is a bit optimistic for a renatus 321 - how is it as fast as a 365 for example?
I think they have the same power output as standard 321s, probs traction effeciency improved like you said.
I think 321s used AC motors - they run under overhead and it would be strange to use DC motors under overhead right?

 

[43096]

Oh did 321s used to have DC traction equipment? It got them to 60 in around 70 seconds AFAIK. Renatus seem about 50 seconds I've heard from eversholt, about 20 secs quicker than the standard 321 then according to that, but I feel 50 seconds is a bit optimistic for a renatus 321 - how is it as fast as a 365 for example?
I think they have the same power output as standard 321s, probs traction effeciency improved like you said.
I think 321s used AC motors - they run under overhead and it would be strange to use DC motors under overhead right?

321s used DC motors from new. The Renatus units (321301-330) have been re-engineered with AC motors.

It’s not strange - prior to the advent of modern power electronics (GTO and IGBT inverters etc) DC motors were easier to control. AC motors require variable voltage/variable frequency drive inputs and you don’t get that in a controlled way from the overheads.

 

[AM9]

Oh did 321s used to have DC traction equipment? It got them to 60 in around 70 seconds AFAIK. Renatus seem about 50 seconds I've heard from eversholt, about 20 secs quicker than the standard 321 then according to that, but I feel 50 seconds is a bit optimistic for a renatus 321 - how is it as fast as a 365 for example?
I think they have the same power output as standard 321s, probs traction effeciency improved like you said.
I think 321s used AC motors - they run under overhead and it would be strange to use DC motors under overhead right?

All (well virtually all) EMU had series wound DC traction motors until the late '80s. Their traction systems were fed from a DC supply - usually somewhere near 750V that was either direct from a 3rd rail source or from a rectified 50Hz tap on the main transformer, that in itself was connected to the pantograph. The speed/torque of the motors was controlled by various means, usually series resistors on DC supplies or on the transformer. By the '80s various electronic control systems were being introduced comprising thyristors, power transistors etc., but they still controlled the DC current through the DC motors.
The latest EMUs have a DC power bus derived from whatever source (3rd rail or OLE) is in use. The ac motors are then fed by electronic inverters that adjust both the current and the frequency required for the load and speed, - i.e. the type of motor on the bogies has no direct relationship with the electricity supply from the track/OLE.

 

[SolomonSouth]

321s used DC motors from new. The Renatus units (321301-330) have been re-engineered with AC motors.

It’s not strange - prior to the advent of modern power electronics (GTO and IGBT inverters etc) DC motors were easier to control. AC motors require variable voltage/variable frequency drive inputs and you don’t get that in a controlled way from the overheads.

It is still a bit strange because both 465s and 365s (made at a similar time) use AC tracion motors despite 465s being on DC third rail.
Might explain why the 465/9s and 365s accelerate super fast compared to a 321 though......

== Doublepost prevention - post automatically merged: 19 May 2021 ==

All (well virtually all) EMU had series wound DC traction motors until the late '80s. Their traction systems were fed from a DC supply - usually somewhere near 750V that was either direct from a 3rd rail source or from a rectified 50Hz tap on the main transformer, that in itself was connected to the pamntograp. The speed/torque of the motors was conntrolled by various means, usually series resistors on DC supplies or transformer taps on the transformer. By the '80s various electronic control systems were being introduced comprising thyristors, power transistors etc., but they still controlled the DC current through the DCmotors.
The latest EMUs have a DC power bus derived from whatever source (3rd rail or OLE) is in use. The ac motors are then fed by electronic inverters that adjust both the current and the frequency required for the load and speed, - i.e. the type of motor on the bogies has no direct relationship with the electricity supply from the track/OLE.

Thanks man

 

[KC1]

So I’ve just been on a class 377/6 into London Bridge. By pure luck, the next leg of the journey was to Enfield Lock where a 387 was waiting. The difference in speed between the two is very noticeable, I’ve always felt the 377s had more to give but never full whack on the fast between East Croydon or London Bridge but 387s, wow, huge difference.

 

[Bald Rick]

It is still a bit strange because both 465s and 365s (made at a similar time) use AC tracion motors despite 465s being on DC third rail.

The Networkers were the first of the units to have AC drive. Something had to be first!

As others have said, what type of current is taken in from the power system doesn’t matter, it is all turned into D.C. on the train and then to AC for the traction sysytem. It is much more efficient, and in theory more reliable (fewer moving parts).

 

[SolomonSouth]

The Networkers were the first of the units to have AC drive. Something had to be first!

As others have said, what type of current is taken in from the power system doesn’t matter, it is all turned into D.C. on the train and then to AC for the traction sysytem. It is much more efficient, and in theory more reliable (fewer moving parts).

Thanks Rick. Didn't know 465s were the first units to have AC drive (since 365 was a tad newer. The reason I say was is because they're not in service anymore).
Explains why 465s (for some reason the metcams more so) accelerate so more quickly off the line than every other 1990s unit.

== Doublepost prevention - post automatically merged: 19 May 2021 ==

So I’ve just been on a class 377/6 into London Bridge. By pure luck, the next leg of the journey was to Enfield Lock where a 387 was waiting. The difference in speed between the two is very noticeable, I’ve always felt the 377s had more to give but never full whack on the fast between East Croydon or London Bridge but 387s, wow, huge difference.

I suspected 387s were faster on DC - according to wikipedia they have 650 more horsepower than 377s (4-car) and have a similar power output to the 5-car ones with less weight

 

[AM9]

It is still a bit strange because both 465s and 365s (made at a similar time) use AC tracion motors despite 465s being on DC third rail. ...

There was a time when ac motors did need to run from an ac supply. In the 1920s when the German railways were electrifying on a grand scale, they used a low ac frequency of 16 2/3 Hz, exactly 1/3 of the global industrial standard 50Hz. That was because the motors were virtually the same as DC types and could run at low frequencies whilst transformers could still be used to distribute the supply to the OLE and reduce it to motor compatible voltages on board locos. Modern trains using the 15kV 16.7Hz (the frequency was later changed slightly for technical reasons), use similar topology to 50Hz ac units with intermediate DC bus voltages followed by solid state electronics in their control system. Indeed this enables some trains to change from 50Hz ac to 1500DC to 16.7Hz etc. whilst moving as they pass from one system to another.

== Doublepost prevention - post automatically merged: 19 May 2021 ==

... I suspected 387s were faster on DC - according to wikipedia they have 650 more horsepower than 377s (4-car) and have a similar power output to the 5-car ones with less weight.

Possible although unlikely given that both 377s and 387s have their maximum power limited by their control software to prevent overload of the 3rd rail supply. This is why judging performance of dual voltage EMUs on ac vs DC isn't really relevant as their 'hardware capable' DC performance (above a minimum value) isn't available for service use, whereas on ac, most trains are free to draw up to their nominal maximum power.

 

[Railperf]

It is still a bit strange because both 465s and 365s (made at a similar time) use AC tracion motors despite 465s being on DC third rail.
Might explain why the 465/9s and 365s accelerate super fast compared to a 321 though......

== Doublepost prevention - post automatically merged: 19 May 2021 ==


Thanks man

Weren't the 321s based on the earlier 317 design. It was probably cheap based on a proven design. 321s Didn't need much of a redesign and most likely a stop gap to get extra trains on to the South East routes quickly.

 

[43096]

Modern trains using the 15kV 16.7Hz (the frequency was later changed slightly for technical reasons), use similar topology to 50Hz ac units with intermediate DC bus voltages followed by solid state electronics in their control system. Indeed this enables some trains to change from 50Hz ac to 1500DC to 16.7Hz etc. whilst moving as they pass from one system to another.

Indeed development of multi-system traction means that a freight from (say) Rotterdam to Milan can be hauled throughout by one locomotive with several voltage changes: 1500V DC > 25kV AC > 1500V DC > 15kV AC > 3000V DC. The bigger issue is the number of signalling systems needed and finding space for them.

 

[SolomonSouth]

Weren't the 321s based on the earlier 317 design. It was probably cheap based on a proven design. 321s Didn't need much of a redesign and most likely a stop gap to get extra trains on to the South East routes quickly.

I think so

== Doublepost prevention - post automatically merged: 19 May 2021 ==

There was a time when ac motors did need to run from an ac supply. In the 1920s when the German railways were electrifying on a grand scale, they used a low ac frequency of 16 2/3 Hz, exactly 1/3 of the global industrial standard 50Hz. That was because the motors were virtually the same as DC types and could run at low frequencies whilst transformers could still be used to distribute the supply to the OLE and reduce it to motor compatible voltages on board locos. Modern trains using the 15kV 16.7Hz (the frequency was later changed slightly for technical reasons), use similar topology to 50Hz ac units with intermediate DC bus voltages followed by solid state electronics in their control system. Indeed this enables some trains to change from 50Hz ac to 1500DC to 16.7Hz etc. whilst moving as they pass from one system to another.

== Doublepost prevention - post automatically merged: 19 May 2021 ==


Possible although unlikely given that both 377s and 387s have their maximum power limited by their control software to prevent overload of the 3rd rail supply. This is why judging performance of dual voltage EMUs on ac vs DC isn't really relevant as their 'hardware capable' DC performance (above a minimum value) isn't available for service use, whereas on ac, most trains are free to draw up to their nominal maximum power.

Thanks so much! Awesome knowledge

 

[edwin_m]

Weren't the 321s based on the earlier 317 design. It was probably cheap based on a proven design. 321s Didn't need much of a redesign and most likely a stop gap to get extra trains on to the South East routes quickly.

All of class 317-322 share the same basic bodyshell, as do 455, 456 and 150. Tractionwise both 317 and 321 have phase angle drive, which only works for DC motors from an AC supply. I don't know if the actual electronics is the same - things were evolving quite rapidly at the time so there may well be some detail differences.

 

[SolomonSouth]

All of class 317-322 share the same basic bodyshell, as do 455, 456 and 150. Tractionwise both 317 and 321 have phase angle drive, which only works for DC motors from an AC supply. I don't know if the actual electronics is the same - things were evolving quite rapidly at the time so there may well be some detail differences.

Maybe