96 tube stock faster than A stock

[retep]

This morning between Dollis Hill and Willesden Green when the Jubilee Line left Dollis Hill there was an A stock and at first obviously it was faster but as the Jubilee Line accelerated for a some seconds I saw it travel faster than the A stock till it had to stop at Willesden Green.
Does this normally happen?

Why does the S stock seem to go slower than the A stock? Not sure if this is true but it seems slower. I know it would be travelling faster than the A stock once it goes ATO.

[Chris M]

The 1996 stock is a much newer train than the 50 year old A stocks on the Met, the latter also being bigger and heavier. Additionally, the A stocks have two settings, one for the City section of the line which prioritises acceleration over top speed, maximising the performance for shortly spaced stations where there isn't time or need to reach top speed but fast accelleration is important. North of Baker Street this system is switched to the other mode whereby the train has a faster top speed but at the expense of slower acceleration, which is the optimal configuration for fewer stations with longer distances between where acceleration is less important than going as quickly as possible over the long inter-station gaps. The Jubilee Line trains only have the first mode, as that is all that line requires.

[metman]

S stock seem slower because they are a bit smoother! If you are doing 50 in an A stock you'll know about it

[trc666]

So the 96 stock doesn't have the equivalent of weak field then?

[jardine01]

The 96 stock has much more superior prefomance than the A stock like you have said, i suppose ATO is in use on the Jubilee line now so maybe the train was traveling at top speed so it must of been traveling faster than the A stock.

[Deleted]

96s don't need weak field, they are 3 phase traction and have a roughly smooth output.

On the other hand the DC motors normally have their strength at the bottom end, and the acceleration thins out towards the top. Compare a 92ts and an 09ts, both about equal in overall performance..

92s accelerate the same at the start, but the rate slows as the speed gets up. 09s just go and go and go!

[retep]

I have an interest in tube stock but don't really know about the technical stuff. What is a weak field.

[retep]

Apr 27, 2011 15:40:20 GMT Chris M said:

The 1996 stock is a much newer train than the 50 year old A stocks on the Met, the latter also being bigger and heavier. Additionally, the A stocks have two settings, one for the City section of the line which prioritises acceleration over top speed, maximising the performance for shortly spaced stations where there isn't time or need to reach top speed but fast accelleration is important. North of Baker Street this system is switched to the other mode whereby the train has a faster top speed but at the expense of slower acceleration, which is the optimal configuration for fewer stations with longer distances between where acceleration is less important than going as quickly as possible over the long inter-station gaps. The Jubilee Line trains only have the first mode, as that is all that line requires.

No wonder even new National Rail type of trains like Electrostars seem to accelerate slower than LU type trains. Although I know some National Rail trains could accelerate fast.

[A60stock]

my the A stock can really accelerate in the city sections! makes you wish they did the same through the entire line!

[metman]

That's the flag down for you.....

You'd have loved the East London Line,

[superteacher]

The Desiro Class 360's accelerate pretty quickly.

[retep]

Apr 27, 2011 21:39:30 GMT superteacher said:

The Desiro Class 360's accelerate pretty quickly.

Class 350 Desiro accelarate kind of fast as well, i see them at Harrow & Wealdstone

[A60stock]

weird isnt it that out of all stock possible for the east london line they chose the a stock, with such nice seating for such a short line!

[Deleted]

Main line trains are geared for higher speeds than those on the tube. 75 mph is the lowest for a main line EMU whereas 62 mph is the maximum on the tube. At the moment a class 378 will leave an S8 standing (30 mph in 20 seconds) - I timed an S8 needing more than 30 seconds to reach the same speed.

Also it's probably unfair to compare the acceleration of tube stock which is lighter than surface stock

[metman]

The East London Line has always had second hand stock. Basically, it used trains from a fleet that had some spare capacity. Originally, it was Ex-Met railway saloon stock, then District handworked door stock. After the war it used F stock from the Uxbridge Line, then it had periods of both CO/CP and Q stock. Before the A stock took over, it even used 1938 tube stock, which illustrates the point well.

The reason is, as it is a short line only about 6 trains were needed to run the service. D stock was used whilst the A stock was being conveted to OPO.

[tubeprune]

Apr 27, 2011 19:44:16 GMT @retep said:

I have an interest in tube stock but don't really know about the technical stuff. What is a weak field.

Try the thread here:
districtdave.proboards.com/index.cgi?board=Trains&action=display&thread=7592

[retep]

Apr 28, 2011 7:13:33 GMT @notatraindriver said:

Main line trains are geared for higher speeds than those on the tube. 75 mph is the lowest for a main line EMU whereas 62 mph is the maximum on the tube. At the moment a class 378 will leave an S8 standing (30 mph in 20 seconds) - I timed an S8 needing more than 30 seconds to reach the same speed.

Also it's probably unfair to compare the acceleration of tube stock which is lighter than surface stock

But then the S8 probably don't accelerate as fast as they could as they have to share the line with the A stock and aren't using ATO yet. 2009 tube stock doesn't even travel as fast as its meant to i think and it has the same acceleration rate as the 1992 tube stock.

[plasmid]

Apr 29, 2011 0:18:09 GMT @retep said:

Apr 28, 2011 7:13:33 GMT @notatraindriver said:

Main line trains are geared for higher speeds than those on the tube. 75 mph is the lowest for a main line EMU whereas 62 mph is the maximum on the tube. At the moment a class 378 will leave an S8 standing (30 mph in 20 seconds) - I timed an S8 needing more than 30 seconds to reach the same speed.

Also it's probably unfair to compare the acceleration of tube stock which is lighter than surface stock

But then the S8 probably don't accelerate as fast as they could as they have to share the line with the A stock and aren't using ATO yet. 2009 tube stock doesn't even travel as fast as its meant to i think and it has the same acceleration rate as the 1992 tube stock.

09ts is faster as the AC motors are more powerful and they have shorter gearbox ratio's due to the lower top speed. They don't seem as fast at the moment because Regen is capped and so is line side voltage. When the 67ts have left these will be turned up and the 09ts should see a gain in acceleration.

Also does anyone actually know the top speed of a 96ts? No...okay then, I've heard people mention that Alstom have it capped to 75mph...not that the Jubilee probably uses over 60mph at present. Should this be true then 62mph isn't the highest speed on LUL.

[Deleted]

I thought all post 1992 stock trains with the exception of 2009ts had a design speed of 100 kph (62 mph)

en.m.wikipedia.org/wiki/London_Underground_1996_Stock

Also 1992 trains have every coach motored whereas 2009 stock dont.

I hope S stock will see an increase in performance before the new signalling is installed (which could take some time )

The thing to note is that the line voltage needs to be increased. Class 378s are notoriously sluggish on parts of the Euston to Watford route due to low line volts despite being a very powerful EMU.