Tube trains speed

[The0]

I wonder if they built a new tube extension eg. Croxley rail link would it be built with cbtc or would it be upgraded later. (this would be assuming that all trains on the line could use cbtc)

 

[Railperf]

And the tripcock system where that is in use as already mentioned.

== Doublepost prevention - post automatically merged: 26 Jul 2023 ==



Not in tripcock-fitted areas they couldn't.

== Doublepost prevention - post automatically merged: 26 Jul 2023 ==



No.

I would imagine signalling overlaps etc and tripcocks on the original met line 70mph sections are still exactly the same? Wasn't it the fragile A stock bogies that caused a reduction to 50mph for the class? When were the 70mph sections of track reduced to 60mph? The only section of 70mph section of LU metals seems to be the non electrified section between Amersham and NR boundary at Mantles Wood now.

 

[12LDA28C]

I would imagine signalling overlaps etc and tripcocks on the original met line 70mph sections are still exactly the same? Wasn't it the fragile A stock bogies that caused a reduction to 50mph for the class? When were the 70mph sections of track reduced to 60mph? The only section of 70mph section of LU metals seems to be the non electrified section between Amersham and NR boundary at Mantles Wood now.

I believe the 70mph sections were reduced to 60mph over 30 years ago, around the same time when Class 165 'turbos' replaced the first generation DMUs on the Chiltern route. The section between Amersham and the LU/NR boundary at Pipers Wood (not Mantles Wood) is the subject of much discussion as a 70 board is in place however the provision of a tripcock-fitted signal JW70 just south of Pipers Wood should theoretically limit line speed to 60 and some Chiltern drivers adhere to the lower speed.

 

[Daniel]

The tripcock only claims to stop a train within the overlap after a SPaD at speeds up to 60mph.

Well, no...

When calculating signalling overlaps, as has been drummed into the minds of anyone attending a Rules & Procedures course on London Underground, they consider the speed of the fastest train, with the weakest brakes (within tolerance)...

So whilst you can't just change the speed limit to a higher amount by replacing the boards trackside, there would be no reason for overlaps to restrict a line speed as where the speed was planned to have been increased, so would the size of the signalling overlaps prior to the change.

If your argument were that tripcocks of today are not designed to be whacked with a rigid bit of metal at more than 60mph, I'd hear you (and be interested to know what changed from before when we had 70mph running), but the overlaps argument doesn't make sense.

 

[12LDA28C]

Well, no...

When calculating signalling overlaps, as has been drummed into the minds of anyone attending a Rules & Procedures course on London Underground, they consider the speed of the fastest train, with the weakest brakes (within tolerance)...

So whilst you can't just change the speed limit to a higher amount by replacing the boards trackside, there would be no reason for overlaps to restrict a line speed as where the speed was planned to have been increased, so would the size of the signalling overlaps prior to the change.

If your argument were that tripcocks of today are not designed to be whacked with a rigid bit of metal at more than 60mph, I'd hear you (and be interested to know what changed from before when we had 70mph running), but the overlaps argument doesn't make sense.

Clearly if line speed was increased then the length of overlaps would be increased in association, although in some situations it would not be possible to extend the overlap due to infrastructure constraints. I would suggest that some kind of SOL incident such as a SPaD was the reason for line speed being reduced from 70mph to 60mph, maybe where a train passed the signal at danger and entered the next signal section, or something similar.

 

[Railperf]

Didn't a set of A stock touch 74mph 'unofficially' on one of the (then) 70 sections on the Met during its farewell trip?

Any advance on 74mph for LU stock...?

77mph is the fastest i have seen on any RPS log - but i haven't analysed every one. Still i have heard claims that faster speeds have been achieved ..

 

[hexagon789]

77mph is the fastest i have seen on any RPS log - but i haven't analysed every one. Still i have heard claims that faster speeds have been achieved ..

I had a vague idea I'd read of 76 somewhere, possibly on District Dave's site.

I understood the balancing speed for A stock on half-worn wheels was supposed to be 72mph - so on full-size wheels and maybe with a bit of gradient assistance - 75mph plus doesn't seem far fetched.

Did they ever manage 80 though... that's a bigger question...

 

[Railperf]

I had a vague idea I'd read of 76 somewhere, possibly on District Dave's site.

I understood the balancing speed for A stock on half-worn wheels was supposed to be 72mph - so on full-size wheels and maybe with a bit of gradient assistance - 75mph plus doesn't seem far fetched.

Did they ever manage 80 though... that's a bigger question...

According to the log and report, 70 to 72mph could be achieved by Chorleywood from Amersham at which point power was cut and the remaining speed was gained by coasting downhill. Keeping power on would act like an electronic brake. It is not know whether 80mph could be achieved by cutting power earlier!

 

[hexagon789]

According to the log and report, 70 to 72mph could be achieved by Chorleywood from Amersham at which point power was cut and the remaining speed was gained by coasting downhill. Keeping power on would act like an electronic brake. It is not know whether 80mph could be achieved by cutting power earlier!

Why does keeping power on 'act like an electronic brake', I wasn't aware that was an effect of back EMF? Just the balancing speed in general.

 

[leytongabriel]

I believe the 70mph sections were reduced to 60mph over 30 years ago, around the same time when Class 165 'turbos' replaced the first generation DMUs on the Chiltern route. The section between Amersham and the LU/NR boundary at Pipers Wood (not Mantles Wood) is the subject of much discussion as a 70 board is in place however the provision of a tripcock-fitted signal JW70 just south of Pipers Wood should theoretically limit line speed to 60 and some Chiltern drivers adhere t

Wasn't there also a story that max speed had to be reduced because the stock was getting increasingly bouncy?

 

[341o2]

I have heard from a former LT staff member regarding claims of high speed running between Mile End and Stratford on the Central line, back in the 70's but can't remember a figure being given

 

[bramling]

I have heard from a former LT staff member regarding claims of high speed running between Mile End and Stratford on the Central line, back in the 70's but can't remember a figure being given

I’d imagine 50 mph, which ironically is faster than the 92 stock achieves in this section today, though doubtless the 92 stock would be able to do more if allowed. Leytonstone to Wanstead was also a fast section in 62 stock days, and of course Epping to Theydon Bois.

 

[341o2]

I recall that the Island Line had a 50mph limit from electrification to when a 40mph limit was introduced during the latter days of the 483s. In the days before Smallbrook was opened, things could get quite lively between St Johns and Brading.
I also recall seeing some of the 1927 stock en route for the Island on the main line. I wonder what speed limit applied.

 

[hexagon789]

I recall that the Island Line had a 50mph limit from electrification to when a 40mph limit was introduced during the latter days of the 483s. In the days before Smallbrook was opened, things could get quite lively between St Johns and Brading.
I also recall seeing some of the 1927 stock en route for the Island on the main line. I wonder what speed limit applied.

The limit was in 483 days, and remains today, 45mph.

An SR Sectional Appendix shows a line limit of 40mph in 1960.