Jump to content
 

Going for the Record?


Recommended Posts

15 hours ago, Patriot87003 said:


Very interesting reviewing the APT record run log and comparing with the recent Pendolino attempt. While both runs appear to have had a maximum speed of 125mile/h, there’s quite a few subtle differences that explain the differences in timings, why the recent Pendolino attempt didn’t beat the record and also explains your correct observation why the APT won Preston to Glasgow by a good margin. I worked within West Coast Route Mod and developed and optimised one of the iterations of the line speed profiles for EPS and journey time analysis.

 

One of the key differences appears to be a difference in the rules/standards for tilting trains around curves with Switches & Crossings (S&C ... aka points!); While current tilting trains are allowed to take advantage of increased cant deficiency limits along ‘plain-line’ (up to 300mm CD for Class 390 Pendolino and 265mm CD for Class 221 Super-Voyager), they are restricted to ‘conventional’/permissible cant deficiency limits through S&C.

 

It appears this wasn’t the case for the line speed profile used by the APT .... in other words, the APT could ‘whizz’ around curves of plain line and those that S&C situated along them ....  but the Pendolino can only ‘whizz’ around curves of plain-line ... but unfortunately not if there’s any S&C along them. There’s a few technical reasons that justify this rule ... around track forces, reliability, increased factor of safety etc.

 

A really good example to see the effect of this rule is through Penrith station: The Up Line is a plain-line curve with no S&C along it. Therefore the max permissible speed is 80 over 90/95. This means non-tilt trains have a permissible speed 80, Class 221’s are allowed 90, while Class 390’s are allowed 95mile/h.

 

The Down line is different: The Down Loop joins the Down Line along the curve at the high mileage end of the platform, thus the Down Line has a max permissible speed restricted to 75mile/h for all trains.

 

There are a significant number of junctions/S&C situated on curves along the WCML, especially north of Warrington ... such as Warrington itself, Dallam, Winwick Jn, Golbourne Jn, Wigan, Lancaster, Oxenholme, Low Gill, Shap, Quintinshill, Beattock Summit, Abington loops etc. Each of these likely to have a lower EPS speed for the Pendolino when compared to the APT. As a consequence, WCRM took the decision to not have any ‘EPS’ between Warrington BQ and Wigan NW stations ... while due to a combination of the infrastructure, pathing and timetabling, no EPS currently exists between Carstairs and Glasgow C (although there is an oddity around Shieldmuir due to a HST differential speed board!). Therefore both of these route sections are ‘tilt for comfort’ sections while the max permissible speeds for tilting trains are the same as conventional trains. Again, the APT run shows significant gains through these two sections.

 

Conversely, since the APT run, the Pendolino took advantage of a few gains from major remodelling schemes ... including a better departure from the remodelled Euston, the remodelled Rugby station, Trent Valley 4-tracking section, the new layout at Norton Bridge and the remodelled Crewe (from the 1985 scheme!). However, the Trent Valley 4-tracking now prioritises the Manchester Route ... therefore the Glasgow route now requires a slowing to 65mile/h to crossover at Colwich Jn to access the route to Stafford.

 

There’s a few other subtle differences through some of the tunnels (aerodynamics/pressure pulses) and it appears the APT was allowed a higher max cant deficiency ... and probably a larger margin of tolerance regarding acceptable over speed (in the pre-digital age before average speed cameras etc!) ... while the Pendolino run appears to be a superb effort in concentration by the driver not to upset the ‘TASS (Tilt Authorisation and Speed Supervision)’ system ... as if the driver oversped and ignores the initial warning, the brakes are applied! So less margin for the driver to cruise at a few mile/h above the line speed profile.

 

In summary ... both runs are very impressive in my opinion for different reasons - well done to all involved! One thing pretty certain .... both of these records likely to be smashed once HS2 is built ... but the Warrington/Preston to Glasgow APT record likely to stand for many years to come.

 

 

 

 

It would be interesting to see a full speed profile for the APT. I saw a photograph on Flickr recently of Carstairs station in about 1981/2 I think with an APT speed board - "APT 115".

 

If the APT also had the benefit of APT differentials where today there are no EPS speeds, that will also undoubtedly have worked in the APT's favour.

  • Like 1
Link to post
Share on other sites

5 hours ago, Compound2632 said:

 

And a generous six-foot between the pairs of lines, for much of the way.

 

Not as much as you would think - most of the quadrupling was done after broad gauge was abolished, so much of the extra space was used for that.

  • Agree 1
  • Informative/Useful 1
Link to post
Share on other sites

On 25/06/2021 at 17:13, Titan said:

 

Not as much as you would think - most of the quadrupling was done after broad gauge was abolished, so much of the extra space was used for that.

 

The Up Relief between Cholsey and the site of the old Moulsford station is on the original alignment of the Wallingford bracnh, which was shortened when the station was relocated.

  • Informative/Useful 1
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...