Class 395 top speed

[williamn]

I know there has been some debate about this before. I understand that they are timetabled to run at 125mph, but have the ability to go at 140mph. This does make some sense as delays perhaps incurred on classic lines can perhaps be made up. But why were they not built for 186mph? Is it because the distances between say Ashford and Ebbsfleet mean that this speed could never be attained?

 

[466.networkers]

The top speed when in service on HS1 is 140mph.

 

[paul1609]

No youd easily get to 186 mph but that would mean higher gearing.
higher gearing means slower acceleration. if you have a lot of stops the slower acceleration means a longer journey time. Where power is limited the acceleration is even slower ( a 375 can see a 395 off on dc acceleration).

 

[starrymarkb]

I think it was worked out that allowing for station stops, 186mph would only save ~2 mins. Then there is the gearing, they have to accelerate from stops, which means lower gearing, but still be fast enough to keep out of a Eurostar's way hence 140mph.

Also remember that HS1 west of Ebbsfleet is limited to 140mph because of single bore tunnels. To build the bore wider would have increased the cost massively and saved all of 3 mins because of acceleration and braking for St Pancras

 

[Aictos]

The top speed when in service on HS1 is 140mph.

Which compared to 125mph running doesn't seem that much faster, although it obviously is.

 

[466.networkers]

Erm, yeah. It's an extra 15 miles in every hour of travel. :P

 

[The Planner]

Its a whole 3 seconds a mile between 125 and 140 (28 vs 25), so you need 20 miles of solid running to get yourself a minute. Once you get above that the differences are really worthless unless you are going long distance non stop.

 

[Waddon]

I may be remebering this wrongly, but I think I heard that trains travelling at 186 mph have been specified to have an entire locomotive length of non-passenger accomodation at each end for safety reasons, whereas the slower Southeastern services can have passenger seating in the front and rear car of each unit. Please advise me if I'm talking total B****cks

 

[jopsuk]

Sounds like you're confused with the (since dispensed with) BR restriction on fast push-pull trains (ie why the "225" has a DVT), which I may be wrong but I think may have been something of a knee-jerk in the wake of the Polmont crash that had implications on design for years in this country. Certainly not a restriction recognised internationally- look at every Japanese Shinkansen design, or the Siemens ICE3/Velaro. The Eurostar design is the way it is as it was based on the existing TGVs, which hadn't changed in basic layout since the original- the next generation "AGV" has passenger accomodation in the driving cabs.

 

[DaveNewcastle]

You are quite correct Waddon and jobsuk. It was the investigation into the 1984 Polmont disaster (train hits cow!) which led to the recommendation that no pasengers would be conveyed in an unpowered leading vehicle. The Politicians immediately pledged that they would make the railways safer (so you're right about the knee-jerk response).
The Report was much more careful in its analysis, and recommended fences to keep cattle off lines (very sensible but doesn't hit the headlines), and hinted (but didn't specify) that the restriction on conveying pax in leading vehicles might only be applied over 100mph.
Here's the full report : Pomont incident 1984
(Anyone else think that's inconsistent with putting the driver's desk and TM's office in there even tho there's no pax?)

 

[GNERman]

No youd easily get to 186 mph but that would mean higher gearing.
higher gearing means slower acceleration. if you have a lot of stops the slower acceleration means a longer journey time. Where power is limited the acceleration is even slower ( a 375 can see a 395 off on dc acceleration).

You'd also then have the problem of crash worthiness. The 395's weren't built for 186mph workings and so they won't be strong enough if they a at that speed. The Eurostar's are fine because they were built for that speed...

 

[Aictos]

I may be remebering this wrongly, but I think I heard that trains travelling at 186 mph have been specified to have an entire locomotive length of non-passenger accomodation at each end for safety reasons, whereas the slower Southeastern services can have passenger seating in the front and rear car of each unit. Please advise me if I'm talking total B****cks

I always thought it was 110mph which is why you get 90s and DVTs on the Great Eastern and more recently on the West Coast Main Line not forgetting the HSTs and the 91s and DVTs on the East Coast Main Line.

 

[ukrob]

I always thought it was 110mph which is why you get 90s and DVTs on the Great Eastern and more recently on the West Coast Main Line not forgetting the HSTs and the 91s and DVTs on the East Coast Main Line.

Pendolinos have passengers in the end carriages at 125mph (designed for 140mph). There is a crumple zone which is around the first third of each end.

 

[poshbakerloo]

They could run 390s on HS1 couldn't they?

 

[MCR247]

They could run 390s on HS1 couldn't they?

Only at 125mph though

 

[ukrob]

They could run 390s on HS1 couldn't they?

In theory you could run most stock almost anywhere, there is no reason why in theory Mallard could not be restored and run on it.

There is no trackside tilting equipment on HS1 though.

I'm not sure if your question is trying to get to a specific point?

 

[jopsuk]

The primary restriction on what can run on HS1 is the signalling system- remember, the 390s (and other high speed trains) are limited to 125mph thanks to the assessment of the safe operation limits of track side signalling. HS1 uses French designed in cab signalling (that DB will have to fit to any ICE units that they want to run through) that's fitted to the 373s and 395s.

There'd be little point in fitting 390s with the TVM equipment- where would they run on HS1? Ashford shuttles? The tilting kit would be completely wasted as well- HS1 is designed to be comfortable at speeds well in excess of 140mph without needing tilt, and I'd imagine that the gearing of the 390s won't allow them to go much more than 140mph (their maximum design speed), let alone the, what, 400mph that would make tilting worthwhile on the long banked corners?

 

[asylumxl]

I'd imagine that the gearing of the 390s won't allow them to go much more than 140mph (their maximum design speed)

I may have imagined it, but I swear in the UK a trains operating speed (140mph intended for 390s) is determined by subtracting 10% from their maximum speed.

I may well have imagined reading it.

 

[jon0844]

I'd hope there's SOME leeway.

 

[ukrob]

I may have imagined it, but I swear in the UK a trains operating speed (140mph intended for 390s) is determined by subtracting 10% from their maximum speed.

I may well have imagined reading it.

Not really how it is 'determined' as they have design speeds, but yes, all stock can do (when new!) at least 10% over its stated maximum speed.

 

[LWB]

So an outshopped 08 could do ........ 16.5 mph!

 

[Chafford1]

Not really how it is 'determined' as they have design speeds, but yes, all stock can do (when new!) at least 10% over its stated maximum speed.

All new stock is required to be tested at a 10% 'overspeed' - I believe the 395s were tested at 156.5mph (252km/h).
--- old post above --- --- new post below ---

In theory you could run most stock almost anywhere, there is no reason why in theory Mallard could not be restored and run on it.

Mallard would struggle with the gradients on HS1!

 

[starrymarkb]

HS1 uses French designed in cab signalling (that DB will have to fit to any ICE units that they want to run through) that's fitted to the 373s and 395s.

The BR406 ICE3M units already have it