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Passenger access to APT-P Non-Driving Motor vehicles


NotAgain
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The APT-P's centrally located power cars had no gangways throughout them or passenger access to them, that much I already know. A shortened APT rake is going to be a centrepiece of the layout I'm working on, and it would be convenient to run it with only one buffet car, so I'd like to know the following:

 

Firstly, why did BR decide to build and run the Class 370s as, effectively, two separate trains, operating back-to-back?

 

And secondly, would it have been feasible to install a passenger gangway through the NDM to allow access from one side of the train to the other, not unlike the Stadler Class 755s that Greater Anglia operate?

 

Many thanks in advance.

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It was still experimental and they couldn't run a power line through the whole train with two power cars unless they were together.

 

The final version of the APT had it reached production would not have been split like that, however, jump forward 40 years and operators are quite happy to run two 4/5 car sets together each with their own facilities and no access between each set.

Edited by woodenhead
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I think the reason for forming the trains that way was to avoid the problems from two pantographs some distance apart travelling at speeds in excess of 100mph.  Unless the overhead is very 'stiff' - as it is on the GWML and HS1 and in France etc - the passing of the first pantograph at gigh speed creates a lot of movement in the contact wire which gradually gets wors and can cause it to move vertically through 6 inches or more.  By having the two pans close togetrher the excessive movement won't have built up too much by the time the second pantograph reaches the place on the wire the first pan had recently left.

 

Until the electrification of the WML the only really stiff ac overhead on BR/its successors was on the original section of WCML electrification on the Styal Loop.  But after that early electrification things were changed in order to reduce cost o n the WCML so the contact wire was far less resistant to vertical movement wjhiel the original headspan in teh ECML was even worse.

 

The ban on passengers passing through the power cars was for safety reasons because of the presence of high voltage electricity.

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5 minutes ago, NotAgain said:

Firstly, why did BR decide to build and run the Class 370s as, effectively, two separate trains, operating back-to-back?

At the time, they were not allowed to run traction power cables between passenger carriages nor were they allowed to have two raised pantographs on high speed trains, and as I recall, they did not fancy the idea of a power car pushing 12 trailers. Remember, APT-P pre-dated high-speed push-pulls on the WCML.

 

9 minutes ago, NotAgain said:

And secondly, would it have been feasible to install a passenger gangway through the NDM to allow access from one side of the train to the other, not unlike the Stadler Class 755s that Greater Anglia operate?

Almsot certainly not. It is the power connection between the two cars that would be the problem.

 

What I cannot remember, though, is why the need for two power cars, unless it was just a way of being able to have independent half-sets that could move under their own power.

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4 minutes ago, woodenhead said:

It was still experimental and they couldn't run a power line through the whole train with two power cars unless they were together.

 

The final version of the APT had it reached production would not have been split like that, however, jump forward 40 years and operators are quite happy to run two 4/5 car sets together each with their own facilities and no access between each set.

It was also prohibited in the UK until the 21st century to run 25kv train power lines along the roofs of vehicles containing passengers.

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I believe the power cars did have gangways, but locked out of use under normal circumstances. I guess under exceptional circumstances, for example if there was a fire in one half rake, then once stopped, & pan down, passengers could be transferred to the other half rake.

Apart from the electrical equipment, there were also 4 cardan shafts rotating at high speed. Although enclosed, I'd imagine a failure of the bolts would not be pretty if someone happened to be passing by!

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4 minutes ago, Jeremy C said:

 

What I cannot remember, though, is why the need for two power cars, unless it was just a way of being able to have independent half-sets that could move under their own power.

Two were required to provide enough power for a full 14-car train with 150mph top speed and generally higher-speed running compared to loco-hauled.

Each power car was only 4000hp i.e. less than a cl.87 - shorter APT formations often used only one power car, up to about 11 trailers worth, especially once it was decided to settle for 125mph max

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Thank you everyone for the information! I suppose the only question left is would it be worthwhile modifying one of Hornby's new 370s to have a single Driving Motor at one end and and a DVT at the other, like this image from https://www.apt-p.com/APTConfigurations.htm

 

Or even to do something like the APT-Q arrangement from the same source:

APT-S formations.PNG

APT-Q Formation.PNG

 

Or whether I ought to just stick with what comes out of the box. I've never modified a model like that, and I'm quite fearful of messing it up on something that expensive.

Edited by NotAgain
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23 minutes ago, Peter Kazmierczak said:

I have walked through one of these, but it's getting on for 40 years ago so the memory might be hazy. Don't think there was all that much protection from all the gubbins, so no way would the public have been allowed through.

 

I think one of the issues was exposing the public to a lot of electromagnetic radiation which amongst other things can cause issue with pacemakers 

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10 minutes ago, russ p said:

 

I think one of the issues was exposing the public to a lot of electromagnetic radiation which amongst other things can cause issue with pacemakers 

Hence the warnings on class 91 internal doors about pacemakers etc. There are some quite strong fields inside the 91s, which could do all sorts of odd things, still have a few magnetised tools caused by this............

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33 minutes ago, russ p said:

 

I think one of the issues was exposing the public to a lot of electromagnetic radiation which amongst other things can cause issue with pacemakers 

Somewhere in my dad's cine collection there is some footage of a coin standing upright on the floor of a moving class 317 power car, being sustained upright by the powerful magnetic field from the smoothing choke.

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14 hours ago, keefer said:

Two were required to provide enough power for a full 14-car train with 150mph top speed and generally higher-speed running compared to loco-hauled.

Each power car was only 4000hp i.e. less than a cl.87 - shorter APT formations often used only one power car, up to about 11 trailers worth, especially once it was decided to settle for 125mph max

To be pedantic - 155mph which the C-APT speed advisory system was implemented up to (later downgraded to a 125 ceiling in service). The continuous installed power was to be enough to maintain the 155 design speed plus 5%, and the record achieved is pretty much spot on a 5% overspeed, the limited overspeed balancing speed was for efficiency reasons, rather than installing even more power but for it was felt limited benefit other than faster acceleration.

 

Also 4,000hp is the only the continuous rating, the power handle had a "boost" notch which enabled the maximum rating (red zone on old AC loco ammeters) to be used for 20 seconds and acceleration under boost was impressive to say the least. 

 

13 hours ago, russ p said:

 

I think one of the issues was exposing the public to a lot of electromagnetic radiation which amongst other things can cause issue with pacemakers 

The working instructions mention no restriction on passengers using the power car gangways, except "persons with pacemakers should be advised against moving through the power cars".

 

Though given the original intention was for fully duplicated facilities in each half-set, there was arguably no need for passengers to walk between sets in normal service anyway.

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On 04/10/2021 at 19:25, russ p said:

 

I think one of the issues was exposing the public to a lot of electromagnetic radiation which amongst other things can cause issue with pacemakers 

 

When training on the 91s we were warned not to go inside when they were running with our wallets in our pockets

The magnetic strip on our bank cards would be wiped when we came out

Don't think that would have gone down too well with the passengers when they got through to the APTs buffet

 

As previously noted, the APT power cars were next to each other so that a 25kv connection could be coupled between them due to problems with two pantographs in use at high speed.

Things have advanced with high speed pantograph design, and OHL  since the APT and speeds limited to 125, but even so, with the 80x when running in 2x5 car formation, both the outer pans must be used for 125 running. One of the inner pans being used limits them to 100, and if both inner pans are used 80

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2 hours ago, Ken.W said:

 

When training on the 91s we were warned not to go inside when they were running with our wallets in our pockets

The magnetic strip on our bank cards would be wiped when we came out

Don't think that would have gone down too well with the passengers when they got through to the APTs buffet

 

As previously noted, the APT power cars were next to each other so that a 25kv connection could be coupled between them due to problems with two pantographs in use at high speed.

Things have advanced with high speed pantograph design, and OHL  since the APT and speeds limited to 125, but even so, with the 80x when running in 2x5 car formation, both the outer pans must be used for 125 running. One of the inner pans being used limits them to 100, and if both inner pans are used 80

My card was wiped going through an HST engine room - must have been a special property the ECML ones had so no wonder the Class 91s could do it too ;)

 

Incidentally class 373 Eurostar power cars could upset a pacemaker the if the person fited with one stood near one that was powering up.

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On 04/10/2021 at 18:24, rodent279 said:

I believe the power cars did have gangways, but locked out of use under normal circumstances. I guess under exceptional circumstances, for example if there was a fire in one half rake, then once stopped, & pan down, passengers could be transferred to the other half rake.

Apart from the electrical equipment, there were also 4 cardan shafts rotating at high speed. Although enclosed, I'd imagine a failure of the bolts would not be pretty if someone happened to be passing by!

Yes, they did have gangways - I remember walking through one when they had an APT-P set at the RTC in Derby at a rare open day back around 1980-ish and you could walk the full length of the train from cab to cab.

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