class 91 brake

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Alan1310

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hi does the class 91 have a stepped brake or is it lap/hold/apply/ i know thats prob not the way it is but any info would help cheers
 
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Alan1310

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thanks for the reply i have a old mate who worked at bounds green but thought i would get a quicker reply here cheers
 

shedman

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As far as I am aware they are still capable of higher speeds. The pass/good switch is still in situ and works. As with most locos they also have a straight air brake which just brakes the loco (3 steps, release, lap and apply).
 

E&W Lucas

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As far as I am aware they are still capable of higher speeds. The pass/good switch is still in situ and works. As with most locos they also have a straight air brake which just brakes the loco (3 steps, release, lap and apply).
That's for brake apply/ release timings, and nothing to do with speed!

Correct about the straight air though.

I believe that some have had their traction motor field diverts modified, which would affect matters.

They have always been limited to 125 in service anyway. HMRI not prepared to sanction running at higher speeds, without in-cab signaling.
 

captainbigun

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E&W Lucas are class 91s physically limited to 125 since the refurb?
They no longer have a safety case for running above 125, so physically no, but reality, yes.
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I believe that some have had their traction motor field diverts modified, which would affect matters.
No diverts as such, the motors are SEPEX, so the fields are controlled steplessly. I vaguely recall a conversation about the field weakening which doesn't start until quite high up the speed range, so aid 140mph running.
 

shedman

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I know what the pass/goods switch is for I drove them for 7 years, I was just pointing out its there and still works.
 

E&W Lucas

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They no longer have a safety case for running above 125, so physically no, but reality, yes.
--- old post above --- --- new post below ---


No diverts as such, the motors are SEPEX, so the fields are controlled steplessly. I vaguely recall a conversation about the field weakening which doesn't start until quite high up the speed range, so aid 140mph running.
Did they ever have a safety case for 125+? It's never been permitted in service, for the reason given above.

My mention of TM fields is also from a half recalled conversation with someone who would have known in detail, and some time ago. Something done with high end field weakening on some of them IIRC.
 

captainbigun

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My mention of TM fields is also from a half recalled conversation with someone who would have known in detail, and some time ago. Something done with high end field weakening on some of them IIRC.
I know a man who will know, I'll see if I can get the full story!
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Did they ever have a safety case for 125+? It's never been permitted in service, for the reason given above.
Yes, as built, they were trialled for 140mph running under flashing greens. GEC would have needed to provide proof that the vehicle was capable of operating under 140mph conditions. (Same for Met Camm with the Mk4s).
 

E&W Lucas

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I know a man who will know, I'll see if I can get the full story!
--- old post above --- --- new post below ---


Yes, as built, they were trialled for 140mph running under flashing greens. GEC would have needed to provide proof that the vehicle was capable of operating under 140mph conditions. (Same for Met Camm with the Mk4s).
I knew about the trials, but never in service. HMRI blocked it, despite the flashing greens being set up on Stoke Bank.

Be interested to hear what you come back with.
 

captainbigun

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The weakening hasn't been altered, it is still as built. The field weaking does start quite high up the speed range, but that is as a result of the gearing not the field weakening itself. Weakening the field earlier would result in any advantage, just less efficiency.
 

Failed Unit

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I knew about the trials, but never in service. HMRI blocked it, despite the flashing greens being set up on Stoke Bank.

Be interested to hear what you come back with.
The have done 140mph in service (but not timetable service) - I think to try and break speed records. The last one was with GNER, not sure on the speed achieved or the exact formation (it was shorterned). They even took all the glasses away from everyone just in case between Grantham and Peterborough.

Likewise I am not sure if their "special" between London and Edinburgh which was done in 3h30 also included 140mph running.

In both cases the lines were cleared of other trains.,
 
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