Why did the class 91s need a flat cab for freight operations?

[Nottingham59]

Not so much a flat cab, but simply a cab both ends, which had been policy for electric locos for decades.

When the decision was made in mid 1980s to electrify ECML, there was assumption that part of the operations would be similar to West Coast with the locos working some freight/parcels/sleeper overnight. A better question might be why did the thinking change around 1990 before they went into service.

My understanding is that the 91s were always intended to run freights at night, which would require a second cab.

Why that didn't happen was, I think, all to do with the Health and Safety at Work Acts in the 1970s and 80s. It became progressively less acceptable to have night-time freights with overnight maintenance crews working right next to a live railway.

The WCML has more four track than the ECML, so overnight freights tended to be routed on that side of the country, where the lines could be closed in a safer manner, with two live tracks and the maintenance only on the other pair.

 

[43096]

My understanding is that the 91s were always intended to run freights at night, which would require a second cab.

Why that didn't happen was, I think, all to do with the Health and Safety at Work Acts in the 1970s and 80s. It became progressively less acceptable to have night-time freights with overnight maintenance crews working right next to a live railway.

The WCML has more four track than the ECML, so overnight freights tended to be routed on that side of the country, where the lines could be closed in a safer manner, with two live tracks and the maintenance only on the other pair.

Or, more likely, that it was down to BR's business sectorisation - the 91s were assigned to InterCity, so they wouldn't be working freight or mail traffic except in extremis.

 

[D6700]

Yes, I remember that. If I recall correctly it usually used what is now platform 10 at York. I think that came a little bit later, once electrification to York was completed. I guess it made sense to dispense with the need to use a Class 47.

There’s a picture here showing a Class 91 with Mk2 stock working 1450 York London King’s Cross, dated 13.01.1991

91023 Colton 130191 img1102-0491mb-a

13th January 1991 91023 heads away from Colton Junction blunt end first with 14:50 York - Kings Cross. When the Class 91 was specified it was expected that they would see regular use blunt end first on slower nighttime traffic where the increased aerodynamic resistance is not as critical. Some...

flic.kr

That photo is an excellent find - and thanks for confirming my memory was reasonably accurate!

 

[Davester50]

If you didn't have a flat end you would have a class 89......

Well, no. You wouldn't. It might have sloped ends like an 89, but completely different.

 

[DarloRich]

Well, no. You wouldn't. It might have sloped ends like an 89, but completely different.

i wasnt being serious!

 

[GRALISTAIR]

In the Equinox documentary "Running to Time", it says they were intending to run sleeper services with them. I don't recall freight being suggested.

 

[Davester50]

i wasnt being serious!

ok.

In the Equinox documentary "Running to Time", it says they were intending to run sleeper services with them. I don't recall freight being suggested.

Interesting. Years since I watched that programme. Thought it was intended for Sleepers and Parcels, but obviously things changed very quickly.

 

[craigybagel]

Something that may or may not be relevant and/or interesting to this thread, is that the MKIV sets that TfW use with 67s are officially now limited to 110mph.

It's somewhat moot as there's nowhere on their network they can run faster anyway, but despite the fact the 67s are still signed inside the cabs for 125mph, and the fact that the coaches spent most of their careers running at that speed, they went to the effort of putting new 110mph max signs inside the DVTs.

I'm not sure if this is because of not having a slab end cab next to the coaches, or the brake controls being different, or using the shackle coupling rather than the buckeye, or some combination of the three, but I suspect there's similarities in the logic as to why 91s were also limited to that speed when running blunt end first!

 

[Doomotron]

Something that may or may not be relevant and/or interesting to this thread, is that the MKIV sets that TfW use with 67s are officially now limited to 110mph.

It's somewhat moot as there's nowhere on their network they can run faster anyway, but despite the fact the 67s are still signed inside the cabs for 125mph, and the fact that the coaches spent most of their careers running at that speed, they went to the effort of putting new 110mph max signs inside the DVTs.

I'm not sure if this is because of not having a slab end cab next to the coaches, or the brake controls being different, or using the shackle coupling rather than the buckeye, or some combination of the three, but I suspect there's similarities in the logic as to why 91s were also limited to that speed when running blunt end first!

Could it have something to do with limitations of the AAR system?

 

[Wilts Wanderer]

Something that may or may not be relevant and/or interesting to this thread, is that the MKIV sets that TfW use with 67s are officially now limited to 110mph.

It's somewhat moot as there's nowhere on their network they can run faster anyway, but despite the fact the 67s are still signed inside the cabs for 125mph, and the fact that the coaches spent most of their careers running at that speed, they went to the effort of putting new 110mph max signs inside the DVTs.

I'm not sure if this is because of not having a slab end cab next to the coaches, or the brake controls being different, or using the shackle coupling rather than the buckeye, or some combination of the three, but I suspect there's similarities in the logic as to why 91s were also limited to that speed when running blunt end first!

Is it possibly due to the shorter length of the rakes in use with TFW? I know HSTs with less than 5 trailers were limited to 100mph (or was it 110mph) and presumably a similar restriction applies to MkIV stock?

 

[Nottingham59]

why 91s were also limited to that speed when running blunt end first!

My understanding is that was due to aerodynamic effects. 110mph is effectively the maximum speed you can run trains with end corridor connections. At 125mph or above, you need a pointy nose

 

[Spartacus]

Something that may or may not be relevant and/or interesting to this thread, is that the MKIV sets that TfW use with 67s are officially now limited to 110mph.

It's somewhat moot as there's nowhere on their network they can run faster anyway, but despite the fact the 67s are still signed inside the cabs for 125mph, and the fact that the coaches spent most of their careers running at that speed, they went to the effort of putting new 110mph max signs inside the DVTs.

I'm not sure if this is because of not having a slab end cab next to the coaches, or the brake controls being different, or using the shackle coupling rather than the buckeye, or some combination of the three, but I suspect there's similarities in the logic as to why 91s were also limited to that speed when running blunt end first!

I understand it's down the the shackles being used.

 

[Western Lord]

My understanding is that the 91s were always intended to run freights at night, which would require a second cab.

A Class 91 would have been of little use for hauling freight. For freight the last thing you want is a lightweight locomotive geared for 140 mph running. They were intended to operate sleepers or parcels trains overnight.

 

[43096]

A Class 91 would have been of little use for hauling freight. For freight the last thing you want is a lightweight locomotive geared for 140 mph running. They were intended to operate sleepers or parcels trains overnight.

The Austrians seem to manage just fine with a Taurus hauling freight - top speed 230km/h.

 

[edwin_m]

The Austrians seem to manage just fine with a Taurus hauling freight - top speed 230km/h.

The 91 has DC motors, where you can design the gearing for either high speed or good traction at low speeds but not both. The Taurus and other more modern designs have AC motors, which are much more versatile.

 

[43096]

I know HSTs with less than 5 trailers were limited to 100mph (or was it 110mph)

Except there was no universal limit on that - some TOCs might have had it as their policy for whatever reason, but there is no technical reason to do so. Indeed EMT ran a 2+4 set at 125mph in passenger service.

 

[D365]

I understand it's down the the shackles being used.

Yes, there’s a situation with the couplings that is yet to be resolved.

 

[FOH]

Is that limit an absolute maximum speed when driven from that cab, or is it just because the loco is going to be at the same end as the DVT causing brake applications to propogate from one end of the train only and not both?

And the fable I was told way back when was it was to do with the suction effect on passing platforms being too dramatic

 

[The Foghorn]

As I understand it, the pantograph is very close to the blunt cab. Thus leading a train blunt end first creates a large aerodynamic disturbance that affects the pantograph's ability to maintain consistent contact with the overhead wire. This increases the risk of bringing the wires down. Hence they are limited to 110 when doing so. Regardless of the above, I have timed 91005 at 123mph leading a MK4 rake south. And in those days it was 110 max anyway as it was a Sunday and they weren't double crewed on a Sunday.