47/7 push pulls

[hexagon789]

In general the Mk2 sets were isolated to the Glasgow/Edinburgh-Aberdeen services an the Mk3 sets to the Edinburgh-Glasgow shuttles, with a couple of Glasgow-Aberdeen returns operated by the Mk3 sets. I have yet to see photographic evidence of a Mk2 rake operating the Edinburgh-Glasgow shuttles (post-1979 that is), the closest to an exception to this was a 1989 Glasgow QS-Edinburgh formed of a standard Mk3 set with one Mk3a TSO replaced by a Mk2d TSO. Not sure if its been mentioned but the Edinburgh-Glasgow formations were:
1979-1985: Class 47/7 (at the Edinburgh end)-4 Mk3a TSOs-Mk3a FO-Mk2f DBSO
1985-1990: Class 47/7 (at the Edinburgh end usually)-3 Mk3a TSOs-Mk3a CO-Mk2f DBSO

The standard Mon-Sat frequency was half-hourly with the XX:00 from Glasgow calling at Falkirk High (XX:20), Haymarket (XX:45 set-down only) and Edinburgh (XX:49), the XX:30s from Glasgow called at Haymarket (XX:13 set-down only) and Edinburgh (XX:17). From Edinburgh the XX:00 called at Haymarket (XX:04) and Glasgow QS (XX:47) and the XX:30 departures called at Haymarket (XX:34), Falkirk High (XX:55) and Glasgow QS (XX:19). Lenzie, Polmont and Linlithgow were served by a few peak services on the via Falkirk High route only, otherwise being served by the hourly all stops Glasgow-Falkirk Grahamston-Edinburgh DMU service. On Sundays the Edinburgh to Glasgow service was reduced to hourly for much of the day with services running via Falkirk Grahamston and calling at Falkirk Grahamston, Linlithgow and Haymarket.

I'm afraid that while my printer does have a scan function, I've yet to figure out how to use it! So I'll just type the diagrams up here for you. I should add that these are for 1986 just before the Mk2 sets started swapping destinations on arrival at Aberdeen and so won't match the Mk2 set diagrams I listed above.

47.701: 0610 Edinburgh-Glasgow QS
0730 Glasgow QS-Edinburgh
0830 Edinburgh-Glasgow QS
0930 Glasgow QS-Edinburgh
1030 Edinburgh-Glasgow QS
1130 Glasgow QS-Edinburgh
1230 Edinburgh-Glasgow QS
1330 Glasgow QS-Edinburgh
1430 Edinburgh-Glasgow QS
1530 Glasgow QS-Edinburgh
1630 Edinburgh-Glasgow QS
1730 Glasgow QS-Edinburgh
1830 Edinburgh-Glasgow QS
1930 Glasgow QS-Edinburgh
2030 Edinburgh-Glasgow QS
2130 Glasgow QS-Edinburgh
2230 Edinburgh-Glasgow QS
47.702: 0620 Glasgow QS-Edinburgh
0730 Edinburgh-Glasgow QS
0830 Glasgow QS-Edinburgh
0930 Edinburgh-Glasgow QS
1030 Glasgow QS-Edinburgh
1130 Edinburgh-Glasgow QS
1230 Glasgow QS-Edinburgh
1330 Edinburgh-Glasgow QS
1500 Glasgow QS-Edinburgh
1600 Edinburgh-Glasgow QS
1700 Glasgow QS-Edinburgh
1800 Edinburgh-Glasgow QS
1900 Glasgow QS-Edinburgh
2000 Edinburgh-Glasgow QS
2100 Glasgow QS-Edinburgh
47.703: 0708 SX Dunblane-Edinburgh
0900 Edinburgh-Glasgow QS
1000 Glasgow QS-Edinburgh
1100 Edinburgh-Glasgow QS
1200 Glasgow QS-Edinburgh
1300 Edinburgh-Glasgow QS
1400 Glasgow QS-Edinburgh
1500 Edinburgh-Glasgow QS
1600 Glasgow QS-Edinburgh
1700 Edinburgh-Glasgow QS
1800 Glasgow QS-Edinburgh
1900 Edinburgh-Glasgow QS
2000 Glasgow QS-Edinburgh
2100 Edinburgh-Glasgow QS
2200 Glasgow QS-Edinburgh
2300 Edinburgh-Glasgow QS
47.704: 0700 Glasgow QS-Edinburgh
0800 Edinburgh-Glasgow QS
0900 Glasgow QS-Edinburgh
1000 Edinburgh-Glasgow QS
1100 Glasgow QS-Edinburgh
1200 Edinburgh-Glasgow QS
1300 Glasgow QS-Edinburgh
1400 Edinburgh-Glasgow QS
1525 Glasgow QS-Dyce
1845 Dyce-Glasgow QS
47.705: 0348 Cowlairs-Glasgow QS (2100 from Euston)
0725 Glasgow QS-Aberdeen
1100 Aberdeen-Glasgow QS
1430 Glasgow QS-Edinburgh
1530 Edinburgh-Glasgow QS
1630 Glasgow QS-Edinburgh
1730 Edinburgh-Glasgow QS
1830 Glasgow QS-Edinburgh
1930 Edinburgh-Glasgow QS
2030 Glasgow QS-Edinburgh
2130 Edinburgh-Glasgow QS
2230 Glasgow QS-Edinburgh
47.706: 0731 Kirkcaldy-Edinburgh
0835 Edinburgh-Aberdeen
1200 Aberdeen-Edinburgh
1655 Edinburgh-Aberdeen
2030 Aberdeen-Edinburgh
47.707: 0654 Dundee-Glasgow QS
0925 Glasgow QS-Aberdeen
1300 Aberdeen-Glasgow QS
1725 Glasgow QS-Aberdeen
47.708: 0500 Aberdeen-Perth
0710 Perth-Edinburgh
1715 Edinburgh-Carstairs
1814 Carstairs-Aberdeen (0730 from Penzance)
47.709: 0700 Aberdeen-Glasgow QS
1125 Glasgow QS-Aberdeen
1500 Aberdeen-Glasgow QS
1925 Glasgow QS-Aberdeen
2235 SX Aberdeen-Perth
47.710: 0626 Perth-Dyce
0845 Dyce-Glasgow QS
1325 Glasgow QS-Aberdeen
1700 Aberdeen-Glasgow QS
2025 Glasgow QS-Dundee
47.711: 1130 SUN Edinburgh-Glasgow QS
1300 SUN Glasgow QS-Edinburgh
1430 SUN Edinburgh-Glasgow QS
1600 SUN Glasgow QS-Edinburgh
1730 SUN Edinburgh-Glasgow QS
1830 SUN Glasgow QS-Edinburgh
1930 SUN Edinburgh-Glasgow QS
2030 SUN Glasgow QS-Edinburgh
2130 SUN Edinburgh-Glasgow QS
47.710: 0800 SUN Glasgow QS-Edinburgh
0930 SUN Edinburgh-Glasgow QS
1100 SUN Glasgow QS-Edinburgh
1230 SUN Edinburgh-Glasgow QS
1400 SUN Glasgow QS-Edinburgh
1530 SUN Edinburgh-Glasgow QS
1700 SUN Glasgow QS-Edinburgh
1800 SUN Edinburgh-Glasgow QS
1900 SUN Glasgow QS-Edinburgh
2000 SUN Edinburgh-Glasgow QS
2100 SUN Glasgow QS-Edinburgh
47.713: 0900 SUN Glasgow QS-Edinburgh
1030 SUN Edinburgh-Glasgow QS
1200 SUN Glasgow QS-Edinburgh
1330 SUN Edinburgh-Glasgow QS
1500 SUN Glasgow QS-Edinburgh
1630 SUN Edinburgh-Glasgow QS
1800 SUN Glasgow QS-Edinburgh
1900 SUN Edinburgh-Glasgow QS
2000 SUN Glasgow QS-Edinburgh
2100 SUN Edinburgh-Glasgow QS
2200 SUN Glasgow QS-Edinburgh
2300 SUN Edinburgh-Glasgow QS
47.714: 0925 SUN Glasgow QS-Aberdeen
1850 SUN Aberdeen-Glasgow QS
47.715: 0820 SUN Dundee-Glasgow QS
1125 SUN Glasgow QS-Aberdeen
1650 SUN Aberdeen-Glasgow QS
2125 SUN Glasgow QS-Dundee
47.716: 1055 SUN Edinburgh-Aberdeen
1535 SUN Aberdeen-Edinburgh
1830+SUN Edinburgh-Glasgow QS +29/6-7/9
1930+SUN Glasgow QS-Edinburgh +29/6-7/9
2030+SUN Edinburgh-Glasgow QS +29/6-7/9
2130+SUN Glasgow QS-Edinburgh +29/6-7/9
47.717: 1250 SUN Aberdeen-Glasgow QS
1725 SUN Glasgow QS-Aberdeen
47.718: 1450 SUN Aberdeen-Glasgow QS
1925 SUN Glasgow QS-Aberdeen
2230 SUN Aberdeen-Perth
47.719: 0850+SUN Edinburgh-Glasgow QS +29/6-7/9
1848+SUN Glasgow QS-Edinburgh (1530 from Oban +29/6-7/9)
47.720: 1830+SUN Edinburgh-Glasgow QS +To 22/6 & Fr 14/9
1930+SUN Glasgow QS-Edinburgh +To 22/6 & Fr 14/9
2030+SUN Edinburgh-Glasgow QS +To 22/6 & Fr 14/9
2130+SUN Glasgow QS-Edinburgh +To 22/6 & Fr 14/9

 

[randyrippley]

Are you talking late 80s? In the early 80s (I last worked at Waterloo in 1982) the only Exeter line trains to have full vans was the 0140 Yeovil papers which was formed of Mk 1s and BR bogie vans (GUV), though there was a 4 plus van set earlier for the late Exeter-Sarum. There are no ex LNE vans, even bogie ones, listed in my 1989 Platform 5.

I do recall seeing LNE type 6 wheeler toplight (not clerestory) vans in Clapham Yard in the 70's, but they wouldn't have been allowed on most SR class 1 trains even then.

Late 70's early 80's
My memory is that the 33s used mainly MkI sets, six coaches(winter) seven (summer) with a full brake or parcels van at each end, giving a total of eight or nine. During the early 80's the class 50s and occasional 47/7 hauled similar sets with the MkI replaced by MkII opens displaced from Glasgow-Edinburgh (ironic). The bogied pigeon van was behind a 33, the six-wheeler behind a 50

 

[randyrippley]

I think this refers to the LNER-design 6-wheeled brakes built well after nationalisation at Stratford Works in the 1950s, to an LNER design. They never had passenger accommodation. No clerestory, although they did have a high level window line like clerestories once did. They were around to the end of the 1970s on the Eastern, and certainly lasted well into the BR blue era. here's one

http://paulbartlett.zenfolio.com/brerbz/h3e5f4e4a#h3e5f4e4a

Only just spotted that - yes it would explain the six-wheeler I saw behind a class 50, but the earlier pigeon van behind the 33 was a bogie set with a carriage number in the SxxxE series

 

[HST43108]

Very interesting details Hexagon. The loco hauled books are great. It seems clear from the above that the locos cycled through the diagrams 701-706 easily, but I am assuming that the also did 707-711 also. How did they continue on into that, would they change on a freight working or a Saturday night perhaps. I am curious to know. I have loco hauled 81-85 but I loaned them out. The guy is going to return them when he back off holidays in 2 weeks, I be away by then so during October I will upload some of them if you like. Was loco hauled out in the 70s or after 86 or was there an equivilant publication. I will check in from time to time when I am away but won't be able to do much till I get home to my keyboard.

 

[hexagon789]

Seeing as this thread hasn't been updated in a while I thought I'd ask if anyone would care for a comprehensive explanation of how the Class 47/7 push-pull system actually worked and/or a list of the individual coaches used in both the Mk2 and Mk3 push-pull sets. Regards, Ben

 

[Cowley]

Seeing as this thread hasn't been updated in a while I thought I'd ask if anyone would care for a comprehensive explanation of how the Class 47/7 push-pull system actually worked and/or a list of the individual coaches used in both the Mk2 and Mk3 push-pull sets. Regards, Ben

I'd like to know a bit about the push pull system Ben. I only went on them a couple of times but always liked them.

 

[Taunton]

Wasn't one of its shortfalls with the Class 47 a lag in control of the loco when at the back, so in the Polmont accident although the driver had shut off and braked when he saw the cattle on the line, the loco at the back was still pushing as the vehicles went into derailment. I don't recall any such lag when it was Class 27 x 2, which as I understood it was just the standard loco Blue Star multiple unit connections put through the standard train lighting connections of the carriages with electronic filters, so there must have been a difference.

 

[Helvellyn]

Seeing as this thread hasn't been updated in a while I thought I'd ask if anyone would care for a comprehensive explanation of how the Class 47/7 push-pull system actually worked and/or a list of the individual coaches used in both the Mk2 and Mk3 push-pull sets.

Mk 2E FO
3245
3247
3248
3265

Mk 2F FO
3284

Mk 2 TSO [Air braked by means of disc brakes]
5146
5152
5153
5176
5197

Mk 2D TSO
5623
5653
5659
5662
5663
5671
5673
5694
5711
5716
5726
5740

Mk 2E TSO
5813 [Unclear if repainted in error as I only ever saw it in CrossCountry sets]

Mk 2D TSOT
6601
6604
6605
6613
6614
6619

Mk 2F DBSO [Converted from Mk 2F BSO]
9701
9702
9703
9704
9705
9706 [Written off at Polmont]
9707
9708
9709
9710
9711
9712
9713
9714 [Replacement for 9706]

Mk 3A FO [11005-11010/11022 converted to CO 11905-11910/11922]
11004 [Written off at Polmont]
11005
11006
11007
11008
11009
11010
11022 [Replacement for 11004]

Mk 3A TSO
12004
12005
12006 [Written off at Polmont]
12007
12008
12009 [Transferred back to InterCity in 1986]
12010 [Transferred back to InterCity in 1985]
12011
12012
12013
12014
12015
12016
12017
12018 [Written off after arson attack 1981]
12019
12020
12021
12022
12023
12024
12025
12026
12027
12028
12029
12030
12031
12051 [Replacement for 12006]

Mk 2 FK [Air braked by means of disc brakes]
13424 [Withdrawn 1987]

I'm unsure of the Mk 1 BGs that also carried ScotRail colours without digging out an old Platform 5 Combined Volume.

I don't think any of the Mk 3A SLEPs used on internal Scottish services ever gained ScotRail colours.

On the locomotive front it shouldn't be forgotten that 47461 also gained ScotRail colours - the only non-47/7 to do so. Other 47/4s gained InterCity Executive colours but with ScotRail branding in place of the InterCity branding.

 

[hexagon789]

Addition to the above vehicles two Mk2a FK were also used in the Mk2 push-pull sets these were 13461 and 13456. Both retained blue/grey livery and were never repainted. The sole remaining E-G Mk2z FK (13424) was withdrawn on 30/7/87. 13461 was brought in from Old Oak Common in September 1986 and 13456 was brought in from Heaton in May '87, these provided cover for the Mk2e/f FOs and could commonly be seen in at least one of the GLQ-Aberdeen rakes, particularly in later years. The 5 Mk1 BG painted in ScotRail livery were used in the GLQ-Aberdeen Mk2 push-pulls between May 1985 and May 1986 after which they went to other parts of the UK. All were fitted with B4 bogies, their numbers were 92061, 92086, 92088, 92091 and 91128. TSO(T) 6613 was also painted in ScotRail livery and used in the push-pull rakes giving a total of 7 these vehicles, number 6607 retained blue/grey but with ScotRail lettering throughout it use in the push-pulls. Some Mk3a sleepers were painted in ScotRail livery though I haven't seen photographic evidence of them in use on the Scottish internal sleeper services. Only two were repainted into ScotRail, both SLEPs, these were 10578 and 10610 based at Edinburgh Craigentinny.

I've never seen Mk2e TSO 5813 in the Mk2 push-pull sets either, and as it was based at Polmadie in Glasgow rather than Craigentinny this suggests that it was used in Cross-Country services rather than the Mk2 push-pull sets. DBSOs 9711, 9712 and 9713 retained tread brakes, the others including replacement 9714 had disc brakes.

Now on to the push-pull system itself: Firstly I'd better explain how the throttle control works on the Class 47s. Diesel locos such as the Sulzers and English Electrics had all-speed governors on the engines, so there were no speed notches as such on the controllers. The power controller operated a regulating air valve, which fed air to a cylinder in the governor. This then operated the fuel racks on the engine, via a set of complicated levers and linkages. An oil vane motor in the governor also controlled a potential divider on earlier locos or a linear voltage differentiating transducer (LVDT) on those converted to ETH, to vary the excitation current in the main generator. This enabled the output from the generator to match the load the engine was capable of delivering for the regulating air being fed from the power controller. The Brush/Sulzer system was very well designed and it was almost impossible to overload the engine.

When the power controller was moved to the "ON" position, this fed about 5psi of air pressure to the governor. It didn't increase the engine speed, but enabled the engine to supply enough torque to apply a small amount of tractive effort at idle speed. With the controller at 1/4, the regulating air was about 13psi and the engine would run faster and be able to deliver a greater load. The oil vane motor would increase the output from the potential divider/LVDT and the excitation current would be increased and the main generator would produce correspondingly more voltage and current for the traction motors. As a result, tractive effort was increased. 30psi was somewhere between 1/2 and 3/4 and 50 psi was full power.

When the loco was being driven from the cab, the regulating air pressure was infinitely variable from 5 - 50psi, but from the DBSO, that couldn't be achieved, without running a regulating air pipe down the train to the loco. A regulating air pipe was a standard feature of all Blue-Star multiple working locos - you can see these on the buffer beams of Classes 20, 25, 26, 27, 31, 37 etc that used Blue Star multiple working, together with the 27 way electrical control jumpers. The regulating air pipe is the one painted white. The original Class 27 push pulls used this feature and the converted Mark 2s were fitted with regulating air pipes and the 27 way jumpers. For the two-wire control push-pulls, standard stock was to be used, so no expensive conversions, apart from the DBSOs. These had 4-position EMU type power controllers so another solution had to be found.

The solution was quite clever: The four power notches were translated by the two-wire control equipment into 4 power demand channels. When those signals popped out at the other end, they energised four power notch relays in the two-wire control cabinet on the loco. These, in turn energised four separate electro-pneumatic valves that fed air into the regulating air system. Notch 1 gave 5psi (minimal amount of power, a sort of "shunt" notch), 2 gave 13psi (about 1/4 power), 3 gave 30psi (between 1/2 and 3/4 power) and 4 gave 50psi (full power).

This made the train less easy to drive in propelling mode because the control wasn't as fine, but the drivers soon got used to it and actually preferred driving from the DBSO because it was quieter and gave a better ride.

Furthermore, if the driver closed the power controller in the DBSO, power would be shut off in the loco pretty much instantaneously. From the Polmont accident report:

"39. The operation of the power controller in the DBSO cab is similar to that in the locomotive cab although the signal has to be transmitted to the locomotive. This is done electrically and consequently without measurable delay, thus closure of the controller in the DBSO results in almost instantaneous removal of power from the locomotive. If the driver makes an emergency brake application at the DBSO but fails to close the controller, the control governor in the brake-pipe automatically shuts off power at the locomotive 4.6 seconds after the initiation of the brake application, when the brake-pipe pressure falls to a certain pre-set figure."

Also many books, web articles and other publications state that the push-pull system used by the Class 47/7 is a TDM (Time Division Multiplex), however this is not the case. The 47/7 and DBSO system in Scotland was designed and supplied by Brush and was an FDM (Frequency Divison Multiplex) system, so it modulated different frequencies to transmit the different channels/messages used to control the loco from the DBSO and for the loco to send messages back to the DBSO.

The systems used on the WCML and ECML were designed and supplied by Plessey and they were/are TDM systems so the different channels are transmitted during predetermined, discrete time-slots in a predetermined sequence. Interestingly, the Mark 4 coaches on the ECML use TDM to control the Class 91 from the DVT, but they also have an FDM system as well. This is used for control within the rake and is used for air conditioning control, lighting control etc.

Another interesting feature of the Brush system was that Channel 1 which was "Engine Start" on the Class 47/7s was also described in the manual as being "Pan Up & Reset" on the Class 81 loco! The Class 81s were never fitted, but the system was designed to be used with them. For each Class 47/7 channel, there was an equivalent described in the manual for the Class 81.

 

[flymo]

Incredible information on the digarams there hexagon789 and stock numbers Helvellyn . I remember doing the Edinburgh - Glasgow runs a lot in the 80's purely for a cracking run on the mk3's and all this info bring back a lot of memories. Thank you so much for posting this information.

 

[hexagon789]

Glad you found it interesting.

 

[Cowley]

Yes, really interesting and well explained, thanks for that.
I can confirm that coach 5813 was indeed a cross country coach because I frequently saw it in Exeter and it was the only item of rolling stock I'd seen in Scotrail livery down this way in the late 80s, as you say, maybe it was painted by mistake.

 

[Taunton]

It would appear that my previous belief for many years (I knew this service best in the 2 x 27 era of the 1970s) that control was via the train line lighting connections has been completely wrong for all that time.

I never understood why the distinct sub-class 27/1 had apparently been modified for the service, when occasionally a stand-in of a 25 or a 37 seemed to work fine without adaptation. One of my fastest runs ever in push-pull days was with a 37 at the rear eastbound.

The Polmont accident report seems to be stating what the theory of the control system should do. My understanding was from the beliefs of crews in the area about what had actually happened.

 

[Cowley]

I must admit to the same as Taunton, I always thought they ran through the lightning system, I learn something new on here every day.

 

[randyrippley]

It would appear that my previous belief for many years (I knew this service best in the 2 x 27 era of the 1970s) that control was via the train line lighting connections has been completely wrong for all that time.

I never understood why the distinct sub-class 27/1 had apparently been modified for the service, when occasionally a stand-in of a 25 or a 37 seemed to work fine without adaptation. One of my fastest runs ever in push-pull days was with a 37 at the rear eastbound.

The Polmont accident report seems to be stating what the theory of the control system should do. My understanding was from the beliefs of crews in the area about what had actually happened.

This may fill in some of the gaps re the 27s and the 25/37 stand-ins
http://www.6lda28.com/shove.html

 

[Skutter]

Glad you found it interesting.

Me too - it's the sort of techie/history detail which is fascinating to those of us who weren't there (or not behind the scenes) at the time but want to know how things really worked.

 

[hexagon789]

Sorry, I should've been clearer. The control signals WERE transmitted via the lighting circuits but only on the Class 47/7 push-pull. This enables the use of any carriage fitted with RCH jumpers to be untilised in the Class 47/7 push-pull sets. The Class 27 push-pull sets needed through electric and air connexions. The Class 27/1 retained their steam heat boilers, while the Class 27/2s had a generator unit fitted to provide ETH. The coaches were dual heated, socould run off of either system. Failures of either system, particularly the ETH generator were common. The usual practice was for one each of the /1 and /2 topping and tailing a set, ETH was preferred but in the event of a generator failure the steam heat boiler provided a back up. The Mk2z coaches as well as having air braking fitted were also fitted with disc brakes and Girling WSP, they retained these features even after the E-G Push-pulls went over to Class 47/7 operation. A unique feature of the braking system was that it was of a two-stage nature, a higher brake cylinder pressure was given at over 60mph which allowed increased braking efficiency. The two-stage system was isolated when the coaches were transferred off these duties.

 

[theblackwatch]

Yes, really interesting and well explained, thanks for that.
I can confirm that coach 5813 was indeed a cross country coach because I frequently saw it in Exeter and it was the only item of rolling stock I'd seen in Scotrail livery down this way in the late 80s, as you say, maybe it was painted by mistake.

I too remember 5813 being an oddball in the fleet, the only Mk.2e TSO to be done and always on XC services. I'm surprised it wasn't corrected, it would have been quite easy to change the blue stripe to a red one.

 

[47271]

My Dad tells me that when the 47/7 push pull sets were introduced first in 1979 they were nicknamed 'discos' because of the variable impact of the DBSO's control on interior lighting.

I'm sure that the story is true, but when I came to use these trains in their final days on the route ten years later, I have no recollection of any flickering?

Mind you, by that time they were so unreliable that flickering of the lights would have been the least of our worries. Apologetic announcements ending with 'this is due to a fault in the locomotive' is all I remember from this era.

 

[hexagon789]

The lights woukd flicker, but only when the power controller was moved in the DBSO. In conventional "hauled" mode no flickering would occur as the driver was of course driving from the loco. Similarly no flickering would be present when a brake application was made as the braking system was unmodified, just a standard brake controller added in place of the guard's brake valve in the DBSO.

 

[Taunton]

This may fill in some of the gaps re the 27s and the 25/37 stand-ins
http://www.6lda28.com/shove.html

That's an excellent article and has filled in more of my understanding of those days when I shuttled back and forth between the two cities courtesy of the 27s (there was an "evening return" in about 1974, which if I remember correctly was 69p return if you started after 6pm).

Thank you to Hexagon for the detailed notes as well.

A small coincidence is that the old dmu cars which had been used on the service prior to the push-pull also had a different through control air pipe system to the standard, but the other way round - whereas normal Blue Square control dmu cars had a through air pipe down the train, the Edinburgh-Glasgow cars uniquely did not, and received a separate White Circle code.

 

[edwin_m]

I'll chek the report again when I get a bit of time, but I think the reasons the push-pull format might have contributed to the severity of Polmont would be:

(1) The front vehicle was a coach with a lighter axleload than a loco, thus more easily lifted off the track when part of the animal got underneath. This particular cause would have been not much worse had the train been a multiple unit. DBSOs were later ballasted and fitted with deflectors.

(2) Heritage diesel locos are underbraked compared with coaching stock, the reason why speed restrictions are imposed on short loco-hauled formations. With the loco at the rear there would be a compressive force in the train during a heavy brake application, increasing the tendency to "jack-knife" once the initial derailment occurred.

(3) The above compression would increase significantly once the front part of the train was significantly derailed and therefore the forces acting backwards on it were much greater than those of the brakes alone. The rear of the train, still on the rails and under deceleration from the brakes only, would be trying to push the front part forward. As it included the heavy loco the compressive force would be more than from a multiple unit of the same length or from the same formation running loco first.

 

[Shaw S Hunter]

My Dad tells me that when the 47/7 push pull sets were introduced first in 1979 they were nicknamed 'discos' because of the variable impact of the DBSO's control on interior lighting.

I'm sure that the story is true, but when I came to use these trains in their final days on the route ten years later, I have no recollection of any flickering?

Mind you, by that time they were so unreliable that flickering of the lights would have been the least of our worries. Apologetic announcements ending with 'this is due to a fault in the locomotive' is all I remember from this era.

The lights would flicker, but only when the power controller was moved in the DBSO. In conventional "hauled" mode no flickering would occur as the driver was of course driving from the loco. Similarly no flickering would be present when a brake application was made as the braking system was unmodified, just a standard brake controller added in place of the guard's brake valve in the DBSO.

There is no doubt that when first introduced the 47/7 powered sets certainly did suffer from flickering saloon lights. I suspect that the negative publicity was sufficient to prompt some sort of modification to be made to the lighting circuits to neutralise the effect on the lights themselves without affecting the control signals so the effect was soon eliminated.