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1st gen DMUs and DEMUs

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Taunton

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White Circle on the 79xxx and 126. Another difference was that the Class 120 had screw couplings and scissors gangways, the 79xxx and 126 buckeyes and Pullman gangways.

The unique feature of the Scottish 120s that I remember best is that they were fitted with Mansons automatic token exchange apparatus operated by the guard, principally for use between Aberdeen & Inverness.
It's ironic that they were fitted on the Great North of Scotland line which Manson had a passing relationship with, but not to the Class 126 on the GSWR single lines, to Stranraer etc where Manson had spent much of his career, and which also had his automatic exchangers. The issue with the tablet exchange, traditionally in steam days a fireman's responsibility with the driver checking it when received, was that while dmu drivers could handle a manual exchange from their cab window, it was a lot more distracting and lengthy to fiddle with the exchange apparatus while going at speed, so it was given to the guard. There were a range of special buzzer signals for "tablet exchanged", "stop - exchange failed", and similar, which were posted on the inside of the guard's door (where the apparatus was mounted) and in the driving cabs of the 120s, which were left there when they finally moved away from Inverness.
 
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edwin_m

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It's ironic that they were fitted on the Great North of Scotland line which Manson had a passing relationship with
Ha ha

I remember seeing this in action in 1979, on one of my last trips as a 14-year-old before starting to pay full fare. I dragged my gran on a triangular trip from Kirkcaldy to Aberdeen and Inverness.
 

hexagon789

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White Circle on the 79xxx and 126. Another difference was that the Class 120 had screw couplings and scissors gangways, the 79xxx and 126 buckeyes and Pullman gangways.

The unique feature of the Scottish 120s that I remember best is that they were fitted with Mansons automatic token exchange apparatus operated by the guard, principally for use between Aberdeen & Inverness.

Yes, the wondrous White Circle that originally wasn't even compatible between the Edinburgh & Glasgow and the Ayrshire sets!

I don't really understand why BR went for a system which had the downside of each power car producing it's own control air supply. If anything it seems a much more complicated system than Blue Square to me.
 

Taunton

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The White Circle cars for Edinburgh-Glasgow were first built early in 1956 before Blue Square came along, when the Yellow Diamond scheme was still the standard. This had its own initial problems and the White Circle were probably trying to overcome these.

Less understandable were the 126 cars 3 years later having it when the new standard was well established, the only reason would be compatibility, but then they had variations done which made them incompatible anyway. I wonder if a scheme was ever worked out to convert them all to standard.
 

pieguyrob

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Going back to the southern DEMU's, weren't their engines compatible with the class 73's to make maintenance easier?
 

hexagon789

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The White Circle cars for Edinburgh-Glasgow were first built early in 1956 before Blue Square came along, when the Yellow Diamond scheme was still the standard. This had its own initial problems and the White Circle were probably trying to overcome these.

Less understandable were the 126 cars 3 years later having it when the new standard was well established, the only reason would be compatibility, but then they had variations done which made them incompatible anyway. I wonder if a scheme was ever worked out to convert them all to standard.

It wasn't so much the basis for the two white circle systems I was questioning, more the use of a system which worked on each power car having an induvidual air control supply.

As built there were control compatibility issues between the two batches of White Circle cars on the ScR. Modifications were made as they most certainly worked together indiscriminately during the early/mid-1960s.
 

DJ_K666

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The old LMS standard gangways were part of reducing the weight of the original alloy-constructed Derby Lightweight units, along with the short 57' length - typical minimalist LMS approach that still pervaded Derby. Notably the Western Region would have no truck with 57' cars, lightweight bodies or bus seating. It was also felt that few passengers would need to pass between cars. Remember on local services they were usually replacing completely non-corridor compartment stock. The gangway approach then carried forward to all the remaining short frame cars from the independent manufacturers, for interchangeability.

For why the form of transmission, you only have to look at the waste of space on a Southern Region 2-car unit, where virtually half of the body of one car is taken up by the engine-generator set, a huge radiator, etc, and a noise that made people put their fingers in their ears when multi-unit lashups passed. The dmu premise was that the power train was straight from commercial vehicles, both engine and gearbox, all underfloor. The bus industry in the 1950s had just moved from conventional front engine mounting to horizontal underfloor engines, and all the lubrication etc issues with engines mounted "sideways" were addressed. It has a nice weight balance in the car with two engines and transmissions, mirror imaged. The difficulties with the later Cravens cars which only had one larger engine, all cars powered, but unbalanced for weight between the two bogies and significant vibration issues, a classic "it seemed like a good idea at the time", caused their early withdrawal. The railway bus/truck approach came from the pre-war GWR cars, by AEC/Park Royal, and an equivalent LMS set with Leyland engines, which formed prototypes.
Ah the good old Thumpers. Built to look like EMU stock with the idea they could be converted should their lines ever be electrified. Of course it never worked out like that. And what a wonderful engine sound. But yes they were pretty wasteful space wise. I did travel along the (then newly electrified) Tonbridge to Redhill line in one. The previous time I'd done that was in a Class 101. On the Southern Region that was pretty much a rarity in itself although there were pockets of 1st gen goodness. [/rose tinted biker goggles]
 

dubscottie

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However, getting back on topic, the GWR was way ahead of the others in adopting the DMU, proving before WW2 that they were viable for secondary and branch services and even running some expresses. Perhaps if it hadn't been for WW2 most of their branch lines would have been run by "bananas" of one type or another.

Many give the GWR credit for the DMU but it was in fact Ireland where most DMU development was done. The companies in NI & the GNR (I) were years ahead of the GWR/BR.

An interesting thing I discovered was that the original Derby lightweight units had the cabs designed so that they could be fitted with a gangway and used as hauled stock if they turned out a disaster. The controls would be removed and the cab would become a vestibule.
 

Merle Haggard

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The old LMS standard gangways were part of reducing the weight of the original alloy-constructed Derby Lightweight units, along with the short 57' length - typical minimalist LMS approach that still pervaded Derby. Notably the Western Region would have no truck with 57' cars, lightweight bodies or bus seating. It was also felt that few passengers would need to pass between cars. Remember on local services they were usually replacing completely non-corridor compartment stock. The gangway approach then carried forward to all the remaining short frame cars from the independent manufacturers, for interchangeability.

My understanding of the reason Derby produced 57' vehicles was that that was the dimensions of the jigs they had. Derby also used the dimensions and availability of jigs as the reason/excuse for LMS locos all having 8' + 8' 6" wheelbase until the Fairburn tanks. But Derby did rule the LMS and possibly this attitude carried into BR days.

I have often wondered why most DMU (and also BR standard loco hauled non-gangwayed stock) did not have Buckeyes/Pullman but weight could well be the reason, as you suggest.

There was a terrible head-on collision in South Wales (in the early 60's) on a steeply graded line between a runaway coal train and a Swindon design suburban unit (though in the Swansea division - WR only had single branch line units) and the design of the unit, with intermediate full-width bulkheads within each coach, prevented the driver and passengers at the front of the train from moving back to safety once their situation became clear. I'm not sure but this may be the reason why doorways were later cut in the bulkheads.

As a item of trivia; when the WR suburban units were fitted with (BS) gangways the source was pre-nationalisation design BG which ran around thereafter with the gangway door sealed and the vestige of the connection protruding.
 

Journeyman

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A 205 was configured on refurbishment to work with EMU’ s. Think it was 205 111. Don’t know if it ever worked in service multipled to an EMU though. Back to 1st gen DMU’s below the sole bar they were all basically the same regardless of whether a suburban or longer distance cross country units. Due to line closures many were used on services completely unsuited to there designed use, for example suburban units used on services of over 2 hours. Whilst Cravens were used on services from Kings Cross. 8 cars made up of 4x2 car units resulting in 8 driving cabs and 4 brake vans in each , completely wasted space.

It was unit 1111, later 205101, and then 205205 when reduced to 2 cars. It survives on the Epping-Ongar Railway. All other DEMUs were unable to work in multiple with EMUs, although the modification wasn't difficult - a batch of six 2-EPB driving trailers were modified to work with Hastings power cars, and didn't take much work besides a bit of rewiring.

SR DEMU lighting circuits operated at a different voltage to the EMU fleet, but otherwise, bogies, traction motors, air compressors, couplings, seats, doors and a whole heap of other stuff besides was completely interchangeable between the DEMU and EMU fleets (although the Hastings and Oxted fleets were a bit less standard due to restricted body dimensions). Given that the Southern only needed about 75 DEMU sets, against an enormous fleet of EMUs, it made sense to allow as much commonality between the fleets as possible, and I think it was a sensible decision.
 

delt1c

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It was unit 1111, later 205101, and then 205205 when reduced to 2 cars. It survives on the Epping-Ongar Railway. All other DEMUs were unable to work in multiple with EMUs, although the modification wasn't difficult - a batch of six 2-EPB driving trailers were modified to work with Hastings power cars, and didn't take much work besides a bit of rewiring.
That was the Tadpoles which had a Hastings power car and TSO with an EPB driving trailer./ When disbanded the former EPB cars (Driving cabs locked out of use) were used as centre cars to strengthen the 2 car 205's.
 

Journeyman

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That was the Tadpoles which had a Hastings power car and TSO with an EPB driving trailer./ When disbanded the former EPB cars (Driving cabs locked out of use) were used as centre cars to strengthen the 2 car 205's.

Indeed. The Southern was very good at recycling! It probably also proves ample justification for their decision to go for maximum compatibility between electric and diesel fleets.
 

hexagon789

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That was the Tadpoles which had a Hastings power car and TSO with an EPB driving trailer./ When disbanded the former EPB cars (Driving cabs locked out of use) were used as centre cars to strengthen the 2 car 205's.

I've since found out that that was where I got the idea of SR EMUs being able to multi with the DEMUs but with more restricted notch control. When driving from the EPB driving trailer, the 4-notch EMU power controller was still in place against the 7-notch controller of the DEMUs. The system was set up in the Driving Trailer so that notches 1-4 on the DT gave 1, 3, 5 and 7 on the power car.

I believe the refurbished Hastings set which was designed to able to multi with EMUs had the same control arrangement
 

randyrippley

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The wikipedia entry for the class 73 has an interesting tale about EMU / DEMU compatibility
No idea how true it is

Multiple working (i.e. when two or more locomotives are coupled together and can all be controlled by ONE driver in the leading locomotive). This was achieved with the aid of the standard SR 27-wire jumper connection system, a design that ensured excellent compatibility. They could work with other 33/1, 71, 74, locomotives. They were also supposed to be compatible with all BR designed (Post 1951 type) EMU electric multiple units and DEMU diesel electric multiple units. However, in an early test with one of the 73/01 (JA) types, a major wiring error was revealed. Not in the locomotive, but in the whole Electric and Diesel Electric Multiple Unit fleets. This involved two of the wires in the traditional SR 27 way jumper. The outcome was that if an EMU was coupled to a DEMU they would try and go in opposite directions. The Class 73/0's had it transpired been wired as per the DEMU fleet, so could work in multiple with these units but NOT the Electric fleet. Rectifying the fault was not thought worth the cost. But the Chief Mechanical and Electrical Engineers department (CM&EE) when ordering the follow-on production Class 73/1s from English Electric, stipulated they should be wired in line with the EMU fleet as this would make these locos far more useful. This, therefore, reveals the reason why the Class 73/0 (JA) could NOT work in Multiple with the Class 73/1 (JB) type
 

yorksrob

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I believe the refurbished Hastings set which was designed to able to multi with EMUs had the same control arrangement

It was a "Hampshire" set, rather than a "Hastings", but it did spend many years on the Marshlink.
 

hexagon789

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That's all right. I miss em all !

Never travelled on one, but I do love that sound!



While we're on the subject of first generation DMUs, there is a given technique for driving the mechanical sets with 4-speed gearboxes (it appears in the driving instructions) but was there similar for the DEMUs or was it just put the power in however you liked does anyone know?
 

Cowley

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I went on it loads of times. Stuck out like a sore thumb from all the others.
My memories of Hampshire units thundering along the lines around Winchester/Southampton/Salisbury etc are very much cherished. Wonderful times.
 

yorksrob

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My memories of Hampshire units thundering along the lines around Winchester/Southampton/Salisbury etc are very much cherished. Wonderful times.

Indeed. I used to love crossing the Romney Marsh in them. Great days, splendid trains - fifty years of service (almost) !
 

Cowley

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Indeed. I used to love crossing the Romney Marsh in them. Great days, splendid trains - fifty years of service !
I’m so going to get in trouble for going off topic, but do you remember the way the engines used to ‘hunt’? And when they were about to pull away they’d die right down before picking up? I loved that.
OK let’s add the caveat:
We know that they weren’t efficient, drank fuel, broke down, bounced around, were rusty, were old fashioned, draughty, dusty, noisy, structurally unsafe compared to modern trains, probably polluting and leaked oil (that should cover it ;))...
I still loved them though.
 

hexagon789

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And when they were about to pull away they’d die right down before picking up? I loved that.

I think that was the way the ETH was set up. When ETH was switched on the engines would idle at 620rpm instead of the usual 450. When power was applied though, the engines would rev back down to 450rpm before traction power was applied and then increase in rpm as usual for each power notch rather than simply going from 620 to start with.

And after reading that I now realise I've picked up way too many technical details like that! Oh dear :oops::lol:
 

yorksrob

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I’m so going to get in trouble for going off topic, but do you remember the way the engines used to ‘hunt’? And when they were about to pull away they’d die right down before picking up? I loved that.
OK let’s add the caveat:
We know that they weren’t efficient, drank fuel, broke down, bounced around, were rusty, were old fashioned, draughty, dusty, noisy, structurally unsafe compared to modern trains, probably polluting and leaked oil (that should cover it ;))...
I still loved them though.

Yes, I remember the engine dieing down before pulling away.

I don't remember them breaking down that much. Nice comfy seats as well !
 

Cowley

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And after reading that I now realise I've picked up way too many technical details like that! Oh dear :oops::lol:
Don’t worry about that. Your input is always appreciated Hexagon. ;)
 

big all

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It was unit 1111, later 205101, and then 205205 when reduced to 2 cars. It survives on the Epping-Ongar Railway. All other DEMUs were unable to work in multiple with EMUs, although the modification wasn't difficult - a batch of six 2-EPB driving trailers were modified to work with Hastings power cars, and didn't take much work besides a bit of rewiring.

SR DEMU lighting circuits operated at a different voltage to the EMU fleet, but otherwise, bogies, traction motors, air compressors, couplings, seats, doors and a whole heap of other stuff besides was completely interchangeable between the DEMU and EMU fleets (although the Hastings and Oxted fleets were a bit less standard due to restricted body dimensions). Given that the Southern only needed about 75 DEMU sets, against an enormous fleet of EMUs, it made sense to allow as much commonality between the fleets as possible, and I think it was a sensible decision.
The alteration to 1111 was specifically with altering all DEMUs to be compatible with electric stock in mind. In actual fact as a one off it was left as DEMU compatible rather than EMU compatible; apparently it would take perhaps a day or a few days to convert from DEMU or EMU jumpers, with perhaps a few other connected alterations.

It had a 63 stock 4 stage controller with I assume the notches best set up for performance with electric stock
whereas the Tadpoles were set up best matched to a DEMU, hence if you had 1111, a Tadpole and a Thumper in formation [never happened as far as i know], you would only have three controller positions as notch 1 [shunt] would be the same on all 3 types; notch 2 [electric series] would cover 2/3/4 engine speed steps [rev up] on say a tadpole with notch 3 [parallel 5], but cover 2/3 series and 3 = 4/5 on 1111 with electric weak field notch 4 = full power on all unit

So make it simple.

Notch 1 shunt = motor contactors closed all units minimum power
Notches 2, 3, 4, 5 are all connected together via [1111 and tadpole] so will give perhaps 600rpm with weak field =full power and revs 850rpm from memory, I think.

Sorry if it looks confusing but to my brain its the right amount of information and no more to make sense :D
 
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Taunton

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I’m so going to get in trouble for going off topic, but do you remember the way the engines used to ‘hunt’?
Hunting ("BRRRRM ... dadadadada ... BRRRRM ... dadadadada ..." etc) when idling was a common feature of diesels in the old days, before electronic controls, when engine speed was managed by a centrifugal governor, that is the two balls spinning round, attached to shafts that rise outwards with centrifugal force as engine speed increases, and are connected on the input side to the throttle and on the output to the fuel flow. Old buses idling used to do the same.

It's just cheap components in the governor. Traditional aircraft engine/propeller controls had the same, to maintain a given rpm, and for generations had stayed spot on.
 

Taunton

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Indeed. The Southern was very good at recycling! It probably also proves ample justification for their decision to go for maximum compatibility between electric and diesel fleets.
I'm not really sure that just six units lashed up from odd spare vehicles provides a justification for a whole parallel development, quite small scale, of diesel units. A 3-car set, half of one car given over to an engine room, vestibule connections between two but not to the third, and I believe the former electric driving trailer accommodation was locked out except on busy school runs. The WR sets which eventually took over Reading-Tonbridge seem to have been much better suited to the run. Whyever were they not used in the first place?

The "Oxted" units were said to be to a narrower profile, but not as narrow as the Hastings units, but then ran turn-and-turn about with spare full size former Hampshire units (and Mk 1 hauled stock). So why the different design?
 
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