1st gen DMUs and DEMUs

randyrippley

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........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?
Probably down to the stupid purchasing policy the BRB had when ordering DMU stock for dieselisation projects. Instead of placing large ongoing orders and allocating units when delivered, they instead ordered small batches - each intended for a specific regional project, and notionally optimised for such. So a lot of small orders of non-standard machines. Made worse by the fact that the managers on the ground were happy to mix-and-match sets, and use them away from the area they were notionally purchased for. The result? Units allocated and used on routes they weren't intended for, or optimised for.
You yourself have commented in the past on the WR habit of using high density DMUs on cross country routes, when they had low density machines purchased for those very routes
 
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Probably down to the stupid purchasing policy the BRB had when ordering DMU stock for dieselisation projects. Instead of placing large ongoing orders and allocating units when delivered, they instead ordered small batches - each intended for a specific regional project, and notionally optimised for such. So a lot of small orders of non-standard machines. Made worse by the fact that the managers on the ground were happy to mix-and-match sets, and use them away from the area they were notionally purchased for. The result? Units allocated and used on routes they weren't intended for, or optimised for.
You yourself have commented in the past on the WR habit of using high density DMUs on cross country routes, when they had low density machines purchased for those very routes
In the 1950/60's there were 3 loading gauges on the SR
Restriction 0 - Tunbridge Wells - Hastings ( tunnel restrictions )
Restriction 1 - Tunbridge Wells Central - West ( tunnel restrictions )
Restriction 4 - Other Routes ( Same as BR C1 )

Hastings units were restriction 0
Oxted Units were Restriction 1
Others were Restriction 4
 

hexagon789

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Don’t worry about that. Your input is always appreciated Hexagon. ;)
Thanks ;), but seriously - I have so much random knowledge and information I've picked up from so many sources it's no wonder I have a habit of mashing bits of it up now and again! :lol:


I reckon given the chance I could drive a 101 without any input from an instructor. One day when this virus situation is over in think I'd relish such an opportunity.


It’s not a good start when the piece claims compatibility with Class 71. As the 71s didn’t have high level “bagpipes” that’s wrong for a start...
Sometimes bits are correct. The reasoning behind the two 73 subclasses being unable to multi seems logical enough when explained though that doesn't mean it is correct. I'll see if I can dig up more conclusive information
 

dubscottie

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From what I can remember from an old magazine article, 73/0 & 73/1 can multi on diesel using the blue star connections. I will try to dig it out as it had a table of what SR stock could work with eachother.
 

30907

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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?
1. I presume the WR units weren't spare at the time, whereas the 6S units were.
2. 3-Hs (and Mk 1s) were not permitted between Grove Jn and Tonbridge.
 

yorksrob

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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?
Not the rattly thing with bus seats I experienced on the route. Totally unsuited to a longish cross-country service.

What they should have done was stuck with the tadpole concept and kept the Hastings guage motor car and trailer, then when they electrified the Weymouth line, replaced the EPB trailers with driving trailers from the redundant TC sets. That way you would have had a fully gangwayed 2.5 carriage set with a comfortable high quality interior more suited to the route.
 

yorksrob

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1. I presume the WR units weren't spare at the time, whereas the 6S units were.
2. 3-Hs (and Mk 1s) were not permitted between Grove Jn and Tonbridge.
Somerhill tunnel has a restricted width - but not as restricted as the ones South of Grove junction.
 
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yorksrob

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Probably down to the stupid purchasing policy the BRB had when ordering DMU stock for dieselisation projects. Instead of placing large ongoing orders and allocating units when delivered, they instead ordered small batches - each intended for a specific regional project, and notionally optimised for such. So a lot of small orders of non-standard machines. Made worse by the fact that the managers on the ground were happy to mix-and-match sets, and use them away from the area they were notionally purchased for. The result? Units allocated and used on routes they weren't intended for, or optimised for.
You yourself have commented in the past on the WR habit of using high density DMUs on cross country routes, when they had low density machines purchased for those very routes
As I said above it was a very sensible policy of not scraping the sides of Somerhill tunnel.

And the fact that they were compatible with Hampshire units was very sensible as it meant that they could be used more flexibly with other units.

The mixing and matching of the tadpole units saved the passenger service between Tonbridge and Reading, so was a very good manegerial decision, particularly as it used spare stock. The redundant Hastings gague vehicles had a corridoor connection, so could be accessed by a conductor guard as many of the stations on the route were unstaffed. The EPB trailer was often used for parcels.
 

Richard Scott

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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.
Would be interesting to know how the fuel consumption compared with the types. Remember seeing the sprinter cars were about 6.6mpg per car so assume 3.3mpg per unit. How do first gen units (with 2 power cars) and a DEMU 3 car unit compare? Anyone have any data?
 

randyrippley

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As I said above it was a very sensible policy of not scraping the sides of Somerhill tunnel.

And the fact that they were compatible with Hampshire units was very sensible as it meant that they could be used more flexibly with other units.

The mixing and matching of the tadpole units saved the passenger service between Tonbridge and Reading, so was a very good manegerial decision, particularly as it used spare stock. The redundant Hastings gague vehicles had a corridoor connection, so could be accessed by a conductor guard as many of the stations on the route were unstaffed. The EPB trailer was often used for parcels.
My point is that a sensible purchasing policy would have built all the DEMUs to the same gauge, same basic design, same framelength as part of a single order for go-anywhere units, instead of multiple small orders of subtley different designs and sizes. Building on three different body widths and two different body lengths was simply ridiculous - everything should have matched the 6L sets in dimension.
The narrow bodied class 33 was another example - all the 33 fleet should have been built on the narrow jigs, as should the 27s which followed them.
 

randyrippley

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Would be interesting to know how the fuel consumption compared with the types. Remember seeing the sprinter cars were about 6.6mpg per car so assume 3.3mpg per unit. How do first gen units (with 2 power cars) and a DEMU 3 car unit compare? Anyone have any data?
When the 73/9 fleet was being converted, someone tried testing the nominally 650bhp EE diesels and found they were only generating around 350bhp.........the DEMUs had the same engines, if they were in the same state it suggests they were very inefficent, wasting a lot of diesel
 

yorksrob

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My point is that a sensible purchasing policy would have built all the DEMUs to the same gauge, same basic design, same framelength as part of a single order for go-anywhere units, instead of multiple small orders of subtley different designs and sizes. Building on three different body widths and two different body lengths was simply ridiculous - everything should have matched the 6L sets in dimension.
The narrow bodied class 33 was another example - all the 33 fleet should have been built on the narrow jigs, as should the 27s which followed them.
You may have a point with the locos.

However, the Hastings units were built for long distance main line services and had a low density internal layout. The Hampshire's on the other hand were built for local short distance services and had a high density layout. In reality, these were two very different passenger markets, and there was little reason for a local service in Hampshire not to make full use of the standard loading guage.

The Sussex units were a happy medium between the two.
 

hexagon789

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When the 73/9 fleet was being converted, someone tried testing the nominally 650bhp EE diesels and found they were only generating around 350bhp.........the DEMUs had the same engines, if they were in the same state it suggests they were very inefficent, wasting a lot of diesel
Given 3-car sets could not attain their nominal 75mph on level track I wouldn't be surprised if the engines had 'lost' hp. I wonder how they would've fared if they had got the Dorman 750hp engines experimentally fitted to one unit for a period
 

big all

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Thanks ;), but seriously - I have so much random knowledge and information I've picked up from so many sources it's no wonder I have a habit of mashing bits of it up now and again! :lol:


I reckon given the chance I could drive a 101 without any input from an instructor. One day when this virus situation is over in think I'd relish such an opportunity.




Sometimes bits are correct. The reasoning behind the two 73 subclasses being unable to multi seems logical enough when explained though that doesn't mean it is correct. I'll see if I can dig up more conclusive information
From what I can remember from an old magazine article, 73/0 & 73/1 can multi on diesel using the blue star connections. I will try to dig it out as it had a table of what SR stock could work with each other.
73/0 extra high level demu jumpers as well as electric jumpers blue star low level lower overall power
73/1 27 way high level emu jumper only blue star low level .
 

B&W

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Thanks ;), but seriously - I have so much random knowledge and information I've picked up from so many sources it's no wonder I have a habit of mashing bits of it up now and again! :lol:


I reckon given the chance I could drive a 101 without any input from an instructor. One day when this virus situation is over in think I'd relish such an opportunity.




Sometimes bits are correct. The reasoning behind the two 73 subclasses being unable to multi seems logical enough when explained though that doesn't mean it is correct. I'll see if I can dig up more conclusive information
73/0 are totally different Locos in terms of wiring and control to 73/1. One designed at Eastleigh and one by EE. Don't take my word for it, look at the schematics.
 

hexagon789

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73/0 are totally different Locos in terms of wiring and control to 73/1. One designed at Eastleigh and one by EE. Don't take my word for it, look at the schematics.
It wasn't that I doubted it was correct, more a comment on Wikipedia's not always correct information.
 

B&W

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Given 3-car sets could not attain their nominal 75mph on level track I wouldn't be surprised if the engines had 'lost' hp. I wonder how they would've fared if they had got the Dorman 750hp engines experimentally fitted to one unit for a period
My point is that a sensible purchasing policy would have built all the DEMUs to the same gauge, same basic design, same framelength as part of a single order for go-anywhere units, instead of multiple small orders of subtley different designs and sizes. Building on three different body widths and two different body lengths was simply ridiculous - everything should have matched the 6L sets in dimension.
The narrow bodied class 33 was another example - all the 33 fleet should have been built on the narrow jigs, as should the 27s which followed them.
The first Hastings units, 6S used existing underframes, the 6L and 6B came later. Argument could be made for making more 3Ls derived from the 6L design in lieu of 3D Oxted units but the other standard width units were built using EMU designs and components so these were not specials. It also meant 3+2 seating rather than 2+2 so more passengers per unit. The EE equipment was used all over the SR and had been for decades so was well known by staff of all grades and far more reliable than a lot of DMMU units, a key decision maker for a railway like BR(S)
The 33/2s came after the 33/0s and the redesign costs helped BRCW to choose to close down, nearly every drawing was redrawn and reissued. Some equipment and electrical trunking had to be relocated and the maintenance access is very poor compared to a standard 33/0.
 

Taunton

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Not the rattly thing with bus seats I experienced on the route. Totally unsuited to a longish cross-country service.
If it had bus seats it wasn't a WR unit as they never bought those, but had some Met-Cam units imposed on them later - which did get onto this line.

I can accept one of the points above, that underfloor-engined dmus may not have been acceptable on the 3rd rail, as there were various issues, such as alternative engine starting, which required the preparing driver to work from the lineside.
 

Islineclear3_1

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Plus of course Eastleigh, who did their own thing and put diesel-electric power units into emu bodies.
Only the Southern Region seemed to get away with building its D(E)MUs to be totally different to the rest of the country. Is there any widely agreed explanation of why the Southern ended up with its own very characteristic DMUs, rather than getting some tweaked version of, for example, Classes 115/116/117 ?
At that time, the Southern was very ingenious in its design and build and capitalised on its own excellent design which was able to be built and put into service relatively quickly
 

yorksrob

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If it had bus seats it wasn't a WR unit as they never bought those, but had some Met-Cam units imposed on them later - which did get onto this line.

I can accept one of the points above, that underfloor-engined dmus may not have been acceptable on the 3rd rail, as there were various issues, such as alternative engine starting, which required the preparing driver to work from the lineside.
Indeed. Perhaps some of the native WR units were more suited. That said, whilst the EPB trailer probably wasn't ideal, Hastings stock provided a perfectly good travelling environment for the journey.
 

Journeyman

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Probably down to the stupid purchasing policy the BRB had when ordering DMU stock for dieselisation projects. Instead of placing large ongoing orders and allocating units when delivered, they instead ordered small batches - each intended for a specific regional project, and notionally optimised for such. So a lot of small orders of non-standard machines. Made worse by the fact that the managers on the ground were happy to mix-and-match sets, and use them away from the area they were notionally purchased for. The result? Units allocated and used on routes they weren't intended for, or optimised for.
You yourself have commented in the past on the WR habit of using high density DMUs on cross country routes, when they had low density machines purchased for those very routes
The Oxted line units were designed to be able to operate through tunnels which were too narrow for Hampshire units but more generous than the much more restricted loading gauge south of Tunbridge Wells. They operated a lot of the cross-country services via Tunbridge Wells West that needed slightly narrower units, but most of the narrow tunnels closed during the Beeching era, so from the late 60s onwards, there wasn't a need for the narrower units, and they could operate interchangeably with the Hampshire units.
 

Journeyman

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Not the rattly thing with bus seats I experienced on the route. Totally unsuited to a longish cross-country service.

What they should have done was stuck with the tadpole concept and kept the Hastings guage motor car and trailer, then when they electrified the Weymouth line, replaced the EPB trailers with driving trailers from the redundant TC sets. That way you would have had a fully gangwayed 2.5 carriage set with a comfortable high quality interior more suited to the route.
The Tadpoles were long gone by the time the Weymouth route was electrified, as there was a need to use the vehicles on the Hastings line again following service improvements, and the Hastings units themselves had gone by 1986, a couple of years before Weymouth was electrified.
 

Journeyman

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My point is that a sensible purchasing policy would have built all the DEMUs to the same gauge, same basic design, same framelength as part of a single order for go-anywhere units, instead of multiple small orders of subtley different designs and sizes. Building on three different body widths and two different body lengths was simply ridiculous - everything should have matched the 6L sets in dimension.
The narrow bodied class 33 was another example - all the 33 fleet should have been built on the narrow jigs, as should the 27s which followed them.
Nope. Quite apart from anything else, the Hastings fleet was built to the mainline/intercity standard of the day for long-distance services, and the other units (Hampshire/Oxted) were built for local services, and therefore there was a need for different interiors and shorter trains. Also, the decision to build narrow 33s was made very late in the day, after the first standard width ones emerged, and it turned out to be very difficult and expensive to construct them. The class 27s and 33s were based closely on the class 26, built in large numbers.
 

yorksrob

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The Tadpoles were long gone by the time the Weymouth route was electrified, as there was a need to use the vehicles on the Hastings line again following service improvements, and the Hastings units themselves had gone by 1986, a couple of years before Weymouth was electrified.
Indeed, but I think that with a couple of years of storage, better use could have been made of some of the redundant Hastings units. Certainly some were knocking around into the late 80's. The Tadpole concept could have been resurrected even if the carriages were different.
 

Taunton

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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.
Not quite. The real development of multiple unit (as opposed to single railcars with individual direct mechanical controls) was the 1940 build of GWR railcars, built as previously in conjunction with AEC, the large bus/lorry manufacturer with works at Southall alongside the GW main line (site now inevitably a housing estate). AEC did the power train, with bus engines and gearboxes, Swindon managed the project, but the car construction was actually subcontracted out to Gloucester RCW. The last four cars of the batch, Nos 35-38, were the pioneer multi-unit cars, a twin set with the controls working both cars, including the ability to insert an intermediate normal carriage, which was not quite normal because it needed a control line running under the frame connecting the two power cars. See the bottom here http://www.greatwestern.org.uk/aec3.htm

AEC had done remote air-operated control of bus/lorry gearboxes from the 1930s, this can be seen in the London RT buses of that era, and these components came forward into the GWR cars. The actual control commands, particularly managing the direction the cars went whichever way they were marshalled (always the difficult bit in MU applications), was subcontracted by AEC to Walker Bros of Wigan, who had some export experience to Colonial railways with this.

When the Irish GNR ordered from AEC in 1947 their first batch of railcars, the whole mechanical side was basically a clone of what had been done for the GWR, including the ability to insert ordinary existing carriages between the single-ended power cars. They had the same AEC power train. Then CIE saw these, and ordered the same from AEC. Park Royal, a bodybuilding company owned by AEC, did the bodywork instead of Gloucester RCW, as AEC were now the prime contractors. CIE added control lines at the nose end of the power cars, which allowed two sets to be coupled together, an approach which had always been envisaged. Walker Bros did the design of this, which was fundamentally the Yellow Diamond format BR used. This got it mostly right, Blue Square was just a refinement of some of the detail, particularly engine starting on the remote cars. The gearchange was always straight out of an AEC bus.
 
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hexagon789

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When the Irish GNR ordered from AEC in 1947 their first batch of railcars, the whole mechanical side was basically a clone of what had been done for the GWR, including the ability to insert ordinary existing carriages between the single-ended power cars. They had the same AEC power train. Then CIE saw these, and ordered the same from AEC. Park Royal, a bodybuilding company owned by AEC, did the bodywork instead of Gloucester RCW, as AEC were now the prime contractors. CIE added control lines at the nose end of the power cars, which allowed two sets to be coupled together, an approach which had always been envisaged. Walker Bros did the design of this, which was fundamentally the Yellow Diamond format BR used. This got it mostly right, Blue Square was just a refinement of some of the detail, particularly engine starting on the remote cars. The gearchange was always straight out of an AEC bus.
And they even managed to get a 'new' lease of life as push-pull suburban sets operating with 'C's until their demise and one set then survived until 1987 with a 121 for traction by which point the carriages were literally falling to bits and the seats had been replaced with plastic stacking chairs!

At least BR didn't do that with our first generation units!
 

dubscottie

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Not quite. The real development of multiple unit (as opposed to single railcars with individual direct mechanical controls) was the 1940 build of GWR railcars
I suggest you read "Diesel Dawn, Irelands contribution to the development of the DMU 1931-1967" by Colm Flanagan 9ISBN 1-904242-08-1). AEC was not the only company supplying engines etc. Both the GNR(I) & LMS (NCC) had single cars that could multi & Single cars that worked with driving trailers in the 30s. When BR started to order DMUs, the manufacturers came over to the ROI & NI for ideas. It could be why most BR classes are similar in style to the 1952 built UTA MEDs.
 

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