Interoperability of First Generation DMUs

[Guest Belgian]

I know that the first-generation DMUs often had different control mechanisms which prevented them from working in multiple with members of other classes, denoted by 'blue stars' and similar designations painted near to the mu-working connectors.

 

My question concerns the multiple working of the various classes which Bachmann have modelled: can any one member of classes 101, 105, 108 and Derby Lightweight work in multiple with any or all of the other classes, and if just some, which ones? I want to have an excursion to a Southern-based model using DMUs and want to have different types if prototypically accurate. (I know the models can work together!!!!).

 

JE

[Gwiwer]

Derby Lightweights were indeed coded yellow diamond for coupling and multiple working purposes. I also seem to recall that not quite all the 105s were blue square either but as always a slowly maturing memory is happy to be corrected if required.

 

EDIT : Found what I was looking for! Not the 105s but some Met-Camms were also yellow diamond. Power-trailer twins E79055-66 + E79266-82 were so coded. So were the Cravens parcel vans M55997-9. So you could if you wish suggest that your train included a mix of those even if the modelled version are not exactly right for the prototype.

[Steven B]

From www.railcar.co.uk :

 

Blue Square:

Class 100 (Gloucester RC&W 2-car sets)

Class 101/2 Met-Camm 2, 3 4-car sets

Class 103 Park Royal 2-car sets

Class 104 Birmingham RC&W 2, 3 & 4-car sets

Class 105/6 Cravens 2 & 3-car sets

Class 107 Derby 3-car sets

Class 108 Derby 2, 3 & 4-car sets

Class 109 Wickham 2-car sets

Class 110 Birmingham 3-car sets

Class 111 Met-Camm 2 & 3-car sets

Class 112/3 Cravens 2-car sets

Class 114 Derby 2-car sets

Class 115 Derby 4-car sets

Class 116 Derby 3-car sets

Class 117 Pressed Steel 3-car sets

Class 118 Birmingham RC&W 3-car sets

Class 119 Gloucester RC&W 3-car sets

Class 120 Swindon 3-car sets

Class 121 Pressed Steel Single / 2-car sets

Class 122 Gloucester RC&W Single / 2-car sets

Class 123 Swindon 4-car sets

Class 124 Swindon 6-car sets

Class 127 Derby 4-car sets

Class 128 Gloucester RC&W single cars

 

Orange Star:

Class 125 Derby 3-car sets

 

White Circle:

Class 126 Swindon Inter-City 3-car sets

 

Yellow Diamond:

Class 129 Cravens single cars

Met-Camm 79xxx series 2-car sets

 

Red Triangle/Yellow Diamond

Derby Lightweight 1,2 and 4-car sets

 

Note that whilst having the same MU working type there is a limit on the number of vehicles that can make up a train of several MU's - might be 12?

 

Happy modelling.

 

Steven B.

[Titan]

I think it was a total of 12 engines, so it would normally be a total of 6 motor coaches, with up to 6 trailers depending on the units used.

[giz]

A couple of notes to add to Steven B's comprehensive list:

 

Only the first batch of Derby Lightweight power twins were red triangle, the all the rest were yellow diamond. Bachmann haven't produced the red triangle version (yet?).

 

The 127s were originally blue square but were later re-coded red diamond (not compatible with the early lightweights though) because of problems running them mixed with gearbox fitted sets. The 127s were torque converter and if a gearbox fitted set was hung on the back the driver could forget to change gear with obvious consequences.

[Gwiwer]

Minor point of order:

 

Class 126 could operate as 3-car or 6-car sets. Nominally they were 6-car with the outer driving motors having no gangways. They could be (and often were) divided between the inner motor coaches which resembled the WR class 123 coaches in having a gangway connection but a near-flat rectangular driver's and second-man's window rather than the wrap-round ones used on the 123s. Thus you could see a 3-car unit in traffic as effectively a half-set with two quite different vehicles at either end.

[SRman]

I think that between Steven B and giz you have a comprehensive summary there.

 

I am not sure if there were any restrictions on the Rolls Royce Cravens sets (class 112 or 113, from memory) as some of these also had torque converters which could have caused problems similar to those giz outlined with the 127s. Maybe they were operationally isolated by geography so the problem didn't arise (and for the record, that is speculation on my part!).

[jonathan452]

The 127s were originally blue square but were later re-coded red diamond...........................

I trust you really meant red triangle.

[Gwiwer]

I also seem to recall that not quite all the 105s were blue square either

I am not sure if there were any restrictions on the Rolls Royce Cravens sets (class 112 or 113, from memory) as some of these also had torque converters ...

 

Those are the ones I had in mind. I was pretty sure they were not blue square but my only available printed source suggests that they were.

[jonathan452]

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Those are the ones I had in mind. I was pretty sure they (Rolls Royce Cravens sets class 112 and 113) were not blue square but my only available printed source suggests that they were.

Thinking about what I read on the old railcar site some of the mechanical transmission Rolls Royce Cravens sets latterly ended up on St.Pancras suburban services, sometimes working in multiple with the Class 127's. At the time the latter unts would have still have had their blue square coupling code.

 

An accident occured at Sandridge (verify location?) in the late sixties due to the previously mentioned issue of mixing gear box and torque converter units in one train. The 'obvious consequences' would seemed to have manifested themselves in this particular accident.

 

I believe that by the time the Class 127's were consequentially redesignated a red triangle code both the Class 112 and 113 Cravens units had been withdrawn. One can therefore assume that the latter units kept a blue square code throughout their (rather short) operational life.

[Derekl]

Jonathan - Sandridge accident apparently not a result of mixed transmissions, but lack of oil in the Cravens unit transmission. The driver and driver instructor accompanying him both confirmed he was driving as manual transmission required.

 

Accident report here, for those interested: http://www.railwaysarchive.co.uk/documents/MoT_Sandridge1968.pdf

[jonathan452]

Jonathan - Sandridge accident apparently not a result of mixed transmissions, but lack of oil in the Cravens unit transmission. The driver and driver instructor accompanying him both confirmed he was driving as manual transmission required.

 

Accident report here, for those interested: http://www.railwaysa...ndridge1968.pdf

Thank you

 

Accident report - an interesting read.

[robertcwp]

A couple of notes to add to Steven B's comprehensive list:

 

Only the first batch of Derby Lightweight power twins were red triangle, the all the rest were yellow diamond. Bachmann haven't produced the red triangle version (yet?).

 

The 127s were originally blue square but were later re-coded red diamond (not compatible with the early lightweights though) because of problems running them mixed with gearbox fitted sets. The 127s were torque converter and if a gearbox fitted set was hung on the back the driver could forget to change gear with obvious consequences.

 

The 127s were recoded red triangle, but that was after the original lightweights had been withdrawn.

 

M51611 by robertcwp, on Flickr

 

Here is a Cravens/hydraulic set near the end of its life, and still blue square:

 

113_Darwen_18-5-68 by robertcwp, on Flickr

 

And here is a Cravens/RR-mechanical set - note two MBSs - at Bedford:

112_Bedford-Midland by Robert Carroll, on Flickr

[Bernard Lamb]

As well as the actual compatability question you need to consider which types were located to the same areas and thus might actually have had an opportunity to work together. I have also come across various references on operating procedures where certain units were not liked at certain locations

Bernard

[Guest Belgian]

With only a cursory knowledge of DMUs, may I also enquire what were the visible differences between the Derby Lightweights (were they never given TOPS codings? I thought even some withdrawn diesel classes received TOPS codings) and the subsequent Derby productions? I have a vague idea that the later types had longer frames but were any of the blue square Derby units visibly identical to the Lightwieghts and thus suitable candidates for renumbering? (I have always thought the original Derby cab front was the most attractive DMU design).

 

Thanks, and also thanks for the detailed discussions in this thread and for the knowledge so kindly and freely shared.

 

JE

[giz]

AFAIK neither the original lightweights nor their Metro Cammell equivalents were given class numbers, there doesn't appear to be a gap left for them. All of the other 150bhp engined units fill the range from 100 to 109 with 110 to 113 for higher powered short frame units and 114 up for the long frame sets.

 

All subsequent (blue square) Derby production featured the cab type used on the class 108s, in fact the 108 was the later version of the Derby Lightweight with the significant difference being the ends of the coaches. The sides are very similar.

 

The other Derby types are:

 

Class 107: visually similar to the 108 but of much heavier, mainly steel, construction

Class 114: long frame (64ft) heavyweight, rather like a stretched 107 (but actually built in between the original lightweights and the 108s)

Classes 115, 116, 125, 127: long frame suburban units