D.M.U coupling codes

[jeffbush]

Dear all 

                  not sure if this is the right place to ask this if not apologies and just ignore me ,

i have a derby lightweight and a Hornby class 101.Can i run these coupled, realistically due to their differing codes and prototypically would this ever have happened.as a child i remember a wealth of different dmu units coupled together in rakes 

                                                                       many thanks 

                                                                               jeff

[giz]

If by Derby Lightweight you mean the original version, not the later 108, no they can't be coupled to a 101. The only units that could couple to them were the early Metro Cammell lightweights and the Cravens parcels units.

 

Most other dmus, like the 101, were blue square coupling code and could be coupled but there were exceptions.

[uax6]

Well thats not strictly true....

 

Two (or more) units of differing coupling code can be coupled together, but instead of being worked in multiple (ie with only a driver in the leading cab) they would have to be worked in tandem (with a driver in the leading cab of each unit).. This applies to locos too, and the current rule book still allows this to happen.

 

Then there are the cases where the coupling code is different, but the control is identical, the one example that springs to mind is the old Bed-Pan units. These were given Red Triangle codes, but were infact standard Blue Square, the idea being to keep them away from the mechanical transmisson units as there had been issues with the way they were driven. One unit at Llangothlen runs with a 127 power car coupled to a 108 or 105 trailer.

 

Then there is the case of Test Car Iris (the single Derby lightweight car). This was built with Yellow Diamond code when new, but later in RTC days the controls were modified to standard blue square, although i belive it kept the Yellow Diamond jumpers.

 

Andy G

[giz]

Then there are the cases where the coupling code is different, but the control is identical, the one example that springs to mind is the old Bed-Pan units. These were given Red Triangle codes, but were infact standard Blue Square, the idea being to keep them away from the mechanical transmisson units as there had been issues with the way they were driven. One unit at Llangothlen runs with a 127 power car coupled to a 108 or 105 trailer.

 

 

 

Andy G

The 127s were originally blue square when built and were, as you say compatable with the other blue square units as long as they were driven correctly. Following the incidents where the drivers didn't change gear manually when in this mode the coupling code was changed to red triangle but no physical changes were made to the units hence they can still operate with blue square units.

[TheSignalEngineer]

A lot of 127 trailers were used in Blue Square sets after the 127 power cars were scrapped. Tyseley fitted gangways to TSL coaches for use on the Cross City line.

[Andy W]

The 127s were originally blue square when built and were, as you say compatable with the other blue square units as long as they were driven correctly. Following the incidents where the drivers didn't change gear manually when in this mode the coupling code was changed to red triangle but no physical changes were made to the units hence they can still operate with blue square units.

Only last week on the GCR I travelled on a DMU rake made up of two 127 power cars and three 101 power cars, most certainly operating in multiple (there were 101 cars either side of the 127s). A fair amount of smoke from all those engines when they set off from Quorn with a totally wedged Bonfire Night special. With a 25mph limit in preservation the issues that caused 127s to be relabelled as red triangle code don't really apply.

[giz]

There is a useful page on the Railcar Association website on dmu coupling codes:

 

http://www.railcar.co.uk/technology/couplingcodes.html