Swanage Railway General Discussion

Snowdonia National park also contains the old Trawsfynydd artillery ranges. The back road from Llanuwchllyn - Trawsfynydd has lovely warning signs warning that there is still a lot of unexploded ordinance...

 

Yes they seem to have been practising invading some one again this week. Much heavy shelling audible from Swanage in the past few days. And of course do not forget the SBS and others dropping into Studland Bay from low flying Hercules.

 

Getting back to Swanage Railway, DMU has been out and about today.

 

The Santa season kicked off today. One from each of the runs.
257 through the recently pollarded trees in King Georges Field and approaching Harmans Cross
SKP at Townsend Bridge and Corfe.

 

And now comes news that the 117 was on test this week at Eastleigh http://carlswatson.com/trains.html


On Saturday night 257 Squadron was left on train overnight to keep it warm.

 

I am trying not to be catty, but doesn't the "M" in DMU stand for something?

 

Indeed it does - "multiple". But that refers to the ability of a multiple unit to work with other multiple units, not that the individual unit is any particular length.

 

Mono

 

Motor when it is a single unit

 

Correct acronym should be Diesel Mechanical Multiple Unit ,ie DMMU, as opposed to them Southern- based Diesel Electric Multiple Unit- DEMU......

 

DHMU ?!

 

Possibly why common parlance saw the separation between "DMU" (where the drive to the wheels doesn't use traction motors) and "DEMU" (where it does). I suspect this is also reinforced by the BR numbering scheme - classes 100-199 for DMU, classes 200-299 for DEMU; a distinction perpetuated to today with class 180 being the 125mph diesel hydraulic units built by Alstom, and 220/221 for the 125mph "Voyager" diesel electric units built by Bombardier.

 

I'm going to stick my neck out here and disagree with you. A multiple unit is a fixed formation set of vehicles that can driven from either end. The fact that it can work in multiple with other similar units is irrelevant. By your defination why are locos not defined as diesel mulitple units as they too can work in multi with other locos. I have always known the class 121 and 122 single units as railcars.

Peter (who has no expertise on this subject and is prepaired to be enlightened)

 

Your comment made me think, both about that example and at the other extreme, about the classification of units like class 700 which could never work in multiple in normal circumstances because of their length. Quoting that well known reliable source Wikipedia, I get the following definition which I think probably covers both of our views:

"A multiple-unit train or simply multiple unit (MU) is a self-propelled train composed of one or more carriages joined together, which when coupled to another multiple unit can be controlled by a single driver, with multiple-unit train control." It goes on to add the following rider - "Note that although multiple units consist of several carriages, single self-propelled carriages - also called railcars, rail motor coaches or railbuses - are in fact multiple-units when two or more of this is working connected through multiple-unit train control (regardless if passengers can walk between the units or not)."

I would suggest this supports and enriches both of our views.

 

Technically, a class 700 is a multiple unit, as it is two sets permanently coupled together. A-F and 6-1, though on an 8 car 2 of each classification are missing.

 

I'll go along with that. Thanks for checking it.

Peter

 

A multiple unit is a powered vehicle (or vehicles) that carries a payload, as distinct from a locomotive which is a mechanically powered vehicle which is not in itself constructed to carry a load. On this basis, HST power cars are technically locomotives.

 

There lies a can of worms, but as the vehicles numbered 43002-43198 were built with guard equipment and to take a parcels payload, the argument for IC125 to be a DEMU is also strong. I write as someone who regards those vehicles as locomotives, not part of multiple units.

 

I always thought of DMU as being Diesel Mechanical unit but as others have already pointed out the right definition is DMMU , The second letter denoting the form of transmission, E, M H etc, there was though only one hydraulic DMU class though the 121 I believe

 

At least one other - the class 180s have a hydraulic transmission.