GREAT WESTERN ELECTRIFICATION

[whole diary]

[Tim]

Distributed power with a diesel at one end for IEP^▸ (Intercity Express Program / Project.) is dead. As I said, because they finally realised it simply wouldn't work in a full-length train and changed the design - again.

Does anyone know why this is?
I did see some horrible performance figures for some of these designs but I can't figure out why this is such a challenge.
 

This is probably not the whole story, but diesel engines are difficult because of new emissions directives.  It is simpler to use small under-floor engines cos they can be derivatives of truck engines that have already jumped through all the emissions hoops than it is to use larger engines that are far less common and where they do have commonality with existing engines they will be in things liek ships that don;t have the emissions requirements to meet.

[paul7575]

What became lost in the general noise of discussion at the time, but is quite clear from Roger Ford's figures, is that the (lack of) diesel power issue was actually only relevant to the 10 car bi-mode.  As posted earlier it was analagous to running an HST^▸ (High Speed Train) around with a power car only at one end.

However a single 5 car bi-mode had the same diesel power pack as the 10 car - yet it was still tarred with the same 'underpowered' brush. AFAICS^▸ (As Far As I Can See) most of the rail media went with a simplified story that all the proposed bi-modes were underpowered.

AIUI^▸ (as I understand it) the fundamental problem with the original 5 car bi-mode was simply the loss of 20% of the potential passenger carrying capacity, but two 5 car bi-modes running together would have been little or no different to a 2+8 HST capacity wise, especially with 26m carriages. But then there's all the other capacity 'pros and cons' such as duplication of catering facilities, first class, train crew and the lack of through access - as seen with Voyagers running in pairs... 

Paul

[Not from Brighton]

It occurred to me that there was something in the original spec that called for commonality between the "commuter" stock and the "express" stock. Clearly this would favour the underslung approach as I can't see the separate power car approach working for 2, 3, 4 or 5 car sets, especially when they're working in multiples.

If this were not a requirement, I can't see that there is anything fundamentally wrong with this architecture for fixed sets of 8 vehicles and over.

Bi-mode diesels of one sort or another certainly seem like they're here to stay.