When did Electro-Diesel become bi-mode?

[John Luxton]

Just been scanning some old slides of Class 73 Electro-Diesels and started wondering why we now refer to dual power MUs and locos as bi-mode?

Why the change in terminology when the original was a better descriptor?

 

[swt_passenger]

Just been scanning some old slides of Class 73 Electro-Diesels and started wondering why we now refer to dual power MUs and locos as bi-mode?

Why the change in terminology when the original was a better descriptor?

I think a 73 probably would be referred to as a bimode if it had been produced using present day terms.

Electro-diesel is perhaps too similar to Diesel-Electric, most of which are diesel locos or units, but don’t use an external power source.

 

[43096]

Just been scanning some old slides of Class 73 Electro-Diesels and started wondering why we now refer to dual power MUs and locos as bi-mode?

Why the change in terminology when the original was a better descriptor?

I think it started when the HST replacement project (IEP) was developing the design: DfT didn't want the word diesel using as it would draw attention to the lack of electrification on Great Western, so they came up with "bi-mode" instead. It is of course far less precise and descriptive than electro-diesel as the modes are not specified - which was probably the point of changing it.

 

[D365]

Just been scanning some old slides of Class 73 Electro-Diesels and started wondering why we now refer to dual power MUs and locos as bi-mode?

Why the change in terminology when the original was a better descriptor?

Perhaps the emphasis on electric because the original Class 73s (much like the Class 88) are electric locos that benefit from a small "tractor" engine.

 

[3141]

I think it started when the HST replacement project (IEP) was developing the design: DfT didn't want the word diesel using as it would draw attention to the lack of electrification on Great Western, so they came up with "bi-mode" instead. It is of course far less precise and descriptive than electro-diesel as the modes are not specified - which was probably the point of changing it.

I'd say that the IEP was being designed was well before the problems that caused the scope of the Great Western electrification to be cut back had appeared. They were going to need bi-modes anyway to run via the Berks and Hants line and to Cornwall. Equally, bi-modes would be needed on the East Coast Main Line to reach Aberdeen and Inverness.

Bi-mode seemed to me a good term to indicate a train that could provide a similar performance as an electric or as a diesel, whereas electro-diesels had a reduced performance on diesel power. But bi-mode now seems to be used for anything that has two types of power, one of which may be definitely subsidiary to the other.

 

[43096]

Bi-mode seemed to me a good term to indicate a train that could provide a similar performance as an electric or as a diesel, whereas electro-diesels had a reduced performance on diesel power. But bi-mode now seems to be used for anything that has two types of power, one of which may be definitely subsidiary to the other.

You only think that because the 73s have a lower rating on diesel as built. Do you call the re-built 73/9s "bi-modes" because they have the same rating in electric and diesel modes?

Bi-mode is less clear: what are the modes? AC power and DC power? AC and battery? AC and diesel? To me bi-mode sounds like something under the LGBT umbrella...

 

[contrex]

About 5 years ago a retired ex-BR Western Region steam & diesel driver told me the new trains coming were "electro-diesels".

 

[Ken H]

Multiple units is another minefield

Using 4 letter acronyms. Describe

Diesel electric ie 'thumper' or voyager
EMU with diesel capability ie 769
DMU with battery so like a hybrid car
EMU with battery to take it off the juice
(Does it matter in this discussion if it has a big battery for long trips off the juice, or just a small one to save particulate polution in covered stations? or in cities?)

And then there are fuel cells.... and bionic duckweed.

 

[Western Lord]

I've always thought that the government's use of the term bi-mode was in the hope that people might confuse it with bio-mode and think it meant that the trains were "green" (which , on Great Western, they are of course)!

 

[Ken H]

I've always thought that the government's use of the term bi-mode was in the hope that people might confuse it with bio-mode and think it meant that the trains were "green" (which , on Great Western, they are of course)!

are they 'green' between cardiff and Swansea, or between reading and Plymouth etc?

 

[pdeaves]

are they 'green' between cardiff and Swansea, or between reading and Plymouth etc?

I think that was a light-hearted comment that they are painted green.


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The thing with bi-mode as opposed to electro-diesel is that the non-electro bit need not be diesel. Hydrogen, clockwork, any number of other methods could be used.

 

[birchesgreen]

I thought bi-mode term comes from the US?