Could the Southern region DEMUs been built as bimodes?

[778]

Could the Southern Region DEMUs of the 1950s been built as bimodes in the same way that the 73s were, with the ability to run on 3rd rail like an EMU and with the diesel engines for the unelectrified lines. Was there a reason why they could design the 73s to run on both diesel and electric power but not the DEMUs?

 

[Irascible]

Cost, I'd have thought - the 73s were meant to go anywhere, and the DEMUs weren't. 73s are considerably less powerful on diesel.

 

[Sun Chariot]

Could the Southern Region DEMUs of the 1950s been built as bimodes in the same way that the 73s were, with the ability to run on 3rd rail like an EMU and with the diesel engines for the unelectrified lines. Was there a reason why they could design the 73s to run on both diesel and electric power but not the DEMUs?

The required mechanical and electrical equipment, for diesel propulsion alone, took up a sizeable space; adding a bimode capability would have further eroded revenue earning (passenger) space.
The Hastings, Oxted and Hampshire units were ordered for specific non-electrified lines.

 

[The exile]

The required mechanical and electrical equipment, for diesel propulsion alone, took up a sizeable space; adding a bimode capability would have further eroded revenue earning (passenger) space.
The Hastings, Oxted and Hampshire units were ordered for specific non-electrified lines.

Also, pre 1973-ish, fuel was cheap and environmental factors hardly considered (diesel was “clean” when compared to steam) so running on diesel over the third rail (on Hastings and Oxted lines runs in particular) was not an issue.

 

[Tony73E]

In a word - yes. However, if you look at a DEMU motor coach roughly half is taken up by engine and generators and half by passenger accomodation. The underframe space between the bogies is taken up with fuel tanks, battery boxes, compressors and control eqipment. A 6 car unit is therefore effectively a 5 car as far as passenger accomodation is concerned. Room for the control equipment for EMU operation (resistance grids, contactors or camshaft plus change-over bits) would have to provided above the underframe as there is no space left on the underframe eating further into available passenger space.

 

[Sun Chariot]

I didn't get to ride a 201-203 or a 'Tadpole' in service - I did, however, ride 205s, 207s and one 210.
The 210, I just recall a) was far quieter than contemporary mechanical DMUs, b) had a rather uninspiring interior, c) it seemed rather small passenger area in the DMBSO.

 

[Rescars]

The ride in a DMBSO could be quite exhilarating if the driver was going for it, especially in their later years when the dampers were getting tired!

 

[norbitonflyer]

In a word - yes. However, if you look at a DEMU motor coach roughly half is taken up by engine and generators and half by passenger accomodation. The underframe space between the bogies is taken up with fuel tanks, battery boxes, compressors and control eqipment. A 6 car unit is therefore effectively a 5 car as far as passenger accomodation is concerned. Room for the control equipment for EMU operation (resistance grids, contactors or camshaft plus change-over bits) would have to provided above the underframe as there is no space left on the underframe eating further into available passenger space.

Would have been possible if the electrical gubbins was under the adjacent trailer.
It would have required power to be transmitted between cars but this was normal for a third rail emu, which had shoes on driving trailers.
I believe EP stock could multiple with DEMUs, although I never saw it happen. 33s and EMUs certainly could.

 

[DelW]

Would have been possible if the electrical gubbins was under the adjacent trailer.
It would have required power to be transmitted between cars but this was normal for a third rail emu, which had shoes on driving trailers.
I believe EP stock could multiple with DEMUs, although I never saw it happen. 33s and EMUs certainly could.

In the specific case of the 3R Tadpoles, the driving trailer was from an EMU, so probably originally had 3rd rail shoes though not the rest of the kit. Had they been formed using an ex EMU driving motor coach rather than trailer, the North Downs might have had bi-modes decades ago.

As an aside, those were three-car units with one-and-a-half cars of passenger space, since I never saw the DTS unlocked when I used the line.

 

[Tony73E]

In the specific case of the 3R Tadpoles, the driving trailer was from an EMU, so probably originally had 3rd rail shoes though not the rest of the kit. Had they been formed using an ex EMU driving motor coach rather than trailer, the North Downs might have had bi-modes decades ago.

As an aside, those were three-car units with one-and-a-half cars of passenger space, since I never saw the DTS unlocked when I used

Would have been possible if the electrical gubbins was under the adjacent trailer.
It would have required power to be transmitted between cars but this was normal for a third rail emu, which had shoes on driving trailers.
I believe EP stock could multiple with DEMUs, although I never saw it happen. 33s and EMUs certainly could.

DEMU's couldn't multiple with EP stock as the wire functions in the 27-way way jumper were different.

 

[grumpyoldman01]

According ti John Glover's book 'English Electric Traction Album'. making the Hastings sets as bi-modes was considered at the design stage. but was discounted as it could not be justified financially because of the additional equipment needed and the complication this would create

 

[mike57]

I have often wondered about this, but I think you need to go back to the 1950s mind set. Diesel wasn't seen as the issue that it is now. Trolleybuses and Trams (electric) were being replaced by diesel buses. Why would you spend time and money on something that didn't deliver any benefits. Complexity and maintenance would have increased. Diesel was cheap. Diesel was replacing steam.

I think it could have been done at the time, the technology isn't very complex, but the question asked at the time would be why bother. This is before you address the issue of where to put the extra equipment.

 

[D7666]

Would have been possible if the electrical gubbins was under the adjacent trailer.
It would have required power to be transmitted between cars but this was normal for a third rail emu, which had shoes on driving trailers.
I believe EP stock could multiple with DEMUs, although I never saw it happen. 33s and EMUs certainly could.

No SR DEMU of any type could ever multiple with an EMU of any type; the 27 way control wires functions differed. When it was refurbled 1111 got 1966 type EMU controller in anticipation of EMU+DEMU mu operation (considered for Oxted line) but the control wires were not altered. More than one publication reported 1111 could mu with EMU but it could not; indeed it had to retain DEMU mu to work with other DEMU.


Moving on a bit allegedly the 210s could mu with 317s etc but there seems to be no evidence this was even tested never mind proven. The same theoretical question about dual mode diesel + electric 210 could be asked but suspect same answer - not difficult to achieve but not needed at the time = why bother.


If you start down this road, why not ask about any class of diesel electric loco why they were not considered for bimode operation too. Answer is likewise not difficult to achieve but not really needed in the days of cheap fuel and no one had green thinking.


It gets worse. Extend the question and ask why SR steam loco tenders could not have had shoes and motors for third rail use (like steam loco booster bogies), and even bimode steam turbine electric. Not difficult to do. Who wanted it though. (But possibly more sense than a Leader as built was.)

 

[yorksrob]

I have often wondered about this, but I think you need to go back to the 1950s mind set. Diesel wasn't seen as the issue that it is now. Trolleybuses and Trams (electric) were being replaced by diesel buses. Why would you spend time and money on something that didn't deliver any benefits. Complexity and maintenance would have increased. Diesel was cheap. Diesel was replacing steam.

I think it could have been done at the time, the technology isn't very complex, but the question asked at the time would be why bother. This is before you address the issue of where to put the extra equipment.

Although I read somewhere that the 205's were designed with half a mind to being converted into HAP units should the need arise.

 

[Sun Chariot]

Moving on a bit allegedly the 210s could mu with 317s etc but there seems to be no evidence this was even tested never mind proven. The same theoretical question about dual mode diesel + electric 210 could be asked but suspect same answer - not difficult to achieve but not needed at the time = why tbother

Moving Off Topic purely to cover the 210:

The 210 fascinated me. I rode 210002 once (my impression of it in post #6). I recall the press of that time, suggesting it was far too over-engineered, too costly and lacking enough passenger accommodation (certainly in the 3-car formation of set 002).
Given their experience with mechanical drive and "underfoor" engine/gearbox/driveshaft, I still wonder at BR's design brief / requirements for the 210? To me, it seemed an odd choice.

 

[mike57]

Given their experience with mechanical drive and "underfoor" engine/gearbox/driveshaft, I still wonder at BR's design brief / requirements for the 210? To me, it seemed an odd choice.

I wonder if the thinking behind the 210 was to develop a replacement for longer distance loco hauled services. The 90mph top speed would imply a longer distance design. Possibly the niche that was later filled by the 158. What was the highest practical power available for an engine suitable for underfloor mounting in say 1980, was this a limit of a DMU type design.

My memories of the SR DEMUs is that performance was quite 'sedate', I used the East Grinstead/Uckfield services quite a bit when growing up, and leaving Clapham Junction heading south they were much slower than the electic units. Had they been 'bi mode' I suspect performance might have been better, but it didnt seem to cause a problem back in the day.

 

[hexagon789]

No SR DEMU of any type could ever multiple with an EMU of any type

The prototype refurbished 205 in theory could, it being rewired to permit this.

 

[D7666]

The prototype refurbished 205 in theory could, it being rewired to permit this.

As I posted upthread, no it was not.

The control wires were not altered.

It gained an EMU controller on refurbling and certain other mods to provide for a future rapid re-wire conversion but the conversion itself was never done.

 

[hexagon789]

As I posted upthread, no it was not.

The control wires were not altered.

It gained an EMU controller on refurbling and certain other mods to provide for a future rapid re-wire conversion but the conversion itself was never done.

I see, some sources suggest it was rewired.

 

[yorksrob]

I wonder if the thinking behind the 210 was to develop a replacement for longer distance loco hauled services. The 90mph top speed would imply a longer distance design. Possibly the niche that was later filled by the 158. What was the highest practical power available for an engine suitable for underfloor mounting in say 1980, was this a limit of a DMU type design.

My memories of the SR DEMUs is that performance was quite 'sedate', I used the East Grinstead/Uckfield services quite a bit when growing up, and leaving Clapham Junction heading south they were much slower than the electic units. Had they been 'bi mode' I suspect performance might have been better, but it didnt seem to cause a problem back in the day.

They could/can get up to quite a good speed on a decent run, particularly the Hastings ones with two power cars.

 

[Sun Chariot]

They could/can get up to quite a good speed on a decent run, particularly the Hastings ones with two power cars.

I think they were theoretically limited to 75mph.

A Hastings DEMU farewell excursion "The Long Thin Drag" ran the WCML and S&C; it was loaded to 14 cars: 2x 6-car sets (1032 + 1011), plus 1001s two DMBS's.

Six Bells Junction

I saw it passing Leighton Buzzard at full "chatter"; it wasn't a patch on what the 85s could do on NSE "Cobbler" services.

 

[hexagon789]

I think they were theoretically limited to 75mph.

And would struggle to achieve even that on level track. Logs of various tours with the preserved Hastings set tend to show maxima of about 71-72mph.

 

[Sun Chariot]

And would struggle to achieve even that on level track. Logs of various tours with the preserved Hastings set tend to show maxima of about 71-72mph.

11th May 1986's farewell trip produced a sprightly run above their theoretical top speed. This extract from 'Six Bells Jcn':
... The speed through Tonbridge was quite hair-raising and the train was still doing well over 80mph through Grove Park.

Six Bells Junction

 

[D6130]

They could/can get up to quite a good speed on a decent run, particularly the Hastings ones with two power cars.

Most of the Southern Region DEMUs had the same power/weight ratio; i.e. 500 bhp for every three cars (or two-and-a-half cars in terms of passenger accommodation....so in theory there would have been very little difference in performance between a three car Hampshire unit with one power car and a six car Hastings unit with two power cars. Don't forget that the original batch of Hampshire units (1101-1126) were built as two car units with the same number of identical motors as the 2-HAP electric units....but with considerably more weight to lug around in the shape of a six cylinder diesel engine and generator. Also the current applied to the motors of the diesel units was limited to the capacity of the generator, whereas the HAPs could draw considerably more current from the third rail. After a couple of years in service all but four (1119-22) of the Hampshire units were given an extre centre car, which diminished their performance somewhat. Two of the remaining two car units were used on the steeply-graded Southampton-Alton service until its withdrawal in 1973....and thereafter on the much less steeply-graded Eastleigh-Fareham shuttles. The other
two spent most of their lives on the Ashford-Hastings line. The later type 3D (class 207) Oxted line units had a more powerful engine (600 bhp - the same as in the class 73 electro-diesel locos) and marginally lighter bodywork, so were slightly better performers.

I think they were theoretically limited to 75mph.

And would struggle to achieve even that on level track. Logs of various tours with the preserved Hastings set tend to show maxima of about 71-72mph.

Back in the mid-late 1970s I've logged Hastings units doing 85 mph down Honiton and Semley banks on the Summer Saturday Brighton-Exeter service with a Salisbury driver and between Stonegate and Etchingham on a Charing Cross-Hastings fast service with a St Leonards driver. Of course this was downhill and using stopwatch/milepost timings (no GPS in those days) but I should have been accurate to within 1-2 mph. Needless to say the riding was distinctly lively and the buffet car stewards were not amused.

 

[Helvellyn]

Moving on a bit allegedly the 210s could mu with 317s etc but there seems to be no evidence this was even tested never mind proven. The same theoretical question about dual mode diesel + electric 210 could be asked but suspect same answer - not difficult to achieve but not needed at the time = why bother?

The use case I heard, but have no proof for, was as part of the BedPan electrification to allow extension beyond Bedford to Wellingborough, Kettering and Corby. Assume would have delivered a speeding up of MML InterCity services and a more frequent service to those Northants towns than a 90 minute InterCity service.

 

[Sun Chariot]

Back in the mid-late 1970s I've logged Hastings units doing 85 mph down Honiton and Semley banks on the Summer Saturday Brighton-Exeter service with a Salisbury driver and between Stonegate and Etchingham on a Charing Cross-Hastings fast service

Happy days My post #23 has a link to the review of May 1986's "Hastings DEMU Farewell", including a running stint "in the 80s"

Of course, I'm now guilty of talking well off topic and getting all nostalgic.

 

[yorksrob]

Most of the Southern Region DEMUs had the same power/weight ratio; i.e. 500 bhp for every three cars (or two-and-a-half cars in terms of passenger accommodation....so in theory there would have been very little difference in performance between a three car Hampshire unit with one power car and a six car Hastings unit with two power cars. Don't forget that the original batch of Hampshire units (1101-1126) were built as two car units with the same number of identical motors as the 2-HAP electric units....but with considerably more weight to lug around in the shape of a six cylinder diesel engine and generator. Also the current applied to the motors of the diesel units was limited to the capacity of the generator, whereas the HAPs could draw considerably more current from the third rail. After a couple of years in service all but four (1119-22) of the Hampshire units were given an extre centre car, which diminished their performance somewhat. Two of the remaining two car units were used on the steeply-graded Southampton-Alton service until its withdrawal in 1973....and thereafter on the much less steeply-graded Eastleigh-Fareham shuttles. The other
two spent most of their lives on the Ashford-Hastings line. The later type 3D (class 207) Oxted line units had a more powerful engine (600 bhp - the same as in the class 73 electro-diesel locos) and marginally lighter bodywork, so were slightly better performers.


Back in the mid-late 1970s I've logged Hastings units doing 85 mph down Honiton and Semley banks on the Summer Saturday Brighton-Exeter service with a Salisbury driver and between Stonegate and Etchingham on a Charing Cross-Hastings fast service with a St Leonards driver. Of course this was downhill and using stopwatch/milepost timings (no GPS in those days) but I should have been accurate to within 1-2 mph. Needless to say the riding was distinctly lively and the buffet car stewards were not amused.

I must admit, I don't think I've ever experienced a 205 or 207 on a fast(ish) run.

Their less than nippy nature seemed fine for the Marshlink.

The preserved Hastings unit has been running around with three power cars of late, which must improve the available power somewhat.

== Doublepost prevention - post automatically merged: 13 Jun 2024 ==

Happy days My post #23 has a link to the review of May 1986's Hastings DEMU Farewell, which including a stint of running "in the 80s"

Of course, I'm now guilty of talking well off topic and getting all nostalgic.

I'm hoping that HDL will re-run the Long Thin Drag one day. That must have been a blast.

 

[Sun Chariot]

I'm hoping that HDL will re-run the Long Thin Drag one day. That must have been a blast.

It's one of the 1980s tours I'd do, if I had my time again. I did 1988's "Fellsman 2" with 50024 + 50050. Vanguard threw an oil leak around Lancaster, so (me being in the front coach) I recall Shap was taken with a thick oily mist.
The Sertle & Carlisle seemed less taxing, so 24 behaved for the remainder of that day. Photo stop at Ribblehead - those days of "de-training and track-walking".

 

[30907]

Most of the Southern Region DEMUs had the same power/weight ratio; i.e. 500 bhp for every three cars (or two-and-a-half cars in terms of passenger accommodation....so in theory there would have been very little difference in performance between a three car Hampshire unit with one power car and a six car Hastings unit with two power cars. .(SNIP)
The later type 3D (class 207) Oxted line units had a more powerful engine (600 bhp - the same as in the class 73 electro-diesel locos) and marginally lighter bodywork, so were slightly better performers.

ISTR the Hastings sets originally had 600hp which were swapped with the Hampshire 500hp engines when the latter were increased to 3-car.

 

[778]

Could a DEMU work in multiple with other 50s/60s built DMUs (101s etc)?