37/4 - why the ETH limit?

[CW2]

They did (ex-Euston) Wolverhampton to Aberystwyth with WCML Mk2 rakes in the late 1980s. Had 37430 from Dovey Junction to Aberystwyth in 1989- Memory is a bit foggy but I'm sure it was a full rake rather than just 3-4 coaches.

When I did it, the Aberystwyth through coaches were load 5, made up to load 10 at Shrewsbury. The 37/4 only worked from / to Shrewsbury, with Wolverhampton - Shrewsbury being in the hands of a 47/4 (because of the ETH index, which started this entire discussion).

(There was a very nice move on a Monday morning, 0204 Crewe - Cardiff booked a 37/4 as far as Shrewsbury for the 0408 (MO) Shrewsbury - Aberystwyth. This was simply a way of getting the coaches for the Aberystwyth - Euston back to Aberystwyth after the weekend, so you could only do an out-and-back move on a Monday morning).

Some of the Saturdays Only services were made up of Mk 1 stock, so they ran as full rakes of 11 coaches. Traction varied from year to year, with all manner of 37s putting in an appearance.

 

[61653 HTAFC]

When I did it, the Aberystwyth through coaches were load 5, made up to load 10 at Shrewsbury. The 37/4 only worked from / to Shrewsbury, with Wolverhampton - Shrewsbury being in the hands of a 47/4 (because of the ETH index, which started this entire discussion).

(There was a very nice move on a Monday morning, 0204 Crewe - Cardiff booked a 37/4 as far as Shrewsbury for the 0408 (MO) Shrewsbury - Aberystwyth. This was simply a way of getting the coaches for the Aberystwyth - Euston back to Aberystwyth after the weekend, so you could only do an out-and-back move on a Monday morning).

Some of the Saturdays Only services were made up of Mk 1 stock, so they ran as full rakes of 11 coaches. Traction varied from year to year, with all manner of 37s putting in an appearance.

Assumed the loco change was at Wolverhampton only due to that being where the wires end- Shrewsbury would need a run-round at the very least, so the second loco change doesn't necessarily add all that much time. Though with two loco changes, it's no surprise that the through services from Euston didn't last much longer.

 

[47827]

Whilst sprinters from the 1980s (taking out the early intro issues with the 155 door issues) were one of the most reliable set of designs built, they were far from suitable for the medium and long distance expresses BR threw them onto. Mk2 PV stock, assuming the corrosion issues had been managed OK and avoided on some of the stock it was flagged up on, were dispensed with anything up 20 years before a train design would normally be considered for scrap (if we take 35 to 40 years life generally to be normal). Many mk1s had a similar fate of early withrawal and scrap 15 to 20 years before they could have lasted until with the correct works cycles. Obviously many Mk1 coaches ended up scrapped but a great many became the bedrock of steam railways once retired. Some mk1s did see out 40 year careers just about thanks to use on summer dated trains or as catering vehicles, but most survivors were thanks to the charter units of BR with an ever dwindling supply among modern private operators lasting a whopping 60-70 years (depending on build date).

The point on much of this stock though links back to the original topic and the fact BR replaced much of the loco hauled stock prematurely (arguably) due to sprinters being cheaper to operate with no shunter and less vehicles to maintain. 31s, 37s and 47s (and 50s down south) fitted with ETH were the later running designs which were the common traction by the end of most of this stock on BR. The 37/4 (and how many were done) was largely only a micro fleet as the first sprinters were already out and about as they emerged. I've a feeling had BR not gone for sprinters when they did and instead replaced some of the clapped out and older stock elsewhere, such as in the London commuter belts (which last well into this century) a bigger fleet of 37s with ETH could have been done. Although I do think more locos may have been done, newer options would have also been considered. Even much of the later build IC stock (such as Mk3s) was withdrawn earlier than its full life potential to enable faster services and a more modern travel environment. Under cascades much of it would seen use on stuff the older mk2s and mk1s (and then sprinters) worked on.

 

[AngusH]

The point on much of this stock though links back to the original topic and the fact BR replaced much of the loco hauled stock prematurely (arguably) due to sprinters being cheaper to operate with no shunter and less vehicles to maintain.

Driving brake carriages were perhaps the best option here, but adoption seems to have been fairly limited except in Scotland.

An alternate universe with class 37/4 and rakes of 4 coaches including a driving cab car on the other end would have been interesting.
I would be curious if might also have been more flexible given that extra mk2 coaches could have been added during peak demand (if the ETH were upgraded of course)

It would also have mirrored north American practice, where this seems routine and multiple units much less so...

And indeed I agree completely that a lot of the stock got a shorter life than might be expected.

 

[fodphil]

Load 6 on the full Air Con rakes.
The summer Saturday trains were MK 1s that had a very low ETH index and a 37/4 could heat them, as it was the summer timetable there was no requirement for train heating and they weren't 'plugged in'

 

[43096]

Obviously the costs of each option would have needed weighing up by BR. The 37/4s ultimately ended up with less than 5 years in some cases on their "designed for" Cambrian duties (when IC trains were withdrawn and 31/1s took over summer dated trains due to issues with Barmouth Bridge). And the Scottish ones 3 to 4 years before arrival of full sprinter operation, except for summer dated trains (which could be 37/0s at a push) and the sleepers which lasted nearly 2 decades longer than everything else. Had BR and various private operators not then found so many uses for 37/4s within design capability (the last briefly as recently as up until March 2020 on the Rhymney commuter trains via Colas and TFW) then using them to eliminate steam heat with most not being needed beyond 1988-1991 (the period when most of the original intended duties ended) off BR would not have justified spending potentially several million or more on fitting 31 of them with even ETH capable of lower level duties simply to help see off steam heat stock, the extra crews needed etc. But, love/hate/indifference towards 37/4s they kept on finding uses up until very recently and are only finally at a point where the capability need is all but obsolete bar an occasional use on a special duty or preservation setting.

Given that a 37/4 is essentially a 37/5 with ETH added, the cost can't have been that much over and above what was in the general scope of the Class 37 HGR* programme. It's essentially the cabling, switchgear and a different alternator setup (the traction alternator is the same for all HGR 37s except 37796-803/905/906). Given that, the ability to see off steam heat, even if only for a short usage period, was likely cost effective as it allowed single manning, did away with the chronically unreliable boilers and their maintenance needs, and gave passengers a better (warmer) service in winter.

*HGR = Heavy General Repair

 

[47827]

Given that a 37/4 is essentially a 37/5 with ETH added, the cost can't have been that much over and above what was in the general scope of the Class 37 HGR* programme. It's essentially the cabling, switchgear and a different alternator setup (the traction alternator is the same for all HGR 37s except 37796-803/905/906). Given that, the ability to see off steam heat, even if only for a short usage period, was likely cost effective as it allowed single manning, did away with the chronically unreliable boilers and their maintenance needs, and gave passengers a better (warmer) service in winter.

*HGR = Heavy General Repair

My own experiences of steam heat don't disagree. I love it for the novelty but it just can't be relied upon. Recall it being useless on a few longer Mk1 sets too.

 

[tomuk]

The 37/4s were used on the daily Cambrian Coast Express Shrewsbury to Aberystwyth and also Cardiff - Manchester services with Mk2s. The summer Saturday workings to Pwhelli could be hauled by anything sometimes 37/4 but mostly no heat 37s and then later 31s.

Regards the length of the stock used to Aberystwyth for a time full length rakes were used later, maybe when the DVTs came in, they started to split the rakes. The Buffet, 1st class and DVT either stayed in Shrewsbury or was taken back to Oxley by the 47. The Euston Birmingham/Wolverhampton rakes were 5 x Mk 2 TSOs, a Mk 3 RFM, and 3 x Mk 2 FOs, with a DVT.

 

[Spaceship323]

Is there any reason DRS appear to be holding on to their 37/4's as only 37/6's and a 37/7 appear on their recent disposal lists?

 

[GRALISTAIR]

I remember the ETHELs on Fort William sleepers. Converted 25s. Electric Train Heating Ex Locomotive.

What is an ETHEL unit?

ETHEL stands for Electric Train Heating Ex Locomotive and was the designation given to three class 25 diesel locomotives in 1983. They were renumbered as class 97s for departmental use and their new job was to supply electric train heating (ETH) to coaching stock on routes or operations where...

www.trainshop.co.uk

They helped with the RA issue and Train heat.

 

[Peter Sarf]

Given that a 37/4 is essentially a 37/5 with ETH added, the cost can't have been that much over and above what was in the general scope of the Class 37 HGR* programme. It's essentially the cabling, switchgear and a different alternator setup (the traction alternator is the same for all HGR 37s except 37796-803/905/906). Given that, the ability to see off steam heat, even if only for a short usage period, was likely cost effective as it allowed single manning, did away with the chronically unreliable boilers and their maintenance needs, and gave passengers a better (warmer) service in winter.

*HGR = Heavy General Repair

Yes. I cannot help thinking that converting a 37 to a 37/4 was not a lot more expensive than to convert to a 37/5. Probably the plan was that after the 37/4s were no longer planned to be needed on passenger trains they would then still be perfectly good for 37/5 type duties. So perhaps the actual costs for five years use might not be significant given there was expected to be further non-passenger work for them ?. As it is many kept finding themselves on more passenger work anyway.

 

[47827]

Is there any reason DRS appear to be holding on to their 37/4's as only 37/6's and a 37/7 appear on their recent disposal lists?

A lot to do with what got spent and when in the past. The 37/4s were having good money invested up until a few years ago so are thus much cheaper to keep going in the short term than reinstating one of the other engines that has spent longer out of traffic and needs a major exam just to be allowed out. 37403 was owned by SRPS affiliated preservationists so is off hire from DRS now and back with them as there are few requirements for every loco they had a few years ago with dwindling uses for them outside of the RHTT season. Beyond the Anglia Mk2 workings even the 37/4s will be dispensed with as soon an easy way out is found. Allowing some seasonal work to go elsewhere or hiring traction in are both options on that front too as each would probably prove cheaper once the works cycle hours expire on the current heritage fleet.

 

[Helvellyn]

The 37/4s for for three specific service groups - West Highland Line, Far North Lines and Cambrian/Marches. The RA5 requirement has been mentioned, but use on the Marches allowed use of 33s to stop as well (Provincial would have been sponsoring these if use continued but they were based on the Southern).

As a new design why provide more ETH than was necessary? The 31/4 and 47/4 conversions were more of the same, so it made sense to keep the same ETH index.

With the 37s, remember the 37/4s were all converted first as part of the refurbishment scheme, plus all came from Batch 3 machines with modified electrical equipment (as built). So in theory the maximum fleet size would have been restricted by the number of Batch 3 37s (49 I think?). Also, when the refurbishment scheme started it was planned a lot more 37/5s and 37/7s would be done than eventually were, and the fleet was very much still in demand for freight, so more going over to passenger duties wasn't a given.

 

[Cheshire Scot]

They helped with the RA issue and Train heat.

And added 70 plus tonnes of dead weight on a heavily graded route, shame they couldn't have just isolated the traction motors on one bogie instead of both, enabling it to contribute to moving the train, but then it would not have been an 'ex locomotive' the advantage of which was it could be started by station staff to preheat the train instead of by a driver.

There have been several mentions on this thread about 37/4s enabling single manning. In theory yes, but whilst I have no knowledge of the Cambrian, on the West Highland many turns remained double manned as there was no PNB opportunity, and probably similar on the north of Inverness routes where in both cases many turns worked to changeover point and back, or with only a short turnround at destination.

 

[Pigeon]

Surely that only applies if the loco is actually providing a greater amount of (ETH) power to the train? What I mean is, if you run (say) a 31/4 on a full length train of Mk 2 Air Cons then the train will be gobbling up a fair amount of power, but if the same length train were to be Mk 1s then there would be more power available for traction, wouldn't there?

Depends how much of a bodge the conversion was - whether it was a proper job or something like "hey, if we undo these wires and put an ETH plug in we'll have ETH" "You can't do that, you'll lose half the traction power" "Yes, but it doesn't cost anything". There seems to be some suggestion that the 31/4s, or some of the 31/4s, were a bit like that; proper technical details of exactly how they were set up so as to confirm or deny seem hard to come by, but drivers' recollections seem to mostly agree that if you switched off the ETH going up a bank it would make a major difference whatever the load was.

The 37/4s I'm pretty sure were a proper job, but as others have already said, they were specifically intended for hauling short trains on the Welsh and Scottish tendrils and there was no point having more capability than they needed for that.

They were part of a bigger objective which was to eliminate steam heat, which was more political than economic because steam heat needed double manning (women traincrew were a tiny minority in those days).

I initially read that as meaning "so there weren't enough women to be set to minding the kettle at half what they paid the men"...

Were there not thoughts of 37/4s for the Birmingham - East Anglian service at one point?

I was just thinking they might have done well for that. I remember it with 31/4s and it was an endless trundle...

My own experiences of steam heat don't disagree. I love it for the novelty but it just can't be relied upon. Recall it being useless on a few longer Mk1 sets too.

It was excellent when it worked, but all too often it didn't. You'd get entire classes of diesels where failed steam heat boilers were more of a cause of unavailability than everything else put together. Not only were all the different makes and models just as crap, they were all amazingly crap, and it still baffles me how they could all be so bad for so long and nobody ever sorted it out.

 

[Magdalia]

Depends how much of a bodge the conversion was - whether it was a proper job or something like "hey, if we undo these wires and put an ETH plug in we'll have ETH" "You can't do that, you'll lose half the traction power" "Yes, but it doesn't cost anything". There seems to be some suggestion that the 31/4s, or some of the 31/4s, were a bit like that;

Classes 47/4, 45/1 and 31/4 were all converted in the same way by replacing the auxiliary generator with a dual wound alternator. That's a major engineering project not a bodge. The only significant difference between the 2 batches of class 31/4 conversions is the automatic voltage regulator (AVR). The nearest thing to a bodge conversion was probably the Deltics. I think this did just draw the power off the main generator, maybe someone can confirm?

It was excellent when it worked, but all too often it didn't. You'd get entire classes of diesels where failed steam heat boilers were more of a cause of unavailability than everything else put together. Not only were all the different makes and models just as crap, they were all amazingly crap, and it still baffles me how they could all be so bad for so long and nobody ever sorted it out.

It is correct that failed steam heat boilers were a major reason for poor loco availability for passenger trains. But it is not correct to say that all boilers were equally unreliable. One of the main reasons for frequent class 31 substitutions for classes 37/47 on the GE and the GN in winter was ability to provide steam heat: the Spanner Mark I boiler was less unreliable than the others.

I initially read that as meaning "so there weren't enough women to be set to minding the kettle at half what they paid the men"...

No that's not what I meant!

 

[43096]

Depends how much of a bodge the conversion was - whether it was a proper job or something like "hey, if we undo these wires and put an ETH plug in we'll have ETH" "You can't do that, you'll lose half the traction power" "Yes, but it doesn't cost anything". There seems to be some suggestion that the 31/4s, or some of the 31/4s, were a bit like that; proper technical details of exactly how they were set up so as to confirm or deny seem hard to come by, but drivers' recollections seem to mostly agree that if you switched off the ETH going up a bank it would make a major difference whatever the load was.

That's not a "bodge" though! There's a limit to what output the engine can produce and anything used for other services such as train heat is going to reduce the amount of power going to the traction motors. So if you switch the ETH off then the engine output that the ETH uses will be available as traction power. The bigger question would be more, why fit 31s with ETH in the first place, given their performance is generally akin to an asthmatic ant carrying heavy shopping. They're not called "Brians" (after the snail on Magic Roundabout) for nothing!

 

[Magdalia]

That's not a "bodge" though! There's a limit to what output the engine can produce and anything used for other services such as train heat is going to reduce the amount of power going to the traction motors. So if you switch the ETH off then the engine output that the ETH uses will be available as traction power. The bigger question would be more, why fit 31s with ETH in the first place.

The first batch of class 31/4s were mostly for ECS movements. Some ECML trains were load 14, which is why the high ETH index was needed. On these ECS movements power for ETH to 14 aircons was more important than power at the traction motors because journeys were short and at low speed between carriage sidings and terminal stations. Apart from a few portions detached from Leeds trains there was no intention for them to be used in passenger service when ETH was first fitted. They retained their steam heating for passenger work.

Some were cascaded to secondary services after HSTs arrived, but then working on short trains of fresh air stock that required little power to heat, so the impact on power for traction was marginal. Most of the second batch did similar work, plus mail and newspaper trains that had previously been steam heated.

Class 31/4s working long rakes of aircon in passenger service is not what they were designed for and only happened because Type 4s were broken.

 

[47827]

That's not a "bodge" though! There's a limit to what output the engine can produce and anything used for other services such as train heat is going to reduce the amount of power going to the traction motors. So if you switch the ETH off then the engine output that the ETH uses will be available as traction power. The bigger question would be more, why fit 31s with ETH in the first place, given their performance is generally akin to an asthmatic ant carrying heavy shopping. They're not called "Brians" (after the snail on Magic Roundabout) for nothing!

Certainly quite true, although most stuff I had them when when I was younger e.g Liverpool to Sheffield (and occasionally beyond) services, plus club trains in the early 90s were timed and within their capability when behaving albeit with farces and delays far from unknown. Equally with some of the other bits around the country. A little more taxing were some of the North Wales trains they worked, often in the summer, during the latter period. It was a little comical if they dropped onto say the SO Blackpool to Holyhead diagram vice 37 but still not as bad as when covering for stuff involving several air cons. More common up until the early 90s but not unknown after that for them to show up right up until their demise. They even went to St Pancras occasionally still before the final BR turns off Derby finished and then after that v96 to Reading and occasionally stuff into Paddington or North of New St could still produce.

I was on the verge of reiterating past points as per eluded to in detail directly above my post. There needed to be 31s capable of doing the jumbo stock moves into Kings Cross and pre heating in the sidings but if you needed them to cover more distance a second 31 or blue star loco needed plugging to cover for the deficiency if a great distance was involved or faster running. Shortish distances like Birmingham to Derby/Sheffield in an emergency or say Liverpool to Manc on a TP service is all well and good though but replacing or assisting with something else going forward makes sense. A souped up "extra" eth 37 would probably have been OK for 6 or 7 air cons (with modest timekeeping issues on some routes) if then not slightly under index, but start talking up to 10 to 12+ air cons as per what the longer IC rakes were and indeed and on some of the tougher routes (later DVT sets) plus medium distance stuff away from the wires or weekend "dragging" beyond short diesel portions of under an hour with longer trains and the type 4 power remained a must. As others have eluded I can well imagine a (possibly bigger) fleet of higher index 37/4s would have gone pinched for the XC network and anywhere else the drivers had competency.

I can also recall 47s plugging into trains well over index and losing power but still coping better than expected, but not seen too many examples of 31s or 37s doing similar without a friend. A load 16 sleeper set in the late 90s with everything switched on and the booked second 47 DIT due to only having 1 driver from Carlisle to Edinburgh via Hexham and the ECML springs to mind. For 31s I recall an odd one being pinched in the early to mid 90s when Crewe hadn't sent enough (or any) 47s up to drag a Sunday morning Euston off Lime St. But sometimes on a good day it'd be 2x 31s so no issue.

 

[43096]

I can also recall 47s plugging into trains well over index and losing power but still coping better than expected, but not seen too many examples of 31s or 37s doing similar without a friend. A load 16 sleeper set in the late 90s with everything switched on and the booked second 47 DIT due to only having 1 driver from Carlisle to Edinburgh via Hexham and the ECML springs to mind. For 31s I recall an odd one being pinched in the early to mid 90s when Crewe hadn't sent enough (or any) 47s up to drag a Sunday morning Euston off Lime St. But sometimes on a good day it'd be 2x 31s so no issue.

It should be noted that the ETH index of the stock is the maximum power demand, which is probably not typically fully used for much of the time. It's only when heating a set of stock from stone cold in the depths of winter that the maximum power draw is likely. Therefore any pre-heated rake of stock can probably be heated by a loco even with a lower ETH index for the loco than the for the stock.

 

[47827]

It should be noted that the ETH index of the stock is the maximum power demand, which is probably not typically fully used for much of the time. It's only when heating a set of stock from stone cold in the depths of winter that the maximum power draw is likely. Therefore any pre-heated rake of stock can probably be heated by a loco even with a lower ETH index for the loco than the for the stock.

You're quite right. The mk3 (and mk4s especially) catering vehicles in full swing too also play a part. The working I referenced above with load 16 and a dead 47 ticked most of the most of the boxes (although probably only hot drinks for the crew and staff overnight) being a freezing cold autumn night with frost. The only saving grace though would have been the fact the set was pre thermed by a 90, I think, up to Carlisle so it only had to maintain the status quo.

 

[CW2]

Ideally, - if Sector management hadn't been invented - then we would have had a fleet of 50 - 60 37/4s, with an ETH index of 60 or more, capable of working (say) 10 Mk 3s singly, or more in pairs. The use generator cars on the Aberdeen and Inverness sleeper portions would have been avoided, the Penzance sleeper could be a single loco east of Exeter and a pair over the hills. Many Cross Country services south of Birmingham (allload 7 by then) could have been 37/4. Would this have been a better scenario than more 47/8s, I wonder?

 

[47827]

Ideally, - if Sector management hadn't been invented - then we would have had a fleet of 50 - 60 37/4s, with an ETH index of 60 or more, capable of working (say) 10 Mk 3s singly, or more in pairs. The use generator cars on the Aberdeen and Inverness sleeper portions would have been avoided, the Penzance sleeper could be a single loco east of Exeter and a pair over the hills. Many Cross Country services south of Birmingham (allload 7 by then) could have been 37/4. Would this have been a better scenario than more 47/8s, I wonder?

In brief. I would doubt it! A souped up 80mph 37/4 would still not match a more powerful 95mph 47/8 but the scenario you give would have made them an option for such things as Wolverhampton to Shrewsbury or Preston to Blackpool. Though still not sure BR would have queued up to replace 47s with 37s on those trains due to the length side. Perhaps things with several coaches or less that a 31 would have struggled with whilst the train heat was on though or the stuff you describe in an emergency.

Said without bias, I will point out that the moment the Inverness and Aberdeen sleepers were merged it reverted to a pool of (parcels) 47s for a reason. A 37/4 with extra ETH supply could have managed the often load 6 Aberdeen quite happily then but would be a little more lethargic. The Inverness would have been a struggle especially in autumn time with an average of load 8 at the time - see Drumochter and Slochd (neither any good if your 47 was ill either).

 

[CW2]

I was thinking of a pair on the Aberdeen and Inverness portions, just dumping the genny van. Realistically load 8+ and a hefty ETH load would be too much for a single 37/4 over the Highland Main Line.

I think you could add Crewe - Holyhead to the list of lines where IC services could have been 37/4. Also Carstairs - Edinburgh - Aberdeen daytime portions.

 

[47827]

I was thinking of a pair on the Aberdeen and Inverness portions, just dumping the genny van. Realistically load 8+ and a hefty ETH load would be too much for a single 37/4 over the Highland Main Line.

I think you could add Crewe - Holyhead to the list of lines where IC services could have been 37/4. Also Carstairs - Edinburgh - Aberdeen daytime portions.

Crewe to Holyhead in an emergency perhaps as even when non ETH 37 dropped occasionally on Holyhead to Euston workings (while drivers signed them) they struggled to maintain the schedule with 9/10 coach DVT sets. An occasion I recall a 37/4 working one Sunday aftenoon those who stayed with it advised that they had to put the standard class into "aux only" (running off the batteries) as it was struggling to power much more with the buffet on heavy use on a busy boat train and move the train properly. A souped up 37/4 probably would have needed a friend. Ironically the reason that 37 worked back out was an ETH fault at one end of 47765. This was in the days when local drivers down there were still passed out to turn a faulty loco at Valley plus there was a 2 hour break so control thought they had gone for the easy option.

 

[Magdalia]

It should be noted that the ETH index of the stock is the maximum power demand, which is probably not typically fully used for much of the time. It's only when heating a set of stock from stone cold in the depths of winter that the maximum power draw is likely. Therefore any pre-heated rake of stock can probably be heated by a loco even with a lower ETH index for the loco than the for the stock.

I'm glad you are not wiring my house! I'm not an electrical engineer but I do know not to overload electrical circuits.

On aircon stock maximum power draw also occurs when the weather is very hot. Without aircon, trains can get very hot very quickly, especially when at a standstill in direct sunlight for long periods of time.

To reiterate my first post, class 37/4 was to meet a particular requirement for an ETH fitted RA5 loco. For other routes class 47/4 and class 31/4 were already available, with no economic case to replace either with class 37/4. In a parallel universe, with enough investment funds for lots of class 37/4s, class 38 would have been affordable. Class 38 and would have replaced class 31/4, and class 37/4 would never have happened.

 

[y3j]

I'm glad you are not wiring my house! I'm not an electrical engineer but I do know not to overload electrical circuits.

On aircon stock maximum power draw also occurs when the weather is very hot. Without aircon, trains can get very hot very quickly, especially when at a standstill in direct sunlight for long periods of time.

To reiterate my first post, class 37/4 was to meet a particular requirement for an ETH fitted RA5 loco. For other routes class 47/4 and class 31/4 were already available, with no economic case to replace either with class 37/4. In a parallel universe, with enough investment funds for lots of class 37/4s, class 38 would have been affordable. Class 38 and would have replaced class 31/4, and class 37/4 would never have happened.

Err.....maximum power draw on air con stock is when it is very cold. On a Mk3 for instance that's 24kW of heating. The air con (cooling) is nowhere near that much power draw.

And I am an electrical engineer.

 

[Magdalia]

Err.....maximum power draw on air con stock is when it is very cold. On a Mk3 for instance that's 24kW of heating. The air con (cooling) is nowhere near that much power draw.

And I am an electrical engineer.

Thanks, and very cold happened more often in those days than it does now.

 

[47827]

Thanks, and very cold happened more often in those days than it does now.

Especially north on the border on long mountain stretches, where it still is frequently.

 

[Pigeon]

That's not a "bodge" though! There's a limit to what output the engine can produce and anything used for other services such as train heat is going to reduce the amount of power going to the traction motors. So if you switch the ETH off then the engine output that the ETH uses will be available as traction power.

No, that's not what I meant... the distinction I was trying to imply was:

Proper conversion: add an extra alternator (or change the main alternator for one with an extra winding) to provide a dedicated chunk of generation specifically for the ETH. The traction power available is then reduced by the exact amount the ETH is taking, just as you describe, an amount varying with train length, stock type, thermostats in coaches switching on and off etc.

Bodge: shove a switch in one of the phases coming out of the main alternator to select whether that phase goes to the traction motors or to the ETH. This would be quite horrible and definitely is not the right way to go about it, but if all you wanted was to add an ETH capability for the minimum possible amount of money and you didn't care you might still end up thinking it's a good idea. What you get then is an approximation to losing a third of the traction power whenever the ETH supply is switched on, regardless of how much the train is actually using or even if there's any train hooked on at all.

The 31/4s were intended for no more than to act as a kind of glorified shunter with ETH; the third-of-the-power bit is about consistent with their ETH index; and the overall impression I get from drivers' reminiscences is that the boost you got from switching off ETH up banks was indeed of similar magnitude regardless of how much ETH load there was; so there did seem to be at least some indication that they could have been converted by some method along those lines.

Now I learn that they actually did have a proper conversion. OK, so it was just because they were crap then.

The bigger question would be more, why fit 31s with ETH in the first place, given their performance is generally akin to an asthmatic ant carrying heavy shopping. They're not called "Brians" (after the snail on Magic Roundabout) for nothing!

I do think it's a shame that they were always so unhappy about 33s being away from the Southern and didn't shift some of them to use on the kind of general-service duties the 31/4s ended up getting used on. The performance difference seemed out of all proportion to the difference on paper in engine output.