Can anybody here with some technical skills and / or inside knowledge please explain to me why the class 37 refurbishment programme which produced the 37/4 subclass limited their ETH Index to just 30? Clearly if they were only going to be hauling a relatively small number of coaches around then 30 would be adequate, but they would have been much more use operationally if they could have substituted for 47s on some workings, e.g. Preston - Blackpool, Crewe - Holyhead / Llandudno (on Euston services with a full rake of Air Cons), Glasgow Queen Street / Edinburgh - Aberdeen. Would the increased ETH index have resulted in too large a power draw from the engine? Or was there some size restriction on the generator equipment? Or was it cost constraints? Alternatively, was it simply a cunning ploy by Regional Railways to ensure their locos stuck to their services, and didn't get nicked for InterCity workings?
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37/4 - why the ETH limit?
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Books I've read have always implied that it was to prevent the theft of the locos by Intercity. This was a frequent occurrence with the class 31/4s that had a higher ETH index to allow them to "preheat" rakes of coaches on ECS moves from depots/sidings, despite their sluggish performance and late running on Intercity workings they weren't unusual performers.
They had specific workings in mind for the locos which they wanted them to be available for - at least until they started wandering on to freight work instead!
They had specific workings in mind for the locos which they wanted them to be available for - at least until they started wandering on to freight work instead!
fodphil
Member
A diesel locomotive can produce so much energy, whilst most of the energy is used in traction power, the auxiliaries (which ETS is part of) take a slice too.
If the ETH index is increased there is a reduction in energy available for traction power.
The 37s were ETHd to mainly cover 3 and 4 coach trains and the the biggest ETH rated train they were diagramed to work was the Fort William sleepers. So and index of 30 was all that was deemed necessary.
If the ETH index is increased there is a reduction in energy available for traction power.
The 37s were ETHd to mainly cover 3 and 4 coach trains and the the biggest ETH rated train they were diagramed to work was the Fort William sleepers. So and index of 30 was all that was deemed necessary.
LNW-GW Joint
Veteran Member
37s were planned to haul Eurotunnel Nightstar stock on the GW route.
Presumably the conversions for Channel Tunnel had adequate power for both hotel and traction needs?
Presumably the conversions for Channel Tunnel had adequate power for both hotel and traction needs?
They were planned to work double headed with converted Mk3 generator vans providing ETH (which are still knocking about in various places having never been used for their intended purpose).
fodphil
Member
The plan was to have generator car sandwiched between them.
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?
So for a 37/4, if the ETH index had been (say) 66 instead of 30, then all the time it was running around on Cardiff - Manchester or Glasgow - Fort William services with just (say) 4 coaches then having a higher ETH index wouldn't be detrimental, but it could have substituted for unavailable 47/4s on services requiring a higher ETH load - albeit with some loss of time in running.
Now that's interesting! So, in theory, it should be possible for a preserved 37/4 to be upgraded to a higher ETH index.
That was the 37/6 sub class, 37601 - 12. As stated above, they would have been marshalled 37 + generator car + 37, with through ETH cables fitted.
47/4s, 45/1s, 31/4s and class 50s had the ETH tapped off the main generator. By the time the 37s were refurbished and fitted with alternators it was only them and the 56s and 58s that were fitted with alternators I believe?
43096
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They weren't all like that. Only 47401-420 and Class 50 had that arrangement, I believe. 47421 upwards, the 31/4s and 45/1s all had new ETH alternators fitted as @y3j has described. I think you are confusing main and auxiliary/ETH generators/alternators - those I have described retained main/traction generators but with alternators for the ETH.
Everything from 41001 onwards (so HST power cars, 56s, 58s etc.) had main and auxiliary alternators.
Correct!
I thought some owners of 37/4's now have upped the ETH index to around 66 by fitting large gauge cable and changed the THOL setting.
43096
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Electric Train Heat.
A grown up way of heating a train, rather than using kettle-derived technology.
Electric Train Heating -or more correctly nowadays ETS for Electric Train Supply, i.e. the provision of electricity from the loco to the coaches to power the heating / lighting / air con etc.
Peter Sarf
Established Member
Electric Train Heat needed for later Mk2 and onward coaches (for Air Conditioning etc). Instead of a steam heat boiler or no heat.
Beaten to it.
A few years ago I had a conversation with someone and he could have been pulling my leg, but he did say he one of the reasons why EWS as it was at the time were reluctant to sell any refurbished 37’s to anyone else was because someone would know how to rewire them and produce 37432, this was the late 90’s early 2000’s so EWS had the fleet at the time and were reluctant to sell them on.
Surely there can’t be be that much difference between a 37/4 and a 5 or a 7? How hard was it to produce 31601/2?
47827
Member
I think by the time BR came to create the 37/4 it was obvious that even a slightly higher powered type 3 would use so much of its available power in heating/powering a bigger train/many air cons that it wasn't worth the extra investment when it was effectively a set of micro fleets for Scotland and Wales that were intended to work short Intercity/Sleeper portions and a short to mid sized rake of PV/Mk1 stock on similar routes for the regional express and stopping services. Had there been a desire to increase the index to a full 66 as per when the 31s were done a much bigger fleet would have been needed to avoid the risk of too many of the 31x eth 37s being nicked for other duties. The main reason I recall for 31s needing a higher index was that after inception they were booked onto some of the long Intercity air con ECS moves into the likes of Kings Cross and needing to power the set in the sidings plus on the way to the station to ensure all was ready for the passengers before the train loco was buckled on. The easy fix to help a 31 in need of some grunt was to give it a fellow blue star pal to plug into and shift the train faster (usually another 31 but not always). Though BR did kick them out on all manner of unsuitable trains often resulting in odd incidents of killing em en route.
Well I agree to some extent, but a 37 has got a lot more grunt than a 31, especially when re-geared down to 80 mph. It might have made more sense to have more "proper" ETH 37s than do the last batch of class 47 conversions. Also, what about that period when the Aberdeen and Inverness sleepers were worked by pairs of 37s with a generator van in the consist? Wouldn't a pair of ETH 37s (or even a mixed pair) have done a better job than this lash-up?
47827
Member
That's right. Although a 37 having to heat twice as much and more would have made it a tad less powerful and perhaps meant it needed pairing up for adequate timings on some stuff.
A 37/4 would have needed an extended index of 75 for those sleepers as pairing them up would not increase the ETH available because it can only be taken off one source/loco at a time. The generator car was still necessary once the higher index ETH 47/6's were taken off the task. A 37/4 with ETH with an index of 75 may be possible on paper somehow but I doubt BR would have gone for it. Sometimes what they did instead was a better option ultimately.
PS realise that other 47s subbed on the sleepers still and were over index but that is another debate.
The ETH class 37/4 was very much a particular solution to a particular need. That was for an ETH locomotive meeting the RA5 restriction to work the Scottish branches and the Cambrian. 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). The economic benefits were marginal so costs had to be driven down as much as possible.
Most of the investment was in more class 47/4 and class 31/4 because they had readily available designs, but neither were RA5. Part of the project was making better use of the class 33, but these failed the RA5 criterion too.
At the same time, BR were coming to terms with a restricted investment budget that had no room for the proposed class 38, and mid life refurbishment of parts of the loco fleet was their response. The class 37 refurbishment included replacement of the main generator with a Brush alternator, probably the most extravagant bit of the mid life refurbishment programme, and I don't know the justification for that. My sources don't say what powered the auxiliaries in a refurbished class 37, and that would be useful information. I also don't know how ETH was provided in a class 37/4, apart from the assertion above. I'd like confirmation that the class 37/4 used the same Brush dual wound alternator that was used in class 31/4, 45/1 and 47/4 because it seems unlikely. The Brush dual wound alternator was a heavy bit of kit and the class 37/4 needed to keep the weight down to stay under the RA5 18 ton axle load. The extra weight of the dual wound alternator is what tipped class 31/4 over from RA5 to RA6.
So the class 37/4 is an early example of engineering designed for a particular need, with minimum specification to drive costs down as much as possible. It is a few short steps from there to Pacers!
Most of the investment was in more class 47/4 and class 31/4 because they had readily available designs, but neither were RA5. Part of the project was making better use of the class 33, but these failed the RA5 criterion too.
At the same time, BR were coming to terms with a restricted investment budget that had no room for the proposed class 38, and mid life refurbishment of parts of the loco fleet was their response. The class 37 refurbishment included replacement of the main generator with a Brush alternator, probably the most extravagant bit of the mid life refurbishment programme, and I don't know the justification for that. My sources don't say what powered the auxiliaries in a refurbished class 37, and that would be useful information. I also don't know how ETH was provided in a class 37/4, apart from the assertion above. I'd like confirmation that the class 37/4 used the same Brush dual wound alternator that was used in class 31/4, 45/1 and 47/4 because it seems unlikely. The Brush dual wound alternator was a heavy bit of kit and the class 37/4 needed to keep the weight down to stay under the RA5 18 ton axle load. The extra weight of the dual wound alternator is what tipped class 31/4 over from RA5 to RA6.
So the class 37/4 is an early example of engineering designed for a particular need, with minimum specification to drive costs down as much as possible. It is a few short steps from there to Pacers!
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edwin_m
Veteran Member
Avoiding the need for a second crew member would have been a significant economic benefit. Also the newest steam heat stock would have been around 20 years old by the time the 37/4 appeared, and some of only had vacuum brakes, so clearly wouldn't have gone on for ever and may have been becoming unreliable.
47827
Member
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.
I think that is a really good summary. Thank you.
Perhaps if BR had not been sectorised by then, the outcome might have been very different, with "full ETH" 37/4s working many of the dated summer Cross Country services, or even the Cross Country services onto the Southern on a regular basis. As it stands, they had a good innings - and the investment in them must have been paid back many times over - but there could have been so much more.
47827
Member
I think, certainly in later years, there would have only been a few things you could have probably put them on due to XC wanting 95mph capability running. Timing an odd train for slower locomotives would have been OK for some sections though no doubt. Reading to Poole used to enjoy a mix of 33s and 47s diagrammed, for instance, up until some point in the 1980s when it tended to be just 47s (certainly as several air cons or more became the norm and 33s were phased out of passenger use).
It was the short period for the payback that made the economic case so marginal. In a different political climate steam heat would have been phased out more gradually and class 37/4 might never have happened.
Or the phasing out of LHCS on regional services could have been more protracted - especially if the Sorinters had been mechanically less successful. Were there not thoughts of 37/4s for the Birmingham - East Anglian service at one point?
61653 HTAFC
Veteran Member
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.
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