søndag 24. august 2014

Play The Dark Isle, Ring 8 Bells For the Past Which is Gone.

This will be the last post for a while at least in my blog of memoires and musings of all things with yellow ends and blue body sides. Both requiem and ulogy.

I first started doing haulage as we called it, behind class 37s as a hobby in 1980, having had a short period as a spotter. Gone immediately was my ambition to clear-everything, that is to strike off all locos in the listings book as being spotted. Instead in was the great game which I fell upon like going through the wardrobe into Narnia or finding a secular meeting going on in the snug of the pub to which you were ushered in, and welcomed as a new believer.

That was it in a nutshell, we were all 'believers' and more over of course 'followers' usually of one faith over the other. By in large that had meant following one of the big five locomotives in the 1970s but by 1981 the smart money  had moved onto the swansong of only one of those , the class 40, and over to the class 37 as it entered a new unexpected era of widespread passenger workings. There were also of course the MacRat crowd, lamenting the spluttering epitaph of the dieing class 27 in particular, which met a more ignomonious end of life scurrying around on the fife circuit and Dumfries route and being subject to frequent failures. One thing most of us could agree on and that was we hated duffs and duff bashers!

Back then on my first visit to a works, St Rollox, there was an immediate feeling of nostalgia, of the railway and rolling stock belonging to an era which was old fashioned yet vibrant. A testimony to british engineering that 1950s technology was reliable and economic 30 years later. Having said that in 1980 the youngest duffs were less than 7 years old, while the syphons over D6950 were still fledgling teenagers. Rolling stock off the main ECML&WCML\&GWML was mostly still mark I steam vacs.

Of course back then there was actually the start of a completely opposite situation of what is now DMU/EMU domination. First generation DMUs were so knackered that something had to be done, and this affected all regiosn where  in particular locos like the 30 something classes found new use hauling semi fast and stopping passenger services. The locos were freed up from the decline in light and mixed shunted freight, the coaches were cascaded down from ECML/WCML where air cons and HST sets ruled the roost even by the mid to late 1970s.  So then the scene was set for possibly the most riotous fun a haulage fan could have in the years forward  to the eventual withdrawal of class 40 in 85.

It was a great game. New loco hauled diagrams. Alterred availability of locomotives. The unreliability of the sulzer LDA engines. Not only on the standard diagrams which were loco hauled or became such in this great era of yellow-blue bashing. The public en masse still took the traditional working class holidays to Blackpool, Scarborough Yarmouth, Newquay and Skegness. This meant addex trains from July to the Aiugust Bank Holiday weekend with whatever old stock they had, and no need for a loco with ETS. Also sets were freed up as replacement rakes in case of failures on DMU and Class 45 /47 routes. By the summer of 1983 the 47/7 fleet and 27 fleet were so unreliable that your were almost certain to get a few 'big' NBs working those routes if you spent a week bashing.  Each new timetable threw up a multitude of tantalising 'bails' which involved running over foot bridges or galloping down underpasses when there was no crew change, just a chance crossing or a pause due to single line operation.

On top of basing yourself with a local transport area day pass from one metropolitan area, there was of course the main event for most back then, and that was going on an 'all line' fortnight for the serious bashers, or a regional rover for a week for us 'neds'. For me that meant one thing and that was the Freedom of Scotland. The aim of either end of the spectrum of expense, was to do routes by loco hauled trains and cover them with a rare loco if possible, while also mooching about the city terminals waiting for 'gen' or 'viewing' particular trains, in our case most often the carstairs portions, the 0715 Ayr/Glasgow and the 1715 Glasgow-Edin.  Many big loco bashers slummed it in terms of loco haul and went for the scenic extremities of the network. Penzance with a 37 or rat. The far north with hopefully a pair of 26s. The infamous 1S81 and its forwarding overrnight to Elgin with a type 2 or boilered 37.

For me the highlights of my short five year career as a syphon basher were mostly on freedoms or on excursions to the west country and midlands.  The best day ever was probably doing the overnight to Inverness, followed by the wick service with a pair of 26s to Dingwall, followed by a 26 to Kyle, then the ferry over to Skye, the bus over said island and then a good thrash down from mallaig again to complete the Scottish grand tour. Then you could say the craziest day was the first day of syphons on the Cambrians, pairs and single big NBs and as many bashers if not more than Ada's and Berts ! Hundreds. They drank the pub at Caersws dry on the fester for the purposefully impossible bail at Mach'. I include a little appendix below which I will maybe update for the sake of accuracy, just being a bit of a disjointed list of best thrashes.

The Skye route was a must do for myself. An itinerant 14 year old lieing to my mum about it being with a gang of pals, I set out to do it alone really after I stepped onto the platform at Dingwall, solo. Other Must-Dos of the time were the riotous 1S81, all the way from Carlisle if you were a 'top man' for the day with most often a roarer on the top. The bail at Blair Atholl, blair aweful to make for a piss poor doss as an overnight, which often ended up being Pitlochry . Down again to cover the 0650 Ft Bill bedz and if that was rancid out towards Ayr for the 0715.

If you took the 0650 Ft Bill then the de rigeurr foot move was from Tyndrum Upper over the Glen to the halt at Tyndrum lower. The cobbled road out the upper station which was original to  the 1880s and the walk through the mist drenched glen before most of the country had got to worrk was the sign of a devoted syphon basher.

Other must dos by 1984 were to get 40s on some of their traditional routes on service trains, this meant Settle-Carlisle, Dundee, Blackpool and so on.  We managed to do 40 118 over Settle , steaming on 5th of january. Booked a dual heat duff we went anyway and it was on. There were a lot of people who would become prominent in the CFPS on that train or its return that day. 40047 on the other hand boasted only me and a man who would go on to be the director of Virgin rail, then a 40, western and v220 nut.

In 1985 various things happend, 40s came to an end and not nearly enough of them have been preserved unfortunetly. Locos like 40155, 170 and so on were in very good nick and it was criminal to cut them up. Also boilered stock took a bow from time tabled diagrams with the advent of the 'combine harversters' aka 37/4s and the cascading of other ETH class types into secondary duties. Sprinters were establishing themselves too and the end was nigh on invisible plakats we hung round our own necks.

I got older,  into outdoor sports more, more sheepishly interested in girls, and lost interest in continuing with ETH stock and no 40s to add variety to endless v12 miles of growling EE type 3s. I lost a whole gang of freinds and all those weird adult aquaintances who on reflection now were at best eccentric and a little school boyish while at worst just a bit sad. 

Regrets? No, not one minute would I miss and not one minute more would I spend. I would be very happy if there was a heritage train on the WHL and far north with type 2 and 3 haulage, and a 40 running in Scotland somewhere, but for me there is no going back and it was a more of less clean break in autumn 1985. It seems like then it was more a nostalgia trip than now when I look at youtube where every so often someome has digitised their 8mm or VHS footage of all things blue and yellow at the ends.

Today I took time to look at some footage from MC Metals, Crewe and Donnie works from the time when the second generation locos were being decimated and the peaks and forties were decaying hulks. Also a look at 37s having their open heart surgery to become the new HGRed sub classes. It was kind of like looking at videos of your grandparents being in hospital and it felt like you were seeing a funeral you couldnt face to go to. It was kind of a catarthis today looking at lumps of blue and yellow steel , just disected boxes now with their lungs, muscles, nerves and hearts strewn around in piles like offal at an abetoir. It kind of gave me some closure in a way. Now 37s will of course continue to rumble over UK metals a while longer, and for the rest of my life at least on preserved routes. However it is more that the era we lived through often felt stolen from us I think. We lived five years of withdrawals of locos we loved. The deltics, the forties, the boilered diagrams.

Like much in life, good eras and good times are fleeting. We think they are constant, they will go on, we can keep on reliving them. In fact they always fade away or die abruplty. Change is the only cliche in life..Our interests change or become impractical to follow. Boats, planes and trains get cut up en masse and a couple go into an endless retirement from their former glory. Freinds move on, lovers come and go. Children consume our middle lives ..the only constants are that there will be decline, decay, death and then renewal, novelty and enterprise again.

So if that was the era for you or an era before, and you like me now find the internet rekindles interest, then just look back and let a tear come to your eye. Maybe take a wander down to East Lancs or NYMR or Boness with the kids and have a wry smile at the enthusiasts and the 25mph workings but dont start ranting on about where and when and all. Those days are passed now, and in the past they must remain.

Good bye.



Memorabilia. The trips and the trashes which stood out in my mind

Class 27 of all things to Oban, with John E Auguston, drain pipes, white socks and massive pentax wide format an' all. Gave me a taste for trundelling along in mark I steam vacs. Later preferred their more reliable cousins, the 26s.

Bailing at Helensburgh upper off a 37 at night, the thrash a foot away from the walkway through the iron lattice work. The thrash was deafening. I was hooked.

Seeing a pair of 37/0s haul the big aluminium ingot train up Arrochar bank while over the other side in the Argyll wilderness with a scout leader 'cheify' on a nature watch pack tour.

Kind of lowlights in a way> turning down 40047 on the ft bill euston bedz from of all places DUMBARTON, it was a dodgey move home for a nipper. Also turning down 40165 i think, or one of the last boilered centre coded 40s on the 22>40 glas -edin mail. on a freedom at the time i think too, much embarressed now. Not taking 40150 further than cumbernauld from mossend. "what a bunch of neds, bailing here, bashing 40s on a transcard" . while on 40s, 40155 replacing a failed peak at chester, we did it to warrington, great forty thrash with a late train and a stick weilding expert up front. 40188 of course, 1040 carlisle leeds 5th january 1985. riot, with a better thrash in the dark on the way home unfortunetly, would have been nice if the driver on the up service had thrashed her as much. Of course 40170 too dropping on the Inverness Bedz as far as perth, and working the return NB. It actually had a bricked second mans window, so allegations that the 40 bashers including the 'bradford bender' had smashed the windscreen on the duff which was booked and on pole position at eastfield are unfounded. They managed to brick the forty's side window, suggesting they were kids not able to chuck track ballast any higher!!! 40047 with a well known railway director, edin/dundee/edin the fife circuit in 1985. Not a great thrash, but I think it was the last steam heat 40 run I ever had if it was after 40118.

37014 made a good few monster runs on the whl and other places. One with load eight on the 1650 ft bill on a hot august evening, the loco was absolutely singing up the crianlarich banks. Also it ran like the wind with the infamous peter walker at the helm, with an hour late ex ft bill eth bedz, ethel in tow, which said PW made up entirely between crianlarich and dumbarton. He knew the route intimately and with this being the only airbraked rake on the WHL, he could really put the anchors on after getting max speed. I have never been so fast on the whl, and it felt like he was doing over 90 through cardross.

37028 on a self imposed eva and brother's  'baglet' tour. voh it was. Quite big, we expected it to be dualled or there were already rumours then in 82/83 about what became sprinters, and locos being mothballed. did it all the way to fort bill, then i think a rancidish 025 or the like mallaig return, and then all the way back.

37188 qrrived as a gleaming blue steed to eastfield in stark contrast to the wrecks which had come to ED from stratford depot, who seemed keen to get rid of dross first, 014 being an exception. I only remember one run on 188 actually out of many dozen runs behind her, with fred the skin head.  it was a very clean running and powerful loco compared to the likes of 025, 027 and the long standing wreck 108.

37264 ex works. This was many a syphon bashers beast, having been one of the only high number 37s to be stratford based with a boiler. It was a good runner at IS and later ED, but the latter gave it the full treatment , ground in all the valves and probably put a new timing chain on her, and she ran like hell fire but with hardly any dark exhaust. Clag was bad then, a sure sign of a loco needing a trip for a D exam.

On clag, 37175 was the worst offender at ED for many years: smoke, flames, and a tendency to over rev. It allegedly hit the 1000 rpm rev limiter and shut down up queen street tunnel one day. It also had messed up field diversion system, and would cut out at full power and try to divert. Had  175 omnce with the returning fake boilered class 20 , a syphon oddity if ever there was one. It was put on on mindays on the ft bill bedz because the line was always slippy due to there not being any sunday services. It allegedly alleviated wheelslip and prevented the train from coming to a hault, but the odd monday I had it on the up service, up being the bigger smoke, not the wee Ft Bill, it was just a nice noise behind a thrashing syphon , kind of a little sister saying " I can run and play with you too, me too !! "

One loco which did get better for a while was 025. I think I had her on the rather slack dumfried route to get the line for a syphon. When it came to the WCML after Annan., the driver went ballistic and the thing thrashed through second and into third field and just pumped away until eithe he got a yellow signal or he reckoned it might be a bit uncool to over run the platform at carlisle.  Also had heating the infamous 1s81, just to have a syphon on it, and it thrashed like hell through stirlingshire. hell fire for a loco which was before and after 1984 a bit of a heap, but was preserved with a functioning boiler at least then.

Also on dumfries , we had 37119, D6700 for posterity all the way to carlisle on a rupert special family rail card extra run having been to bristol to bash what ever was there.

37 296. Little did we know it would become a humdrum ED class 37/4, it just appeared on Scr during the miners strike and dropped on the infamous 1715 glas edin. excess ticket ensued. great thrash. all the macrat 27 neds including the worst, sellers and blakey, were on it to get a line in the book. Perth man said they had to jack the tunnel up / it was so big you see. it struggled to get over 75mph or maybe the driver didnt botherr too much.

I did also a 37 12x to stranraer for the route. nothing of note on the way down, but after telling the driver it was a good loco, he decided to give it welly up the galloway banks and it was a thrash to remember from the itinerant big nb. Also not much to write home about as the power unit was sick, we did 37292 at 2000bhp on a euston-stranraer, getting the maybole /kilmarnock route for syphon at the same time. In that guise it worked only a handful of passenger trains during the miners strike of 84.

I think also my first run to Brora or Helmsdale with 37262 and another on return  must be up there, because thundering through the night up there in december with sleet and rain was cool. also that month in 1983 decmeber i took 37183 with the empty flat bed wich had a through steam pipe for the stock, on the only mixed goods passenger train then running in the UK. have photo to prove it.

Riots then, well doing the far north bashes and when 37s  as above, dropped onto the stranraers, the dumfries route, the carstairs portions and the odd glas edin service, plus them doing the skegnesses and scarbororuhghs from either newcaslte or edinburgh on return to glasgow. 37174 showed the fife tip top a clean pair of heals out of haymarket with load 9 vs load 4 pah, 27 junk.

we had hoped Ethel would mean that any old ed or ML syphon could drop on the sleeper, but alas the loco was booked onto the mrk 1 steam vacs still used to mallaig at the time. The only riot was when 133 was sent up in a dual header on the 1650 or the 1820 oban in the winter to releive a failed loco, probably 025! Unfortunetly the drivers took the pair up easy, but at least they bothered to connect the blue start up.

The biggest ever riot was of course the completely barmy first day of syphons on the cambrians. there were undoubtedl more bashers than punters. riot. total utter riot. we drank the pub dry at caersws.

other things of note, first family rail card run to bristol with rupert. 50008 , the shreddies and that mad 4511x on the glasgow bedzx to brum. up[ lickey like it wasnt there. much better than a duff . I thhink we went just out of NB season and there were no 37s to be had, with only one or two dual heat workings possible out of cardiff then. We also saw part of a very eventful or rather fateful test train for british locomotive production: we saw a stone train being hauled under test by a pair of 56s and it was those tests which lead to the class 59 being considered a better loco, whcih they are, and then the yingy shed 66s being ordered with public money.
My first ever shreddie was part of another type of tour , a mystex, which was going to chester or shrewsbury from glasgow. We kidded ourselves on we didnt know where the mystex was going. we bailed at crewe to take a shreddie down and very impressed were we too. lovely movers, so much betterr than their vermin relatives.

I'll finish where I started now that I have mentioned vermin type 2s. Syphon bashers had a soft spot for 26s partly because if one turned up on the far north route, you were as well to take it, but more over that it annoyed 25 and 27 bashers, because the crompton equipped machines with their early 6LDAs were better made and more reliable than their after comers from BRCW. I had a rare run on a pair of them on the first wick & thurso one cold october morning frrom snechie, and in a pair they could inflict dammage on that route as far as tain at least. But back on the WHL, and one wet but icey cold satruday we all turned out as usual to put more mileage on the usual ED suspects, especially 188 my beast, when lo and behold the whole line had gone back ten years and it was teacuppping heaven for macrat fans. Only the sleeper and one other service got a 37 that day, there was some blah blah gen about the boilers all needing inspected after a failure of one. It almost doesnt need to be said, but every train that day ran bloody late and the whole affaire was pedestrian until finally we piled on the 1650 Ft Bill which had a decent bit of v12 kit on the front. Vindicated. Sypohon Bashing, I LOVED YOU

lørdag 16. august 2014

Locomotives In a Spin> High RPM and Multiple Power Units versus Mid Speed

It is interesting that some things return full circle to the way engineers thought in the late 1940s and into the 1950s when presented with a problem to solve> Back Then it was replacing steam with quite literally,. a turn key solution, while now it is replacing the second generation of 1970s&80s Diesel locomotive with locomotives which can comply to the outrageously strict emissions and noise legislation laid down by the EU commission and also lead by California who have pointed their judicial compliance bow to zero emission locos. This in itself is a farce becuase even diesel loco hauled trains are many hundred times more efficient over any long haul route than the equvalent 20-50 lorry loads or 200 - 300 personal car journeys. Rather than painting power units in locos with the same black brush as mass anarchy transport, they should be setting a sensible level of progress on these fronts, all be that very much quieter locos than we enthusiasts may like to hear pounding the metals..

Today Seimens present a modular power unit loco with possibility for dual power (over head or maybe third rail units top be popped in) and / or battery packs. One key benefit they quote for today's operations is that the locomotive can dial in and out power as it needs it, with the power units then working at their most efficeint peak range more of the time when they are on, thus reducing fuel consuimption and emissions,. In their Marketing PR launch discussion they talk with no reference to the long history of multiple power working doing just this, dialing in more power when needed, while then saving fuel by cutting back on parts of the route which do not need so much horse power. Rail actually requires a large tractive effort to start a train and to take a train up a steep or continous gradient, but since the days of Rocket it has been known that there is a lot of coasting and low tractive effort haulage going on due to the inherent efficiency of running on rails, particularily with roller bearings and optimally loaded axles. Thus you are actually dialing in power a lot more in a train than you are in a lorry which has a lot more relative wind and rolling resistance than a train, and you can times that by as many as 60 in europe for the biggest 2000 tonne trains

I can't remember if the PR release mentioned engine redundancy in case of power unit failure, but this has to some extent been quoted as the reason for multiple engined locos. This may have been at some point someones 'also ran' selling point, be that point made by a supplierr on internally to British Rail western regiona and the Deutsche Banen in particular. In fact the notion is largely a red herring : in the case of the German multi engined V200s/220s and the British Deltics, the attraction was more horsepower per se from a single locomotive within some technical limitations. Interestingly those limitations were quite similar and both technical. In the 1950s there was a desire for light locomotives with 2000kw output approximately to sustain speeds of over 90mph/150 kmh and run ideally cruising at 100mph//161kmh.  The limitation were on both diesel electric and the hydrualic mechanical transmissions at the time.

Both systems were limited to about 2000hp per power unit by technical limitations. Firstly in the electrical generators, where English Electric had a size limitation and a knowledge of flash over (which would later plague the class 50 and competitor's class 47 locomotives ) in the dirty railway environment for the then DC generators. The biggest EE could offer was about 1.75 Mw , brush and AEI offered slightly higher while the American locomotive manufacturers could offer their home market around 2.2 by the early 60s with the larger loading gauge. The DB in Germany had opted for Diesel Hydraulic for their higher speed services and much of their other locomotive provision in the 1950s. The limitation to them was that at that time for the footprint required at least, neither Voith nor Mekhydro could offer power transmissions of over about the same 1.7 mw, or actualy at rail about 1500 hp.

One efficiency advantage of diesel electric in this respect is that a single engine can be employed to deliver the maximum applicable kw to the traction motors at start and low speed in a light weight express locomotive. In the Deltic this means that the power control handle does not activate the second engine until approximately 18 - 22mph is achieved. With the secondengine revving up to deliver power to the same level as the first and then both going onto rev further to deliver 50mph 
, the system as a whole is very efficient for passenger workings because they require exactly this type of acceleration avoiding a field diversion(electrical gear change). A typical 350 tonne passenger express of the late 50s'1960s requires light starting effort and offers actually not very much momentum to push through field diversion  . This explains why the class 50 out accelerates a deltic to over 30 mph, while a class 37 will out accelerate a deltic to 18pmh hands down because it can lay down far higher amps as its single engine is delivering maximum mechanical effort in the first field which dies at around that speed. Both these classes however could be plagued at speeds of under 50mph by trains not having enough momentum to push through the diversion, then meeting a gradient, or by a speed limit or signalling which meant the engine hunted between two gears as a manner of speaking about the automatic detection and switching equipment. The twin engined deltic and presumably Brush "Falcon" overcame this issue by dialling in the power and avoidimg low speed diverts, while the former offered quite low starting effort and maximum continuous effort due to having a lower amps/ higher voltage system (amps are a measure of torque where as higher voltage relates to spinning if you like, groossly over simplified) 

Diesel hydraulics however have a different advantage in having their torque convertor 'half gears' ie slippage in the fluid coupling followed by the married phase, as well as having a range of 'hard ' gears to change up to.  Correctly engineered this makes for a very smooth acceleration with virtually no wheel slip and quite a high starting effort. Both engines can power their respective bogies from a standing start without the typical electric overload of 1950s first generation DE locos, they are designed to be geared correclty for this tractive effort and the limiting factor is how long you can cool the hyrdaulic  transmission oil when it runs in fluid unconnected phase (slipping stator relative to rotor). For all types of trains in fact, a twin engined diesel hyrdaulic has another slight advantage over DE designs of the late 50s at least, and that is that one complete transmission bogie system can be left on maximum power while the other system reves down and changes gear for its next bit of the cherry so to speak, thus the train can be kept at a constant speed if not on a steep gradient. Field weakening on DE is a just a natural physical barrier for the entire system if it is to run smoothly, although a complex out of phase double system coudl be concievable, where the two bogie/traction motor sets are tuned to different field weakenings. Instead as in the deltic, the number of gear changes to 100mph is just three versus effectively six for diesel hydraulics even when they are more powerful as in the german V classes. 

As touched on in the pre amble above, the redundancy of twin engined locos was a secondary selling point in effect then. However it did mean that the most important express services on the GWR and the ECML could limp home at about three quarters speed in the mid 1960s when the whole genre of diesel was still to be proven as a mass produced item. Further into the 1970s, the HST IC 125 sets had two power cars in order to deliver the magic extra thousand over deltic services to go 125 mph., but the betting on effectively two power units per train proved prudent in terms of limping home as both the Ruston Paxman valenta and the Mirrlees power units prove to be less reliable than anticiapted for their service intervals in the reality of the dusty conditions and high thermal cycling loads placed upon them by the nature of having more stop starts than originally discussed with the manufacturers. The 125 was actually designed with train crew changes en route and fewer stations than the deltic and class 52 services they replaced. 

In terms of fuel efficiency then I have not heard of westerns warships havbing one PU shut down, but it happened regularily on Deltics which would have their second engine shut down on the slower Ediinburgh-aberdeen section of the expresses from KX. Presumably after ETH was introduced this required that the second PU be on a heat only selection, revvving not far boave idle I do not know. Deltics did limp home and run light loco on a single PU, and especially with the teething problems with pistons they encouuntered, this became a very fortuitous feature.

In post war Europe and the UK there was still materials rationing and oil was imported from the US and Middle East, so the use of multiple workings, dual or more locomotives is for those historical reasons far less wide spread than it is in the USA/Canada, coupled to a steady decline in freight from the 1960s to the 2000s as the road network improved. The states on the other hand and canada had a heavier loading gauge and bigger, more economic commodity and produce loads to haul by rail and thus it was economic for them to run multiples and 'robot'  locomotive arrangements were widespread by the early 1960s with multiples of up to 4 at the head and more down the train. I do not know of any european robot multiple locomotives apart from shunters like the class 13 and some on the continent, robots being a unit which lacks a proper cab and are only used in multiple with cabbed locomotives leading. By 1960 the BTC/BRB had abandonned through connection doors for locomotive design, although many were in still in production then, and were stipulating that type 4 motive power be above 2700bph and not fitted with multiple working ( a decision reveresed in the class 50 due to the gradients of the WCML and the ambitious timetables laid out in the run up to electrification in order to keep the route competitive in respect of the new M6 /M74 and the advent of the Glasgow Airport-London shuttle. Class 50s were not fitted with these as a response to theirr reliability issues, which were in fact somewhat better than their rival mass priduced brush type 4, which required a massive rectification at a cost of over three million pounds back then. That class 50s were delivered without multiple working cables t first has been cited as being because of availability of the materials at the time, safety testing not being complete, the price of the class 50 running into problems and then this being taken as part of the hire-purchase scheme they were bought on, subject to absolute rquirement for the faster timetables north of Crewe and later Preston)   

So at the end of the day you have to examine what your actual missive for tractive effort and maximum speed is, and in fact this is where DE wins over DH:  For the same horse power and power unit arrangement, " Faclon" was a better performer than the class 52 Western hydraulics with their voith systems. The limitation here was that the v12 MD655 engines were not powerful enough for the  third gear on the Voith transmissions which were presumably very similar to those fitted in the more powerrful German V2xx locos. It may have been possible to have fitted tiwn v16 MD870s or alternatively a Mekhydro gear case could have provided a better matched power deliver for running at over 75mph. The Voith transmission is in theory smoother than the Mekhydro due to it working on a priciple of triple, sequential torque convertors and hydraulic actuation of these three main gears. Although Westerns and of course Hymeks saw a lot of working on relatively heavy freight services, the similarily powered Falcon and the Class 37 EE type 3 both out performed their respective DE cousins in standing lift and progress, all be that with some degree of wheel slip on the EE type 3. Deltics did work a very few freights in their lifetime and heavier night mail/sleepers of over 650 tonnes, famously last year D9000 working some heavy lifts to the rail head due to lack  of class 66s.  Falcon, the class 53 one off from Brush, excelled at both freight and passenger working, and indeed ended its productive life on ore and coal traffic, slugging them around south Wales. Class 50s were designed on out set to be a stop gap passenger loco for the WCML but also then to have the possibility to work higher speed freights of upto 1000 tonnes, being in fact prepared with mounting points for buck eye coupling as if it was going to happen in the 1970s.  

We have then come full circle in which transmission system suits which traction missive: For light passenger trains of 40 mph to 80 mph the vast majority of diesel services in the UK are now sloshing oil over convertors with mechanical hydraulic tranmission. This was a decision taken a very long time ago by some engineers, probably ironically enough, about two or three years after Western Region lost their last main line DH locos. For heavy freight you want to slug it out with 25 tonnes per axle at least and over 3000hp in DE, while also the hands down winner for mixed traffic is the DE too because of the controllability and range of electrical traction systems. This is reflected in the delivery of the latest class of locomotive to the UK, the mixed traffic class 68 which is pretty much the type of locomotive the GWR would have ordered if they had been forced to run with a larger proportion of DE locos. The main point lacking here is that we do not see many multiple power unit locomotives with their specific advantages and redundancy, but that in main part is due to the amount of power available in reasonably sized single power units in mid or higher speed * GM versus Caterpillar, MTU and the most powerful per weight, the VP185 from Rustons /MAN, and also that there has been no specific missive for this type of locomotive. Even in DH we have seen several Vossloh locomotive classes and the Anglo Belgian powered freight class emerge with only single power units. It seems the reliability and modern engine management have by in large rendered twin engines obsolete, where as the Seimens loco can carry up to four power units.