mandag 15. desember 2014

Twin Engines Drone and Whine Again? The Shape of Diesels to Come

The latest round of locomotive developments seem to be in part at least, back to the future. This is in terms of locomotives returning to higher speed engines , once shunned in favour of 'mid' speed , marine derived power units. Also we have seen a fragmentation of new types of locomotives, post the mass public purchase of the Class or Type C 66 as it is known across Europe. Quite a few of these have been diesel hydraulic too, especially from Vossloh and indeed Voith of course with their monster.

It seems that there is a new king and queen in the power unit world and they are both v16s with the choice of either Caterpillar from the USA or MTU from the father land. In rail application they run about the same rpm with the former being quoted as having a higher output. It is presumed by the Author that in fact mid speed engines from MAN group, EMD, and GE are no longer in favour due to emissions profile, higher rpm seems to then suit  better combustion in smaller cylinderr volumes. Taking this to its extreme the interesting rival from Seimens, the Traxx loco, takes a completely different approach by utilising not just two but up to five power units of presumably automotive origin or smaller industrial marine type diesels, or perhaps based on static generators.

The concept here being that of each power unit is working most of the time at above 80% output when engines are allegedly at their most efficient. You then dial in extra power units as the demand increases. This is no crazy idea because once a load ie train, is started and taken up to a speed of between 40-80kmh it requires far less kilowatt power to maintain rolling, given light gradients of less than 1/110 say. Also a bug bear for low carbon emissions is running empty trains, many of whose rolling stock is restricted to a top speed unloaded of under 120kmh. Some rostered container diagrams vary greatly in actual tonnage to be transported, yet the driver has the same diagrammed time to hold to despite being able to go faster with a better power to weight ratio. Power units of the mid type are as I say allegedly not very efficient below 80% max rpm, but that was probably not the case for the ruston SVT and CSVT whose smallish , multiple turbos provided good fuel economy when only 50% power was demanded.

Given that a major global player in the market, Siemens, is now pushing multi power units as a solution and no doubt presenting lots of figures in endless powerpoint slides to support their teutonic assertions, then it seems inevitable that other loco manufacturers and PU producers will offer the same, most likely in a two or three unit solution.

Post war, the Deutsche Bahn took almost exclusively a ' high speed' motor option with hydro/mechanical transmission. Faced with a very similar practical limit for single drive in the 1950s as with generators,  they twinned up with the famous v200 series of locomotives, which influenced of course the BR Western Region most, but is of course a daily fact of life on the remaining high speed diesel lines in the UK, where Intercity 125 HSTs operate with two power cars, effectively a twin engined system. Deltic and Falcon were in the bidding too, but limitied to only 24 locomotives out of many thousands of diesel electric, single power unit locos (ignoring the ill fated 'Claytons' )

In the 1950s then the transmissions only handled about 1.3 kw / 1800 hp of output, with perhaps the best generators from Brush taking towards 1.8. So BR twinned up for their premier high speed passenger routes where 2000 hp was just for starters, they needed really '3000hp under the bonnet' . DB went a little further than BR of course by using twin v16s in the infamous DH4000, v320 which is a mighty bit of oil sloshing kit, being uprated to 3800 hp and still running today in contrast to the single venture prototypes of BR days. The v320 is fitted with twin v16s as against the v 12s of the BR DH and DE 125s . The D1000 'Western' class should have surpassed the performance of several type 4 DEs of the time, but the Voith gearing in the triple convertor was a little high at the top end for the v12s, presumably this hydraulic gearbox was the same as fitted to the v320. It is also revealed now for posterity that Falcon, with the same power units but DE drive was superior in the lickey bank trials. It wouold be interesting  to have seen westerns fitted with either 1) Hymek transmissions, with gearing tailored to the engine output  2) the v16 Maybach/ MTU as choice.

DB moved away from twin units quite quickly into the 1960s with the v160 type, fitted with a single v16, and only odd and shorter lived flirtations with a secondary power unit.  DB found out of course my own contention that type three power , 1.3kw, was adequate for the typical 300 - 600 tonne trains of the day, and of course today passengers are no heavier, while freight can be handled by multiple locomotives. Later of course there was the demand for ETS (ETH as it used to be called) and trains which were yet faster than steam, so fortuitously MTU could offer far more power from the same footprint v16 over time and the v160 type evolved and dominated much of western german loco hauled transport through the 1960s and 70s.

DB later favoured single power unit locomotives with the v16 in DH going up to 2700hp while then more powerful DE locos were introduced in the late 60s and onward. The same is actually not true in Britain, where firstly IC 125 units are essentially dependent on two power cars, and then of course there was all and sundry rubbish of multiple units with several power units per train. Also DH transmission is by in large restricted to sub 100 mph operations for some reason, but is very useful for lifting heavy loads on gradients and can produce a lighter power car / loco for any given horse power.

In the 1950s the attraction of twin engines was not only overcoming the limitations of transmissions, but also provided a means of redundancy ie back up in break down of one PU or drive system. Back then it was also conceived that single power unit operation on lighter trains or slower sections was perhaps desirable. Indeed Deltics allegedly ran North of Edinburgh on one power unit to Aberdeen as a matter of routine to save on engine hours and probably fuel too. The NBL warships had early reliability issues with their power units, so redundancy helped GWR a bit at least. Wwith subsequent twin engine locos all the way to the hst and its notorious mid eighties reliability issues caused mostly by cracked alloy turbo casings, there is a means of limping home or at least running off the main section before the need for another loco and multiple knock on details on the blocked line.

An internesting historical bit of politics about twin engined trains was that the hst protoype was launched to the public at large, the promotional film was edited carefully to only show a single, leading power car. This was because it was the beginning of the early 1970s oil crisis, and two thirsty power units may have not gone down well during petrol rationing and power cuts. Back to the future once more, fuel costs and taxation rising and te desire for a lower CO2 profile for rail travel, just as with all others. It is a little infair in both respects here. Firstly to do 125mph with a 300 tonne train gross weight, you need 4000hp and then you need another 500 for 'head supply' ie heating, lights, aircon', kettles,  and auxilliary loco supply like compressors. Secondly how many car joiurneys saved in the last 40 years since ic 125 came into service?  ....with congestion at Sheffield, N. london or Birmingham rendering them much longer and less environmentally freindly.

Now uk rail on diesel lines is 99% mutliple  power units. They are being used in the wrong way though. One per carraige often. There is the inevitable loss of efficiency in each transmission, heat inefficiency, and also weight inefficiency due to many duplications of auxilliary equipment. In the three car single unitary train, this is actually arguably less notable while when you reach Six or nine cars you are more efficient again with one or two powerunits in a loco or hst style  power cars according to some work done by Virgin trains.

The future  looks to the past then but also to the mistakes. Take for example HSTs- ruston paxman delivered high powered yet light V12 valentas. They took on a missive for long distance super expresses, non stop  with crew changes under way via the communication doors at the back of each power car. By time of operation, BR had some clowns in their planning dept who decided trains should stop far more often in order to serve a bigger overall potential market per sevice. In one fail swoop they blighted the reliability of the design, and also dammed BR to semi stoppers and journey times often comparable only to normal  car journeys door to door.  Also while on this specific train-set, they are quite heavy all up and the driving style from a standing start seems to use a lot of energy up getting off their marks, reaching the first electrical gear change with both locos having been run up to near full power. It would seem that v200/western system would be preferable, where only one changing at a time maintains tractive power and hence momentum

There in lies what the usa with conrail and private operators have done with the longest trans rocky mountain freights and dial on power units in 'robots' along the arrangement. Computers have been assisting this since the 1980s. Route mapped performance and power demand is still in its infancy in the uk, where shorter sections between signals and congestion may seem to negate their use. However trains still need to accelerate, cruise and deccelerate. Now they have to keep the Kyoto men happy with co2 output though.

So the body of work is all their in the annals of dieselisation, now we have the technology to move forward, twin engines or not......just one step ahead of the 25kv overhead lines.....

torsdag 11. desember 2014

HS2 Sums Not Adding Up for the Passenger

High Speed 2 is upside down in development and fundamentally bad for the midlands and north of UK. Phase one which is realistically all that is politically committed to so far, is basically about delivering more skilled workers to London,. and admitting defeat as to the Midlands being an area for development of financial services and corporate head offices. It is a big ADSL link - asymetric in passenger traffic, assymetric in brain drain.

London centricity on public spending is then maintained by the leverage all the up-for-grabs and marginal seats in the South East which is unfortunetly all that UK politics has been about until the last 18 months with the rise of the SNP and UKIP as major powers, and the inevitability of coalition governance and possible proportional representation. Labour have given up canvassing in many of their traditional areas in favour of geotargeting and social media, which they will pay for in the next election just as much as the backlash against on the one side Austerity and meagre pay rises, while on the other the island monkey drift to UKIP at all levels of society, notably top and bottom.

Why is this an assymetric link? Quite simply the laws of natural competition and the labour market. The South East has never had the mass unemployment and uncomfortable de-industrialisation the midlands and especially the North of Britain endured in the late 70s through to the mid 90s. There is low unemployment amongst British ethnic adults. Wages for skilled labour are significantly higher, with a natural London Weighting in order to attract and retain staff in the region with some of the highest house and rental prices in the EU. The midlands / north have lower pay, lower prospects for promotion, less job security and higher unemployment. You just are not going to get skilled workers from London to travel daily north in any large numbers, and given there is then a further drain on resources south, what would business advisers and potential investors travel north to?

HS2 is an admission of defeat - that government cannot stimulate the economy north of Watford Gap and is powerless on this apart from giving a massive injection to of public money to what will be a privately run railway monopoly. You could say that it is petrol on the flames of London overheating too, a sub prime investment as a sticking plaster for the north, upturning the perception of the SE being the only place worth locating service, financial companies  and national or EU Head Quarters to, or investing in.

There may be a slow 'trickle up' north where by investment skills and networks move north with people's inevitable desire to live nearer their workplace and have less time commuting. But if you live within 20 minutes of the new stations then you are quicker to a job in the city or west end even that if you had to use the m6 through 'Brum' at rush hour. Like the rail routes of the late 19th and third rail radial routes built between the wars, London gets a new commuter belt.

Also you have to then ask, what good is this for the economy? What will all these new investment experts be investing in?  Well the jobs down south will not be in value adding manufacturing, more likely riding the next wave of consumer credit, house price -mortgage fuelled lending and hedge fund speculation. At the end of the day, Britain needs to create fundamental value and use oil revenues to rebuild the UK on small to medium , high growth, high qaulity, unglamerous companies and the skills and local infrastructure they need.

lørdag 15. november 2014

Electro Diesel Tantalus

Maybe it is just a crossed wire shortcircuiting my memory, but I have a lasting image of an electro-diesel deltic in my old railway memories from a general arrangement drawing, an outline sketch and no more, of an EE half an half.

Even by 1958 it was clear that the deltic with a turbo T18 engine could deliver traction rated power of 2200hp in a very light weight package per power unit, and so using the other engine bay completely for electrical AC equipment and replacing the radiator group at that end with a pantograph.

From EE this would have been in AC form a 3300 bhp continuous output loco with the aforementioned DE mode being ample for dragging 700 tonne trains from the freight rail head, or running 400 tonne passenger expresses beyond the wires of the West Coast Mainline.

Of all power units, the deltic at that time was the only one capable of providing such an enourmous power output per tonne of loco, and basically in being part of the only viable dual mode main line, express speed locomtoive at the time and for the following ten years with the advnet of the high powered valenta.

Why then did this never come to fruition or beyond a sketch?

There are several reasons for this, but basically the need was probably not that well defined at the BTC /BRB. Branch lines were  by  in large not envisaged for electrification and certainly not many railheads to freight customers. Electrified mainlines though were very much in the plan for a new british railway. Back then we had a different outset than we have today, where trains were still largely marshalled and apart from some coal pit to smelter/power station loads, this meant that several locomotives would be involved with type 1,2 and lower powered shunters haulinbg to the big marshall yards which still stand idle today in a few places like north of Carlisle.

Deltic itself was a ten year 'stop-gap' measure prior to the planned electrification in the late 1960s of the ECML, which ahem meant that the drone of twin napiers went on for another whole decade and was replaced for almost another whole generation by the shrill whine of the IC 125. In another slight irony, deltics in the days of steam heat fairly often ran to Aberdeen on one engine norht of Edinburgh with the slack sections of Fife hardly warranting 3300 hp while perhaps engine hours could be kept down in this way a little. Thus for the reach north as electrification stretched ever more towards Carlisle and Glasgow Central, a dual mode deltic could have provided a reasonable performer even at the non turnbo 1650 bhp rating of a single PU in a dual mode loco.

Another reason there were not more dual mode locos in the first two phases of removing steam locomotion, was that there was rationing of many materials to industry in post war 1950s Britain and for some military materials like aluminium, this went onto the 1960s.  Also back then the 25kv AC locos were still not fully proven and perhaps the electrical systems would have had trouble in rectifying and transforming down to the amp /volt ratings of the same traction motors as run by the DE output, I would have to have a check on the types used.

Economics played the part in the expense of proving such a loco, although the successful class 73 demostrates the usefulness of dual mode locos,. in fulfilling different roles even when one of the modes becomes periodically obsolete due to lack of demand or other traction being available or multiple units replacing loco hauled. They find new routes, new types of trains and so on.

Economics foresight should though have played a far bigger part in railway planning, and in fact the nearest we came to an economically self sustainable railway was the full might of Dr. Beeching's dreaded proposals. Wage rises, fuel prices and the accession of freight to long haul road, and personal transport to small affordable commuter cars,  on the motorway network could have all been predicted and acted upon  by 1960 even.

In harder nosed BTC/BRB relationship, the dual  mode deltic could have had a place, as haiuling direct trains to an dfrom railhead to the AC trunk routes and making trains more economic in terms of tractive power allocation, train crews and size of minimum and maximum load tacklable economically. BR missed out on this trick, while the French and Germans did not, and modernised towards larger customers and larger road/to/rail transfer depots, reducing the amount of martialling. In the UK it just died a death with the advent of the tent sided 20 tonne lorry, and later of course, container and tanker traffic to 38 then 40 tonnes.

There have been two big game changers since then in the railway and freight in particular. Firstly, it has remained and expanded its economic superiority to road in large point to point volume freight, and secondly there is now the Channel Tunnel. Now we have super/marhsalling and private railheads acting on behalf of other end users in transfer to road or even in co-location of factories or warehouses to the railhead.

The next game changer is the cost of fuel and price then per mile of in particular, container and small container traffic, and soft sided domestic market containers. Also UK companies will be looking to continue to use scale to competitive advantage and also to supply more to europe as the main market. Added into this is the potential move to several more 'deep' water container terminals, in the SW of England, Hunterston and Aberford in Wales, where monster ships bigger than the 120,000 t "panamaxes" will be able to connect with europe, save a day's sailing and even maybe  these will be too big to pass through the shallow english channel at all but spring high tides of a SW swell!

With that type of traffic then a type 3 or just 4 dual locomotive seems a bit underpowered, but dont forget that shunters used to handle trains at low speed from railhead to main line siding. Much of that operation is over with class 66s doing shunts on whole trains and there just being gaps when there was not enough cargo to fill a train rather than the expense of martialling. However then the expectations today are to be able to lift a 2000 tonne train and tommorrows railway will probably be looking at 3000 tonne trains from large scale plants or to distribution centres in order to be most economic. Then you need specialist traction, the heavy diesel type 5 and type 6. This is still why there is so much diesel under the wires, because there is a shortage of electric locos and no real incentibve for using two train crews.

Trains though of 500 tonnes, not forgetting that is upto 20 or 30 lorry loads may become more economic if they are point to point or transconintental, or in plkaces where rail is as fast as road or faster, but much more reliable. Take the tesco use of the highland line, these are only a few hundred tonnes of net freight in the kighter services.

Now it becomes clear that the real use of a dual locomotive for tommorrows railway would not be in frieght necessarily. More likely to be in passenger, where trains of upto 600 tonnes can be managed admirably with less than 2500 bhp and on semi fast routes, 1650 hp would be enough. Deltic through is for now too smokey, so we woul d be looking at the now MAN owned VP series which replaced Valenta , with v6,8 or 12 configuratiion most appropriate.

There are some engine techmoligists researching opposed piston engines for some odd reason, they have mayve kidded themselves on that they are so much simpler that there must be a way of getting them to work within modern emissions demands, and they are allegedly looking into car engine sized opposing four and six piston units in diesel.  How they will overcome the inherent smokey issues is yet to be seen. IT could all be like the last great experiment in the 1990s into two stroke, supercharged engines by ford which lead to zero point zero products and profits.

Dual mode in both locos and passenger multiple units is very attractive too either if privatisation is opened to real competition between companies for diagrams on the same routes, whereby those willing to invest in dual mode will gain most on winning cross power source routes or be able to employ their rolling stock on alternative contracts if they do not win their first choice from the list.  There  is also talk of an under/the(wires levvy for diesel trains in order to encourage use of electric locos or dual mode stock.

On "BR" today even the latest electric locomotives in network use, the class 92 are arguably coming to the end of their economic and safe lifespans. Class 66s are in need of heavy general repair , and the class 60s have already been rationalised. The remaining second generation locos , 47s , 56s and 57s are passed their use by date well and truly. If all pre 1995 ie now two decade old stock and older, was removed then the railwya would run to a hault in terms of passenger services.

There will be some dual and even multimode trains, multiple units and dragged electric loco set ups in the near future, but will we ever see a mainline dual mode Diesel Electric/AC Electro or DC thrid rail?

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.

fredag 4. juli 2014

Deltic Rebirth? The Opposed Piston Engine Strikes Back?

I "stumbled upon" in my own way, the "new" breed of opposed piston engines which are allegedly being funded by the Bill Gates Foundation. They are two stroke turbo diesels which use a double cylinder per bank, with long conrods connecting the outer piston effort to a common single axis crank shaft.
Although this approach solves the "problem" of reconciling forces* at both ends of each cylinder into a single power stream, it does still have the main inherent emissions issues of a swept port,  two stroke design  ( * in the Napier Deltic this  necessitated an expensive gear box which reverses the one gear lower sump shaft with the other two while then marrying all three axis to a single power output shaft)  

The main issue is that lubrication oil from the piston side walls and the sumps or injection sprayed "dry sumps" ends up exiting with the exhaust and burns partially, or worse, builds up (especially after time on idle )around both the exhaust and the air intake vents/ports and then leads to incomplete combustion when injection and final compression to ignition happens. Incomplete ignition is one thing usually completely avoided in four stroke diesels and modern 2 stroke traditional cylinder head motors like the EMD 645 derived engines.

Deltic pistons are more complex than traditional pistons because they require oil routing in order to effect cooling of the piston. In the absence of a heat dissapating cylinder head with water cooling or oil cooling channels in such heavy casting, then much of the heat from ignitions builds up on the piston heads and in napier's development process they identified that this needed oil cooling for the piston heads:  which means even more lub' oil than  the spray injected crank ends and bearings area can gather in the legnth of the cylinder where it meets the pistons. Inevitably some of this lub oil migrates along the piston head and is swept into the combustion area of the cylinder and exhaust chambers. The air intake side is under positive pressure by super charging (roots blower in a deltic) and turbo charging, and this stops build up to some extent at the lip of the intake but that may exacerbate migration of oil into the cylinder due to this positive pressure.

This oil migration to the combsution area of the cylinder is limited by the piston rings around the top third of the piston head however they do not provide a complete scraping or sealing when they sweep over the "gas"  ports.

One way of further reducing oil ingress to combustion areas is to then add more piston rings along the head and /or an oil scavenging scraper collar which is a consumable part fitted to the piston's base and scraping a swept path at a desirable D400s /BR Class 50, one reason they were too effective in preventing oil getting to the piston walls were it is needed.  In a swept port dry sump two stroke engine with oil cooled piston heads such a collar may well work quite well, and may be something which can be fitted from the crank case inspection points in a larger engine or by at least avoiding taking the pistons out as a outward end extra ring would otherwise.

Deltic "clagg" ie smokey exhaust  was always a feature of the power units when they were first revved from idle. All the excess lub' oil suddenly gets heated and blown out, some burning and there is also a lot of water vapour formed if the exhaust collective is cold , leading to plumes of white to grey smoke steam with a rancid smell. Add a little incomplete combustion of diesel from the air- in-port side issue and you get nasty deltic clagg, not good if you ever want to hear that Napier drone in new locomotives, gun boats etc.

Under way however, as you will see in the opening credits of the 1960s classic 'Get Carter', the deltic power units produced quite little smoke in service life.  So at 1500rpm lub oil was not able to build up due to the scraping of the piston and higher positive pressure on the intake side.

General motors EMD have overcome much of the issue with swept air ports while also steadily increasing the volume and pressure of air which is aspirated by/into the cylnder. So it is not a wild goose chase to clean up a deltic.

One approach is to use a different porting and exhaust rooting design, where you may have a positive pressure at the crucial timing points when the piston sweeps. Another is altering porting design , perhaps with multiple ports, which resist ingress of lub oil.

Alternatively the most complex which is not soild state, ie it requires new moving parts, is to utilise a rotating valve mechanism on the exhaust port which allows for the port to be shut when the piston is sweeping it (or if exposed to the crank case side on an imaginery longer stroke design). This could be a fairly simple cam lobe type arrangement on a single shaft per bank of cylinders, where the valve is wheel like and has an open side cut which is designed to be timed in with necessary exhausting. Alternatively a camshaft lobe  valve actuation could be used, if then introducing a degree of complexity into otherwise an elegant design with a high degree of "solid state" solutions.

Another alternative is to reduce the amount of lub oil needed to lubricate the walls of the piston and to dissapate the heat of combustion from the piston head. Here in Napier's day there was nothing available apart from metal with the best qualities to work with oil cooling, but now ceramic piston heads, rings and cylinder liners are realisable. The deltic has modest piston sizes, modest compression and kw/cylinder and a design which lends itself to cooling circuit improvements in the cylinder linings and design of the triangular engine "block".  All these point to use of low lubrication ceramics as a possibility.

I prefer the idea of the following set of " solid state" technolgies over cam shaft valve systems:

1) ceramic piston heads and rings
2) oil blocking and scraping system on the crank side of the piston which prevents most crank case oil from entering the swept area and reaching the gas ports or combustion area of the cylinder.
3) a high tech solution for the small amount of piston wall and conrod pin which need lubrication: perhaps using low pressure diesel injection, or a complete burning lubricant or a non burning synthetic lubricant.
4) Twin scrolled air intakes which are thus always providing a positive pressure at the in-port side, even at idle from super and turbo charging
5) a design for exhaust manifold which enables a slight positive back pressure on the exhaust port when it is being swept such that it presses lub' oil away.

onsdag 9. april 2014

Goyles past Loch Goil? 31s vs 37s on the WHL

The West Highland Line in all its glory is actually a god aweful way of grinding locomotives into the granite hillsides. It is a fairly infamous annal of the more inglorious moments of the Brush Type 2, aka Gargoyles in the 1950s and 'Peds' latterly, that the locomotive was the only diesel electric to be failed for the route on ground of poor traction and it has to be said high overall weight.

Hang on a minute there. The loco ventured up yon-bonnie-banks with the v12 JSV  Mirrlees engine which was deemed a failure in all its original guises, and was kicked out for the reliable 12SVT already proven in use in Australia and in the 16 cylinder variant prototypes of the UK in the 40s and 50s.  So the Class '30' that never was stenciled on a loco, was the failure not the class 31.

How suitable then would the class 31 have been for the west highland line and if they had been technically suited, why were they then never utilised ?

It is probably pretty arguable that the loco was failed due to poor traction when compared to the class 20, 24 and 26 contemporaries of the late 50s and the 27 and 29 after comers. Also the locomotive at 104 tonnes as a 31 and presumably less as the JSV Vac (vb) predecessor,  weighs less than a Black 5 kettle but the arguement about wheel diameter and contact area and tractive effort perhaps persisted until the BRCW and BR type 2s showed their worth or were shoe horned into service.

If you want to call a 31 a pedestrian loco, then  you should get hauled by any other type two on the WHL. 27s were occaisionally out in force even in the 37/0's halcyon days when there was some issue which 'grounded' the fleet, if I was informed rightly at the time this was either issues with boilers or issues with tyre wear - HSE siding on ban them all, especially before the rather better maintained welsh and higher number 37/1s came to supplement the good bad and dross split boxes sent from stratford in 1979/1982.  You could note straight away that the progress was rather lacsidasical with a 27. It was like being hauled by a 37 which was on its last legs and just on the point of failure. Standing start acceleration was all that beating drum tip topping and not a lot of progress. 

 True on stretches with speeds of 45/50 mph you could maybe see an advantage as the 27 burls along, as do other 6LDA teacup/rattlers . A speed range much as on the favourite monotomous bash of the jockular vermin's fan base , the dreadfully dull 40/55 mph fife circuit where a 40 or a 37s superior power is capped by bumping in and out of field diversion all the time once out of the frequent stations and out in the bland pastoral landscape with its curiously serpentine route.

Rat and Mac-rat bashers always say that if you had load eight then you could shove a pair of the vermin on the front and hey presto, bye bye syphon and ponderous class 40. But hey, a pair of 37s will once again piss all over them, and managed most of the Aberystwyth diagrams as singles, on arguably better timings than the paired 25s judgin by the festers at the crossing stations with the then newbies in 1985, outperforming the timetable handsomely.

27s and other Mac Rats do have a certain charm in plodding through the spectacular countryside along the precarious shelf/cuttings and through the tunnels and over the viaducts of the West Highland Line, however the road improvements were in place by the late 70s and further work planned threatened to make the route pretty much unviable as a competitive form of transport vs the bus (which is now actually my preffered mode of public trans' to Oban at least since sprintershitation, faster, just as scenic and often a better view in fact and most of all, quieter!!) With private car ownership on the rise too, the WHL needed a boost and that meant more bhp within the RA5 confines

The 37 diagrams were simply a lot faster than the 27s and other type 2s and not only that but all forms of 37s regularily kept well ahead of most of the diagrams with only a few being a bit of a squeeze to the crew change point most often being Arrochar. Usually there was a 'dreadful fester' at Arrochar as the crew had gassed on the faster sections to Glen Douglas to have extra time for tea at arrochar. The same was even true of the 'up' sleeper with its 400 tonnes odd some nights with the lady ETHEL enterage, which if driven a bit gingerly while using the advantage of more powerful air brakes could run well ahead of time and lead to festers in the up tae Glesga direction too.

In fact in my honest opinion of app. 9,000 miles behind class 37/0s and /1s on the route I would say that the 37s were by in large overkill for any loads under 6 mark 1s or ETHEL on five. Drivers in charge of load three to five, took full advantage of the storming acceleration and then let the locos often poodle around in second field opening up to get momentum up to third field in order to get 50/60 mph up on sections which were 40/50 speed limits. The fact that the stalwart 37014 made up almost an hour from Crianlarich to Dumbarton on the ETHEL warmed sleeper with load 6 one night is testimony to both the loco and of course the devil himself, Peter Walker at the stick. 

So the class 31 should have maybe had a chance? Similar gearing and some very similar diagramming on terra-flatta in the south and west country seem to point to the 31 being pretty much a type 3. In fact you could easily say that the venerable 31 with its high reliability and simplicity probably delivered 1470 bhp a good deal more often than some of Stratfords poorer heaps which ED depot was landed with, such as 37025, 37081 and 37108 which often seemed to be doing as bad a job as  Rottus Caledonia.  Boilered, Ra5, with good visibility and a history of snow plough mounting , standard blue star on general examples of the on.

Many have speculated why indeed 31/4s were not simply diverted away to work ETH services on the whl. The firts, the sleeper, went down to load 5 which a ex loco heating unit like a 31/4 coould plod around with at less than 40 mph.

An issue may have been with the gearing, which I do not have a source for the figure of,  but the loco was only 15% or so less powerful, so notch 6 of 8 was your comparison in the 'class 30 failure' on the WHL. Certainly you have to understand that a 37 is in its element thrashing up a gradient with a couple of hundred tonnes and then maintaining 30-40mph which is the speed limit on a very large proportion of the line. A 31 pootles up slower and then has an awkward field diversion at 28 mph or so, just when drivers would want to be picking up power to get back up to the speed limit after a tortuous curve or on a minor summit. 

The issue here is not actually a straight hypothetical technical comparison. Despite there being both other SVT and RK classes allocated to Eastfield from the 1950s, there was experience with the superior power of the 37s from allocations in the 1960s forward. It must not be overlooked that at the time in the late 1970s the planned aluminium trains from Ft Bill were probably going to be the most torturous of any freight diagram... . comparing to the infamous Llanwern iron ore trains and the 'Gunnie' Cement....both of which of course were under the command of 37s during the 1970s. 

The matter is more of allocation and planning of classes>  because of course during the 1970s, 31s spread their sphere of allocation as they prove to be more useful on faster or heavier services than 6LDA rodentiae, and were replacing diesel hydraulic services too as locos like Hymeks were phased out. 

The success of the 31/4  ( the first ETH ex locomotives as some wags put it) re-purposing lead to the class being an obvious choice for replacing XC DMUs which were frankly completely and utterly knackered by 1980.  With the early examples being withdrawn, there was actually no land-grab available whereas stratford were pretty keen to get on with ETHing and standardising on the ubiquitous duff /4 and eventually /5 and /6 as they churned them out with the wee extra orang boxes on each end.

 Their 37s had been there almost two decades for some examples, and it meant they could rid themselves of the least reliable locos to general repair and reallocation to ScR and ED in particular. We inherited some right old timers from other depots too, like the vb 37 017 originally ED in its first caledonian guise and the eventually rare to bag 37 028 in its 'vo' guise although I think it was actually 'vi' when I had her to Ft bill on a staking hot summer's day in 1983.

Although 37s for passenger work were new to Eastfield and Inverness, there had been freight allocation to first Grangemouth then eastfield from the 1960s to the 1970s , plus motherwell getting them at some point, so there was some experience and driver knowledge on them. Plus in the late 70s the class 40 came to run most every express out of Queen street, the cab and controls being similar enough to a 37, while the maintainence is not miles apart when it gets down to using bloody big spanners on cylinder heads to big-ends.  At one point it was rumoured that ED would become a 10 inch bore shed for all SVT /CSVT / RK engines of SCr, even gaining class 50s to work the Aberdeen expresses, while Haymarket would get all oily over the 12 LDAs and keep the pestolent 6ldas going a few more years after 1982. This rumour must have been based on something because Chris Greene denied it to Jail Enthusiast Rag in his first year in the Throne of ScR.

Anyway we in terra scotia, got intercooled Ruston engines in a nice looking, punchy package the EE type 3, syphon gee.  Not all was all that well though. It is a bit strange that by in large the western region 37s reallocated to Scotland inn 1982 onward were in much better condition than the eastern /GN locos from stratford, gateshead and so on barring the latter boilered flock around 37260/262/264. The welshies had had a hard life Boyo, up in the valleys on all from loose fitted to big nasty airbraked lumbering runs of the black burny stone stuff. However them being a squeeze newer and perhaps drivers being trained to respect them , plus seemngly much better maintanence at CD etc, meant that they were on average far superior to the split boxers.   East field and St Rollox too soon rolled their sleeves up though and got to work on their engines and boilers, and paint work too. Some went into Doncaster or other BRE main works, others had very good work achieved under the victorian rooves of Inverness's sheds. However this was usually in vain as particular notorious drivers chose to 'notch 8' them at any given chance from a standing start or whenever they were a bit bored and the resulting wheel slip and tyre wear kept the tyring shop at St Rollox and the top o' the bank in business. This coupled to flange and bearing  wear, probably caused by drivers abusing speed limits on the Crianlarich/Craigendorran sections, lead to the trials with 'bendy bogies' in fact swingy axles  would be a better description. 37/4s were never fitted with them, the lower gearing perhaps curbing some excesses or better driver discipline giving them actually a longer, healthier life than their older bretherin originally transfered north of the border five to six years before their emergence.

I digress into a bit of nostalgia and speculative ranting, so back to the topic> 
It would be interesting to shove a 31  /0 up the WHL on similar loads and let a pair work a simulated freight like the aluminium services. Then of course you could put a 31/4 on a load four sleeper no issue, maybe turn off the heat for the bigger banks if the story of them being segregated out of that power is not true that is. 31/4s would no doubt keep to the slower sprinter timetable on a bigger capacity train. Did  you actually know, dear syphon basher insect of post 1988 start, that they fudged the outgoing 37/4 timetable with an extra forty minutes or so put on most trains between the penultimate stations and their destinations, mainly noticebly at Dunbarton and upon arriving gleefully early at GSQ, evern with the low level diversion in place????

Anyway, given a different twist in fortunes the Goyle creatures could well have purred and burbled their way over Whistlefield bank and glanced down upon Loch Goil below as the spectacular vista of the Argyll hills and Lochs is suddenly unvelied coming out of the cutting as you pass the Green Kettle. Had they chosen to keep Hymeks, had they scrapped more 6LDAs in the 70s, had they ordered more Goyles, had they never been ETH fitted can go on and on. Technically the 1470 hp goil with a boiler would have been superior to the tinny rodent classes which pagiued the WHL and struggled to better the steam diagrams they were introduced to surpass.

A glorious waste of 1750hp deliverd with gusto then entailed on all trains for just over half a decade and then remarkably outlived any class of locomotive used on the line before them in charge of the 'Ftr Bill ETH Bedz' , and still finding use on PW and schedule tour trains today. How the Glens and Lochs reverberrated to one of English Electrics finest creations, and how we enjoyed sticking our heads oot the windaes to breath a mix of pure highland air and class 37 exaust fumes as we revelled in the experience of the thrash, the beauty of nature and the banter of the railway men and boys back then in the early 1980s.


torsdag 27. mars 2014

Diesels We Nearly Had: Western Region....

I stood better informed about the warship and western class after an internet expedition into Hymek Land.

The interesting points to me are that

1) we could have had hymeks rated at 1940 hp with the engines as fitted, or even higher with upgrades as Maybach (MTU ) improved the design or modified things like cylinder heads.

2) The Western had a weakness in third gear : it did not have enough grunt in the v12s. Had it been fitted with twin 870 v16s from the Hymek, this would have been solved. Even further derated to 1500 hp or thereabouts, the power and torque would have made the westerns better suited to their envisaged tasks, especially 100mph trains. The V16s would have run cooler than the v12s which were pretty pushed at that rating in 1960. Voith and Mekydro units were in a "footprint" which followed the DB wish to have interchangeability, with V200s sometimes running with BOTH types of transmission, one on each PU. The extra weight would have been a matter of four to six tonnes.

3) Do we have an answer to oil sloshing diesel-hydraulic-mechanical locos vs diesel electric in Brush's Falcon? It seems falcon could start a heavier train on a steeper gradient and achieve 100mph more adequately on 400-500 tonne trains than its' torque convertor cousins. There was a straight head to head trial actually, but no doubt BR did not want to show Brush up or be shown to be lagging in their own Swindon built design. Had the western region been a bit more objective, they should have purchased a fleet of falcons to cover the inter-regional ScR- SW, NW-SW services which were earmarked ETH even by the early 60s.

4) the real trick western region missed was probably to take the best of German transmission design and couple it to the lightest, most powerful English configuration in a twin deltic engined monster of 3300 hp.

The Deltic engine lends itself eminently to the whole design ethos of DH: 1500 rpm in rail application, very light weight, compact, smooth torque curve and rate of acceleration.

Furthermore the advantages over the Maybach powerunits dont stop there. The deltics weigh about 5 tonnes for the PU and the collective gear box, the modern v 12 MTU is about 6 tonnes. The deltic is actually a good deal less complex than the v12 MB650/655 because it has no turbos ( in the preferred rail version 18 Cylinder, 36 piston) , no intercooling and no valves or cam shafts.

The "stack height" is not an issue. Maybach and the now MTU (owned by Rolls Royce Ironically enough now!) have stuck to a design with twin turbos mounted mid engine, which keeps the legnth of the unit minimal compared to the convention on almost all UK and US locomotive prime-mover/power-units with the turbos at the ends of the cylinder banks. This means though that stack height is rather high, and there is little room for free space for the engine radiator cooling groups.

The deltic overcomes this issue, with the Cooling Units being shaft driven directly above the power units,  on the classic twin engined class 55 locomotive in the UK. The "GWR Deltic" would have possibly had three fans per power train, the additional one for the hydraulic cooling groups. They may have also suited themselves to ETH by the rebuilding of the collective gear case to include a running circuit to a dynamo.

One thing which would have suited the deltic power units well, especially with the Voith transmission, would be that both engines are engaged from start and their is less lag in "gear changes" compared to the weak field diversion volt-amp resets on the deltic. The DE locomotive collected power from both PUs to supply both bogies, with the first unit running the train to about 18 mph before the second one comes on line, actuated by a cam on the power controller under the drivers control board. This and the field diversion set up meant that the engines had time to gather lubrication oil while at low rpm which made them very smokey.


Alas all this was  not to be, neither the DE versions of the Hymek and a productin version of Falcon. It is with some irony that the majority of passenger traffic on western region now is handled by DH DMUS mostly with voith transmission and many with MTU (Maybach ) power units.

If the BTC and BRB had in the outset studied the German locos more and had GWR been more cautious with the DH introduction then perhaps certain niches in terms of start-lift, route, speed and tonnage could have been identified and DH locos developed on a national basis. Crazy? Non Standard? Well what do we have today in terms of diesel passenger trains on a national basis?

For me that would mean a few classes of shunter (switcher) locos upto 1300hp the higher ones having mainline potential, while the betting being on the v16 in a type 3 / type 4 development as the Hymek , with engines being swapped out as hp increased over time,  and a twin engined version of this or the v12 by the same merits, with this or the twin DH Deltic being the master of long express traffic in the GWR or further a field.

tirsdag 25. mars 2014

Mekydro and Personal Enlightenment on the "Oil Sloshers"

Type three locos are a bit of a dark eve's obsession for me now, as much as chasing 37s about in the 1980s was then.

The one I regret not being in service when I was a nipper, was the BR Class 35 Hymek. With its' tractory, thrashy v16 single engine and petite and pretty looks the loco design seemed to punch over its weight, and many a Hymek nut who worked on them in service life, will tell you they were the best Diesel-Hyrdaulic Locos in the UK.

I was delving deeper into the Hymek story when i actually fell into a great disappointment or rather a hole in my knowledge due to being a presumptious of understanding, runs in the family, son #1, 5.6 y.o. bullshits away to me about how things work or are too. I happened upon a set of GA drawings (general arrangement) for the whole loco, and the bogies. It struck me that for a large part of the last four years I have been going over GA drawings being a technical outsourcing purchaser , and that I had actually bought some diesel hydraulic off the shelf equipment: a rotary table with turbine motor run from the "main circuit" in turn probably run directly from a diesel unit like a v16 cat or a rustons v12.

So I decided to cast my eye more critically upon the drawings and saw a "whole bunch" of cardan shafts. The Hymek type 3 has of course only one power unit so must distribute the drive to both bogies unlike most other DH locos of the time.

It dawned on me that I had gone along in a little myth about DH locos which was a self told fallacy : I had thought that the locos used a gear box and torque convertor to pump oil into what we call a hydraulic motor or turbine motor at ever higher pressures as speed went up, with hosing going to each driven axle and a final drive turbine motor arranged around the axle. Well the name is Diesel Hydraulic ???

In fact though I now discover to my ignorance, that the term Mekydro coined in good old Deutscheland is far more accurate: Diesel hydraulic loco is a misnomer!!! These locos are mechanical with hydraulic torque transmission.

Given a single torque convertor in fact, the amount of oil in the system would be probably no more than in an equivalent big mid speed engine like a 12 CSVT or 8LDA of around the same output. You of course run the fan and you need to have a volume and cooling heat exchangers to suit the thermodynamics of the oil so that adds, but the point is that a single torque convertor transmission for a v16 MTU today would be relatively small, with a matter of tens of litres of circuit volume for fluid in action so to speak.

So anyway, self made mad myth busted ( unless someone tells me the final drives are cardan shaft driven turbines or fluid mechanical gear joints), I started thinking more about how these things work in practice and what the issues are with them and what the advantages over diesel-electric are or other tranmission forms?

Why are DE and DH Favoured over Mechanical Geared Direct Drive in almost All Locos over 1000kw ?

There are several shunters, light self driven rail cars or sets (DMUs) and of course the whacky Fell locomotive of much more horse power,  which use gearing and clutches to achieve transmission. In 1987 a pal of mine who was technically minded asked me why there were not more mechanical direct drive locos and why they resorted to DE or DH drive....

The main issues in using direct mechanical drive in a loco, from the type you would find  in a car with a standard clutch or a motor bike:

1) Wear and tear on gears and clutches, due to high starting loads, variable speeds, and uneven travel
2) heat in the gears and oil
3) requirement for a great many gears for higher speed, higher horse power to reduce and apply the power successfully
3) difficulty in starting heavier trains

The last two matters really hit the head of the nail, whereas the first two are actually problems partly shared in DH locos because they are mechanical-hydraulic drive with basically the clutching of main engine drive being the hydraulic bitty.

In order to start heavier trains , just as in slipping the clutch on your car on a hillstart, you need to be able to exact a stationary starting force on the axles in order for them to have enough torque to start to rotate.

A bit like getting a nut opened with a long bendy spanner, you need to ease in the power without it :

1) on the one hand resulting in instant slip as the right pressure is met and then quickly exceeded by the leverage of gears on the axle,
2) on the other hand  that there is deformation of the gears or excessive wear on the clutch plates.
3) Pull a third hand out from paddling kids at Sellafield: You need to change gear immediately after you start as the gearing is so low to achieve this "bendy torque wrench" effect, thus making progress awkward and potentially stalling the train anyway.

Here is where DE and DH locos excel and why the first series of uk diesel multiple units were erm, a bit crappy. They can both start a much heavier train and retain reliability and sensible construction of the transmissions.

How the MEK is Attenuated Nicely by the Hydro

As I realise to my own chagrin, DH is an overstatement: we are talking an automatic ford granada is technically spot on compared to the turbine breaks of the APT-P.  Now there happened to be a lot of old Granada Automatics in the  UK in the 80s and 90s and of course Americania lasts for ever from the fifties and sixties (before they got too fancy and all gay with their trann'ies pun, pun) so in fact the system would seem to have some longevity benefits.

Usually DH locos have a transmission shaft "stator" array which passes through several turbines , ie the donut shaped torque convertors themselves. The torque convertor looks a bit like a triallabite but it is actually a marvel of simple, wonderful engineering. It allows basically for a slipping clutch without any mechanical wear on its internal exchange surfaces unlike a standard car or oil encased multiplate oil clutch, the motor bike type, which are incidentally common in machinery. This slipping of the clutch is effectively a form of variable gearing allowing for both

a) a standing force to be built up progressively while the drive shaft is loaded up with torque smoothly
b) the engine to carry on to apply more power from its own torque output , the curve of which may be a lot higher than a direct mechanical system could take, thus burning out a clutch slipping.
c) Effectively this is a continuosly variable gearing until the rotor speed matches the stator speed at which the application of torque becomes linear - until one or the other slips -
d) coming back on that point in c- this also means that there is an inbuilt resistance to slipping in the convertor as the blades do not want to pump oil backwards but rather the system will slip  if the speed differential becomes greater than the designed flow.

Now here is a great claim in C and D we must come back to

The best and worst is really to be heard in the sprinter units which have fairly small engines which have to be revved hard to get the starting force going, and then there is either a gear change or the engine backs down to allow for synchroyny in the torque convertor, which it sounds like it does and feels like from the speed being fairly un -sprinty.

We have looked at a single torque convertor which would be fine in itself: this would in effect mean that a locomotive with an engine rpm range effective of 700 rmp engaged to max would run a single mechanical gear much longer than if it was directly connected to the output drive shaft, ie the clutch was let out and stayed on. You would need more gears to cope with the torque differential. Here also as you go from a starting torque and reach maybe synchrony in stator -rotor speed which should in theory be linear, a peaky v12 say can continue to exploit the slip of the clutch in applying its own progression of rpm and torque which the wheels catch up at the end of the day.

Back to sprinters then: horrid things, they rev far too much for the progress the rather light train should be making. The 170s and after comers, are a bit better at applying power though but still irritating compared to a loco up the front. The point being here that if you have a revvy, low torque engine you have to rev a lot to get the starting force out, noisy, vibrat'ey, and then you have to change gears a lot at lower speeds to continue to overcome the inertia of the train until the resistance is then more friction: 170s are pretty quiet when powering along at "high" speed.

The irony of these horrid plastic rail-bus thingies,  ie modern DMUs, is that the majority of non electrified routes are now DH driven! How a few long gone GWR traction engineers must have sniggered in oily-sloshy heaven when that day came in the late 1990s.

On a more powerful loco then you have a lot more torque to play with from a big engine but you have then a lot more torque to control and apply and more potential friction in both mechanical components and in deed on the hydraulic oil.

You need gearing but by in large that is limited to three forward and a reverse ( I wonder if they have a heavier system to change direction of travel so that the gear direction is fully reversed? ) In effect your torque convertor is also giving you an extra low first gear without a gear change to second slow speed acceleration gear, and then onto a third.

However the clever Gerry Clogs at Voith a very long time ago now, came up with the idea of multiple stator-rotor turbines arranged along the same shaft. You then engage these by hydraulic actuation of each circuit with it being essentially on low pressure, lubrication when the circuit does not pump oil in. This means that you can probably then (?) rev the engine down less to change up a gear because

a) you can slip out of gear and into the new without major issues in just engaging the new donut down the line and phasing out the current gear
b) the new gear will be able to catch up by the very principle of torque conversion.

The sequential convertor gearing, three stages of them on a Western Voith transmission, are then based on delivering progressively higher pressures to the rotor drive shaft or would that be higher flow at lower pressure? looks like they go down in size like mechanical gears and that also the power relies on a longer smoother application of torque /rpm from the main mover Power Unit.

Now anyone who has driven a modern lorry over 10 tonnes will know that they have a lot of gears, and you use most at low speed, as above noted for DH drive. Another approach is to have more gears on a single torque convertor.

The benefit here is that you reduce the complexity of the hyrdaulic transmission and control, while also you can have the gears in a smaller volume per gear because torque convertors and their associated hydraulic control and cooling equipment take up more space than gears with multi plate clutches.

I think if I remember right, the warship class had each mechanical gear case on the engine side of a single torque convertor, whereas the Hymek have their single gear case after the convertor. You introduce then the need for mechanical - hydraulic feedback control for speed in order to shift gear automatically and not have the driver doing it (crunch, screeach, kangeroo starts and so on....safer to give them a simple couple of levers to pull on and let t' loco look after hesself)

Also in having three or more gears in a mechanical box, you introduce more points of maintenance and more parts which wear out. Torque convertors of this type cannot run in reverse and in fact the stator is locked in a single rotational direction to ensure this! Otherwise pressure differentials could brake and reverse the stator potentially

Surely a better compromise would have been to have a twin gear hydraulic torque transmission and two more gears in a gear box with also the main direction of travel ? Or maybe an inboard gear box, two gears, then the double convertor system and then a "reverser" ? Essentially then you get a very broad range of operation speed-tractive effort with a combination smooth progress when you most want it, over then efficiency when you switch the big mechanical gears? Also in that arrangement, you reduce the opportunity for heavy mechanical forces being applied to the main gear box, while also making that gear changing box simpler by taking out the reverser? If you do get some kind of damage caused by a nasty sheering force ("negative torque" torquing back to you so to speak LOL ) or when the loco crashes or jolts its bogies, the simpler reverser gear box takes the hit and is designed to break somehow limiting damage "up river".

Advantages DH vs DE

If you could have had greater reliability in the higher speed power units necessary for DH in the 1960s then you could have a big advantage over DE straight away because then your service interval is longer for major out of traffic overhauls, and given there is no damage, the worn parts can be changed out quickly. The parts list is allegedly cheaper than DE of the time of big dieselisation.

The other big advantage which is alleged is that DH designs are very resistant to wheel slip. I guess this is for two reasons- firstly there is a lot of built in inertia and friction up line in the carden shafts and bevel gearing, and secondly because the torque convertor is both locked in forward direction and the rotor will encounter resistance if it tries to go faster than the stator. Unlike in a car, the engine will not be dragged into the wheel slip by suddenly being free to rev a lot faster.

In older DE designs, wheel slip had occured before anything was done about it, and in the lighter designs or those like the 58 with poor bogie design, the rate of damage by wheel slip on steeper routes must have been frightening for the depots accountants.

The jury is a little out on the wheel slip thing. It seems maybe that electric traction motors can apply a far higher starting force and a higher / faster application of torque through the speed range than hydraulic locos, and that a lot less power is lost to heat ie they are more efficient at converting power even though they go through a tortuous mech-electric-mech route rather than the oil sloshers more direct path.

The wheel slip advantage is something the jury is out on with the new Voith loco 3.2 kw jobbie DH, erm , gaining traction in the market. However given you are allowed to run bloody heavy stuff like 66s and 60s and the new electric creep control and wheel slip avoidance / detection control and SEPEX not in the least, then the benefits of DH are diminished.

Disadvantages of DHs as built in the 1950s / 60s in the uk are

1) engines can be thristy relatively on idle
2) both the engine (power unit) , gear box and especially the hydraulic transmission are /were prone to overheating
3) General Heavy Repair can be very costly requiring many new gear parts

If the fleet of DH locomotives for the GWR were for some reason, out to tender today and not in 1958, then we would see of course the use of computers and  a lot more experience in building and operating them in Germany. Then you could optimise the whole system for a given use, tonnage and speed range and keep it within its boundaries, while having very very efficient gear changes due to computer monitoring and control. Also as has been recently obvious, 1500 rpm engines in the 1 - 2.5 kw range are seemingly necessary in order to meet the new emissions standards, and GE / Catipillar boast long service intervals on these units. Finally materials, machining tolerances, lubricants, and of course hydraulic oils have all become far more advanced since 1958.

So today the GWR would get an interesting bunch of locos, probably including Voith's own monster and some Vosloh "dog bone" locos which would no doubt compare favourably to the class 70 in particular for freight work, and be a far nicer way of applying oily mediated progress to passenger trains than those rather horrid 3rd gen DMUs.