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.
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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.

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 class...so 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  .....you 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.

 

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.

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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.

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.

Deltic - Dinosaur or Died too Early?

I remember deltics well of course, even if i had a fleeting relationship to them in their BR service swansong when I was a nipper. Deltics weren't a locomotive you just saw and heard, you felt their power and prescence.

By the last old days of 1980 the deltic reign had ended. All be that ten years after the anticipated life time on  the ECML metals. Just as with the pacific steam locos the deltics replaced, they themselves were superceded . They had become dinosaurs.

Or had they? In reality the fleet got a stay of execution in 1978 and ploughed on with various east coast and the final rather ill suited liverpool - newcastle semi fast diagrams. Rationalised with two of their brethren becoming parts bins,  the rest in reality kept as an exhibition fleet into 1980.

The remarkable thing is that the remaining  locos have survived much longer in preservation: now more than half as long again as their active service wijth BR. The "third age" of the deltics with proffessional management and main line certification.

What then for the alternative history where BR or a private body supported their utility say another decade in service?

Well if privatisation had been happening in the 1970s then gyou can bet that they would have been. A private railway would not have invested in a hundred 56s and the entire class 58. Standardisation versus reliability was a BR mantra , the opposite has been seen across europe and the usa. So the brush type 4 and its under delivered promise and poor reliability would have stopped the later builds. Class 50s would have been sent back to by then GEC leaving deltics, peaks and the more reliable hydraulics to be the main 100mph service providers outside HST diagrams.

Another alterntaive future would have been re-engining.  By 1980 the Ruston Paxman Valenta would have been available in either a v8 at 1650bhp or a v16.  Twin v 12s could maybe fit in a deltic, giving them thus standard units to hst and an RA 6 not to mention 4000 bhp plus!

Maybe other improvements to lub oil and piston / crank systems in the deltic power unit could have made them less smokey and extended service interval to over 3000 hours. Or a turbo version tuned for efficiency.

Whatever the locos when compared to ageing 45s and dodgey engined 47s , deltics were only a tad more smokey and it was burnt oil not spewing diesel and lub. They werent the only relics of the rush to dieselise which were environmentally non PC even by the mid eighties.

Where would they have worked?

If there had been a gap for them to work in an extended lifetime, then it would have been in the west country that they would have thrived. Well into the 1980s there were enough north to south west diagrams with loco change from WCmL or the need for speed from Newcastle or York right through.

However there were also 50 class d400s and seemingly endless ETH peaks in the post oil-sloshing GWR. Not to mention duffs a plenty, one fails send out another until you are down to 47/3s and ice cold trains!

Deltics had higher ETH capacity than 50s and arguably better performance in the 85 to 110 mph range. However it was only the eastern depots, Paxman colchester and donnie works who had the expertise needed in the early 80s in order to keep an ageing fleet going.  Newcastle could then have been a centre for diagrams NE-SW with temporary stabling and driver training only at brum and bristol.

As a small, specialist fleet though there could be a case for remote allocation of servicing.

My own choice would be phasing out 50s over to HGR and including an upgrade to their eth. Thus allocating them to semi fast passengers, over night sleepers and speedlink on the ecml,. Then having 15 deltics allocated to Doncaster with a preserved demo fleet of four to newcstle and haymarket for railtours.

The donne main liners would actually work the west country with extensive drijver training for the wcml to Sw services during the day and the brum and newcastle sleepers at njight. This would be only to 1986 when boilered "bedz" were finally erradicated and enough hsts were released from ecml electrification to free up class 50 to take over any remaining GwR services in their new proven and fully rectified guise.

Full Circle with the Development of the CSVT engine

Proving the internet is a fragmented place not particularly suited to amateur qausi academic research with any comprehensive coverage, I finally complete the full cycle of the history of the CSVT power unit prior to it becoming the RK270 as fitted to the class 56 and 58, and with around 35-75% more power per cylinder than the two 1960s locos in the UK fitted with said beasty, growling power units, the 37 and the 50.

The first two links in this evolutionary tale come from in fact the V8: used in the portugeuse Switcher type locos and the NIR class 101 "thumper" class , where I had heard they were rated up at 1500 hp, but Wiki informs us 1350 the same as the iberian ones. At around the same time, the Aussies had successfully rated the v8 at 1760 hp in the KTM Class 22, which prove to be more reliable than both the Class 50 and the 101s of NIR.

The KTM class 22s were built in the early seventies in Aus' by EE / AEI. The clue here is that they used the CSVT mark III engine. It seems that this engine was not developed in Europe, where the major project was the metric RK instead.

Indeed then the Aussies were pretty keen on EE and developing locos as the power unit technology advanced, seen perfectly with the v 12 going from say the QR class 1270, 1300 (1540 and 1800 hp respc.) up to the 2350 a the same nominal bhp, and there is a quote of taking it to 2550hp ( far short however of the 3300 hp in the class 58) . The RK270 was then first installed in 47 601 at the time, in 1974 thus being built at the same time as the aussie MrkIIIs and probably sharing technology.

The Mrk III engine was the last used in Aus,  I believe from EE and its later GEC who by then owned all of EE and subsidiaries including Rustons and those in Aus. It differed from the predecessors in having gear driven cams and a single stack cumulative exhaust route deliverying to a single, very much larger turbo charger. In the 2350 (at their full rating, not the Tasrail down throttelign to 1750) they sound most like the RK215 engines in fact, spluttering a bit and couging rather more than dubbing, but still recognisable as a thrashy v 12 from Rustons, as in fact is the v12 in the class 58 if you listen carefully or see the video from Tinsley depot, which included footage of them running around with their silencers removed.

The mark II is familiar in the class 37 and class 50, being at ratings of  167 bhp / cylinder in the 50 and 37 292 (2000hp experiment) and 145bhp. Meanwhile the aussies did the KTM at 220 bhp per each of her 8 cylinders, and the eventual 2350 at 195 bhp per cyclinder in her v 12.  This compares to "47 601 " and the class 56 at 3250 hp overall, as 203 hp, and the 47 901  v 12 er then at the massive 275hp. Jumps of 30- 40 horse power then per cylinder in the early seventies and finally the sky was the limit for rustons and the smooth running v 12.

However now the missing gap in my mind, within the evolution from 10000/100001 , the humble class 08, the 20/40 rating and the UK ratings of the CSVT for traction use. A jump of 40hp per cylinder to the Mrk III and then a while went by before the class 58 came along. I sigh a little sigh of relief

The APT: Britains Most Succesful of Failures

Back to another of my chestnuts - the APT - P in particular and a glance at the " E" for experimental predecessor.

The concept of tilting trains dates back some considerable time before even the APT- E (experimental, the single gas turbine version) made the light of day. 1970s technology was adequate for the APT-P , the prototype.

Only we didn't get a prototype, the first of it's type, we got six pre-production types, the class 370.

The crux of the matter lies in this very over ambition. Yes a gas turbine one off had been produced but it was a running laboratory using an already disfavoured power unit supply. Proof of concept was established. However what was needed was a single prototype of the APT-P and not a whole pre-production class.

Why not though, produce a further proof-of-commerciality if you like by having a viable class of APTs running actual passenger specials which reflected the belief in BR management that this was a faite accomplis, as before the HST and the Deltic and electrification had been. In the 1970s though and into the 1980s this arrogance would meet its match in an in patient, road-oriented Magaret Thatcher.

There are major issues with managing a project with six train sets: firstly you have a longer time for delivery and your overall budget is much bigger, despite being lower per unit than a single set. Secondly and most crucially, when you have something go wrong on one set which is serious, then you have to take all the other sets out of service (tests, PR visits and demonstration ADDEXs essentially) . Further to this you then have a very much larger burdon on resources and spare parts when you come to repair the problem or redesign the system.

The tilting system was somewhat problematic however all reports are that eventually this was solved to a level of reliability concordant with operational service. The braking system's design oversights would have been typical "punch list" items for the redesign between and APT- P single electric unit and any pre production run or actual production run (squadron)

Launching the train officially as an operational Faite Accomplis in a January was really just another example of project management not removing elements which could challenge the reliability of the project and its then key PR presentation.

This reflects on poor project management and too much power invested in decision making in BR in my opinion. Today if the railways were still public, or as with HST2 a public-private alliance,  then the project would be subject to tender and also to an expert committee and nost likely the "quantum leap" from the APT-E to the electrified prototype would be managed by a single unit or in fact competing designs.  Subsequently a fleet of pre-scale production models could have been established to introduce the trains such that the flagship services could be accelerated gradually and revenue returns on a 3 hour London-Glasgow, and shorter timings from Manchester, Liverpool and the West Midland towns on the WCML,  services be assessed.