By doing a kind of Google vox populi, I come across what seems to a majority of blogs and class descriptions which quote that the class 47 was the ipso facto best DE locomotive of all time on UK rails.
This was very much far from the perception of the class through its' entire fleet history and not in the experiences of most enthusiasts and many rail staff. This is especially true when the troublesome early years of the class at the original design rating of 2750hp are taken into account.
There are a good few emotions which can arise on discussing "duffs" given so many insects today have suffered such main line deprivation as to fall to the dark strumming side. Putting the memotions and love of any other class's noise, look and performance to one side, why were the "duffs" not the best?
1) Success of Original Design in Operation: FAIL
Background to the failure of the Class 47 to live up to its' original design is as follows:
Following the mixed fortunes of the "peak" classes, and the somewhat low performance of the D200s, more modern type 4s of higher horse power were desired by the BTC & /BRB.
For sound principles of purchasing (risk managing large capital renewal, whilst also some dubious political motivations, the modernisation plan in it's first phase intended to spread the risk and supply of public money to diverse UK manufacturers. Unfortunetly the mixture of principles and politics produced acquisition of motive power from no less than xx suppliers, entailing two major traction transmission- DE and DH- , with xx power units (PUs: diesel engines) and variations within those PUs and transmissions, creating yet more diveristy and lack of standard equipment.
However the folly of this race to dieselise and keep many constituencies happy, was evident to the BTC & BRB almost immediately by 1960. Such a wide "spread betting" on types and manufacturers demanded that every class had its own introductory run in and rectification, and every class required it's own list of consumables and spare parts. This obviously placed huge strains on not only training labour to work on these machines but also maintain them.
In a rapid change of strategy towards standardisation, by 1962, BTC & BRB had a new ethos in the future of DE being the flat ended, single power unit running at medium speed (rpm) , 110 to 124 tonnes max (19 t / axel) , CoCo . As if by some sudden flash on insight, the BRB had decided that a far greater degree of standardisation from far fewer suppliers was the economic way forward.
The concept of a such a lighter, more powerful type 4 was already mixing in the ether. Even a single super engined Deltic variant was drawn.
English Electric had delivered the most reliable range of locomtives to date, and themselves realised the gap in their power range between the D6700s/D200s and the Deltics. EE utilised one of the two spare deltic locomotive bodies to test the "16 CSVT" air charge cooled version of the RK derived v16, in producing a private and speculative second prototype, appropriately numbered DP2.
BRCW prepared the immaculate looking "lion" prototype, with the higher horse power 12LDA intercooled engine uprated to the desirable 2750hp and with an axel wieght of less than 19 tonnes. This locomotive is in appearance the obvious forerunner of the class 47. Also its less than reliable history in service was a forerunner to the disatourous introduction of the class 47.
Despite the superior reliability of nearly all their types, and the supremacy of the Deltics on the premier ECML route, BRB did not want to commit to a single supplier and did not take up the DP2 as a potential class in the early 1960s. Perhaps the BTC &BRB decided EE - rustons were too dominant a supplier by that time. Brush had already had major issues with their type 2 AIA, which were dventually entirely re-egined to EE-Rustons 12 SVT, and the class 46 which required serious remediation after only a couple of years in service.
To defend Brush however, who had pehaps more experience of higher ampage / voltage generator-motor equipment than AEI who supplied BRCW for "Lion", on paper the class 47 looked like being a winner and in outset deserved at least a significant proportion of the new type 4 order, if not the "lion's " share which BRB/BTC came so soon to regret. Also of some noteworthyness in Brush's design, it was not only the highly durable electrical equipment which prove the test of time. Also the innovative stressed frame has shown itself ideal for performance and longevity. In this major structural strategy, the loads of haulage are carried by the entire body frame elements and not a traditional, heavier twin "I" beam "chassis".
The key issue was that the 12LDA as mass produced at 2750hp, was over rated and the stress on the twin bank engine resulted in serious faults. This has been attributed to Sulzer engaging sub contractors, but in essence the design had probably reached its ultimate reliable rating at 2500hp/750rpm. However it is no mute point that Sulzer later withdrew from traction power unit production.
Thus the 47 did not live up to its original design missive and furthermore, was a hugely expensive folly. Not only was the power unit more than twice the cost of the superior 16 CSVT, the cost of rectification carried out at Vickers in Barrow ran into the millions of pounds, and in todays money this would be tens of millions of pounds.
This cost of rectification and the loss of revenues in delivering lower performance and reliability than anticipated of this large class of locomotive, far outshadow the design and reliability issues with the 50 D400s from EE.
2) Superiority to the 16 CSVT : Little Comparability
DP2 reportedly delivered both a higher performance and more reliable operation than expected, as initially trialled and also after the refitting with the advanced KV10 engine and power control equipment. Projected service interval was in excess of 6000 hours and performance in acceleration was superior to the twin engined deltics.
However when coming to eventually order from EE as policy, for part of the higher powered type 4 CoCo supply, (having bought so many 12LDA type 4s alread yet not wishing to place all eggs in one basket), the BRB/BTC demanded the most advanced equipment, much of it still experimental, be implemented and the locomotives. Furthermore these untried technologies would be introduced on the most demanding high speed passenger route in the UK : The northern end of the WCML.
In effect BRB ordered 50 advanced prototypes.
Had EE been free to produce a simpler locomotive based on proven equipment, as they did for the portugeuse with the 1800 class, then the comparability to Brush type 4 CoCo would have been more apparent. Also given any discussion on reliability being extended by a 10% downrating in power unit output then the 16CSVT would have no doubt enjoyed more reliability. in practice being the same output per cylinder as the ubuiqtous and very reliable class 37 /D6700.
It has been suggested by some commentators that a senior manager at BRB/BTC proposed replacing all the 12LDAs in the 47s with 16CSVTs given the documented performance of DP2 and the yet to transpire issues with the overly complex D400s / class 50s. At less than half the price of the swiss-franco 12LDA, there may have been a comprimise in seeking reparative costs from the suppliers.
IIronically then, in their next significant order for locomotives, Brush actually opted for this very combination in designing the class 56 with essentially an uprated 16CSVT engine with a turbo configuration not unlike that found in the Portuguese 1800s.
Another point on comparability of class 50 type 4, post 1980s refit, and the 47. Class 50s were from outset charged with the most demanding passenger operations on the network and this followed them onto the western region. In the 1980s they continued to work 100mph load 10 + expresses before being relegated to the unsutiable MULE services out of waterloo amongst others. In comparing MIles Per Casualty ( MPC) then the comparison was made previously on the interweb, that class 47s fair no better on high speed expresses with punishing accelerations.
The fleet of original 47/7s were frequently lacking in availability and demanded much extra attention at ED and HA depots in order to keep them running on the Edin-Glasgow, Glasgow-Aberdeen and Edin-Perth via Markinch services.
On the other measure of "fleet availability %" 47s could enjoy availability by declining need for traction. In fact even derby sulzer.com includes a quote from the mid seventies, where Crewe works alone had 38 members of the class in for repair, almost 10% of the fleet requiring works attention at only one of 5 works who conducted major repairs upon them excluding the manufacturer.
In their favour, the twin crank, single turbo 12 cylinder LDA PU was easier to rectify and generally faster to resolve faults on that the more complex v16 from EE/ Rustons. In addition to simpler control and electrical delivery systems, this undoubtely contributed to a rosier picture of fleet availability as the class 47 locomotives despite failing quite frequently, could be turned around at shed's quicker than many Ruston engined locomotives. Also the Brush electrical equipment has been quoted on the itnerweb, as being easier to work upon by fitters.
FOOTNOTE: The One That Got Away: The class 48
Despite the LDA being both a well grounded 2500hp power unit and only uprated 10% to achieve the desirable 2750hp, the engine appeared to be at it's maximum practical rating at 2500hp, at least within the engineering design and build committed to for the price. However for somewhat bizzarre reasons, the 12LVA engine was also offered.
This engine is quite a departure from the twin bank engine, but by the mid sixties had already shown its performance and reliability being the prime motive DE power unit of SNCF in France.
Some "duff" enthusiasts cite this engine as being the major let down, but this is far from the truth. The issue with a simple locating pin on a tool used to assist fitters in mounting and this lead to incorrect positioning with dammage to the "dowel" resulting in metal parts in the crank case, and probably other more serious acute failures which were not attributed to this.
SNCF enjoyed lognevity and relaibility from their LVA engined locos which were encharged with a range of express passenger services, such as Paris-Basel, and diverse frieght and regional workings.
Further to this was the 16LVA engine as mounted in the speculatively produced "Kestrel". This suffered the same fate from poor alignment of the bearings, but the issue was rectified.
The power units of LVA woudl have been a welcome variety to railway enthusiasts. and no doubt reliability being built to more modern tolerancies demanded in a Vee form. A class of Kestrel derived locomotives could have challenged the later supremacy of the IC 125 and provided 120mph + extended running on services where a locomotive change was practical between electrified and diesel routes.