It was fascinating to hear that in the race fora type four power over essentially type two double headers, that brush were also in the game with a design featuring an EE power unit.
The timing is what could be quite the crux of the whole matter: EE proposed the csvt and co-co construction be adopted for later runs of the EE type four D200. This was maybe as early as 1959 by which time ee had sold some 12CSVT locos to africa and no doubt fully evaluated the power unit at upto 2000bhp and even beyond for a marine constant output rating.
Btc/brb in their wisdom knew the d200 proved a useful design and reliable. It is still strange that they did not opt for a lighter RA6 co-co with the svt engine because bogies are life time items with probably little to gain in purchase and maintainance costs over the life of a loco. One hundred and twenty forty 'zeros' would have been a significant class in its own right by 1960. A subsequent csvt class in co co would have followed even more standardisation with the EE type 3 : bogies and many other features like cabs, noses and boilers. For a loco with no boiler space required the 16 csvt can actually be fitted into a 37, with the c1800s exported to portugal being the same weight range as the venerable 37s.
The ee outcome would have been an ra6 syphon with 100mph capability if ordered to a 1960 design, nose end and no KV10.
But what of brush?
Well in 1960 it would have no doubt been a stretched class 30, but probably without a corridor door . Incidentally the mirlees engines of the brush type 2 were not swapped out until 1964, so it is interesting that earlier cooperation was aired, probably under the proposed stipulation of standard power units being employed across manufacturers. Sulzer being swiss were expensive and left brush and btc/brb exposed to any weakness in the pound. Also as happened later, brush lacked capacity to meet demand from european railways and began using various sub contractors to build major components or even complete power units and the fiasco with the uprated 'duff' PU was somewhat inevitable.
EE rustons scaled their work well in the 1950s and had a successful expert sub contractor in Robert Stephenson and Hawthornes in derby.
A later order would have resulted in the BTC stipulated slab end lion and then hymeks and later variants. Probably with under window indicator opanels but at 2350bhp brb may have wanted multiple working with high side connection. The same fate befell the d400s rather clean initial design while the duffs escaped multiple working which would in fact have extended their utility on freight immensely and on the larger midland and west country passengers and sleepers.
What ever the body design, the design outcome of the mechanical electrcal traction gearings chosen would have fascinating. Would brush have opted their preference for high amps on a somewhat lower torque, higher rpm engine than the 12LDA they had some exposure to in the peaks by then. Or would they have opted for acheiving the same as EE, a higher voltage set up with effectively lower gearing but arguably more progressive delivery of electical power from the longer rpm range of the ruston big vee.
If this had come to be in 1960 then you could bet that brush would have made a relaible locomotive with performance better than the Peak heavy weight on expresses. There after a further uprating to 2700 hp and two or three suppliers would have made the big dubber the standatd PU and far more push back against BtC for all the prototype gadgetry emloyed in the first ten years of class 50 life.
On many types of services the non KV10 delivery or higher amps a brush loco may have employed, the locos at the 2350 hp would have given the class 50 more than a run for their money head-to-head, and tackled freights better at low speed and gradients due to the over caution excised by the kv10 controller. Furthermore as with the 37s, 31and C 1800s of portugal, the reliability would have been far better than either the EE dubbers or the Brush sulzer duffers which came to pass into railway legend for their idiosyncracies.