I believe some of the complaints wrt the AC on the Class 158/159 fleets is less to do with the transmission arrangement, and more to do with how poorly the system has handled the transition from CFCs to less Ozone-destroying refrigerants.
Creep control relies on very accurate control of the wheel's rotation speed to be a tiny bit faster than its speed over the rail. This is probably easier to do with electricity which can be switched much more quickly and accurately than hydraulics.
Various reasons have been cited as to why it doesn't work very well, and no doubt with enough time and money a system could be engineered that delivers reliable air conditioning based on what is essentially a mechanical rather than an electrical power source. But it would be a very bespoke application, and it's not too surprising more recent train aircon has been electric. It can take advantage of technology developed for the much larger automotive market, it can be fitted anywhere, and it can take its power over a jumper cable.
True, but they appear to have been conceived as 57xx replacements, whose duties certainly included shunting.
I would suggest that the WR was familiar with DM units as the GWR operated the only fleet of them pre 1954.
Half of the Power Twins were DM, so your total is 170 cars (plus 40 for the Lea Valley sets on the ER if you like).
That was an experiment, so i`ll caveat by saying mainline , mainstream loco
The GWR streamlined cars had the same transmission as the AEC company had devised for the classic London RT bus, which probably many senior members here were familiar with in their youth. The Preselector gearbox had a small lever to choose the gear in advance, and then a foot pedal which operated the compressed air-assisted actual gearchanging, including on the remote car in the twinsets. There is a fluid flywheel in the transmission, which allows the gear to be engaged while the car is still at rest, and eliminates a clutch, until you open the throttle, so really a combination of mechanical and hydraulic transmission. Later GWR cars also had the AEC overdrive selector used on long distance buses.
Actually originally developed for the earlier Q-type. This had the engine and gearbox remote from the driver, to allow a front entrance - it was under the stairs in the double deck version. This required a remote gearchange - exactly the same issue as a railcar, where the gearbox has to be remote from at least one of the cabs.
I think the answer is that the WR was not so much pro-hydraulic as unfamiliar with electrical engineering.
It was just a few years between the first WR main line hydraulic (D600) and the start of their very large fleets of Class 37 and 47. The opening day photographs of Landore diesel depot have their three main types, Class 37, 47 and 52, nicely lined up in echelon. Electrics in the majority.
To the best of my knowledge, creep control was only possible with electric transmission. I guess though we’ll never know what the upper haulage limit of a single hydraulic loco could have been.
52s used to work the stone trains ; whislt they could match a 47 on teh flat, it was the continuous effort at a lower speed which was far better. TBH, they should have kept them for heavy freight and not waste the money on the 56s
Possibly because they weren't available ... the WR went for dmus quite early, their large Birmingham and South Wales suburban schemes being among the first, whereas the hydraulic drive cars, with Rolls-Royce engines and transmissions, came later, because only then had Rolls-Royce put them on the market, coming from the onetime Sentinel plant at Shrewsbury which they had ownership of then. You can't buy what isn't being sold.
presumably on a hydraulic transmission to get any form of creep control you'd need to fit limited-slip differentials on the axles - which there probably wasn't room for. Besides which you'd introduce a whole new gamut of wheel/rail interface problems with the wheels rotating at different speeds. You'd need completely new wheel cone profiles for a start
As far as I'm aware all locos with creep control have conventional wheelsets, not independent wheels. But I'm not convinced that sort of accurate speed control and rapid response to changing conditions is possible with hydraulics in the control loop.
The ER's suburban DMUs, with Rolls Royce engines and hydraulic transmission, were a bespoke order to meet a specific requirement, not a part of their general traction policy. That was for EMU standard performance on peak hour Liverpool Street-Bishops Stortford via Lea Valley trains as part of the Chenford electrification scheme, completed in 1960. The Lea Valley between Clapton Junction and Cheshunt wasn't electrified in 1960 because it had heavy coal traffic. A 6 car train with Rolls Royce engines had 8*238hp engines, giving a total 1904hp, they were the ER's DMU equivalent of the Deltics.
Surely the Heavy Coal Traffic there had all come down through Bishops Stortford and Cheshunt, which was electrified ...
The reason the WR went for DH locos was a lack of experience with electric traction. This weas irrelevant for DMU procurement since there was no prospect of electric traction for DMUs (except of course for the Southern, who DID have a lot of experince with electric traction), and the Western had plenty of experience with mecahnical transmissions for DMUs.
My point was that if you were going to have any kind of creep control (which is effectively a wheelslip elimination system) on a hydraulic drive then you would need independent wheels
In every mention of "independent wheels" I've heard (in 38 years in the rail industry) it has referred to wheels on opposite rails not linked by an axle. Are you actually referring to axles that aren't mechanically geared together?
I was thinking of something on the lines of a limited slip differential so the driving axles consist of a pair of linked half shafts
I don't understand why that's necessary at all, as no creep control locomotive has it, and why having a hydraulic drive with creep control would make it necessary.
The pre-selector gearbox used on the Q and RT buses was a product of Wilson/Self Changing Gears Ltd, not AEC (Leyland became SCG's majority shareholder in 1957, and took over AEC in 1962).
18100 was ordered from Met Vick by the GWR as well before WW2 but delayed due to the war
Paxman provided plenty of high speed diesels for minesweepers and submarines during WW2 and after that had sufficient power rating to match Maybacks but either drove props through gearboxes or via generators in the case of submarines.
A lesson might be not to let the prejudices of the CME affect the choice of engine. In retrospect the Sulzer 12LDA28C was not as reliable as the EE 16CSVT!
Indeed it had to be down rated in the end
Indeed. The final step in the evolution of the locomotive classes mentioned was the Class 56. I still think DP2 is the design that got away, spoiled by too many bells and whistles in Class 50.
Wasn't the Class 56 notoriously unreliable due to Ceausescu's Romania mucking the whole job up?
The Class 47 was a development of the Peaks, and the Class 50 of the Class 40 - uprated engine, redesigned body, dispensed with the carrying axles. Indeed, the first twenty Class 47s were originally going to be Class 46s.
And the Class 40 was an uprated version of the Ivatt twins and Bulleid trio (the latter of which ahd the same bogies, and in one case the same uprated engine)
