What Ifs, and Locos that never were.

I expected a bit more reaction to the idea of the Sentinel engines replacing the Bulleid powerplants, to be honest. Discuss!

 

The unsprung weight looks a bit fierce, to be honest, with half that kit hanging straight off the driving axle, although I suppose the relatively small wheels are a mitigating factor. Interesting that the axles were uncoupled, given that most Sentinels had chain drive to one axle, even if there were two engines, and then coupling chains between the frames. I suppose it harks back to the Drummond Double Singles (and Webb compounds, for a less SR-centric reference), but they were hardly famous successes. The drive layout does eliminate the major issue with Hackworth gear, since the link isn't going to move relative to the driving axle.

While I like the Sentinel shunting engines as a concept (small cylinders to warm up, appropriately sized quick responding boilers, superheat, tractive effort, no unnecessary speed capability), I find most of the direct drive steam motor designs slightly unconvincing, they just seem to introduce unnecessary duplication (or triplication, or quadri....).

Perhaps a loco with the Bulleid turf burner bogies (two cylinders, piston valves), a slightly more conventional boiler and a central cab. Admittedly, the turf burner was apparently 120 tons, which is a lot for 19925lb tractive effort and a 22 sq ft grate (not significantly more of either than a 60 ton M7), but the turf burning gear must have added at least some of that weight.

What about a nice BR Standard 4 2-6-4T?

 

Bulleid could have done a 2-6-4T but that wasn't on his agenda, he was looking for a reduced maintenance costs compared with a conventional steam loco. As for coupling driving wheels, diesel electrics don't do that so why bother if using steam "traction motors"?

 

Instead he produced higher maintenance costs; see S.C. Townroe's comments.

PH

 

Looking at the pictures the Columbian loco is pretty big

Someone once said to me that the essential requirement for a pre nationalisation CME was to be a bit of an egotist, which the Pacifics & Leader both demonstrate rather well.

 

I don't think you could level that charge at REL Maunsell. The history of his tenure at both the SECR and SR was dominated by clever adaptation and reworking of existing designs to produce the locos the railway's he worked for needed, aided where appropriate by choosing his key staff well and then letting them get on with things.

Tom

 

Can I add Mr Churchward to this as well? He took over from Dean without undermining him, then letting people like Holcroft get on and do their own thing too.

 

I cannot imagine that anyone got to a job as senior as CME without a very solid regard for their own abilities. Equally though once the greasy pole has been climbed a vital skill is to get the best from your staff, and its clear some were better than others. It would be interesting to know more about the Holcroft-Bulleid working relationship for example.

 

He had that reputation at Inchicore also.
I suppose it helped that during his tenure the Southern had other sources of publicity (e.g. Southern Electrics) and wasn't looking for headline-grabbing locos, but useful ones.

 

"Locomotive Adventure" says very little about his time under Bulleid. It's speculation on my part, but I get the feeling that the absence is indicative of a strained relationship, but being tactful, Holcroft preferred to say nothing rather than speak his mind of a former colleague who, at the time of writing, was still alive.

Tom

 

I suspect you're correct.

 

Yes, he was, and I love two of the concepts: fully enclosed valve gear and 100% adhesion; I even think the double cabs would have been viable if the locos were oil-fired. However, I have always felt that the various rotary cam valve gears and/or strategic application of roller bearings solve the valve gear problem much more neatly. Although nobody could accuse the Leader and Turf burner of lacking adhesion, they were also spectacularly heavy for their power and tractive effort, despite much use of fabrications for things like cylinders. 120 tons for the turf burner will near enough get you a Nord 4.1200 2-8-2T, which could reasonably be equated to a push-pull fitted 9F in suburban tank engine form. Let's not even think about what 150 tons of Leader could be used for instead.

If Bulleid, who was responsible for two designs with excellent power-to-weight, couldn't make these pet projects measure up well on the scales, compared to some very conservative designs using traditional technology like the Standard 4 tank, I suggest the concept was intrinsically flawed. Unnecessary multiplication of equipment tends to have that effect.

Diesel electrics with uncoupled axles tend to have anti-slip controls to catch one axle running away by cutting power, the problem being that one axle slipping will not necessarily be detected by the driver. Obviously, all traditional articulated locomotives can slip on one engine unit, but losing half the total tractive force is probably rather more obvious than 25%, especially at speed.

 

In 1924 Beyer Peacock, after discussions with the Sligo Leitrim and Northern Counties Railway, produced drawings for a Garrat locomotive intended for that line. The SLNCR survived until 1957, and until the end it's staple traffic was livestock from the west of Ireland for shipment through the port of Belfast, mainly to Scotland and the North West of England. While this traffic could, at times, be heavy, it does not seem to justify the building of such an engine, apart from the fact that it could probably do the work of two of the existing engines without exceeding axle load limits. Sadly the engine was never built, but the attachment shows a model, built from the initial drawings, and displayed at Cultra during the Model Show in November last.
Ian

 

I've always thought that a Garratt would have been a better bet than Leader. It could have been a double 0-6-0 with rotary cam valve gear, say. A Kitson Meyer type loco might also have been successful.

 

I would have thought an Ivatt 2MT or Fairburn 4MT - some of which were sent to The Southern on Nationalisation

 

I'm sure that old Dugald Drummond would be laughing in his grave at the suggestion it would need a 12 coupled Beyer Garratt to replace his M7 0-4-4Ts when they wore out!

 

Very true (and the previous post) - I didn't mean to meet the duty intended (for surely even Bulleid cannot have thought Leader proportionate to replacing these fine little locos) but some of the more general aims in terms of adhesion, bogies for track-kindness, operating equally both ways, enclosed valve gear. But although the Garratt (and Meyer) concept has many merits, it was almost always found to be overkill for all but the heaviest demands, which is why all of the later Garratts were huge (or at least very large for their gauge) and few smaller ones were built. As you say, why bother if a conventional loco worked fine.

 

It certainly wouldn't be surprising to find the only known instance of Drummond laughing was after his death!

Tom

 

I received a book on the Bulleid Light Pacifics for Christmas. Leader is touched upon and it seems that the Leader was intended for much more onerous duties than a mere M7 replacement so I'm wondering where that story came from.

 

It's a while since I read Kevin Robertson on the subject, but my recollection was that the M7 replacement was the original requirement and justification, but that the design was developed to do much more.