Best & Worst Locos to Drive

Tom - the two reversers may have been of the same basic design, but you point out yourself that a number of the components were significantly different. Smaller diameter piston with a longer stroke, differences in reversing shaft locking clutches, lack of a pilot valve - and, of course, a much lighter motion. In principle, the two systems had much in common, but as any draughtsman can tell you, the devil is often in the detail.

The early models of the Hawker Typhoon sometimes suffered catastrophic failure of the fuselage just in front of the tailplane. As a quick fix, small reinforcing plates were added around the end of the fuselage, to get the squadrons back in action in the run up to D-Day. After some serious head-scratching and research, Hawkers worked out that the problem was caused by certain maneouvres at specific speeds inducing high-frequency flutter of the control surfaces. This in turn caused fatigue cracking in the monocoque fuselage. All it took to solve it was a tiny change to the shape of the control surfaces in question, and the pilots could then thrash the Tiffies to their hearts content without fear of the tail falling off.

I can't speak from personal experience about MNs and BoB / WCs; I've never even stood on the footplate of either type, as original or as rebuilt - let alone have I delved into the components. But you have confirmed that there were differences between the two, and that the differences were a direct cause of the frequently erratic behaviour of the Bulleid pattern.

What I can say for sure is that, over 30 years ago, I was told by footplate staff at the Bluebell that their Maunsell Q was their favourite engine for their famous 'Monday morning shunt', and had been ever since the engine arrived there, "because the steam reverser is such a doddle to use"; though I grant you that I don't know if it had been modified at all from the original design.

The other point is that Bert Hooker spent years on the mainline with the Spamcans, and would almost certainly be familiar with other types of steam reversers used on SR engines - and I'm in no position to argue against his first hand experience.

With best regards,

Jack

 

Comparing the cost of maintaining an unrebuilt Bulleid with almost anything else might be interesting as well! Whilst I agree with a deal of what you say I fear that the "inner gricer" needs to be kept well under control in terms of making sure train lengths and weights are kept reasonable and well within the haulage capacity of the available motive power.

PH

 

Also no two lines are the same there is a huge difference in loco required to operate 7 mk1 on the great central a class 2 or the north Yorkshire moors at least a class 4.
There is no one size fits all rule for ideal motive power.

 

I was going to offer some thoughts on firing 53808 and 53809 but I'll wait until the thread calms down a bit! For now I will say that they are quite different. Prep of 53808 has also been made easier by the "Minehead modifications". I imagine that most active heritage footplate crew have to prep their own loco in this day and age? Of course that comment also raises the authenticity question!!

 

Original Bulleid Pacifics are quite straightforward to maintain, so long as you suspend belief about how awkward some bits are to reach, and just get on with it.
The issues about some bits being more complicated and harder to reach, are balanced by the same bits not needing to be attended to as often as conventional locos because of almost perfect lubrication and cleanliness in the oil bath.
From experience of maintaining both original and detuned types of West Country locos, the most noticeable issue for a preserved railway, is that the originals do use a bit more coal and water than the detuned ones. Originals are more powerful.

 

Doesn't quite fit with what the late S.C. Townroe had to say about the number of fitters needed to keep them in service, compared with other locomotives in his care but there we go!

PH

 

Presumably that would have been when they were working much harder than just trundling along at 25mph though?

 

This talk of reversers makes me wonder; is it planned to run 2999 on the main line? If so I wonder what crews will make of it's lever reverse. I think an earlier poster mentioned criticism of the lever on a 4700.

 

I was told by an old GWR driver back in th 70s that they were almost impossible to move while under steam so to notch up it was close regulator, adjust reverser, open regulator. The struggle I say at Reading may have meant that the steam chest was still full of steam. The reversing leaver was very long on GW engines maybe to give more leverage.

 

I can only comment on the three lever reverse GW locos with piston valves that I have driven but I've never had any difficulty in altering the cut-off with steam on. In fact, with 6619 I often used to hold the lever mid way between notches to fine tune it. Probably being OTT to do this but I did!

 

I think a steam (or at least power assisted) reverser is a very good idea in principle for any loco needing frequent big gear changes (shunting, for example). But, in the UK at least, they seem to have been very hit and miss. I believe in other countries they were more successful (US perhaps?). If my recall is correct, why?

 

Unless there was any particular design deficiency aggravated by speed, presumably the ratios would be much the same.

PH

 

With bigger locos the weight of valve gear made powered reversers a necessity. Even the mechanical advantage of a screw reverse has its practical limitations.
As we're talking about reversers, I wonder how successful the Bouch Barrel reverser was. The fact it was not more widely used tends to indicate it wasn't very good in reality.

 

The loco I saw the driver have trouble with was a 4700 so fairly big

 

I take it you're not very keen on 45379 then?

 

Was that similar to the combination of lever and barrel shaped screw reverse used on Dean 2-2-2s Nos 9 and 10? Holcroft seemed to be intrigued by it. Perhaps there were patent royalties involved.

 

Just found a photo of the reverser of the Bouch 0-6-0 in the NRM, it seems to be just as Holcroft describes. It does seem a sensible idea but the ergonomics of the lever look to be a bit awkward in forward gear.

 

Interesting question. I'd throw out a couple of hypotheses (no more).

One is that on many British locomotives, the reverser mechanism was hidden between the frames, which made maintenance and preparation a bit more difficult. One exception to that is the Stirling reversers on SER / SECR locos, which are carried on the running plates, and which always seem to work very reliably.

The other hypothesis - more speculative: power-assisted the reversers I have seen on foreign locos (notably in NZ) were compressed air driven, rather than steam. I wonder if that makes a difference to their long-term reliability? Interestingly, when Beachy Head is completed, it will have a compressed-air driven power-assisted reverser.

Tom

 

GW/WR policy at the end appeared to be to use lever reverse for freight/shunting and screw reverse for passenger. Arguably this illuminates discussion on what some classes were designed for eg 6400 screw, 7400 lever and 9400 screw, 1500 lever.
Power reverse does seem a logical way to combine advantages of both, provided that it's as accurate and reliable setting and the cost and maintenance overhead is acceptable.
Screw reverse gear was designed for the 4700s in the mid 50s, I'm sure the shade of Dusty Durrant would be delighted to see it fitted to 4709.