Bulleid Pacifics - Past or Present

A lot will depend on the driver. There is a lot of steam in the circuit between the regulator valve and the cylinders, that's why on opening the regulator nothing happens for a few seconds. I stand to be corrected but from observations on Bulleid Pacifics the correct procedure is to open the regulator about halfway then almost shut it, wait for the first sign of movement and then gradually open it further. I don't doubt that any other Pacific will be the same. The slipping reputation of Bulleids probably originated with the unrebuilts when there was a lot of leakage from the oil bath splashing all over the place. Why did Bulleid insist on welding the sides of the oil bath to the frames that will flex and inevitably lead to leaking weld seams. At least with riveting there is a little bit of 'give'.

 

The problem with film evidence is that people don't normalise for frequency. There are currently two Merchant Navies on the mainline (and one on a heritage line) as against one Peppercorn A1. All else being equal, you'd expect more film of a Bulleid slipping, simply because there is more opportunity to observe it happening. I'm sure that at least some of the reputation that Bulleids have for slipping is related to the fact there were large numbers of them still operating on a daily basis in the late 1960s when almost all other pacifics had been withdrawn. The result was enthusiasts chasing round to watch them while they still could, resulting in lots of observations. Inevitably sometimes they would slip. But if on average a loco slipped once in five on starting, but you saw a hundred Bulleids out of Waterloo and half a dozen Duchesses out of Euston, your memory (and film evidence) would say you saw Bulleids slipping "frequently" and Duchesses "rarely".

There may be other reasons as well (*), but I'm sure observation bias is part of the reason for the reputation.

(*) And those other reasons are statistically difficult to control for: for example, one particular platform at I think London Bridge had a bad reputation with an uphill start on a curve at a point where locos stood and dripped oil. But of course, Bulleid Pacifics were observed slipping there but not any others, because they never got there. Not many Bulleids slipped on starting at Crewe, but plenty of Duchesses did ...

Tom

 

Its a power to weight ratio thing, all locomotives and hot cars these days have wheel slip prevention, not available back in the day. A good driver possibly allowed a little slip (I believe that the class 59 ran on 5% slip on starting?) to get away, violent slipping showed poor management, or a very greasy rail.

 

All this talk of slipping made me think of this video of 46229 slipping so badly on the S&C that the rails were worn down:


Apologies if this has been discussed before but what actually happened here? Looks like water carried over and caused the regulator to get stuck open. Was Duchess of Hamilton damaged during this incident? Watch to the end as the shocking state of the track is shown. Were train services stopped due to the condition of the track?


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It has indeed been discussed as I have answered this question before now. Without going back to my notes at the time what happened was this. The train was a Cumbrian Mountain Express with the addition of three extra coaches from the NRM (two MetCam Pullmans and ex Royal Train Brake 5155). It was booked to stop at Dent for a photographic run past but this was cancelled due to the late running of the train (to say nothing of the foul weather). However an operating supervisor from Carlisle (a MOM in today's terminology) was already waiting at Dent to oversee proceedings so the loco stopped briefly for him to hop aboard. The driver then tried to get away without waiting for the brakes to fully release on the long and heavy train. The result is what you see in the video. Luckily the loco was undamaged but the railhead was sufficiently badly worn that the rails had to be replaced that night.

I have heard of a Duchess slipping like this (ie stationary) for several minutes at, I think, Rugby and that it wore the railhead almost completely away, but I'm sure others more knowledgeable than me will confirm if this is fact or fiction.

Peter
(46229 support crew member in a previous life)

 

From what I've read, the Duchess slipping at Rugby during BR days wore the rails down to the web.

Richard.

 

Wasn’t there a similar incident written about by Derek Cross somewhere north of the border? Have a hazy recollection it might have been on the GSW?

 

having watched former Eastleigh drivers close up, yes that was the way they started a train, half regulator, slam it shut, once the wheels started to move, open it a bit, pumping the regulator, until you were moving cleanly, then close regulator, adjust the cut off, and then give it full regulator,

 

I drew attention to the York video because it was the same location on the same day, with the Bulleid slipping several times on both starts and the A1 not slipping at all. Just one small piece of evidence, no more than that.

 

Thank you. It must have been a terrifying experience for the support crew at the time.

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Crikey.

 

It also must have been a terrifying experience for the folks on the platform too, judging by the way they scarpered round the corner of the station building...

Richard.

 

A strong reason for smokebox regulators on the outlet end of the superheater header, as used in some more enlightened countries in later days.

 

Different locos require different techniques. Not every loco has a steam chest pressure gauge and not every steam chest gauge reacts quickly enough to be a good indicator. Even with a steam chest gauge you are effectively pumping the reg, though, if you react to the rise in pressure by shutting it. With saturated locos I usually just open the reg and, if it’s slide valves, as they usually are, you’ll hear the valves clunk onto their faces.

 

Some excellent points. Elsewhere on the Southern, the exit from Victoria sees locos climbing from a stand to Grosvenor Bridge. The 'up' exit from Bournemouth is severely curved, ditto Salisbury, Exeter comes with it's share of operationally challenging features and at Dover Priory, tunnels exist at either end of the station. All these locations hosted some of the heaviest regular trains in the UK. Some of the very last steam hauled too, with the Bournemouth Belle proving a particular gricer magnet .... and practically anything could slip on the sadistic gradient leaving Ilfracombe (WC/BoB territory), which began pretty much where the platform ended.

With posts mentioning other examples of pacifics slipping, I can't help recalling the 1994 incident south of Durham, where slipping onA2 60532 (the rotational speed of the drivers was reckoned the equivalent of around 140mph!) resulted in severe damage to the loco, the enquiry deciding it was a consequence of a crew unfamiliar with the particular habits of Mr Peppercorn's design.

 

‘Bias’ is affected by frequency of observation; certainly for various reasons, pre and post 1968, Bulleid Pacific’s
‘suffered’ possibly from over exposure to photographers.

I believe the offending platform at London Bridge was Numbef One. The usual culprits were ‘Schools’ not
WC/BBs on services emanating from Cannon Street. ( the Schools with limited adhesion were always a
challenge starting a heavy train but once under way arguably more a 6P than a 5P.)

It was rare to see a start from Waterloo with a MN/BB/WC without a slip ( with or without a push from the
buffers by whatever loco had brought the empty stock in) I remember seeing a WC with the full Bournemouth
Belle consist come through Vauxhall still slipping. Instances of the 4-6-2s slipping at speed were not
unknown.

Were they worse than other 4-6-2s. I remember writing to the RM in 1956 ( when there was an ongoing
debate wrt propensity of various locos to slip ) based on several days observations at the East end of
Edinburgh Waverley, that with the exception of A4s most locos slipped badly on starting. I had the
teenage temerity to suggest this was due to Driver casualness !

Certainly Southern crews IMHO learnt to live with ( dare I say it ) Bulleid foibles.

Yes there were some awkward starts on the SR ( as with other parts of the Kingdom ) but it is noticeable
that whether starting from Weymouth or Bath Green Park WC/BBs were permitted unassisted similar
loads to Class 5 4-6-0s.

For what it’s worth my personal feelings ( despite my predilection for all things Southern) are that in
their ‘as built’ form the Bulleid Pacifics were particularly prone to slipping both on starting and at
speed as compared to other British Pacifics.

Michael Rowe

 

If i'm not mistaken, wasn't one of the Bulleid Pacifics fitted with a Giesl Ejector.(i think the wheel slip talk has gone far enough.)

 

34064

 

Thanks.