Why are Bulleid Pacifics more prone to slipping than other designs?

I've never quite understood the logic behind the BR Standard 'bacon slicer' reverser. It involves an extra unnecessary bevel gear so must be harder to work. I assume for reasons of space the Class 4 Tanks had a reversing wheel set at 45 degrees butr the odd ones were the Caprotti 5s that had a conventional LMS type screw reverse. Does anyone know the reason why?

 

I'm not sure I would agree with that charge in the case of the Bulleid Pacifics; pretty well all accounts from the time reckon they had very well designed cabs - certainly by the standards of the day. There were innovations as well, such as electric lights and luminous dials to help at night. The one criticism that seems to come through was that the cabs were a bit too enclosed, making them hot. There were also plenty of labour-saving devices for P&D crews, which were a direct benefit to the men, since P&D was done on a piecework rate according to an agreed schedule for large locomotives, so saving time in disposal didn't actually save the company any money, but was a direct benefit to shed staff.

I'd say that overall, the whole conception around the design of the Pacifics was about saving time and effort for all involved: footplate crew, p&d crew, shed fitters. Not everything worked as well as was maybe hoped, but the design intention was very clear.

Tom

 

Really, Tom? I heard that the fitters on the Great Eastern weren't impressed when a light Pacific was tried out of Liverpool Street.

 

I get the point of the boiler being slimmer at the front to fit over the other stuff there, but why not have the whole bottom at that level? What is the benefit of having it deeper at the back?

And not relevant to Bulleids, but as it has been mentioned, I think I read somewhere that Riddles had footplate experience and intended the reversers of the standards to be ergonomically better, because you can apply more force in a fore and aft movement of your arm than in a sideways movement. What went wrong with that idea?

 

Well that may have been an innate "not invented here syndrome".

As I said, not every design feature worked as well as intended - but I think the intent was clearly about labour saving and, for the time, user-friendliness.

Tom

 

Perhaps I should have said pre war steam days as the BR Standards were well laid out apart from the wretched bacon slicer

 

They handle S15’s more or less the same In Yorkshire. The regulator has three positions; shut, start and go. As you say, the pilot valve is fairly useless for anything other than starting. You then wind the reverser right back and shove the regulator right over to the stop. Anywhere in between and it gets too hot to touch. Control is generally on the reverser. Cracking engines.
As for standards, I love them. I’ve no experience of the 5’s but the 4’s of all types are a joy to drive. I don’t have a problem with the reverser and will constantly adjust it to keep the needle at a steady 25 on the climbs.

 

S.C. Townroe wrote that it took more fitters to maintain an un-rebuilt MN than a "Nelson" Despite this, the latter had superior availability. He was in a position to know.

 

To revisit the title thread of "Why are Bulleids more prone to slipping" and suggest another reason why that is the 'stereoptype', I thought it might be interesting to share this (paraphrased) explanation from ex BR Driver Clive Groome, taken from the DVD 'Driving and Firing The Southern Engines:
"What you have to remember is that up to that point the top link drivers had been driving King Arthurs, mostly, there were only 16 Nelsons. And those Arthurs were as heavy as lead and practically wouldn't slip no matter what you did to them. And then suddenly they were faced with this incredibly complicated machine with all these dials, and it just couldn't be started in the same way".
So I wonder if it was partly a matter of going from one 'extreme' of a surefooted 4-6-0 to the other of a very light-footed Pacific, and if you're a driver used to driving one way and you suddenly get a new engine which cannot be driven the same way, by the time you work out how to treat this new beast the reputation for slipping will already have been established. Admittedly, this doesn't take into account the presence of 40 'Schools' which I think were reputed to be a little light footed as well.
This might also explain why LNER Pacifics didn't get as much of a rep for slipping, as the previous top link engines had been Atlantics rather than 4-6-0s, which I imagine would have been a little more prone to slipping and demanded a more similar driving style.

 

I've often thought that this was the explanation.