Bulleid wheelslip question

Were you on the footplate at the time? If not then I fail to see how you can possibly know the cause of the slip.

 

Watch the last thirty seconds of the clip then

 

I believe that this phenomenon was experienced by some crews with Britannias on the G.E. when they first came into service. I'm not sure that the locos actually slipped - my engineering mind can't get my head round the physics of it - but gave the impression of slipping. Anyone who has been on the footplate of a loco that goes into a slip will know the feeling without actually seeing the wheels go round or observing it on the speedometer.

 

And you're an experienced steam loco driver with the knowledge to form such an opinion? I actually thought that the driver should be praised for having the guts to re-open the regulator in an attempt to get it shut, which he eventually did.

 

The steam locomotive. You can have decades of experience in handling them but they will still catch you out. They are not as simple as some like to believe and are never totally predictable. But we love them anyway.

 

It is easy to be critical but you may be interested in the circumstances of this situation. While I was not on the engine at the time I was there as part of the support crew and remember the event well.

We were booked to stop at Dent to allow everyone off for a photo run-past. To supervise this operation a local Traffic Manager from Carlisle had come out to Dent and was to return to base on the train after the run-past had taken place. In the event the train was over an hour late due to problems on the WCML that day so the run-past was cancelled, but the hapless Traffic Manager still had to get home again, so it was arranged to stop very briefly to pick him up. As we came to a stand he jumped onto the train, and the driver, keen to regain what time he could, set off again. As can be seen he was a bit too eager to get going , given the poor railhead conditions and the fact that the brakes down the train had not fully released yet. Not his finest moment I'm sure but I bet there is not a steam man out there who has not been in this situation at some time or other - it happens and you learn from it. There was no damage to the loco but the rails were changed that night.

Hope this is of interest

Peter James

 

There is surely no other explanation than the driver either doing something seriously wrong or being unable to close the regulator. You don't need to have been there to know it must have been one or the other. Or can you indeed suggest a third explanation?

I think you're agreeing that it was a stuck regulator.

 

These are big, powerful machines, and it is very easy for one to get away from the driver, as happened at Dent and, indeed, several times in LMS and BR days to drivers who were thoroughly familiar with them. With the power available, it is very easy for one to get into a huge slip. When this happens, even if the regulator is instantly closed, there is enough steam in the circuit for a further one and a half revolutions of the driving wheels with the engine at maximum cut off. But if the wheels are revolving at high speed, which they can be, there is a heavy flow of steam past the regulator valve which can make it very hard to close. If the water level is high and water in liquid form is carried with it, this column of 'solid' water can make it impossible to close the regulator until the flow of steam is reduced. And while there are ways to deal with this situation, they are not instantaneous, and the driver, before resorting to them, will attempt what should be the fastest action: forcing the regulator closed. It will take a small but measurable time to realise that this isn't going to work before trying the others, themselves taking time, and so on.

Having a large pacific such as a Lizzie get away from him does not condemn a man as a poor driver.

 

Going back to slipping and design, I just came across a quote from a book called "Through the Links at Tyseley", by LC Jacks. The author was obviously a GWR fireman, so arguably biased, but its still interesting. He wrote
"among the heaviest workings ... were the iron ore trains. A good locomotive was essential... The favourite was a GWR28xx... Great Central RODs ... had no speed but was strong and reliable ... Foreign engines ... could not keep their feet and there were some long faces if an Austerity or LMS 8F was substituted".
There's surely no great difference between 28xx, 8F and Austerity from the point of view of adhesive weight, power, weight transfer and the likeso if the difference was as stated it must surely have been down to more subtle design factors.

 

8Fs could be a bit light on their feet, but that didn't stop them taking loads approaching 1,000 tons through the Peak District, or similar over the mountains from Ahwaz in the Middle East!

 

But why were they light on their feet? The weight transfer thing is frequently quoted for Pacifics, although I find it unconvincing, but if 8Fs were significantly more prone to slipping than GWR 28s it can't have been weight transfer, wheel arrangement, or power output since they were all very much the same. If it could be established why those two classes, basically rather similar, differed o the road it might be illuminating on others.

 

LMS 2968 has adequately answered you so I don't need to repeat it. It's also worth saying that driver can be timid and gently coax a train along and lose time or he can try and push it to the limit to regain time. Perfection is when you are the smallest bit below that limit but very few are perfect. I'll leave you to decide whether the good engineman is the one who errs on the side of caution and loses time or the one who takes the calculated risk to keep time. Sometimes called rising to the challenge.

 

I was responding to your apparently challenging Deepgreen's right to suggest possible explanations while you were also agreeing with one of them. I was agreeing in turn. LMS 2968 has provided more detail of how it can happen that the driver is unable to close the regulator. As far as I can see we are all in violent agreement.

 

I was mainly challenging his right to say it was diabolical driving. In my experience, diabolical drivers are rare and don't last long for that very reason, certainly not long enough to get their hands on a steam loco on the main line. If he had said bad driving , I might have simply moved on to read the next post.

 

I don't actually know the answer to this, just that it was so. But there's a lot more to it than simply the wheel arrangement, which was about all that was common to the 28XX and 8F. The wheelbase was different and, possibly, the springing (I'll have to look under 2857 next time I'm at Bridgnorth). But they had different valve gears (Stephenson and Walschaert's) and, probably more significantly, regulators: the 28XXs' was in the superheater header while all but the first twelve 8Fs had it in the dome.

But in reality, the 8Fs could and did shift big loads. L.C. Jacks comes across as the archetypical GWR man to whom only something designed at Swindon was any good (another GWR man, Harold Gasson, once wrote that the 8F was the best engine to emerge from Swindon Works, so it doesn't always pay to generalise). One of his complaints against the 8Fs was that the valve gear was on the outside so the driver didn't need to go between the frames to oil it!

 

All down to details of phrasing and interpretation. He didn't say that it was diabolical driving, only that it could have been. My interpretation of his posting was "either diabolical driving (which can happen, but would be very unusual indeed) or a stuck regulator". Evidently a stuck regulator sometime happens. The driver and/or someone else on the footplate may then deal with that brilliantly, adequately or, as with Blue Peter, very badly.

 

Yes correct ,I've seen 8F S climbing(1 in 125 ) out of Kettering with over 1000 tons ,flat out and down to less than walking pace, get into one of these massive slips, and with very experienced loco' men. With two men hanging on to the regulator handle it wasn't possible to shut. The only way to stop the slip is to wind the loco into middle gear and equalise the pressure either side the regulator valve .Not only this the weight of the train pulled the train back down the gradient whilst the loco 'was slipping, admitted only slightly. A friend and I used to meet most evenings about 1955/6, even on the coldest ,to see the 6.45 pm Kettering to Toton which loaded sometimes to well over the 1000 tons, and was a firm favourite to get in-to trouble It was possible to follow on a push bike by road. Some drivers managed to restart the train after the slip,but most waited for a banker ,the down sidings shunter ,usually a Midland 3F . It was a good half an hours performance .I never heard of any rail damage and I had a few mates in the PW dep't,
The last time I saw this happen was in the mid 80s with 6201 Princess Elisabeth starting away from Abergavenny on a Welsh Marches Express.

 

Don't the 28xx have equalised suspension between the pony and the first pair of wheels? Not sure, but it runs in my mind that they do. I'll gudgingly admit() that the GWR smokebox regulator is a better effort than the more usual regulator in the dome, simply becaue it is lubricated. Although I can't think of a main line loco with it, quite a few industrial locos have lubricators on dome regulators and the difference is certainlty noticeable when so fitted.

 

I think you're right, Steve. Certainly the big prairies had equalised suspension so, knowing Swindon's tendency to simply take parts off the spares rack, it would follow.