Boilers & Accidents

I doubt if any engineer would have snowdrifts in mind when they were designing a boiler.

 

If you run into a snowdrift you may stop relatively quickly but I doubt that the retardation would be that significant. It’s not like hitting a brick wall or the back of another train.

 

[QUOTE="Ploughman, post: 2582323, member: 2875"...................but the NRM's plough at Shildon is Dumb.[/QUOTE]

MODS! MODS! He's insulting the NRM's snowplough by saying its Dumb!

 

Oh absolutely!

 

If you taper the boiler down to a point it would cut through the drift, just like Bryan’s plough. Not sure what you’d do with the boiler tubes, though.

 

I've just revisited the transcript of the IMech E meeting in 1906 where this was discussed (apologies, I said 1908 earlier)

To quote from the discussion following the presentation of Churchward's paper
"There was a Paper read by a member of the Institution in 1887, Mr F.R.F. Brown, the late Superintendant of Motive Power of the Canadian Pacific Railway, on "The Construction of Canadian Locomotives," in which it was stated clearly that the coned barrel was designed originally to prevent the water in the firebox from being shot ahead into the barrel of the boiler when the engine plunged into a snow-drift. By that arrangement the water was kept approximately where it was most wanted, namely over the fire-box"

So yes, it's protecting the boiler crown rather than anything to do with water-hammer.

I also seem to remember hearing that there was a similar concern with water movement in the boiler due to the change in gradient on approaching the Severn Tunnel. Could this have made the tapered boiled more attractive to the GWR?

 

I haven't come across that paper. Is it available on line.

 

More benefit if the plough blade were sprung from the frame, but doubt that is possible.

 

It can be downloaded by members of the IMechE, It isn't in the public domain.

Non-members may be able to purchase a copy

 

https://journals.sagepub.com/doi/abs/10.1243/PIME_PROC_1906_070_016_02

 

Ah thanks, I have a copy of Churchward's paper, which was reprinted in "the Engineer" but not the IMechE discussion. There was no reference to snowdrifts in it. But it seems the actual source is the Brown paper on Canadian Locomotives, it wasn't anything Churchward said.

It seems to be available here, https://www.canadiana.ca/view/oocihm.61634/5?r=0&s=1 I shall read...

Aha. The paper lists snowdrift ramming as being only one of a whole collection of subsidiary advantages of the "wagon top" boiler, and states that it "is primarily to obtain by increased height of firebox a sufficient area in the firebox tube plate for inserting such a number of tubes as will give the most efficient proportion of heating surface"

It would seem that the gentleman who contributed to the IMechE discussion didn't quite correctly remember the content of the paper he was referencing. Just goes to show how important it is to go back to sources! It seems discussion contributors then were no more reliable than forum posters now!

 

The contributor who mentioned Brown's paper was C.E.Cardew

 

A downvote for Mr Cardew then [grin].

 

Thanks for sending the link.
It sounds like "snow bucking" was done deliberately when required, and could have been something important for the Canadian Pacific at the time.

 

We seem to have moved on to boiler water levels.

I’m sure the Severn Tunnel was not a consideration in boiler design other than overall power maybe.

The gradient change at Imberhorne for example is from 1 in 55 to 1 in 60 much worse than going to or from Wales under water. There are countless examples of sharp summits on railways.

As for braking or slamming into a snowdrift, even if the water does go out of sight briefly the tide will come back in soon enough. Bulleids do indeed have the quality of a small change in water level when going over a summit, the regulator doesn’t alter it much either.

There’s sometimes a bit of undue concern in some quarters about the water dipping out of sight. It’s something the crew has to manage and comes with experience. I often wonder what the gauge glasses were showing when stopping from 90 mph +. I bet the water was gone for quite a while. The crown sheet doesn’t instantly melt!

I often brake to the water level, that is going chimney first you can keep the level safe by varying the brake force.
I think the front taper was a good thing on high speed engines for this reason as well as the weight mentioned by others in this thread.

Clive Groome’s observations are interesting, sadly I never fired to him that often, although I learnt a lot when I did and he wasn’t given to idle chat during a turn.

 

You mention stopping from 90 mph - this is one of the concerns you have if you miss an AWS/TPWS warning, or are too slow in acknowledgeing it. The brake goes in and the driver has no control over the situation whatsoever. At high speed, and 75 mph is quite fast enough to my mind, your water goes to the front and stays there a long long time. Not long enough for the crown sheet to melt but you keep fingers and everything else crossed that the fusible plugs are ok. There is the world of difference between a controlled stop and an uncontrolled one.

Peter

 

I wish all drivers did that

 

I'm certainly not advocating it as something to be relied on, nor to do an experiment to find out, but reading some of the accident reports from when crown sheets collapsed often seems to suggest a period of running of quite a long time with low water. There are sometimes comments that the plug may have been dropped for five minutes or more before the crown collapses. Fortunately I have never been on a footplate when a plug has been dropped, but I do wonder how easy it would be to detect on a loco that was working very hard - which seems to be a common feature of such accidents. Not something that can be simulated in training either.

Tom