Off the Rails - Train Stuff

[Renegadenemo]

Wow! That turbine powered machine has a lot of grunt. It sounds angry too. Impressive stuff.

When I was a kid my dad had a yard along the bottom of which runs the main north/south line up to Edinburgh but back then it also hauled a lot of coal and I well remember the whistling of the big Deltic engines as they powered up to climb the slight grade in the track at that point. Last time I heard one of those was when we were aboard HMS Quorn in Altafjord looking for lost midget subs. Fantastic engine.

[mtskull]

Couldn’t resist sharing this:
https://youtu.be/cD3QlR98--A

[ThornyBush]

.... strangely hypnotic....

[Renegadenemo]

As a bit of a Conan Doyle fan I was re-watching the BBC Sherlock series last week and decided to Google the fake houses at Leinster Gardens in London as it featured in one of the episodes.

http://www.urban75.org/london/leinster.html

But what caught my interest is that the text says that the back of Leinster Gardens was a good place for the underground steam locomotives to 'blow off' because they were fitted with condensers and had to do this periodically. Any of you railway buffs know about this?

[mtskull]

As a bit of a Conan Doyle fan I was re-watching the BBC Sherlock series last week and decided to Google the fake houses at Leinster Gardens in London as it featured in one of the episodes.

http://www.urban75.org/london/leinster.html

But what caught my interest is that the text says that the back of Leinster Gardens was a good place for the underground steam locomotives to 'blow off' because they were fitted with condensers and had to do this periodically. Any of you railway buffs know about this?

I’m no expert on the intricacies of working the London Underground in the age of steam but one of the drawbacks of condensing exhaust steam is that you lose the draught on the fire (to the detriment of the boiler’s ability to produce steam) that would otherwise be created by the steam exhausting via the blast pipe and chimney.
The early Metropolitan Railway locomotives were fitted with valves which enabled the footplate crew to switch from condensing to non-condensing mode and I would imagine that the opportunity to revive the fire by doing this was welcomed by the crews.

[Renegadenemo]

The early Metropolitan Railway locomotives were fitted with valves which enabled the footplate crew to switch from condensing to non-condensing mode and I would imagine that the opportunity to revive the fire by doing this was welcomed by the crews.

So condensers were used on railway steam engines then?

[mtskull]

The early Metropolitan Railway locomotives were fitted with valves which enabled the footplate crew to switch from condensing to non-condensing mode and I would imagine that the opportunity to revive the fire by doing this was welcomed by the crews.

So condensers were used on railway steam engines then?

Yes but these were designed only to reduce the amount of steam in the tunnels, not to improve the efficiency of the locomotives.
They were fairly crude devices which fed the steam back to the water tanks. They quickly became ineffective in use due to the water temperature in the tanks rising to near boiling point.

[mtskull]

.....what caught my interest is that the text says that the back of Leinster Gardens was a good place for the underground steam locomotives to 'blow off' because they were fitted with condensers and had to do this periodically. Any of you railway buffs know about this?

Having given this some more thought, I think that what is being referred to is the practice of “blowing down”. This involves briefly opening a valve on the bottom of the boiler, enabling the escape of water which also ejects impurities that have settled in the bottom of the boiler. The water, being hotter than its ambient boiling point, immediately flashes into a lot of steam, making this an undesirable practice to carry out in a tunnel.

I suspect that a writer has at some stage got the wrong end of the stick and assumed that this was a practice unique to condensing locomotives. It isn’t; it has to be done regularly on any steam locomotive but obviously crews working on routes in the open would have a lot more choice as to when and where they could do it.

Another (IMHO less likely) possibility is that what is being referred to is “blowing up”. This refers to the expedient, when a loco is short of steam, of bringing it to a halt and opening the “blower” -a valve which directs a jet of steam up the chimney, thus increasing the draught on the fire and hopefully increasing the steam pressure. Again, this would not be something that it would be desirable to do in a tunnel.

[Filtertron]

Generally the blower is used when the loco is either coasting or going downhill to maintain the draught, as the exhaust from the blastpipe isn't drawing the fire anymore. The blower is used in the excercise of regaining steam (obviously), but it could entail the whole fire being rebuilt if it has clinkered up, or the fireman has fired incorrectly.

[Renegadenemo]

Only ever got close to a steam loco once. I was asked to develop a means to internally shot blast the ends of a zillion pipes in the boiler so a swaging tool could be reapplied inside the ends of them to re-seal them to the endplate. They had been sealed but the story went that someone had opened the wrong door on the boiler when it was hot and a load of cold air had swept through and shocked all the pipes loose through sudden contraction. The poor dead thing was sitting dripping water when I arrived. Always wondered why it had such a door and what it was supposed to be used for and why and how someone would open it at the wrong moment. Anyone?