West Somerset Railway General Discussion

I know I'm going to regret asking this Michael. Your technical knowledge is much deeper than mine.

How is overall thermal efficiency less when using a shorter cut off? I would have thought it gave more chance of holding the steam pressure up and getting better superheating, thus getting maximum expansive work out of the steam?

BTW your calcs seem to assume that we always operate boilers at the red line? A fine thing if it can be done but two practical considerations if I may. The first is that we tend on the WSR to set safety valves to lift a little light, typically 10lbs before the red line. The second is not even the best fireman can constantly hold a loco bang on the mark. We tend to try for within 10lbs of the point the safety valve lifts but even this is not possible 100% of the time.

 

40 mph . We can only dream .

 

He said the opposite of that (less than with a shorter cut-off; not less when using a shorter cut-off).

Tom

 

Shock, horror!! I thought the whole reason why the GWR didn't use pop valves was because it enabled you to run at the red line with a feather showing. For the avoidance of doubt, a feather is not blowing off. You can't run at the red line with a pop valve because, once it opens, it knocks the pressure back several psi.
Can't see the logic of setting the valves 10 psi below the red line, though. It isn't really going to do anything to increase boiler longevity.

 

The classic position as written (ie probably by people without the slightest idea) was that the G.W. pattern safety valve favoured "feathering" around blowing off point. Having steam pressure right at the mark in a typically G.W. under/lightly superheated boiler brought a few vital extra degrees of temperature to the steam. In contrast, if this was tried with "pop" safety valves it was likely to produce large steam losses.

It all sounds a bit O.S.Nock but it might be so.

PH

 

"Locomotive Driving - is it an art or a science?" was written by G A Weeden who was of both the
Mechanical and Loco Engineers and Motive Power Officer on the Southern Region. The magazine was
"Trains Illustrated" in early 1960.

Aged not quite thirteen I carefully kept all the issues with the three parts of it - March, April and May - and I still have them.
The explanations and diagrams became part of my mental furniture. I think there were several good letters inspired but only have one of them
is in the months I have and I am tantalised by what I can dimly recall of another ....."further obtuse calculation reveals" ?
I really should have kept the next few copies as well. Definitely something memorable.

 

If you are clever, you can regain a good bit of that 14% by shutting off at the right point and coasting to a stop, using that extra kinetic energy up and without dissipating any energy with the brake!!

 

Surely all that is needed is something like a fire hose to allow a quick 'splash and dash' if needed?

Onn the other hand if you have to pay for a mains supply at Minehead might a supply from the river at Williton save money?

 

See- I knew I'd regret it. been doing a Steam Engineman Taster all day today, it must have fried my brain.

 

Our feathers start as low as 60 p.s.i on some loco's

 

Back in the day water was taken from the stream at Williton AFAIK. Not allowed nowadays of course.
In previous discussion we heard from Aberdare that in all probability a Stirling Engine was used to pump water from the stream to the water tower.
Not sure a fire hose would be fast enough

 

A UK Fire Hydrant should have a minimum delivery of 1500l/minute - that is about 300 gallons. If we assume a delivery of about 33% of that - 100 gallons per minute, I would have thought that 3-4 mins would be more than enough to get a loco 'out of trouble' - As @Jamessquared has pointed out you don't need to fill the tank to the brim

 

Several Irish NG locos featured a "pulse pump" to lift water directly from rivers. However they worked (and I've never seen any details), they appear to have been cussed and slow devices in use and were abandoned before grouping in 1925. (It's probably changed by now, but anyone who saw mains tapwater in some border counties, even 20 years ago, will tell you that the quality of local supplies could be..... rather variable.) If you come across a photo of a C&L 4-4-0t sporting a mysterious rectangular feature on the side of the dome cover, it indicates a loco thus fitted.

 

Possibly a type of hydraulic ram pump? They tend to work with a pulsing action.

 

One of the Snailbeach & District WD Locos had a traction engine water lifter fitted

 

You can't just tap into a fire hydrant and use it, though, unless it belongs to you. It would then probably have to be fed off a tank with a pressurisation set. If you have that, you may as well have a conventional tank.

 

Probably a Weir type pump which is not too dissimilar to a Westinghouse air pump in its operation. Such pumps were often used to fill industrial boilers in the days before electric pumps.

 

Oh!!

 

I do love it when it all gets technical .

 

West Somerset Railway - Then and Now # 77

Williton 1989 / 2017

Steam services pass at Williton in 1989 using the layout left by the 1968 shortening of the loop at the Taunton end to avoid replacing a double width span over the Monksilver stream. This reduced the effective length of both platforms; the 'up' (righthand) platform because the track curved away from it, and the 'down' (lefthand) because of the need to draw a down train into the down platform clear of the narrowing where the tracks came together.

By 2017 the 'up starter from the down platform' has been replaced by a shunt signal. In 1989 an appreciable number of services turned back at Williton in either direction. By 2017 this was rare and the most common use of the signal is for light engine movements to Bishops Lydeard.

Copyright Mark Wilkins / Robin White

1989


2017