Boilers & Accidents

In "Swindon Steam" Cook records that the GWR insured their fleet by the 1930s, but they may have been self insured earlier. Perhaps by that date there were sufficiently few really expensive accidents that the money men felt the risk was worth spreading?

 

I cant help feeling 6202 was something of a "bitza". Princess boiler , frames and running gear . Coro front end , but single chimney. Seems as if the rebuild was built from spares , and that may be why it died

 

Not really. It was rebuilt with cylinders to replace the previous turbine drive, which meant replacing the front frames section as the turbine had needed major changes. So the rebuild had the following from a Lizzie: smokebox, chimney, boiler, cab, rear running plate, coupled wheels, bogie and trailing truck. Coronation: cylinders, motion, leading frames and leading running plate. Had it been replaced as a Lizzie, with the exception of the front running plate, the replaced parts list would have been the same.

 

See Post 13, bottom of first page.

 

8134

 

Not sure if it would fit, but I'm sure it would be wanted. I had read through it a number of times and found it fascinating. Well researched and thought through.


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If the driver of the up express had not missed the distant signal he would have been aiming to stop at the home signal, which presumably was a little way north of the station, protecting the crossover. Clearly he did miss the distant. Are you thinking that he might have seen the green light of the up fast starter from a long way back and therefore assumed a clear road and not worried about missing the distant, whereas without seeing that light he would have played safe and applied the brakes?

 

Was the taper on the boiler barrel altered? The Bulleids are unusual in having more taper on the bottom of the barrel than on the top. This reduced the weight of water

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Yes. The actual design is flat on the top, tapered on the bottom of one ring and parallel on the other.What was changed was that as built, the front ring (smokebox end) was tapered and the rear ring (firebox end) was parallel. That changed to the rear ring being tapered and the front ring being parallel, but of smaller diameter because of the taper. That took a significant amount of weight out (both in steel and water) without changing any of the fundamental properties of the boiler, i.e. tube numbers or surface area etc.

On understanding such subtleties does the drawing office earn its corn ...

Tom

 

A fair few Bullied innovations come under the heading "now, why didn't anyone think of that before?" Of all Bulleid design considerations, boilers (other than CC1!) seem the least contentious.

 

While not wanting to big up the Swindon crowd, was there a reason for the Bulleid taper being at the bottom of the barrel, unlike GW boilers where the taper was at the top. The latter lowers the top of the boiler and smokebox and allows a taller chimney, doesn't it? or have I missed something?
Pat

 

At a rough guess, I assume the reason was the height of the inside cylinder, all cylinders driving on to the intermediate wheelset. There is limit to how high you can mount the boiler, so lowering the rear end would allow more volume above the crown sheet and at the firebox tubeplate. I don't pretend to be an expert on Bulleid's Pacifics, though!

 

As stated by Richard in an earlier post, it was down to volume of water. All other things being equal, the volume of the boiler may be the same whether the taper is at the top or the bottom but having the taper at the bottom means that, for a given height of water over the firebox, there is less volume of water. Consequently, there is also a greater volume of steam. Having less water provides a considerable saving in weight, which as we have just been saying, can be critical. In initial steam raising, there is less water to heat to reach working pressure and thus a small saving in fuel costs. I think that the only possible downside is that there is less reserve of energy in the boiler but this has never been a problem with Bulleid pacifics.

 

I’m not an expert but it may have been to leave enough space for a hapless fitter to get inside the oil bath. I’ve crawled around under the boiler of 35028 a few times and there’s plenty of room to get the the centre motion

 

I'm not sure that OSVB was that bothered about the ability of fitters to reach parts of his engines, in a similar way that F.W. Webb never concerned himself that footplate crews could reach the footplate controls of his engines, at least without causing themselves some injury!

 

With a multiple jet exhaust the height of the throat of the petticoat pipe/chimney above the exhaust nozzles is a little less than for a single orifice. It occurred to me today that designing a steam loco is actually putting together a group of interacting compromises.

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Fitters don’t need to go in the oil bath often. Only for periodic maintenance. It’s a very clean environment so there is much less wear from ash and dust than exposed motion.
In addition to the vertical hatch at the rear of the oil bath, the rear section under the crank axle is removable, as are two smaller hatches to access the 3 throw crankshaft and oil pump.

 

I don't think ergonomics was a known science back in steam days. GWR drivers probably got a permanent right hand curvature of the spine leaning across the reverser to see out of the cab window. I know Gresley and the formidable Dugald Drummond used to make a point of chatting to loco crews but who would want to argue with the CME about the shortcomings of their creations!