Draughting arrangements for Bulleid Pacifics including the Giesl ejector

After all the things that have been said on here about thread drifts, had you noticed the title of this thread?

There's also a general Bulleid Pacific thread, and one for GSN, for the other stuff.

 

Is doing both an unrealistic aspiration?

 

IMHO any new build that’s intended to go mainline ought to have draughting and lubrication optimisation on the list of possible improvements. Reliability is a key issue and both these factors play an important part. Leaving lubrications aside (ok - roller bearings and latest best practice around the valves and pistons) the exhaust can generally be improved for little extra cost. Eg a Lempor give a serious improvement over more commonplace systems, and is cheaper than a Kylchap. No one is doubting the ability of a MN to produce steam at high outputs, but it’s not doing so as efficiently as it could, and at lower outputs it’s worse. Let’s not forget that much of the mainline work these days is done in ‘cruise mode’. By way of practical illustration there’s video of a WC actually drawing its own exhaust back down the periphery of the oversized chimney at low speed.

 

Any major improvement in efficiency would require Chapelon's holistic approach, with numerous large and small changes to design. There is clearly little will for any such changes on any of the surviving Bulleids, or indeed any other current British steam loco. A modest improvement in efficiency by improved draughting may be of low priority for 35011, but on the other hand would involve only modest cost in design, materials and labour, and it could be done during the rebuild or left until later, after the loco is operational.

 

And over a month a saving of £800, over a year £8000 (depending on use), over a ten year boiler cycle £80,000. (@ 4 trips a month for 10 months of the year for 10 years).

I am surprised that a cycling fan such as yourself would not be in favour of searching for marginal gains. (And much easier than a jiffy bag of T-gel or a motor in the stem).

Are we not always told that the profit is in the last wagons?

That is missing the point. The aim of the game is to be able to do that using least amount of coal, save money and save resources. If improved drafting enables that then why wouldn't you take advantage of it?

 

How many mainline locos do 40 mainline trips per year for ten years?

Tom

 

Fair enough, those were whack numbers. Six Bells gives Clan Line doing 14 trips and British Indian Line 16 and Tornado 27 in 2019. But even if you knocked it back to average 10 trips over a ten year people that is still a saving of £200,000. Which is a significant chunk of cash, extend that over time and the savings increase.

If someone was firing for you and they were wasting coal and water would you let them carry on and do nothing?

 

So not really hypothetical at all. No one is saying that that people are not doing their best but someone learning or even someone who is experienced on a loco can end up wasting fuel or water. Coal, water, oil, it all adds up, especially if you are sending it up the chimney, out the safety valves or all over the track.

 

Optimum running on 20-25% cut-off and part regulator sounds pretty inefficient to me for a 3 cylinder engine. I would relate this to high exhaust pressure being required for the blast pipe to do its job, but there might be other reasons. Compare with something like an A4. If a more efficient exhaust is fitted to 35011, it would be interesting to see whether the best cut-off and regulator position remain the same.

 

From the podcast on the GSN thread, the group seem to be confident that they can make the chain driven valve gear reliable by using modern materials. My question is, if BR had achieved this, would the locomotives have been rebuilt?

 

Well, I think mainline locos generally only do seven years - so 10 trips over 7 years is about £14,000, not £200,000!

Of course you want to be efficient - but let’s not pretend there are magic gains to be had out there.

Tom

 

At which point you have to deal with a steam reverser not known for absolute finesse in control. It’s not the kind of device to change cut off by a percent or so up or down while the regulator remains in the roof.

We all know it is possible to make a more efficient Merchant Navy. BR did it in the late 1950s, and 35011 could be restored in that form. But the group have committed to rebuild the loco in a less efficient form ...

Tom

 

10 is a low end figure and comparable locos (in a range of places in terms of the 10 years) - 6233: 14 35018: 16 35028:13 60009: 15 60103: 17 60163: 26. So 15 x 7 gives us a saving of £21,000.

And if someone offered you £14,000 to a locos next overhaul you'd say 'nah'?

No, nothing magical, but it is just like not wasting £10 a day of coal, water and oil it adds up over the weeks, months and years. It is marginal gains.

 

Who actually pays for the coal used? I'd be surprised if it is the loco owner, even if they supply it. If it isn't, there's little incentive for them to improve their locos performance. I'm not involved in railtour organisation in any way so it's a genuine question.

 

I assume it depends on the relationship between owner of loco and tour operating company. Maybe it makes it profitable for the organisers who can put the money back into other tours. It isn't like people are getting rich off the industry and the money is going to be syphoned off to pay for private island in the Caribbean.

Again, why wouldn't you want your loco to be more fuel efficient?

The objections to improving drafting seem like an ideological argument searching for a justification.

I could understand the objections if the spec said we are rebuilding a faithful recreation of locomotive x exactly as it ran in 'chosen year', but it isn’t.

 

When I helped set up the current 35011 group the objective was to restore it to as it was in 1959 before it was modified but keep things like the BR grate with the dampers.

 

The only difference between originals and rebuilds that would be perfectly obvious even to Joe Schmoe is the spam can cladding. If you put that on a rebuild, I suspect most of the public would be none the wiser. Obvious to those of us who frequent this forum would be the presence or absence of the outside Walchaerts valve gear. Is there any other difference that is easily visible from outside? Modified draughting would be invisible, but besides saving a bit of cash for coal it would also save the firemen some effort, and that does seem worth doing unless someone can point out a downside.

 

The possible downside has already been pointed out - diversion of time, energy and materials from more important aspects of the job.