Imaginary Locomotives

[Johnson044]

On 02/08/2021 at 17:17, 33C said:

Damaged, boxed, Airfix "Biggin Hill" Found for a pound! Now one of the rare Bullied Atlantic's of the "Sea Battle" class, 21B1-12. This is 21B5, "Gravelines" one side and 21B9 " Taranto" the other. Other members of the class are from 21B1 "Battle of the Atlantic", 21B2 "Glorious 1st of June", 21B3 "Chesapeake", 21B4 "Sluys", 21B6 "Barfleur", 21B7 "La Hogue", 21B8 "Nile", 21B10 "Quiberon Bay", 21B11 "Trafalgar" and 21B12 "Jutland". Free running but i will fit with a Triang chassis in the future....... A new spin on the "Atlantic Coast Express" !    

The inevitable question- did the Sea Battle class ever get rebuilt without the air-smoothed casing and with Walschaerts valve gear? In proportion maybe not too far removed from a GWR Churchward Atlantic. I don't have the heart to take a saw to a Dublo Barnstaple but possibly a starting point? Maybe the boiler a bit smaller on the Sea Battles though. Don't know the origin of the Bulleid taper boilers - GW or Stanier influence perhaps? Maybe Mainline Class 4 boiler might be about right...

[Clive Mortimore]

57 minutes ago, rodent279 said:

What do you mean by "Swindonised"? The thing is, there's a lot of things that can claim Swindon ancestry in the BR standards anyway.

If you mean top feed and safety valves combined under a brass casing, I reckon that would have disappeared anyway. The standard 4 effectively has a Manor boiler, with a dome, safety valves over the firebox, and top feed moved further along the boiler.

The outside valve gear would have happened anyway, I guess the other regions wouldn't have been happy with inside gear. The only other noticeable non-Swindon thing is the inclined outside cylinders, probably a necessary compromise to fit within the composite loading gauge.

I don't honestly think a "Swindonised" BR std 4 would be drastically different. Maybe the cab & footplate would be a little different, maybe the tender would have been a smaller version of a Hawksworth tender.

No the standard four had a LMS class four tank boiler, slightly extended. Which in turn was the taper version of the MR G9S s fitted to the compounds.

[JimC]

5 hours ago, Corbs said:

To lengthen the 15xx chassis without needing carrying wheels I guess you'd move the rear axle further under the cab and the centre one closer to the firebox,

 

Its not easy. The 15 was already heavier on the leading two pairs of wheels than the trailing ones.  If you move the rear axle back it gets even more front heavy.  If anything the leading wheels need to go forward to make the weight balance more even, but of course they can't go forward because of the cylinders.

Here's a sketch of the boiler, wheels and motion of the 1500 with the 9400 wheels superimposed. 1500 wheels in red, 94 wheels in blue. They're aligned with the boiler in the same place. As can be seen the 94 takes advantage of the inside cylinders to have the leading wheels a good bit further forward, and consequently the trailing wheels can go further back.  I hadn't appreciated until I sketched this just how very constrained the design of the 1500 was. It looks to my inexpert eye as if the only way they could have got a longer wheelbase on the 15 would have been to give an extended smokebox and mount the main part of the boiler further back, but that would have added  weight to what was already a heavy locomotive. There was a 1945 study of a 2-6-0 outside cylinder pannier tank, and I now understand much better than I did before why this was considered.

 

 

[33C]

3 hours ago, Johnson044 said:

The inevitable question- did the Sea Battle class ever get rebuilt without the air-smoothed casing and with Walschaerts valve gear? In proportion maybe not too far removed from a GWR Churchward Atlantic. I don't have the heart to take a saw to a Dublo Barnstaple but possibly a starting point? Maybe the boiler a bit smaller on the Sea Battles though. Don't know the origin of the Bulleid taper boilers - GW or Stanier influence perhaps? Maybe Mainline Class 4 boiler might be about right...

You have given me an idea.....

[DenysW]

Every time a Garratt  for freight duties is mentioned (and I'm a fan, but a muted one) it gets pointed out  - correctly - that it would have taken massive investment in loops and overtaking lanes on most routes to go from the normal maximum ~60 wagon loads to the 90 or so the LMS Garratt could pull, worse as you get into bigger versions. It's also true that  anything bigger than the LMS ones would have required automated stoking, which uses a different size of coal - more infrastructure costs, now at every coaling point. More again if you decide to add 90'+ turning circles to avoid coal dust in the cab.

 

However, it's almost always asserted as well that they'd lose traction as they used up their water and coal, and it's this I want to rebut. The LMS drawings (in 'The Book of the LM Garratts' by Ian Sixsmith) for that version had an adhesive ratio of 6 light engine, and just under 8 fully loaded. The weight onto the two engines stays pretty well equal also, with the rear always taking about 4 tons more than the front. Possibly by carrying non-productive weight, but Beyer Peacock didn't want the wheels to spin.

 

I've not the drawings to say if Kitson Meyers had also overcome this pitfall - I'd assume so.

 

[Corbs]

Yes Huw Jones said the same when I interviewed him for the Garratt episode of the podcast, that the loss of the water in the tanks barely affects adhesion.

[JimC]

25 minutes ago, DenysW said:

asserted as well that they'd lose traction as they used up their water and coal, and it's this I want to rebut.

Not sure you can really rebut it, since its true, but its just as true of big tank engines, and in both cases its not that great a number in percentage terms. One may as well get excited about the loss of braking adhesion on a tender engine when the tender is empty, which seems to me a much bigger deal, especially with unfitted trains.

[Gibbo675]

9 hours ago, tomparryharry said:

I don't think there was a preference for side tanks as such.  The Western had some 500+ of the 57xx pannier, most of which were still  a residual asset value.  The Eastern were still making J72's for the same reason.  I'm still thinking the 18" Austerity was 'about right'.  If you put an Austerity on  the top quarter (can't remember which one) you can oil up from the top of the footplate.  It's quick, simple, and properly done.  The only downside to the loco is filling the tank, and emptying the ashpan.  A hopper ashpan would have sorted hat out, or cutouts in the frame to to  allow  side doors  on the 'pan.  (as per SAR locomotives).  Refinements, such as proper springing & balancing the motion, goes a long way. 

 

The Western 15xx is perhaps the (almost ) ideal locomotive in this regard. Everything is 'get-atable', and probably far better than the equivalent 57xx pannier.  Its ride is terrible, so  lengthening the wheel base  to improve  the ride quality would be a positive improvement.   

Hi Tom,

 

What are you on about with all this "OIL UP" nonsense, you need to use a little more imagination !

 

Even those archaic contraptions known as BR standards had grease lubrication on the valve gear pins which means once a week and done by a fitter rather than the preparation crews.

 

Gibbo.

[The Johnster]

18 hours ago, rodent279 said:

Going back to a BR standard 0-6-0T, BR obviously didn't think it had a need for such a thing because of the success of the 350hp diesel shunter. If it had felt the need for a steam replacement of the hundreds of 0-6-0 tank engines it had, some very elderly, it could have done a lot worse than either acquire secondhand, or build, a batch of Austerity  0-6-0ST's. No real need to design one from scratch.

The 350hp shunting diesel was a no-brainer by 1948, but was really only suitable for yard work; it’s adoption in a ‘road switcher’ role following the demise of steam 0-6-0s with longer wheelbases and driving wheels in the mid 4’ range that could run up to 40 or 50 mph, and the early scrapping of the various Type 1s that had been conceived for that role left BR with a fleet of 08s doing trip work on running lines that was a bit too slow and caused pathing problems.  The Southern’s 500hp transfer freight loco might have been a better bet and the WR’s D95xx is another couldabeen.  But the 15xx proved their unsuitability by wobbling all over the place on the Old Oak ecs trains, and a Hunslet ‘austerity’, basically a heavy industrial beast, with similar sized wheelbase and driving wheels to an 08, would have been no better.  
 

A BR standard 0-6-0T was never needed in steam days as BR had inherited loads of them, some fairly new, and Riddles’ answer was versions of the Ivatt small prairie, followed by the 1955 plan’s Type 1s, a dead end for various reasons not least the loss of the traffic.  
 

Had one ever materialised, something like a J50 with a hopper bunker and side windowed cab would have probably been what was built, suitable for ecs, trip, transfer, and at a push branch passenger work. 

Edited August 4, 2021 by The Johnster

[tomparryharry]

1 minute ago, Gibbo675 said:

Hi Tom,

 

What are you on about with all this "OIL UP" nonsense, you need to use a little more imagination !

 

Even those archaic contraptions known as BR standards had grease lubrication on the valve gear pins which means once a week and done by a fitter rather than the preparation crews.

 

Gibbo.

 

Oh dear! Gibbo! The art of oiling up has several benefits, not least as you get to inspect the moving parts.  I know one so-called 'driver' who thought it didn't apply to him.  "Why won't it go?" A quick inspection revealed a lifting link had broken; something he hadn't noticed.... An 18" Austerity requires attention to the motion, even with a mechanical lubricator.  The old adage of starting at one point and working around holds true, just like  generations before. The Austerity is pretty bomb-proof.  I do know the NCB panniers were oiled up by chucking a bucket of oil over the motion....

[Gibbo675]

2 minutes ago, tomparryharry said:

 

Oh dear! Gibbo! 

Hi Tom,

 

Eighteen years of rebuilding and maintaining steam locomotives at Riley and Son's, while also working as a Network Rail approved examining fitter for EWS tells me, let the fitters sort it out.

 

Gibbo.

[tomparryharry]

1 hour ago, Gibbo675 said:

Hi Tom,

 

Eighteen years of rebuilding and maintaining steam locomotives at Riley and Son's, while also working as a Network Rail approved examining fitter for EWS tells me, let the fitters sort it out.

 

Gibbo.

Good enough mate, different strokes for different folks.  

[The Johnster]

18 hours ago, rodent279 said:

The standard 4 effectively has a Manor boiler, with a dome, safety valves over the firebox, and top feed moved further along the boiler.

Not this Standard 4, the 76xxx mogul.  The 75xxx 4-6-0 used a domed boiler based on that of the Swindon no.14 from the Manor as you describe; the class were all built at Swindon. 
 

The 76xxx boiler was basically derived from the LMS Ivatt 4MT mogul, in fact the classes are essentially identical apart from styling differences. 

[rodent279]

1 hour ago, The Johnster said:

Not this Standard 4, the 76xxx mogul.  The 75xxx 4-6-0 used a domed boiler based on that of the Swindon no.14 from the Manor as you describe; the class were all built at Swindon. 
 

The 76xxx boiler was basically derived from the LMS Ivatt 4MT mogul, in fact the classes are essentially identical apart from styling differences. 

Thanks, I thought I had read somewhere that the standard class 4 had a Manor type boiler, but missed that this was the 2-6-0 variant.

[PenrithBeacon]

3 hours ago, The Johnster said:

... The 75xxx 4-6-0 used a domed boiler based on that of the Swindon no.14 from the Manor as you describe; the class were all built at Swindon. 

...

IIRC this is not so. The BR4 4-6-0 used a lengthened version of the boiler used in the BR4 2-6-4T in that the parallel section of the boiler was lengthened, the coned bit stayed the same. The BR3 engines used a modified version of the Swindon boiler off the large 2-6-2T

[DenysW]

A question, really. Does use of a tapered-at-the-bottom boiler release the designer to use larger wheelsizes on articulated locos for the forward/engine wheelset? Thus making Beyer Peacock's 4-4-0+0-4-4 express proposals more of a reality and less of a fantasy (or protest)? (same for Kitson Meyer types as well). The logic is that articulateds of these types  have the wheels much more at the front, so they  benefit more if the axles can be moved upwards.

 

[The Johnster]

The taper is horizontally level at the bottom, which means that the boiler is actually a complex elliptical shape rather than a straightforward cone.  The centre line of a tapered boiler rises towards the rear to half the extent of the top profile; the boiler is effectively tipped forward.  I used to think as a child that the taper helped increase the pressure towards the front, which of course it doesn't; the taper is merely the visual result of connecting a large hole in the firebox front plate to a slightly smaller one at the rear of the smokebox drum. 

 

Clearance for driving wheels is ultimately a matter of the height limitations of the loading gauge; the designer must compromise between driving wheel diameter, and thus potential top speed, and boiler diameter, and thus boiler capacity to supply steam at a high rate when the loco is working hard at high speed under load.  A study of the enlargement of the GW Castle from the Star and then into the King will show most of the issues that the designer encounters and deals with.  The boiler must conform to the loading gauge and fit between the top limit of this and the axles, including the inside motion of the driven axles, and must allow room for the tops of the driving wheels, only about 28" from the centre line of the locomotive and possibly needing sideplay which increases the width of the splashers.

 

A larger loading gauge of course gives the designer more leeway in terms of the size of driving wheels, and boilers (as will a wider track gauge), but he will still be limited to cylinders that the boiler can raise steam quickly enough to feed, and ultimately by axle loading, even in America...

 

Early attempt to overcome this problem included the LNWR's 'Cornwall', which had 10'6" diameter single driving wheels and the original boiler slung beneath the driving axle, and the GW's 'Hurricane', which carried the boiler on a separate 6-wheel wagon type frame and had the engine mounted on a 2-2-2 frame with large single driving wheels and nothing over them; it inevitably failed due to not having any tractive weight over the driven wheels.  As applied to a 4-4-0+0-4-4 Beyer Garratt for express passenger work, again the designer will attempt to keep the axles and motion out of the way of the boiler as much as possible; my feelling is that a 4-coupled set up will not leave enough room for a long enough boiler to feed at least 4 and possibly 6 or 8 big cylinders.  There is a trade off between cylinder size (i,e, bore x stroke) and the steam raising capacity of the boiler to feed them.  Make the boiler too short and you won't provide enough steam, too long and the hot gases will be cooling at the front ends of the tubes and again steam output will be insufficient.  Look at the Pennsylvania's T4 duplex; the boiler, and thus the smokebox stops well short of the front of the loco despite the 'sharknose' streamlining, as there is no point in making it any longer than it is.   The way to go might be more in line with the very fast and successful Algerian 'double pacific' streamlined Beyer Garratts, arguably the ultimate in articulated express passenger design.

 

The compromises that limit the designers of fast express steam locos require the greatest level of ingenuity to solve, and by the nature of compromises perfection cannot be achieved in more than one parameter at a time, as all parameters affect all other parameters adversely.  This is one of the things that make the study of such locomotives so interesting and why the names of Stanier and Gresley are spoken with a degree of awe.  It is, in comparison, relatively easy to design a 5MT or 8F loco, which is by and large the most power you will need for such traffic in UK steam age conditions.

 

The only comparable situation for steam loco design TTBOMK, where all the parameters have to be pushed to the best compromise possible, is in the matter of the American superpower fast freight Malletts. culminating in the UP Big Boy, specifically built to single head very long and heavy fast freight trains over long sections of single track in mountainous terrain in order to maximise paths in the sections.

Edited August 5, 2021 by The Johnster

[Miss Prism]

1 hour ago, The Johnster said:

which means that the boiler is actually a complex elliptical shape

 

No. Every transverse cross-section is still a circle.

 

[Gibbo675]

Hi Folks,

 

The purpose of the tapering of boiler shells is two fold:

1. Reduce the volume of water within the boiler to gain efficiency in the production of steam.
2. Reduce the mass of both the boiler shell and mass of water carried within the shell.

The taper of the boiler of the Bullied pacifics was placed to the underside of the centre line so that a greater manifold effect could be gained in the steam space over a traditionally tapered boiler which has the taper to the upper side of the centre line while retaining the advantage of total reduced mass.

 

Gibbo.

[MikeOxon]

1 hour ago, Miss Prism said:

 

No. Every transverse cross-section is still a circle.

 

It depends on your viewpoint.  If the coned boiler is tilted, then a vertical cut to fit the vertical smokebox or firebox will be elliptical, as shown in the sketch below:

 

[Gibbo675]

1 minute ago, MikeOxon said:

It depends on your viewpoint.  If the coned boiler is tilted, then a vertical cut to fit the vertical smokebox or firebox will be elliptical, as shown in the sketch below:

 

Hi Mike,

 

If you were really pedantic and altered the axis of reference to that of the central axis of the cone rather than perpendicular to the central axis of the cone, which actually defines the shape of the cone, then it would indeed be trapezoidal.

 

Gibbo.

[Gibbo675]

Hi Folks,

 

Poor joke joke warning.

 

All this fancy talk of cone slicing is pure HYPERBOLA !!!

 

Well I thought it was funny.

 

Gibbo.

[rodent279]

So there you go, a hidden link between steam & electric. Hyperbolic functions, catenary curves, truncated cones, it's all in there.

[Gibbo675]

6 minutes ago, rodent279 said:

So there you go, a hidden link between steam & electric. Hyperbolic functions, catenary curves, truncated cones, it's all in there.

Hi Rodent,

 

Have a read of these:

 

https://www.bfi.org/about-fuller/big-ideas/synergetics

 

http://www.rwgrayprojects.com/synergetics/toc/toc.html

 

Gibbo.

[The Johnster]

2 hours ago, Miss Prism said:

 

No. Every transverse cross-section is still a circle.

 

If you regard it as perpendicular to the central axis of the boiler, assuming that the form of the boiler in this attitude is circular, but if you regard it as perpendicular to a horizontal plane, it becomes elliptical.  I would contend that the correct way to regard it is as perpendicular to the horizontal plane as it is fundamentally a water containing vessel, and water, as a liquid, tends to find it's own horizontal level. 

 

On GW taper boilered locomotives, the bottom of the boiler at it's lowest point is horizontal and parallel with the running plate.  Any parallel sections of the barrel, such as are found in no.2, 3, and 4 boilers, feature elliptical sections of the tapered part of the boiler at the point at which they join the parallel section.