Atlantic's works: Portable layout update

[Atlantic 3279]

Presumably the hole for the fixing peg of the banjo, even if solid, will be back on the sloping part of the boiler, whereas the round dome goes on the band where the tapered and parallel boiler rings meet, so there will be an exposed hole to fill anyway?

East Kent Models certainly list the Hornby A1 single chimney, which is both nice and cheap as well as easy to bond to the plastic boiler, but I cannot see a dome.

SEF are very helpful, but I haven't seen the dome quality. A look at the earlier parts of Rob's thread (the chap from Cork, currently on the Raven A2) may reveal an image of an SEF A1/A3 with their round dome*. I don't think DJH release parts unless you are a member of the Royalty, or a very influential model press journalist.

Or just ask Mick whose reply nipped in before mine........

[Atlantic 3279]

These latest Hornby Pacific chassis really are quite versatile you know.......

Smooth as silk from the first turn of the wheels, and goes round a 3 foot radius or less. How much less I do not know, not until I carry out more testing anyway. It will certainly need pick-ups on that extra set of wheels, and some brake shoes at least to make things look right. Brake rodding and cosmetic springs too? We'll have to see.

Quick! Somebody call for the men in white coats, I've obviously forgotten to take the tablets

[Atso]

I wish I could get that kind of success with my N gauge chassis!!!!

Excellent work there Graeme, looks like Gresley's 4-8-2 will live after all! Are you planning to build it with the angled front end to the running plate or produce something a little more in line with Gresley's other loco's?

[Atlantic 3279]

Even if those high frame front ends, lopped off at an angle, are portrayed in the drawing in RCTS 10A as being covered by a matching shape of running plate (and this is copied in the Jack Hill painting) I believe that comparison with the frames in other drawings and with typical LNER design evolution of the period suggests that an entirely different interpretation of this loco's likely final shape is fully justified.
I think the drawing also incorporates some other features that may not have been very satisfactory and which may have had to change before batch production took place.
My intentions will become apparent in due course .

[davidwest]

Wow

[Atlantic 3279]

Maybe this ought to appear in the Locomotives and Rolling Stock section, but it is in direct context here, so here are a couple of debatable points from that RCTS 10A 4-8-2 drawing to get the little grey cells going:

1. It appears that an all out effort had been made to keep the loco + tender short enough to still be a reasonable fit on a 70 foot turntable. Hence the coupled wheel spacings are reduced to almost the practical minimum of 7' 0" rather than the 7' 3" of the Pacifics (I'll ignore that on the model) AND the cab and firebox are in a "cramped" relationship. The extra length of the P2 / W1 style firebox all appears within the cab (not in front of it as on those other locos and on the proposed reboilered super-A4s) shortening the crew space by around 15" I reckon. When the Doncaster style cab was fitted to a batch of K3s a few years previously, without any lengthening of the frames, the same business of mounting the cab well-forward over the firebox arose. In order to accommodate the reverser etc. the driver's seat had to be fitted in a position well-back and in which his neck and shoulders were in the cold draught from the rear cut-out in the cab side. Complaints arose, and (much to Gresley's annoyance I believe) the cabs had to be modified thus eliminating the traditional Doncaster cut-out in the rear edge and creating the GS K3 cab also used on the K4s and with modification on the K1s.
Although the 4-8-2 drawing still shows the "true" Donny A1/A3/A4/P1/P2(& B17/D49) style cab, would the same K3 type change to the sidesheets have occurred, or in the interests of access to the firebox sides for servicing and to be aesthetically acceptable to Gresley would the cab have had to move back, and would the Board have sanctioned installation of more new, longer turntables to allow the beast to usefully roam the rails?

2. Only a single chimney is shown despite the 50 sq foot grate size, the extra boiler length, and the required power output. As Doncaster already knew (or was learning quickly) about the advantages of the Kylchap double exhaust system, would the performance restriction and fuel economy implications of the single chimney have been tolerated in a loco intended to be worked hard taking heavy trains up-gradient at speed - even if fees had to be paid out for use of the Kylchap arrangements?

[S.A.C. Martin]

Absolutely stunning chassis conversion, really looks the part.

RE the cab, surely a W1 style cab would be the best bet? Best of both worlds, I can't see the LNER not using a windcutter cab with the A4 style sidesheets, whilst using a standard 8-wheel tender.

As for the chimney arrangement - perhaps sharing more in common with Humorist's smoke deflector experiments, seen here:



http://myweb.tiscali.co.uk/roysrailpage/frame/A102.jpg



http://mikes.railhistory.railfan.net/imfile/04770.jp

(The photographs remain the copyright of their owners and are replicated here for educational purposes only).

Personally speaking, the above pic, with the sloping front to the smokebox, is very handsome and shares some commonality with the A4s - the chimney.

[Atlantic 3279]

Ta Simon. I think there may be a misunderstanding here, as it is not the "outside" length of the cab that struck me as the potential problem. It was the small amount of it shown on the drawing as actually being "aft" of the backhead, I imagine for the sake of keeping the loco short. The ultra-long W1 cab wouldn't help if all the extra length were still pushed over the firebox. The "normal" length of pacific side-sheet would be perfectly adequate for accommodation of crew and controls if it were mounted in the otherwise "normal" position as on other classes, i.e. with 12 to 15" more projection rearwards from the backhead than is shown on the 4-8-2 drawing, but the loco and tender would then be almost impossible (or outright impossible) to get onto a 70 foot turntable deck.

ANYWAY, more good news about the chassis. Rear pick-ups are installed, I've found some nearly-matching spare etched brake shoes for the rear wheels, and tonight it ran (albeit at slightly reduced speed) around at 2 foot radius and when static on that curve still seemed to have a little "slack" suggesting that it might manage a slightly tighter curve still .

Cunning plans and preparations for the cuts needed to stretch the body are also advancing nicely.

[S.A.C. Martin]

Ta Simon. I think there may be a misunderstanding here, as it is not the "outside" length of the cab that struck me as the potential problem. It was the small amount of it shown on the drawing as actually being "aft" of the backhead, I imagine for the sake of keeping the loco short. The ultra-long W1 cab wouldn't help if all the extra length were still pushed over the firebox. The "normal" length of pacific side-sheet would be perfectly adequate for accommodation of crew and controls if it were mounted in the otherwise "normal" position as on other classes, i.e. with 12 to 15" more projection rearwards from the backhead than is shown on the 4-8-2 drawing, but the loco and tender would then be almost impossible (or outright impossible) to get onto a 70 foot turntable deck.

Ah, gotcha now! That is tricky...the thought did cross my mind that the LNER used something on turntables to turn engines that were too long in some cases, but I can't remember what it was called. It was basically an extension of rails at one end, lifted slightly off the floor and above the rails, that allowed a tender to be reversed onto it and the engine then turned.

Failing that, perhaps a shortened cab as on the K3 is required, as you say.

ANYWAY, more good news about the chassis. Rear pick-ups are installed, I've found some nearly-matching spare etched brake shoes for the rear wheels, and tonight it ran (albeit at slightly reduced speed) around at 2 foot radius and when static on that curve still seemed to have a little "slack" suggesting that it might manage a slightly tighter curve still .

Sounds rather epic to me - a 4-8-2 getting around 2 foot radius curves is no mean feat by any stretch of the imagination!

[Bill Bedford]

Ta Simon. I think there may be a misunderstanding here, as it is not the "outside" length of the cab that struck me as the potential problem. It was the small amount of it shown on the drawing as actually being "aft" of the backhead, I imagine for the sake of keeping the loco short. The ultra-long W1 cab wouldn't help if all the extra length were still pushed over the firebox. The "normal" length of pacific side-sheet would be perfectly adequate for accommodation of crew and controls if it were mounted in the otherwise "normal" position as on other classes, i.e. with 12 to 15" more projection rearwards from the backhead than is shown on the 4-8-2 drawing, but the loco and tender would then be almost impossible (or outright impossible) to get onto a 70 foot turntable deck.

I think the drawing office was well aware of the problem. On the Peppercorn pacifics the grate is slightly shorter at 11'4.5" against 11'9" for the same 50 sq ft grate. On the 1947 4-8-2 drawing the firebox is reduced to 8'6" and a combustion chamber is built into the boiler, which would be a different way of solving the problem.

[Atlantic 3279]

That reduction is quite radical Bill. Are you comparing like with like in those dimensions? I believe there was some variation in the style of LNER diagrams over the years, sometimes total length of firebox being shown, sometimes the horizontal length of the grate, sometimes its sloping length.

Another thought occurred to me after I'd posed the questions on here. As rear edge cab cut-outs were made shallower from the mid thirties, would a repeat of the K3 cab debacle have been avoided (or at least have been lessened) had the 4-8-2 simply been built as drawn? Yet another thought, had the shallow cab cut-out still been a problem might the problem have been solved without upsetting the aesthetics by installing some discrete/recessed framed glazing behind the cut-out?

[Atlantic 3279]

Having now looked at the post -war diagram that Bill mentions I see that my suspicions were well founded. 11' 9" on the 1939 diagram is the full length of the firebox including its A4/W1/Wolf of Badenoch style combustion chamber. The much shorter figure on the 1946 4-8-2 is simply the horizontal length of the grate, although there is clearly a much longer combustion chamber above the rear coupled wheels. Looking at the drawn outlines and dimensions at the rear of the two locos, I believe the grates are the same or almost so. In both cases the line of the backhead is almost aligned with the trailing edge of the Cartazzi wheels and these are set 9' 6" aft of the rear coupled wheels. The 1946 diagram DOES however show the cab a foot further back, with 5' 2" 1/2 overhang behind the Cartazzi axle, rather than 4' 2" 1/4 on the 1939 diagram. This gives more crew space, and the straight-rear-edged cab is there too. BUT, with revision of the coupled wheel spacings back to the standard 7' 3" Pacific figure, and the repositioning of the bogie to accommodate the indepentant middle valve gear and divided drive, the total (engine + tender) wheelbase has shot up from 67' 4" 5/8 (1939) to 69' 7" 5/8 (1946). I can imagine the former being a practical proposition on a 70" turntable, but allowing for the flanges on the wheels I cannot see how a mere 2" 3/16 "spare" beyond each end axle would ever allow the loco to be turned on a conventional 70' table

[rob]

Will be following this with a deal of fascination! It looks as though you've got to consider the engineering problems at lifesize,then transfer to 4mm where no doubt the lifesize problems will produce a whole new set of difficulties great,this could be your most interesting yet Graeme......big thumbs up from me for this venture!

[Atlantic 3279]

The murder is out! My 4-8-2 has streamlining - as if the red wheels on the chassis were not a big enough clue. My view is that as the shape of the front of the frames of the 4-8-2 in the RCTS drawing is the same as those of the A4s, and so many Doncaster design schemes of the era included streamlining at one stage or another, there is adequate reason to think that the 4-8-2 was earmarked for possible streamlining.

There are still some rough edges to knock off the model, the details of the cab/firebox geometry to decide, possibly a chimney to change (no views expressed on that point yet I notice) and details to add/reinstate, but the basic beast is complete .

I'm toying with the idea of a number in the 4905 - 4980 series, and maybe a name that patriotically honours one of the Royal Navy's battleships of the Dreadnought-or-later era.

[rob]

Yoiks! Thats a seriously impressive beast! For what its worth,I reckon double chimney by then,I'd stick with a racehorse name though myself as was done with most of the Peppercorn locos,a lovely tradition.....have you looked at it with regards turntables or will it be dependant on triangles?