Remodelling a B12

[Pebbles]

To my knowledge, wherever possible, John Edgson used works drawings, but in the case of the B12/3 none were available in 1990. However, John E had drawings for the B12/1 and details for GER tenders and many LNER "standard" parts. Turning to the Isinglass drawing; John E quotes the boiler diameter over the cladding as 5ft 9.5inches (scale 23.17mm) which if I recall is the B17 dimension. In the case of the cab and smoke box details I'm not sure where John E obtained these.
The GERS drawing by John Gardner is a generation later when access to the NRM collection was possible. John G quotes the boiler over cladding as 5ft 11.5inches (scale 23.84).
As the Crownline (PDK) B12/3 emerged in 1997 I assume it used John E's drawing.
Where does this leave us? Well if building from the Crownline/PDK kit use the Isinglass drawing, if starting from scratch the GERS drawing beckons. Either way the Isinglass drawing contains many useful details that can save a great deal of research.

[Atlantic 3279]

I don't dispute the figures, but I find them curious. I believe the B17 and B12/3 boilers were very close relatives, the B12/3 having a shortened B17 barrel and specially adapted firebox shape (partly to allow it to sit astride the rear coupled axle of the B12). Did not both barrels consist of two telescoped rings, one of about 5' 4" outside diameter and one of 5' 6"? Doesn't this latter ring size make the quoted outside diameter(s) of either 5' 10" or 5' 11.5" for the B12/3 cladding "sound about right", perhaps in contrast to the rather slim-sounding 5' 9.5" figure for the B17? Why lag/clad to different thicknesses on two variants of the same boiler?

[Pebbles]

The B17s, so we are to believe, were designed by the NBLC, they had built other Doncaster designed locos and one could conclude that they were following Doncaster practise.
In the case of A1/3s the front parallel section of the boiler was some 5ft 9 inches whilst the cladding was barely 6ft. Q5s had a 4ft 9 inch boiler with cladding of 5ft 0.5 inches. H1/A8s had two diameters of cladding, one similar to the diameter of the smoke box the other more closely tailored to the boiler. Both the B12/1s and D16s had cladding some 6 inches greater than the nominal boiler diameter. It is most likely that in the case of the B12/3s Stratford practise was being followed.

[Atlantic 3279]

Interesting. Sounds as logical an explanation as any!

Also confirms that a substitution of even a correctly modelled B17 boiler for the skinny Triang B12/3 original would be futile, as my Vernier measurements of the Hornby B17 boiler had suggested. I have not however ruled out a scheme to clad the Triang boiler moulding at the same time as increasing the length, recognising of course that much else will still be inaccurate. If I go ahead, then in this case it will be more of a matter of seeing how much improvement is reasonably feasible, rather than striving for total perfection.

[coachmann]

Surely there is a limit to how much plastic-bashing is worthwhile. All that effort would be better expended on building a correctly profiled footplate in Plastikard. An etched tender must be available from various sources.

[Bill Bedford]

So is there anything else wrong with the Isinglass drawing?

Why use the Isinglass drawings when clearer, more detailed, ones are available from the GERS?

[60526]

Bill, I'd already bought the Isinglass drawing before putting the knife to the Hornby body and from what is being said here the PDK kit that I've bought is also wrong? The other question I asked was whether the B12/2 has a smaller boiler and firebox. There something in the green book about this.