Not a lot to report at the moment although quite a lot has been happening behind the scenes.
First off I need to fill in some background. To the best of my knowledge there is no 100% accurate GA drawing of the Coronation Observation Cars in existance. There exists a partial GA showing the front of the vehicle as shown here:
The official diagram book drawing follows that form but does add the back of the vehicle:
Note that in both drawings the width of the vehicle over observation window in plan view tapers inwards. This appears to differ from how the original was physically built (and coincidentally how the recently announced restoration has been carried out). The problem is that it is thought that it was impractical to curve the cornice in two planes as specified resulting in Doncaster building them curving in one plane only. Unfortunately the Isinglass drawing largely copies the incorrect diagram so is not a lot of help.
When I do a 3D model I like to work from as accurate drawings as I can obtain. With none available I set out to produce my own drawings using Inkscape, yes I know Inkscape is not a CAD program but I tend to use it as one anyway, even using it to produce etching artwork. Having never visited or measured the restored 1729 I had to rely heavily on photographs and try and scale the various elements from there. I did hit a few issues and had great difficulty envisaging how to represent the complex curves on the prototype in 2D. To resolve those I produced some 3D models on the way then chopped them in slices to see how they would be represented on a drawing. I eventually arrived at a drawing I felt I could use and started the modelling process which resulted in the model you have seen previously. At various stages the 3D models were printed then compared against official photographs of the prototype.
Attempting to do the lettering identified something I had avoided on the drawing and that was lettering sizes and positions. We know the size of the "CORONATION" from the official drawings but not the size of the "LNER" and "3". Back to the drawing board (or more accurately Inkscape) and I added all the lettering.
This is the drawing I produced:
First off the test lettering has been applied to an earlier body and I am reasonably happy with the result however it is clear I can get away with the lettering being finer especially have since determined the correct sizes. Not very accurately located here:
I have tried printing some 4mm passengers and tried them in the moulded seats. The original seats were based on the diagram and comparing with photographs do not appear to be correct. I have since reworked these on my drawing and trying to decide if I can be bothered to print a new refined set or go with the originals:
I did try and print a revised set but ended up printing them undersized and my 3D printer needs some maintenance work done before I use it again. I did however manage to print off a set of 8'6" Heavy Duty Gresley bogies ready to use: