Was the detailed design of a standard gauge R class actually completed by the VR or did it stop at a more or less 'concept' stage?I find that I am lacking drawings of the R class cylinders.
What mods to the steampipes were needed and how were they done, please?
My understanding is that conversion of an R class to SG was not quite as simple as it theoretically might/should have been and that there was quite an amount of design work required before the conversion of 766 could occur.
A cylinder diagram in Carlisle's book indicates that there was a 45 degree flange just above the valve casing on the live steam pipe. This would move 3.25" inward and would require a shorter main steam pipe with a different shape to pass through the existing holes in the smokebox at a steeper angle which would then curve to mate with the flange, compared to the straight pipe on the BG locomotive. The exhaust steam pipes are within the half casting and will just move to be 6.5 " closer together and I'd expect that a new narrower design of blast pipe casting would be needed.
Other than that I'd expect that the brake gear would be the main additional work apart from the actual gauge change.
Carlisle's book has a good frame drawing, showing the spacers in the valve gear brackests.