Thanks for the kind words.
There are trade-offs for everything in the world, and dad traded off detailed drawings and exact valve gear calculations for building speed and efficency. And dad generally went for an overall look of a model, while sacrificing much of the exact details and fine finish of a given engine, which means many of his replica engines don't adhere to the originals very closely.
My preferece is to document old engines exactly as they were originally built (with 2D drawings), with valves and valve gear timing that matches the original engines.
This requires infinitely more time, but gives an accurate historical record of exactly how the old engines were designed, such as the Speedy Twin. There are only a few original Speedy Twin drawings that still exist at the Soule foundry/manufacturing plant/museum, and I intend to recreate the entire set accurately, and have been working on that.
My desire has never been to build model engines per se, but rather to built exact miniature replicas of old engines, down to the last detail, and this includes a complete and exact reverse-engineering of the engine.
My ultimate goal is to be able to build small full-sized workshop engines (gas and steam) that are so accurate that if someone finds one 100 years from now, there will be no way to tell if it was constructed in 1890 or 2021.
The hobbyist now has access to the technology that will do this, both in design software and backyard foundry equipment.
.
