Hello Pat
I'd be more than interested if you do get around to detailing the Robertson Engine. I've found little detail other than the e-book you referenced. I've searched some patents to no avail but I do recall seeing a model reported at one or other of the UK or European shows and believe that it was by Herbert Stumm but I've not had opportunity yet to follow up on this.
By the way many thanks for the work on the Bernay and Daker.
Keep up the good work
Best wishes
John