Like you, I was intrigued when I discovered these cyclecars, so when I found a website (www.aosmith.com, I think) that had made available the original blueprints for the vehicle, I was determined to build a replica. I used the exact original dimensions, and used a bike motor to drive the 5th wheel. I did a lot of research and found that the original engine is the grandfather of all subsequent B&S small engines! If you google "Smith motorwheel" or "Briggs motorwheel" you will find a lot of information. I wrote two entries for Wikipedia on the motorwheel. I am attaching some photos of my replica.