Hello Israel, welcome to the forum.
Being a model engineering enthusiast myself, I am quite familiar with George Luhrs' micro engines, he has built many different types. He is not alone, it seems many model engineers try to make things as small as humanly possible. I suppose that is the challenge they seek to conquer.
If you haven't yet, you should peruse the Model Craftmanship Museum website, by the owner of Sherline.
http://www.craftsmanshipmuseum.com/luhrs.htm