This "invention" is born of necessity. Actually it's not much of an invention at all, since there are many towbars out there that could do the job. It's just that they are either part, or some or none of the things I wanted. All the thing had to do was make it easier for me to push the Bonanza slightly uphill and over a door track to get it back in the hangar.
The little units that have a gas or electric motor mounted on a single wheel with forks that clamp onto the front axle are really nice but they are expensive! The reason they are expensive is that they're for moving AIRPLANES. Any thing that has AIRPLANE attached to it is expensive. What I did was scrounge up a riding lawnmower ($325 on Craig's List) some adapters from a friend for my axle ($60), a hitch socket from Harbor Freight ($12.95), and thin-wall steel square tubing ($180, including welding). It comes out to about 1/3 the cost of a purpose-built AIRPLANE towmotor AND I can always earn a couple of extra bucks for flying by mowing grass!