Bob Horn sent in a couple of photos of a motorcycle he built back in 1991. As soon as I saw them, I knew I'd seen them before and, sure enough, the bike was featured in Motorcyclist magazine in October of that year. The bike you're looking at is Bob's proof of concept for some ideas he had about motorcycle steering and suspension and rather than getting into long winded debates about whether or not it would work, Bob is the type of guy who would rather build something and find out. Bob bought a Harley Davidson Sportster, and after keeping the engine and electrical parts, sold the rest and began building his bike.
The most unique component in this design is the steering setup. Instead of a conventional steering head with a pivot on a single axis, there is instead a ball joint. Two pivot arms with heim joints connect to either side of the front axle and to the frame. Since the ball joint allows movement in more than one axis, the bike can be steered and, according to Bob and the road test in the magazine, it works quite well and even has anti dive characteristics under braking.
Bob, who was working on airplanes for the Air Force at the time, got a lot of materials and parts for the bike from Aircraft Spruce and Specialty, a company much more familiar to experimental airplane builders in the EAA than motorcycle builders, but you go with what you know.
Bob no longer has the bike. He says he put 4000 miles on it and then sold the engine and tranny to help finance some other ideas and in 1993, sold the bike itself to a fellow in South Dakota. Since then, he's lost track of where it went.
If I have any concern with this idea, it would be in the ball joint. As the joint began to wear you might get some unintended and interesing variations in steering geometry. Also, the joint might be more susceptible to breaking than a standard steering head, but there's no reason you couldn't take that into consideration in further refinements, as already stated, this was a proof of concept, not a finished design.
In an interesting "small world" note to this story, Bob said his motorcycle was written up in a few other magazines, among them, Battle2Win. He forgot what specific issue it was but he remembers it was the same issue that had an article on another builder familiar to readers of The Kneeslider, Curt Winter of Big Twin Racers. Interesting.
Some might argue over the aesthetics of this bike but that wasn't what this was about, he was interested in what works and what doesn't and by putting in the time and effort, he found out. I like that, a lot.
Remember, if you're a builder and would like your bike featured or know of someone who should be, let us know and we'll check it out.
Photo of steering head: Motorcyclist magazine