OK... I think you're trying to build a four-wheeled human-powered contraption of some sort. "Lefty" hubs are supported on one side, so they work kind of like a car wheel.

You need to look at recumbent trikes- almost all of them have a couple wheels that are supported on one side. There's a couple different ways of doing this, but a popular method is to get "downhill" mountain-bike hubs that use a 20mm diameter axle. That's plenty big enough to be supported on one side, and they usually have the fittings for a disc brake, too. Building a hub into a 24" wheel is a simple job for a good bike shop.

Many trikes use Sturmey-Archer hubs that have built-in drum brakes. These have a 12mm diameter axle, which is about as small as I would go with a single-side mount. Here's the info: http://www.sturmey-archer.com/products/hubs/cid/2/id/51
and here's who sells them in the U.S.: http://www.biketoolsetc.com/index.cg...hair/Recumbent



If you're building something like this Volvo "Gravity Racer", I think it'd be pretty cool:




There are a couple companies that sell par