Attaching sprocket to wheel

I am wondering how I can attach sprockets to a wheel such as colson wheels. I dont want to attach it to the axle. any help would be great. I am looking at 6 by 2" wheels

You are talking about Colson wheels, not their casters, right?

Right

Check here for ideas: http://www.cncbotparts.com/colson_hubs.htm