Sorry but I don't have plans available. That's a long story. I spent over $20k on the design and ramp itself and there is an unresolved dispute over the rights to the plans to which I don't care to get into but If that changes, I'll post an update.
Unless you have access to a complete machine shop, it's unlikely that you will be able to build this on your own. It's got a lot of milled and machined aluminum parts. If you took out the rotating aspect of it, it would be a piece of cake to build.