Well, I've been running some ideas through my mind, and I'm wanting to put them to paper (so to speak) before I forget them.

I've been thinking about ways to conserve energy so that it can be output when the energy is really needed. The thing that comes to mind first is a flywheel. I know that older tractors used to use very heavy flywheels, and they tend to conserve large amounts of inertial energy in order to be released when the need arises. I'm thinking about using this along with a centrifugal clutch to engage after it reaches a certain RPM. That could let the flywheel absorb the draining of energy, but make sure that it doesn't go below a certain RPM so it doesn't have the effect of making you turn the flywheel from a dead stop every time it takes a load. With hillclimbing the addition of a ratcheting system that prevents you from rolling backwards, and that could be engaged for forwards and backwards would be awesome. That way you could stop on a hill and build up the energy in the flywheel without constantly being fought against by gravity. Each time the flywheel reached the appropriate RPM's, it would deliver a burst of energy. This allows your legs to maintain the optimum RPM's at the edge of the point where the centrifugal clutch would engage, thus delivering spurts of power capable of slowly crawling you up a hill, or over an obstacle. The flywheel would be delivering the inertia, you would simply pedal it back to the appropriate RPM, which wouldn't be much further than the point the clutch would engage.

Another idea I've had is to set up dual axles on the back. If it's going to be carrying a large load of weight on itself, or in a trailer, I think that the vehicle will need as much help as possible to not sink into soft earth. By distributing the weight across multiple tires, I believe that you can have better traction and less chance of the vehicle sinking. The real issue is whether I want both axles to be pulling axles, or just one. I've also still not determined whether I want to use a differential, or just have a direct drive via a sprocket.

Just some ideas, please feel free to give me some feedback and tell me what you think. Thanks for the time.