Okay, after doing some more research I have organized my main ideas for this project. The update is as follows:
I plan to use either a pre-1980's automobile starter motor or an automotive/farm tractor DC generator (dynamo), connected to a set of heavy-duty batteries (not sure of the type yet--I guess whatever I can find) via PWM circuitry for the throttle. The bicycle will be chain-driven, with a sprocket connected to the motor shaft and one connected to the rear bicycle wheel. Because of the way the bike is designed, it will not be possible to run the chain from the motor to an existing sprocket, as it would turn the pedals and could cause an injury. Instead, I will be welding a sprocket to a sort of "flange" (not the right word, but you get the idea
) on the rear wheel. This way, the "freewheel" mechanism will allow the wheel to turn freely when the motor is switched on. To avoid a motor stall (and therefore, excessive current draw), I plan to pedal up to speed before turning on the motor (depending on the torque of the motor). This would only work, of course, if I matched the speeds perfectly--otherwise it would put intense strain on the rear wheel or the motor chain as the speeds begin to equalize. This is a part for which I could use some more suggestions.
I also hope to set up some sort of regenerative braking system to recharge the batteries. I hope to be able to use the motor for the regenerative brake generator, if possible. I had originally hoped to have a switch on the handlebars to select between "Drive" and "Charge", and charge the batteries by pedaling, but I was told the losses would be too high. That is why I decided on using a regenerative braking system, but I need more information.
That is the main idea thus far. I will post more updates as I get more suggestions.
Thank you all very much!
Der Strom