An apparatus is provided and includes a hub, including first and second opposing faces, a first sidewall fixed at opposite ends thereof to the first and second opposing faces to define a first interior between the first and second opposing faces and a second sidewall fixed to one of the first and second opposing faces to define a second interior within the first interior, a first assembly, disposed within the second interior, to generate current from input mechanical energy and a second assembly, electrically coupled to the first assembly and disposed within the first interior, to generate mechanical energy from current associated with the current generated by the first assembly.