text: For that ($50 US?) you might build a working model.  Something that helps people is often good, as in for the disabled.  I have something in mind, an arm driven walking device for someone with limited leg usage.  I have checked U S Patents and found nothing similar.  Will forward sketch upon request.  Our senior design was awarded Patent #5,104,280, Drexel University, Philadelphia, Pennsylvania, USA, 1989.