Round Belt Drive
From DT Online
Small pulleys used in model making can be driven using just thin elastic bands or ‘O’ rings. Round Belt Drive are a step beyond this but still only suitable for transmission of light loads such as in various forms of instrumentation.
They are however very flexible and can easily be used to route the drive around obstacles, drive pulleys in different orientations or be twisted to reverse drive directions. Modern round belts are made of plastics but traditional old sewing machines, for example, used round leather drive belts.