an apparatus is disclosed for winding a strip of thin material such as paper . the apparatus is particularly suited for use with variable speed printer - plotter machines which discharge paper over a wide range of speeds . such machines require that the tension applied to the paper by the paper take - up mechanism be minimized or maintained within pre - selected limits so that printing - plotting quality is maintained . to this end , the apparatus permits the paper to fall in a free loop between two points of support and includes a sensor which monitors the condition of the loop and actuates a take - up motor when the loop achieves a predetermined magnitude .