Various pulley designs were tested to make sure the pulley can sustain the tension in the string, while minimizing its weight.
The pulley is approximately 1 ft in radius, and is
required to hold up to 80 lb of string tension.
The radius is designed such that the gear ratio
between Judy’s string-pulling gear and the rotor
would yield the desired rotor RPM.
The rotational rate for the pulley is designed to be up to 20 RPM, which means the pulley holds approximately 140 ft of lightweight string that should suffice for the required one minute flight.
All pulleys were tested on a test stand to make sure they can sustain the string tension. Pulley materials include lightweight foam, and carbon fiber composite materials.