Andrea, There’s a user named Sepio that’s done a lot of redesign of Art3 through Art56. His project log on this page:
https://hackaday.io/project/26341-building-and-improving-the-thor-robot-arm/log/70087-day-18-redesign-of-art3-and-art4
contains a Art3LowerBody with a fan added to it.
Drew