Caleb is right, we removed the spring as we found it would create a harmonic that caused ink to pump up the tube ... it was discovered in the very first production models and it was not present in the prototypes .. we removed the spring & it resolved the problem. The new Gen 8 however has the return spring and a host of new features & will be out in the next few weeks ... It is a return to the original Swashdrive mechanism and offers a bigger motor and adjustable give that goes from really soft to rock hard with a very simple mechanism ... Tony the R&D guy is seriously impressed with it, and thinks it will make a lot of people take notice ...