Re: Inspired by a Classic 1960's Design and Powered by an Innovative New Eterna Spherodrive Movement
The spherodrive winding barrel is suspended in low friction ball bearings rather than the usual bushings. That is an interesting enhancement from the company that provided ball bearing supported rotor.
Developed in the late 1940's it was arguably the last significant enhancement to the rotor wound movement. The lower friction bearings used in the spherodrive are supposed to deliver greater accuracy (no details) and a longer power reserve of 56 hours. Because the barrel turns so slowly I would like more information on how accuracy is improved by using ball bearings. My gut reaction is that not much improvement could be gotten that way. Seiko got a 50 hour power reserve in the 6R15 by switching to a non-metal mainspring. I can see how lower friction bearings could allow the mainspring to unwind for longer but that would be using lower torque and accuracy could suffer. I wonder if Eterna used either longer mainspring or one made of a composite.
The spherodrive winding barrel is suspended in low friction ball bearings rather than the usual bushings. That is an interesting enhancement from the company that provided ball bearing supported rotor.
Developed in the late 1940's it was arguably the last significant enhancement to the rotor wound movement. The lower friction bearings used in the spherodrive are supposed to deliver greater accuracy (no details) and a longer power reserve of 56 hours. Because the barrel turns so slowly I would like more information on how accuracy is improved by using ball bearings. My gut reaction is that not much improvement could be gotten that way. Seiko got a 50 hour power reserve in the 6R15 by switching to a non-metal mainspring. I can see how lower friction bearings could allow the mainspring to unwind for longer but that would be using lower torque and accuracy could suffer. I wonder if Eterna used either longer mainspring or one made of a composite.
