No rotor means thinner watches and an ultradense weight swinging around a greater radius means a better chance of achieving a greater power reserve with same amount of arm movement. See also Automatic quartz ETA movements Jewel bearing Miyota 8215 Regenerative brake Explanatory notes References External links A visual guide to the gears that make bi-directional winding possible A detailed evaluation of the mechanics of the Seiko 7S26 automatic watch movement Photos of early automatic movements on German watch vendor site, including the Harwood Energy harvesting Transducers Watches