Hi In the newer Technical Guide from 2013 the power reserve for the caliber 550 is mentioned to 38h. The Ranfft movement guide states 50h. Quite a difference, my own experience is in the higher 40h's. 38h seems quite low i think, is it correct or a misprint? Was it also 38h in earlier Technical Guide's or has the powerreserve been lowered? Thanks.
I always understood that, with the advent of the seven revolution spring, the reserve on chronometer versions to be 50 hours. Maybe on the 17 J base calibre they used a different mainspring?
I would have to go digging around in my workshop to find earlier technical guides, but I'm certain I lifted the reference of 50 hours from an early technical guide when I wrote essays on movements. Can't think what has changed, perhaps different mainspring for later parts supply. Maybe Archer could offer an opinion? Cheers Desmond
Just checked Kreutzer in Omega Designs who also lists 50 hours....p179. Also Hampel, Automatic Wristwatches, P 242, shows 50 hours for chronometer grade cal 551/561/564
I would caution that the Ranfft site, while a valuable resource to many, is not always accurate. Omega officially lists the power reserve for all of the 55X, 56X, and 75X family as 38 hours. These all use the same mainspring. Keep in mind that companies often list the power reserve as being shorter than some watches can run. I just had this same conversation not long ago on WUS, but referencing the PR he has listed for the ETA 2892 and the Omega 1120. The number of hours listed by Ranfft for the Omega were not what is officially listed as, so I have no idea where he comes up with these numbers. Cheers, Al