2 mainspring in serial

[laith]

hello 

i have a question and was wondering how can 2 mainspring directly being conccted in serial ? the way i imagine it is when the first one finsh winding and tehn the second starts then the first one is going to get winded right ?

i am really confused i am would apprecaite it if someone can explain

 

best reagrsds

[nickelsilver]

Are you thinking like the Longines 990/ Lemania 8810? That's a fairly unique movement. There are two barrels, of different size, geared together (the barrel teeth gear into each other). Both barrels also have hollow barrel arbors, with keyways, and there are wheels with arbors that traverse the barrel arbors and key in. So, when you wind, you are winding one of these keyed wheels (or the automatic works wind it). It winds the barrel arbor, which makes the barrel want to turn, and it does, and winds the other barrel up. The smaller of the barrels has a fixed mainspring, the larger has a slipping mainspring, so when the first barrel is fully wound, it continues to wind the second- and when that one is fully wound, the spring slips along the barrel wall like any other automatic watch. The wheel keyed into the second barrel is what drives the gear train of the watch.

 

It's a very clever design, and provides a very even power output for the duration of the running. The keyed in wheels make the barrels effectively motor barrels, as opposed to going barrels, which some feel has certain advantages. Of note, a motor barrel can be made to be a little more "stable" than a going barrel, like Hamilton's motor barrel design. In the case of the Longines/Lemania movement, the part that drives the gear train is the keyed in wheel, which rotates on its pivots like any normal wheel; this is more stable than the short bearing span of a barrel riding on its barrel arbor (going barrel), and probably does contribute to the longevity and stability of the watch. In most iterations this wheel rides in beryllium copper bushings, but in some cases (like Vianney Halter's use of this caliber) it's jewels. Either way the bearing surfaces are easily renewed in case of wear, unlike in a going barrel.

 

Aside from that caliber, most double barrel watches I can think of just have two barrels that are wound simultaneously and also simultaneously drive the center pinion.