Any increase in capacity of timepiece drive mechanisms is limited by the volume available for the barrels comprising the energy storage springs. The available volume is delimited by the space available in the movement, and thus by the size of the drum incorporating the mainspring, and by the geometry of the barrel arbor which must be sized to transmit the maximum torque safely.
U.S. Pat. No. 3,846,974 A in the name of ETA discloses a barrel with drawn longitudinal grooves, for supporting the mainspring and hook. U.S. Pat. No. 820 252A in the name of PORTER WILSON discloses a similar arrangement.
U.S. Pat. No. 3,846,974A in the name of GIGER discloses a barrel with a very simple cylindrical arbor, having grooves drawn along generatrices, carrying the mainspring and ratchet. The ratchet has an inclined toothing to hold the arbor axially.