Spring preload for traction drive

A method of setting a preload in a planetary traction drive comprising:

• interfacing outer roller traction surfaces of a plurality of planet rollers with a sun shaft;
• assembling a ring roller assembly comprising a ring gear, a sprung traction ring, and a second traction ring;
• interfacing said sprung traction ring and said second traction ring with slanted inner roller traction surfaces of said plurality of planet rollers;
• placing a preload spring between said ring gear and said sprung traction ring that provides a preload force on said slanted inner roller traction surfaces of said plurality of planet rollers during assembly and operation of said planetary traction drive;
• connecting said sprung traction ring and said ring gear through an anti-rotation mechanism such that said sprung traction ring can slide axially on said anti-rotation mechanism wherein said anti-rotation mechanism transmits torque between said sprung traction ring and said ring gear.

A planetary traction drive comprising:

• a sun shaft assembly comprising:
• a center shaft;
• a two-piece traction barrel located around said center shaft and concentric to said center shaft and connected to rotate with said center shaft, said two-piece traction barrel comprising:
• a first traction barrel piece with a first slanted barrel traction surface that is connected to said center shaft;
• a sprung traction barrel piece with a second slanted barrel traction surface that is coupled to said first traction barrel piece through an anti-rotation mechanism that allows said sprung traction barrel piece to slide axially on said anti-rotation mechanism and transmit torque between said sprung traction barrel piece and said first traction barrel piece;
• a preload spring located between said first traction barrel piece and said sprung traction barrel piece that provides a preload force on said first slanted barrel traction surface and said second slanted barrel traction surface during assembly and operation of said planetary traction drive;
• a plurality of double roller planet rollers with outer roller traction surfaces that interface with said first slanted barrel traction surface and said second slanted barrel traction surface of said sun shaft assembly;
• a ring roller assembly comprising:
• a ring gear;
• a first traction ring and a second traction ring located concentrically with said ring gear that interface with inner roller traction surfaces of said plurality of double roller planet rollers.

A planetary traction drive comprising:

• a sun shaft;
• a plurality of double roller planet roller assemblies, each double roller planet roller assembly comprising:
• a sprung planet roller and a second planet roller rotationally coupled together concentrically through an anti-rotation mechanism that allows said sprung planet roller to slide axially on said anti-rotation mechanism while transmitting torque between said sprung planet roller and said second planet roller, where both sprung planet roller and second planet roller have outer roller traction surfaces that interface with said sun shaft, as well as slanted inner roller traction surfaces;
• a preload spring located externally to said sprung planet roller that provides a preload force on said slanted inner roller traction surfaces of said sprung planet roller and said second planet roller during assembly and operation of said planetary traction drive;
• a ring roller assembly comprising:
• a ring gear;
• a first traction ring and a second traction ring located concentrically with said ring gear that interface with said slanted inner roller traction surfaces of said sprung planet rollers and said second planet rollers of said plurality of double roller planet roller assemblies.