Flexible rollers can be made with springy or expandable material .

Rollers can also be shaped to be expandable, opening a wide range of possibilities for variable torques and speeds.

Sheet coiled into a roller is used as an icon to represent any expanding diameter roller Fig. 29

Note: more examples of variable diameter rollers can be found in the Link: Thomas Register (pulley, variable diameter)

Expand - increase rolling-friction (ie: brake, speed, governor) Contract - decrease rolling-friction (ie: slip-clutch, load-clutch) Link: Hollow Roller Inserts	Fig. 30
Inversely variable proportional input/output Reverse-coil: as A gets larger - B gets smaller (and vice-versa) (ie: variable speed changer) (band tension stays constant) Rotate in different directions.	Fig. 31
Fixed input = I Inversely proportional outputs Rotate in same direction (band tension constant)	Fig. 32
Orbit to center Note: speed/torque ratio applications need no outer sleeve Rotate in same direction. (See also: Size ratios)	Fig. 33
Orbit to orbit Rotate in different directions. Externally controlled ratios.	Fig. 34