From Team 449 Wiki
Encoders (rotary encoders) are devices that measure the angular position or rate of a shaft. Team 449 typically uses optical encoders, which use one or more light sources (typically LEDs) pointed at a code wheel (either stripped or slit) and two detectors that are 90 degrees apart. Based on the phase difference between the signals is used to see what the leading signal is, which helps to detect the direction of rotation.
Skewed Surgical Tubing Mounting
In previous years, Team 449 has used short sections of surgical tubing to couple the encoders shaft to the shaft whose rotation was to be measured.
This method allows significant offset between the two shafts, since the surgical tubing is very flexible. This features is convinient when mounting the encoder on a non-static axle.
This has been used in previous years, including ROUS (2016). When driving axles from a gearbox using chains, the non-driven axles are often mounted on movable Versablocks so that the chain can be tensioned.
This method is highly inadvisable as the wobble caused by the offset result in significant oscillation in the encoder output, making any control loops that use the encoder output much less accurate and effective.
These are flexible metal cylinders that can be coupled to the encoder on one end and the shaft on the other via set screws. Use these whenever possible.