Removing Protective Shells

When to remove shells

In general, the shells should only be removed when specifically called for by a page on this wiki or by support personnel. The exception to this is the rear shell, which protects the battery and will need to be removed to access the battery for charging.
NOTICE: All shells should be properly installed at any time the robot is standing or walking

Front Shell

The front shell protects the battery, and is attached to the pelvis by three spring-loaded latches, indicated by the arrows in the picture above. To remove the shell, press the unlocking lever on the top of each latch, and pull up on the latch handle. NOTICE: when replacing the shell, make sure that the battery cables are clear of any pinch points

Shoulder Shells

The shoulder shells protect the abduction and yaw gimbal assemblies, and are attached to the pelvis by four M6x8 button head screws each (8 total), as indicated in the picture above. The shells are not symmetric, but they will only fit on the robot in the correct configuration, so it is impossible to install them backwards.

Rear Shell

The rear shell protects Cassie's core processing and power distribution electronics, and is attached to the pelvis by four M4x12 button head screws as indicated in the picture above. There should be no reason during normal operation to access these electronics, so the shell should remain in place at all times. If a troubleshooting procedure calls for removal of the rear shell, when replacing it make sure that no wires are pinched between the shell and housing.

Thigh Shells

The thigh shells protect the aluminum electronics housing on the thighs, and are attached by a velcro strap, as indicated in the picture above. Note that the strap fits around the stator housing, between transmissions for the hip and knee, not around the entire thigh assembly

Shin Shells

The shin shells protect the knee joint and shin carbon fiber tubes, and are clamped around the shin assemblies by 8 quarter-turn plastic fasteners as indicated in the picture above (4 fasteners are on the other side of the leg). The shin shells are most commonly removed to perform the calibration procedure, and should remain in place in all other situations.

To remove the shell, pop the plastic fasteners out with a flat-head screwdriver as shown in the picture below. Once the fastener head is out as far as the picture indicates, the whole fastener should easily slide out of hole. Once the fasteners are removed, the two halves of the shell should pull apart and can be removed.

To replace the shells, place both halves around the shin and line up the plastic tabs with the fastener holes on the other half. Make sure that all four plastic tabs go underneath the other half of the shell. Push the fastener housings through the holes, and when it is fully seated, press the head in until you feel a click. You may need to twist the head slightly to find the place where it snaps in.

Tarsus Shells

The tarsus shells protect the tarsus carbon fiber tube and the toe output crank, and are clamped around the tarsus and toe actuation assemblies by 4 quarter-turn plastic fasteners and a zip tie as indicated in the picture above (the zip tie is not pictured, and 2 fasteners are on the other side of the leg). There are no normal maintenance tasks that require the removal of the tarsus shells, so only do so if instructed by Agility support personnel.

To remove the shell, remove the plastic fasteners as per the instructions above, and remove the zip tie. The top half of the shells is most easily removed with the leg in its fully extended state. To remove the bottom half of the shells, the toe connecting rod must be disconnected at the toe. Note: this is the one of the very few components on the robot that are non-metric, so be sure to use a 1/8" Allen key to remove the shoulder screw. NOTICE: Take special care when removing and replacing the shoulder screw, as misalignment can cause binding and damage to the tapped hole. Once the toe end of the connecting rod is disconnected, flex the leg up to more easily remove the bottom half of the shell. The shell will have to be deformed with some force to fit around the carbon fiber spring.