Mechanical Design

The mechanical component of our device contains a gear motor with an interface with Lisa’s original joystick mount. This interface consists of an aluminum part (see below) to transfer the motor torque to the bar of her joystick mount and a steel fixture (see below) to mount the motor onto the wheelchair part. Here are the CAD models for each: aluminum part, steel fixture

Left to right: aluminum part that rotates the arm; steel fixture to mount the motor onto the wheelchair

The motor we used is a Cytron 12V 17RPM 194.4oz-in Spur Gearmotor that was purchased. We also purchased a mounting bracket to assist in attaching the motor to the joystick mount.

The aluminum part was machined from 1” Aluminum 6061 Extruded Bar stock. First, the stock was milled to create a 1”x1”x1” cube. A ½” end mill was used to cut a centered .52” wide groove, .375” deep to fit around the bar of the joystick mount. A .325” deep, hole ½” in diameter was then drilled through the center of the groove to fit around the nut that holds the bar in place. Subsequently, a hole was drilled to fit around the motor shaft, which is 6mm in diameter. To connect this part to the motor, a set screw hole was drilled and tapped to accommodate a set screw of size and thread 8-32.

The motor was attached to the joystick mount using a simple bracket made from 1mm thick, steel sheet metal. This was attached in between the rotating bars and the frame of the mount, allowing the bars to have free rotation, while still allowing the motor access to them.

The mechanical system, including the motor, interface with the joystick mount, and motor mount.