Design

We began by researching several mechanisms that could function as the rope gripper. Knowing that we wanted the device to be powered by an electric motor, the mechanism would also have to be able to incorporate a rotary source motion.

Figure 1: Robot gripper mechanism 1

Figure 1 above shows a, 8-bar robot gripper mechanism. The simultaneous and parallel motion of both arms of the gripper would allow a user to align its center with the rope and have the arms close upon it.

In order to build a prototype of the mechanism as a proof of concept, we had to make some modifications with its design. The original piece had the slider move two contact links. However, due to the known difficulties of proper slider contact, we redesigned the slider and the contacts into pin joints. Figure 1 below shows the SolidWorks model of the mechanism below.

Figure 2: Initial mechanism model

Manufacturing

To manufacture the mechanism, we used 1/8th inch acrylic and a laser cutter to cut the various links as designed in the CAD files. A combination of bolts and nuts were then used to replicate the pin joints. The constructed mechanism is shown in Figures 3 and 4 below.

 Figure 3: Closed view

Figure 3: Open view

From the proof of concept mechanism, we noticed several action items that would need to be addressed in the upcoming prototypes. Firstly, a rotational to linear motion mechanism such as a crank slider will need to be added to properly use the motor input. Next, in order to better grip the rope, a proper grip will need to be added. In this case, foam was added to the base of the grips. Lastly, while bolts allow for quick prototyping, the rotation of the bolts while the links rotated caused for the nuts to be loosened.