Over the past few weeks..

We have finally finished testing all the different balls and trying different way of slicing the balls so that they stay securely on the chain.

Unfortunately, all the balls except the Wiffle ball had major issues staying on the chain and not popping off under the pressure of our "drop test".

Here is a Pugh chart that summarizes our conclusions:

We were therefore forced to add another component to our design - that kind of ruins the simplicity of the idea - which is velcro. The addition has helped the ball stay on the chain and so it actually works now, which is great.

We glued velcro on to the racquetball, bouncy ball, and Wiffle ball. We then took a trip to CRI for feedback. They seemed to like the Wiffle ball, but didn't think it would be sturdy enough to withstand repeated drops. They liked the pliability of the racquet and favored it. However, after further testing we confirmed that the racquetball was too easily ripped at the holes and would not work. 

Wiffle ball testing at CRI

We decided to run with the Wiffle ball, since it was the only one that could hold up. Since CRI didn't like the "feel" of the ball, we experimented with different textures to make the plastic Wiffle ball seem more like a rubber ball. However, the PlastiDip we used to coat the ball was messy and took away from the aesthetic of the original prototype.

We asked Larry about the best way to attach the velcro to the ball and he suggested we glob a bunch of glue-gun glue onto the velcro strip and then press it onto the ball until the glue squirts out the sides. Then when the glue dries, cut off the access with a Xacto knife. This method worked great, and we have clear edges now. 

Our presentation is ahead, and we are almost done making 6 replicas of our final prototype!