Wednesday, September 10, 2014

The Making of Gertie - Part 3: Engineering the Jump

The next challenge was to create the right springs for Gertie's hopping mechanism. They would fit in between the leg and the servo. The springs would compress as Gertie landed from his first jump, storing some of the energy as potential energy, that could be released on his next jump. This would improve the height of Gertie's jumps, while taking some of the stress off the servo motors as well.

In the end, I was unable to find the right springs for my needs: ones that had the right strength/resistance and diameter. I decided to make my own springs, so that I could make them to my exact specifications, using the music wire below:

To create the springs, I created a wooden jig, after some trial and error--and eventually got some great results! To research spring-making, I referred to this immensely helpful website: How to Make Springs. The spring-making jig I created was different from the designs on that site, but I was able to leverage many of the concepts they described. I'll go into more detail on my particular jig, and how it works, in another post!

Here you can see the springs attached to Gertie's legs, and assembled as a bare skeleton! This was one of the first working iterations, and it was very exciting to finally see all the pieces together.

Here is a video of Gertie jumping for the first time, and the delta kinematics at work:

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