Science Buddies: "Ask an Expert"

I am doing a science project based on Grasping at Straws : Making a Robitic Hand. I started to assemble the hand last night but am confused about some of the steps. I threaded a string through each joint and tied it to a ring based on the picture 7a. So for each straw or finger there 3 rings except the thumb which onlyhas 2. I am confused by the final picture on the project shows 6 rings total for each hand. If i continue i would have 14 rings. Am i doing something wrong?

Hi bclampff,

You aren't doing anything wrong - this is a design choice you can make. The project shows pictures for a few different options. Figure 8 shows a single finger with 3 joints and 3 strings (1 to control each joint). However, you don't necessarily need 1 string per joint. You can control a whole finger with a single string that makes all the joints bend at once. That makes the design simpler, but gives you less control over how the individual joints bend (what you see in Figure 10).

In general you don't have to build a hand that looks exactly like the one in our pictures. For some that look very different, see this "STEM Activity" version of the project. This one is written as a "just for fun" activity, so less formal than a science fair project, but the concepts are the same.

https://www.sciencebuddies.org/stem-act ... robot-hand

Hope that helps!

Ben