When two linked bars are nearly parallel their connecting joint can easily flip orientations and cause the linkage to lock. This phenomena is known as a "Dead Point". Here's an example of what Klann Ver 1 experienced, since it used a configuration of the linkage where the "shoulder" joint came close to being straight :
The below right picture is near the Dead Point, where two bars highlighted in red are nearly parallel:
Due to the force on the foot, the joint can "flip" as shown below, which causes the linkage to lock::
Linkages need to prevent joints from ‘flipping' at these Dead Points. Below are a few ideas to prevent joints from flipping in LEGO builds.
This solution for Klann Ver 1 simply blocked the joint from flipping by the addition of a 2-hole red LEGO beam:
As shown below, Strandbeest's knee joint can also flip:
Strider also has a dead point that needs to be managed:
The below solution uses an additional linkage on the inside of the joint that allows the joint to bend toward the robot, but prevents bending away from the robot. Note: Strider Ver 2 blocks the joint from flipping with a LEGO pin.
Welcome to DIYWalkers! My name is Ben Vagle, I'm 17 years old and I've been building mechanical walkers for the past 5 years. I started this blog to share what I've learned, and to collaborate with you. Let's see if we can take walkers to the next level!