Just after I published my book Kinematic Synthesis of Mechanisms with its emphasis on leg mechanisms, I found two more interesting eight-bar legs from the designers at DIYWalkers.com
This is a Geogebra animation of the leg mechanism for the Strider walker. It is a symmetrical design that allows the formation of a second foot assembly by simply adding two more bars.
This is an animation of the leg mechanism in the TrotBot walker.
The animated four-bar linkage FHJD is constructed using dimensions as the quadrilateral ABCD. The dynamic geometry software Geogebra maintains the dimensions of FHJD as the points of ABCD are moved. The result is that the animated linkage changes to match the new dimensions. This can be seen in following Movie. For more information see Kinematic Synthesis of Mechanisms.
Here are the eight Movies in Chapter 6 of Kinematic Synthesis of Mechanisms.
Here are the four Movies in Chapter 5 of Kinematic Synthesis of Mechanisms.
Here are the four Movies in Chapter 4 of Kinematic Synthesis of Mechanisms.
Here are the four Movies in Chapter 3 of Kinematic Synthesis of Mechanisms.
Here are the six Movies in Chapter 2 of Kinematic Synthesis of Mechanisms.
Here are the three Movies in Chapter 1 of Kinematic Synthesis of Mechanisms.
This book is an introduction to the geometric theory used to design linkage systems that are critical components of machines ranging from vehicle suspensions to robot arms. The focus throughout is on graphical synthesis of linkages to control the movement of the legs for a walking machine.
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Increasingly complicated walking machines obtained from patent drawings, art and technology are used to motivate the theory. Starting with legs formed by rotating cranks, we move to legs constructed from four bar linkages with specially shaped coupler curves. This leads to a search for coupler points that have near straight line trajectories, and motivates constructions for the inflection circle and cubic of stationary curvature. We also consider cognate linkages and those with symmetric coupler curves.
The use of an RR chain controlled by the coupler of a four-bar linkage is our introduction to six-bar linkages. Then skew pantographs that provide scaling and reorientation of a coupler curve for better walking movement yields eight-bar linkages. The legs designed by Theo Jensen and Amanda Gassaei are shown to implement four bar function generators that control the joint movement of an RR chain. This leads to graphical two and three position synthesis of four-bar function generators, which are applied to the design of legs with two and three specified configurations.
We end with a description of the duty factor and support pattern needed for two, four and six legged walking machines. The challenge of steering and suspension is left for the future.
R. A. White is the author of Chop Wood Carry Water and Superluminal. He often writes under the pseudonym R. W. Frost. Here is his IMDB page. He is a lecturer in the theater arts program at UCLA, and the director of the Toni Martini Variety Hour.
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RA White and MD101