Initially, I had the intention of creating a model from the Karakuri book. After looking through it, I got inspired by the following model:
Figure 1: Walking Beagle [ 1 ]
I liked the idea of using gears to provide the rotating motion for links to move and make an object seem like its walking. Since this model had already been done, it seemed a little too simple for me. I wanted to challenge myself mode by exploring alternative designs and configurations, but still keep the same inspiration. I decided to look into link configurations in order to get a better understanding of how one could make a walking mechanism out of links and joints. I found the Klann linkage configuration and decided to learn more about its mechanics. With the Klann linkage, the leg is in contact with the ground the same amount of time that the other leg is off the ground, like a human that is walking or a horse that’s trotting. The leg pairs would look the same but have a crank angle offset of 180 degrees. Making one leg be in the opposite position as the other one. Similarly to how we walk and usually have one foot on the ground as the other foot is moving forward in the air. The way that the linkage works is by utilizing one of the links as the crank of a 4-bar mechanism. This actuating circular motion of the crank then causes a rocking motion at the opposite ends of the other grounded links. The combination of these two rocking motions allows the biggest link (the leg) to alternate its position and move back and forth in order to produce the walking motion.
Figure 1: Klann Linkage 2: Klann Linkage [ 2 ]
I wanted to make something that utilized this linkage system and used some stuff from the book. I went ahead and made 2 pairs of these Klann linkages in order to maintain the most balance. Initially, I thought about making the walking mechanism have four legs like a horse. But then I recognized that synchronizing all of the legs to be in the right place and distributing the motion to the front and back of the model would be rather difficult to do, especially with the materials being cardboard and cardstock. So I modified the order and made all of the links be aligned on the same axis so that there will always be two feet touching the ground and up in the air. To make sure this wouldn't just topple over, I decided to add a pair of supporting wheels in the back.
Figure 3: Organization of the Model
In order to distinguish between which leg was supposed to be on the ground and in the air, I labeled them X and Y. Therefore, in this configuration, the two middle Y legs will always be synchronized and have the opposite position as that of the X legs on the outside.
References:
[ 1 ] Saka, K. (2007). Karakuri: How To Make Mechanical Paper Models That Move. New York, NY: St. Martins Griffin.
[ 2 ] Mechspdcm. (n.d.). Mechanical Spider. Retrieved from http://www.mechanicalspider.com/