Extra Simple Walking Mechanism

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I’m a mechanical engineer, and I have a technical degree in precision mechanics (mill and lathe),...

Intro: Extra Simple Walking Mechanism

For a college course I was required to build and analyze a mechanism, so I decided to make a walking mechanism, because since I had a LEGO Technics I always wanted to make a walking robot but I was never successful. Now with a lot more of knowledge I made it happen.

Step 1: Designing

     When you investigate a little bit about walking mechanisms the first thing you might find is the “Strandbeest” from Theo Jansen. It is a great design but is more complicated that what I was looking for.
     I then found a cartoon sequence that shows how to draw a character walking. Observing this cartoon I notice that the walking action follows kind of a drop form, and I remembered that some 4 bars mechanisms did this shape, so using a program named “4 Bars” I searched for the best option for my purposes.
     Wanting to make my walking “bug” very stable I decided that the best way to accomplish this was with a tripod, so I need to make a six legged “bug” so at all times there will be at least three legs on the floor. I also didn’t wanted to use chains or belts to drive all the mechanisms, so I try what is called a symmetrical mechanism and make that one mechanism drive the next one and so on. So I ended with four identical mechanisms in each side that needed just one axel to drive one mechanism in each side.
     Later I draw it on Inventor to solve some constructions issues, like how to connect everything together in a way it wouldn’t be so bulky and didn’t interfere with each other. Then I built it with LEGOs and notice that the step couldn't be very hight because it requiered more power from the motor.(For a more detailed way of how I design it you can send me a message or post a comment)

Step 2: Construction and Assemble

      The construction was really easy because all the parts were almost the same. I print out the blue prints for the design I made in Inventor, and make all the parts using a press drill, a file and a welding machine. For the connection between the motor and mechanism I used a combination of endless screw and straight teeth gear. I had the gear from an old remote control car, the endless screw I made it on the lathe, and the motor I took it off a can opener because I wanted a slow and powerful electric motor.
     I feel more comfortable working with steel because of my background in precision mechanics, that’s why I used a square steel bar to make all the parts.
     The easier way I thought of making the connections between all the bars was with rivets. I just put a piece of tin in between the pieces I wanted to assemble, so when I removed the piece of tin there will be a gap that allows the movement of the parts.

     Here is a video of the mechanism working. It goes pretty slow but it gives you time to appreciate the complex of the movement and the beauty (that’s how I feel about it) it has.

Step 3: Finishing Touches

    I add on top of it half of a water bottle to make it look like a beetle, and give it more of a bug feeling. Later I paint it green, and this is the final result.
    Hope you enjoyed this Instructable, and if you have any question about anything feel free to send me a message or post a comment. And thanks for “watching”.

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    25 Discussions

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    AkshayP64

    2 years ago

    Hi, I am about to start making the working model of this mechanism. Can you please provide me with the dimensions of the links and materials used.

    I will be grateful if you provide me this information. Thank You!

    2 replies
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    fado1986AkshayP64

    Reply 2 years ago

    Hi, you could make it of any size you want, and of any material you have. The thing is that the size will be very influenced by the material you use, and you have to keep the size relations. In my case, if I recall correctly, I used 1/4" AISI 1020 square bars, and they were 8 cm long.

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    AkshayP64fado1986

    Reply 2 years ago

    Thank you sir for your response.
    I think the sizes of links will matter. because if we fix the lengths of any two links; crank and coupler, then for obtaining the same path travelled by the legs, the positions of fixed pivot get displaced from the horizontal line. In my case, front and back leg were following the path correctly but when I placed the middle two links, the mechanism became a structural member.
    But at last, I was able to design the working mechanism.
    Thank you

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    nqingru

    2 years ago

    Hi, I'm learning 4 bar linkages and mechanisms right now in school, and your mechanism is awesome! (: I was just wondering what you meant by a "symmetrical mechanism" such that "one mechanism would drive the next one"?

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    fado1986nqingru

    Reply 2 years ago

    Symmetrical means that if you cut the figure "draw" by the leg in half in a vertical axis, one half is the mirrored image of the other one. This is accomplish by having the same length from the driver bar to the center of the leg as from the pivot of the leg to the center, and well, the leg have to be twice as long for it to work. Sorry if this part doesn't make many sense, but it's been a while since i last wrote in English and I founded hard how to explain it. You can found more about four bar mechanism in a text book from Robert Norton. Thanks for your comment .

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    sarowie.

    2 years ago

    Nice simple mechanism. I would not want to ride a vehicle with this linkage, but it is one the simplest walking mechanism I am aware of.

    https://commons.wikimedia.org/wiki/File:ExtraSimpleWalker.gif

    ExtraSimpleWalker.gif
    1 reply
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    fado1986sarowie.

    Reply 2 years ago

    Thanks. And thank you for making thus great animation.

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    ppanchal1

    3 years ago on Step 2

    Could you be more specific about the drive mechanism?

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    rimar2000

    5 years ago on Introduction

    Esto se define con cinco palabras: ¡es pec ta cu lar!

    Si lograras reducir la reducción (valga la redundancia) sería más notable todavía.

    Felicitaciones.

    6 replies
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    fado1986rimar2000

    Reply 5 years ago on Introduction

    Gracias!!! Vieras que he tratado de hacer que vaya más rápido, pero para hacerlo tengo que cambiar las relaciones en los engranajes, y en este momento no tengo las herramientas para hacerlo. En una parte lleva un tornillo sin fin y he intentado hacerlo de dos entradas, pero por el diametro y el paso que tienen no engrana bien con el engrane de dientes rectos... Pero estoy analizando otras opciones. De nuevo gracias, y en especial por darme mi primer "patch".

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    rimar2000fado1986

    Reply 5 years ago on Introduction

    Es muy difícil, si no imposible, cambiar la relación de un reductor a gusano. Pero como tú no manejas en este caso grandes fuerzas, podrías arreglártelas con un par de poleas de madera o plástico y una banda de poliuretano de 3 o 4 mm de diámetro. Esas bandas son baratas y muy fáciles de trabajar.

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    fado1986rimar2000

    Reply 5 years ago on Introduction

    Que buena idea lo de las poleas. Podría intentarlo sin modificar mucho lo que ya tengo, y pudiendo regresarlo sin problema. En cuanto a la fuerza, vieras que en realidad si es considerable. El peso de todo el mecanismo es de 2kg, y en los cálculos que se realizaron como parte del proyecto, se observan picos de fuerza debido al movimiento oscilante (hacia arriba y hacia abajo) propio del movimiento, que si eran considerables. Pero creo que si se le podría demandar un poco más de potencia al motor.

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    rimar2000fado1986

    Reply 5 years ago on Introduction

    Yo estoy con el mismo problema, haciendo un pequeño molino de bolas. Intenté conseguir un motor viejo de limpiaparabrisas, sin mucho éxito. Me querían cobrar 150 pesos (unos 20 U$S) pero me pareció demasiado. Lo bueno de esos motorcitos es que ya traen el reductor incorporado y están preparados para funcionar todo el día sin recalentarse. Usé uno de un levantavidrios de auto, pero a los 2 o 3 minutos de funcionar se calentaba bastante. Finalmente usé un motor de ventilador de pie y una polea hecha con MDF (Fibrofácil). No lo puse a trabajar por horas todavía, pero por lo menos en un rato no se calienta, creo que va a aguantar.

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    fado1986rimar2000

    Reply 5 years ago on Introduction

    Que bien! Espero que el motor de ventilador te funcione.
    Me imagino que como muchos otros motores de ventilador que he visto, este debe de ser de jaula de ardilla. Si se te llega a calentar, le podrias soldar unas aletas a la carcaza, y colocar un pequeño ventilador en el otro extremo del eje del motor para ayudar a enfriarlo.

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    rimar2000fado1986

    Reply 5 years ago on Introduction

    No tengo idea acerca de eso de jaula de ardilla, pero el ventiladorcito ya se lo agregué. Iba a incluir una foto pero el editor no le hace caso al botón Add Images.

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    fado1986archerdraven

    Reply 5 years ago on Introduction

    Jajaja. There was a plan to make it larger, about 1m height, and use human power to move it (bicycle pedals), but we needed a bigger budget...
    Thanks for the comment.