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)
<p>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. </p><p>I will be grateful if you provide me this information. Thank You!</p>
<p>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&quot; AISI 1020 square bars, and they were 8 cm long.</p>
Thank you sir for your response.<br> 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.<br> But at last, I was able to design the working mechanism.<br>Thank you<br>
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 &quot;symmetrical mechanism&quot; such that &quot;one mechanism would drive the next one&quot;?
Symmetrical means that if you cut the figure &quot;draw&quot; 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 .
<p>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.</p><p>https://commons.wikimedia.org/wiki/File:ExtraSimpleWalker.gif</p>
<p>Thanks. And thank you for making thus great animation.</p>
<p>Could you be more specific about the drive mechanism?</p>
Me encanta. Dejalo as&iacute; de lento. Parece un camale&oacute;n
<p>Gracias!!! Aprecio mucho tu comentario :D</p>
Esto se define con cinco palabras: &iexcl;es pec ta cu lar! <br> <br>Si lograras reducir la reducci&oacute;n (valga la redundancia) ser&iacute;a m&aacute;s notable todav&iacute;a. <br> <br>Felicitaciones.
Gracias!!! Vieras que he tratado de hacer que vaya m&aacute;s r&aacute;pido, 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 &quot;patch&quot;.
Es muy dif&iacute;cil, si no imposible, cambiar la relaci&oacute;n de un reductor a gusano. Pero como t&uacute; no manejas en este caso grandes fuerzas, podr&iacute;as arregl&aacute;rtelas con un par de poleas de madera o pl&aacute;stico y una banda de poliuretano de 3 o 4 mm de di&aacute;metro. Esas bandas son baratas y muy f&aacute;ciles de trabajar.
Que buena idea lo de las poleas. Podr&iacute;a 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 c&aacute;lculos 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 podr&iacute;a demandar un poco m&aacute;s de potencia al motor.
Yo estoy con el mismo problema, haciendo un peque&ntilde;o molino de bolas. Intent&eacute; conseguir un motor viejo de limpiaparabrisas, sin mucho &eacute;xito. Me quer&iacute;an cobrar 150 pesos (unos 20 U$S) pero me pareci&oacute; demasiado. Lo bueno de esos motorcitos es que ya traen el reductor incorporado y est&aacute;n preparados para funcionar todo el d&iacute;a sin recalentarse. Us&eacute; uno de un levantavidrios de auto, pero a los 2 o 3 minutos de funcionar se calentaba bastante. Finalmente us&eacute; un motor de ventilador de pie y una polea hecha con MDF (Fibrof&aacute;cil). No lo puse a trabajar por horas todav&iacute;a, pero por lo menos en un rato no se calienta, creo que va a aguantar.
Que bien! Espero que el motor de ventilador te funcione. <br>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 peque&ntilde;o ventilador en el otro extremo del eje del motor para ayudar a enfriarlo.
No tengo idea acerca de eso de jaula de ardilla, pero el ventiladorcito ya se lo agregu&eacute;. Iba a incluir una foto pero el editor no le hace caso al bot&oacute;n Add Images.
...Can i ride it?
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... <br>Thanks for the comment.
great design!
Thanks ;)
I tried to make it move faster, but it presented two problems. The first one was that the whole thing was skipping rather than walking. The other problem was that as it is all made of steel, it is pretty heavy and to make it move as fast as it was required a lot of power. The electric motor was consuming 30 amps at 7.2 DCV!!! I have tried to gear it up to something in between but I don&rsquo;t have the tools to make it happen. <br>To answer you other question, as it is it can&rsquo;t steer. You will have to put on a second motor, so you could control each side individually, so you could steer like tanks do. But it would be a lot of trouble, and the original idea was to make it as simple and reliable as possible. <br>THANKS FOR YOU COMMENT!!!
That's a nice smooth action - have you tried gearing it up to move more quickly, <em>and can you make it steer?</em>

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Bio: I’m a mechanical engineer, and I have a technical degree in precision mechanics (mill and lathe), but my interests and skills go a lot ... More »
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