In the beginning, Aleja and I wanted to create a robot that moves forward in water. We thought of many animals that swims in the water like the ray, frogs...etc. Since the motor had to be out in the air, we thought making a ray was a bit of challenge because it would move the best if it could go in the water. Therefore, we decided to design a frog that has a motion much like human breast strokes. Two motors were to be used for the frog; one for the front arm and the other for the back legs. A off-centered circular was to be attached to the motor, pushing the legs out as it rotates. The push in the back leg would cause it to move forward. The rubber band tied to its feet part would bring the legs back in. The gears for the front arms would be tilted so that the arm moves in and out pushing the water out of the way. We rejected this idea because the we were not sure if the force on the back leg would create enough forward for the whole body to move forward. Also, it was possible that the rubber bands would undo the initial motion of pushing out the water by bringing the legs back in.* * * * * *
Our second idea was to create a rowing boat. It would have two gears that are touching perpendicularly. One of the gears would be attached to the motor while the other motor will have a circular piece above it. The circular piece will be connected to a rowing stick that pushes the water out of the way as the circular piece rotates. There would be a wall that, by the time the rowing stick gets to the rear of the boat, lead the rowing stick into the air so it does not row making a circle in the same position. We created a Lego model for it and it is shown below.
When we made it up with Lego parts, we realized that we will need use a lot of Lego parts when we really should avoid doing so. Furthermore, it would be too much in a circular rotational motion when we had to manipulate the rotational motion into some other motion and have the machine move forward. Therefore, this second idea was rejected as well.
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Our third concept was to create a moving dog in the actual dog steps, which is in the order of left front leg, right back leg, right front leg, and then left back leg. We decided to use the off-centered circular piece to generate the force to move the legs forward. The legs would be connected to a horizontal piece with elliptical holes in the connection, so that the legs would be able to move back and forth. However, we had some problems. Once the off-centered circular piece pushes the front leg forward, then the back leg, it would not move forward anymore because the motor would be staying in the same position as described in the "motion" part in the picture. Therefore, we came up with our second design for the dog, in which the motor itself is connected to the horizontal piece the same way as the legs are attached. On the contrary, the back leg would not have the elliptical hole, but rather would form one piece with the horizontal piece. Instead of using a off-centered circular piece, we decided to use a teardrop-shaped piece. Front leg will still be moved forward first and when the back leg gets a push forward from the rotating teardrop-shaped piece, the whole horizontal piece would be moved forward, putting the motor back to its original position. To rotate the teardrop-shaped rotational pieces, we decided to use rubber bands because making gears with Solid Works seemed to be a waste of time since they do not work very well and because we did not want to use much Lego parts. We rejected this idea because we realized that the legs would be too heavy for the friction between the rubber bands and the dowel to create enough torque for the teardrop-shaped pieces.* * * * * *
Our fourth idea came from the motion of a gorilla as illustrated in the picture above. It was just a simple design because after coming up with first three reasonably complicated designs, we realized that making the machine move forward was more important than the complexity in mechanism. This gorilla robot would move forward by the rotating four arms that would stamp on the ground, lift up the body and swing the body forward. We made a model with form core and the picture is provided below.
We rejected this idea because it was moving almost in a rotational motion and because we decided that it was too simple.
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Our last idea is based on the motion of a hopping rabbit. This design is the one that we decided to stick with because it is not in the rotational motion and is not simple in design. It will have two front legs, the connecting piece on each side, two back legs, and the body part where the motor will be fixed. The two front legs will be connected to the motor along with the connecting piece. They will be tight fit so that they rotate with the rotating part of the motor, which thankfully is a hexagonal shape. We have decided to create the holes into a hexagonal shape so that they have enough torque to rotate. We also have decided to make two types of front legs: a pair of walking ones and hopping ones. The hopping ones are to be longer in size so that they lift the whole body of the rabbit robot (It is illustrated in the pictures below). The front legs will have rubber bands glued on the bottom of it to create friction so that it does not slip off the ground, hopping in the same position. The body part where the motor will be placed will be made up of three pieces: the bottom piece and the two identical pieces as walls. The wall pieces will have two teeth that will fit into the two holes on the bottom piece like puzzles. In between the wall pieces will be the motor. We will use 1/8" for every parts except the two back legs; we will use 3/16" for stability. We will use 1.6mm stoppers to keep the front legs and connecting piece in place. We will use 5/4" long steel alloy dowels to connect the back legs to the connecting pieces. 1/4" dowel pins will be used for the ends of the steel alloy dowels. In between the connecting piece and the back legs, we will put two 3.2mm stoppers to keep the distance. The back legs will rotate 180 degrees to the front. Then, the body part will rotate 180 degrees with the help of the two front legs.
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