Instructables

Step 6: Beak Mechanism

Picture of Beak Mechanism
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The beak mechanism is the “creme de la creme” of RoboBrrd. To illustrate its elegance in words, the beak mechanism allows for the two beak halves to open at once, rather than lifting one half of the beak.

To begin with the beak mechanism, we first have to mount the servo for the beak. This should be placed in the middle of the back left platform. We will then attach a 4-point servo arm to the servo and glue on the popsicle stick arm. The popsicle stick arm should have a hole near the end, and it should also be securely glued onto the servo’s servo arm.

We will thread the beak halves with a 10cm piece of coffee stir stick. Now, in order to make the rotation of the beaks on these coffee stir sticks about a more central fulcrum, we need to cut some small ‘blocker’ pieces that will stop the beak from falling. There should be a couple of millimetres of clearance between the blocker and coffee stir stick.

Next, we need to mount this coffee stir stick to the face. Sometimes adjustments have to be made, so it is better to first measure everything and temporarily mount them with sticky tack.

When both halves are mounted onto their coffee stir sticks, you should ensure that there is enough room to open and close the beak. The gap between the two beak halves should be a little less than 1cm. When testing this, it is important to be rotating the beaks about their fulcrum, which will be closest to the back of the beak where the vertical popsicle stick is. The blocker that was just mounted should be assisting you with this.

Now we have to measure the length of the axels that connect the beak to the popsicle servo arm. To do this, it is critical that the popsicle servo arm’s hole is located directly where the middle of the two beaks will be.

To measure the length of the axels, take a blank popsicle stick and hold it on the beak where the hole is, and move the other end to where the popsicle servo arm is. Draw a line for where the axel should be cut. If this is done correctly, they should be the same (or very close, within a few mm) length.

Poke holes in each end of the axel and attach them with some solid core wire to the beak and popsicle servo arm.

Test the mechanism by manually moving the servo. You should check and see if the beak is able to smoothly open and close. If it does not, see where the modifications need to be made. Usually it is something blocking something else from moving.

When the testing is complete, you can remove the sticky tack from the coffee stir sticks and mount them using hot glue.

Next, we need to prevent the beak from moving horizontally. We will use small coffee stir sticks mounted vertically to assist with this task. They should be placed about 1cm apart from the center to allow for some wiggle room.

As always, test the mechanism to ensure that it is working properly. To make the wires not come unraveled, loop them tightly to the popsicle sticks and use hot glue to keep the windings secure.

In programming the beak, it will be important to properly set the boundaries for this servo for the open and closed positions. Doing so will ensure that we are not going to cause any accidental damage on the front face.
 
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