October 14, 2012

New Project: Nyan Hat

For Halloween, I'm making a Nyan Hat, which is pretty much exactly what it sounds like.  The base of the hat will be a blue top hat, with a pixelated rainbow encircling the middle of the cylindrical part of the hat.  A mechanical Nyan Cat, complete with moving head, tail, and legs, will move around the rainbow, on the outside of the hat.  The blue part of the hat will be embedded with white LED's controlled to mimic the star patterns in Nyan Cat.  Finally, built in speakers will play the Nyan Cat song while the hat is turned on.

All the movements of the cat will be controlled by one single motor, so I built a frame for the cat made of of interlocking plates and bushings  that connects the motions of the tail, legs, and head all to one rotation point. 

Technical drawings on a picture of Nyan Cat:

The plates were manually milled out of acrylic (yes, I probably should have just lasser cut it...) and the bushings were made out of brass rods on a lathe.  The head and tail mechanisms are linked to the leg plate.  The vertical slot in the middle of the leg plate is for a scotch yoke mechanism, to convert the rotary motion of a shaft into the back-and-forth motion of the legs.

The poptart-supporting part of the acrylic, which stays fixed relative to the head, tail, and legs, was fixed to an aluminum piece that supports the rotary part of the mechanism.

The bearing that supports the shaft is held in via a clamp, so it can be taken apart:


The Nycan Cat will be moved around the outside of the hat by a low-rpm gear motor in the middle of the hat.  The motor will be connected to an arm that will span the radius of the inside of the hat and connect to the cat mechanism.  As the motor turns, the cat mechanism will roll along a wavy rainbow-shaped track that circles around the hat.  As it moves along the track, the protruding metal cylinder that is linked to the scotch yoke mechanism will rest against the track and act as a wheel, thereby turning and actuating the cat's appendages.

To create the side-to-side motion, a a 4-40 screw was screwed into the aluminum cylinder, slightly offset from the axis of rotation.  As the cylinder spins, the cap of the screw moves the acrylic below it back and forth.

The aluminum arm attached will eventually be coupled to the gear motor:

One last shot of the mechanism:

And a video of it working:

In other news, my scooter seems to have gotten a case of spontaneous motor failure, even though I replaced a dead motor a week ago.  I was riding on flat ground at around half speed when one of the motors became flaky, and eventually gave out.  Unlike the other failures I've had, this time I wasn't doing anything silly like towing a hexapod or full-throttling up a long hill.  It could be that the motor was already near failure, and finally gave out.

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