Trash collection is one of the stranger things about this city, from an outsiders perspective. I believe it happens once a week, though I'm pretty certain there've been longer stretches of trash pile up where I live in Bushwick. I'm also suspicious that the neighbours pile their trash near our bins bins since they're behind a fence, out of sight. But I'll give them the benefit of the doubt.. there's bigger fish to fry.. such as the mutant rat that took a liking to our trash this past weekend, and ruined what was supposed to be a relaxing end-of-day cigarette break.. Twice.

And so this final fabrication assignment is dedicated to mutant rat (who has thankfully moved on to grosser pastures).

rat killing plans. one motor driving two shafts, one rotating the other linear. this will get entangled. 

I began with planning the mechanics and movements for my rat killing adventures, taking inspiration from Ben's video of crazy toy translating rotational motion to linear motion. I wasn't sure if it would really work out using just one motor, and sometime after drawing these plans I realized the shafts/joints would entangle.

I found a kit of 6 X [dc motor+switch+battery pack] and some gears and shafts on amazon for $10, which I concluded was a good enough deal.

parts of the kit ordered on amazon

Thankfully, this kit came with a really useful part to connect two shafts at 90deg, which solved the entanglement issue.

connections with T connectors

I used some cardboard to prototype, and tested the motion by moving the disc with my hand, before getting to soldering the connections.

testing motion
motor goes crazy

Once I powered the motor up, it went completely crazy. I tried putting a small load on it to slow it down - a nut with some clay, but it didn't help much.

I decided to leave this problem for later, and went about making the box/enclosure. I first created a neater version of the cardboard with hand, to see how accurate my measurements for this were. And then went on to laser cut, along with some variations to test with.  

top panel variations

The original measurements proved to be the best, but after assembling things and creating the rat head with clay, the load turned out to be too much on the motor. The horizontal shaft I was using for displacing the rat was too long and without support, and the force of the clay at that distance was too much for the motor. So I created a small support for the shaft.

shaft support

I then worked on the clay model for the rats body, carefully mixing pink and gray clay for its tail. I tried various versions of the hammer to get the right weight – just clay, clay + aluminum wire, and finally settled on foam board with a thin layer of clay on top. The end result is a little finicky at times – sometimes the rats head falls too close to the box surface, creating too much friction. Or the body gets too close, absorbing a lot of energy when the head hits it, or the hammer makes contact with the rat....

It would have been nice to figure a mechanism where the actual contact of the hammer displaces the rat's head, perhaps using a spring. Clay is obviously a heavy material to work with so a stronger motor + components would have helped.

dramatic photograph number 1
dramatic photograph number 2