Piston Cuckoo Clcok

Group: Chan, Deb, Michael, Søren

Description

Our group was very intrigued by the idea of reciprocal motion, that is, converting rotational energy in a single direction, to back and forth motion along the same axis.  Originally we intended to do this with a reciprocal rack and pinion gear cut from cardboard (http://robives.com/mechanisms/recip#.UVuuzKt35fE).  This would allow us to use a DC motor, spinning in one direction, to drive a sled back and forth.  The sled pushing the doors open, and pulling them shut (via strings attached to the sled and doors).  The bird would then be mounted on the sled.  Cardboard wound up being poor material for gears, so we needed to figure out another method of moving the sled back and forth.  Still liking the idea of reciprocal motion, we chose to implement a piston (http://robives.com/mechanisms/piston#.UVuvoat35fE).  

The piston provided some new challenges.  In order for the rotational motion to be transferred to linear motion, the motion of the sled had to be restricted, such that could not swivel side to side or twist.  If the resistence to those types of motion was not high enough, the sled would twist or swivel instead of sliding forward and back.  We solved this problem to building walls for the sled to ride inside, akin to the cylinder for a cars piston.  This worked fairly well. The final problem, which we did not overcome, was fixing the armature to the motor's shaft in such a way that did not break the armature, but still provided enough friction to keep the motor shaft from simple spinning.  A gear on the motor shaft, and inside the armature would allow for this, but requires more precise tools than we had access to.

Materials

Shoe Box - for base and top

sled - we used a piece of metal with holes in it

tongue depressors - for armatures

soldering iron - for burning holes in armatures

nuts/bolts - hardware to assemble armature 

a bird to put on the sled

string - to pull the doors closed