These are 3 different machanical animals. They are all pretty basic mechanical devices that turn rotary motion into more of a linear motion. My kids (and their friends) have gotten a real kick out of them. I drew them all in sketchup.
Jumping Prairie Dog Turn the crank and make the prairie dog jump up and down.
Diving Dolphin Turn the crank and watch the dolphin dive through the waves.
Wood Pecker Turn the crank and see the wood pecker peck away. (This was originally posted as a pecking bird, but my kids all call it the woodpecker, so I'm putting it up as part of this collection).
Hopefully it is fairly obvious how these go together. I print the washers on a raft because the flat surface it creates is nice and helps the various axles seat firmly. Pretty much everything else is printed raftlessly.
Take a look at the other various things I've posted for tips on how I've configued my Makerbot for better raft/raftless printing if you're running a Makerbot.
The part all snap together very nicely for me with a little pressure. I've designed all the axles to be stronger by making them extend through the entire bases they stick out of, rather than just being stuck to the top layer by one interface of plastic. This helps things hold together and if you need to take apart parts that are pressure fit tightly together, you can without breaking things as often. This was a trick I learned when designing the train wheels on an earlier project.
If anything that is suppose to move it tight, you should sand/scrape a little excess plastic off it so that it glides smoothly. These all work very fast/smoothly for my when I turn the cranks.
One tip with printing larger things that I've found in-valuable for my TOM MK6 extruder: The thumbscrew that holds the plastic against the feeder has a tendancy to loosen after 30-40 minutes of running. A simple fix I've found is to put a couple c-clamps on it, or a small vice grips, so that it cannot turn. Make sure there is clearnace for when the z-axis goes up and down (the camps need to move with it). I'll try to remember to post a picture of my rig at some point.