Once upon a time, I found a toy in a store. It's appeal was immediate: a well-made pull-toy for small children that had an interesting action. But it was expensive for its limited "difficulty", and I was sure I could make one myself.
I was right. But boy, I sure couldn't make it for the same expense.
This is the original. The wheels to either side of the "worm" have an off-centre axel that causes the body of the worm to rise and fall as the wheels turn. The body itself is articulated in three places, hinged on small axels.
I hung up the pieces as they dried.
painting the wheels
That's right, I shot it in black and white!
the assembled piece
Clearly, Mari and Kenny weren't home at that time.
the final product
Here's a (surprisingly twitchy) video of the boy pulling the thing. I don't know what Youtube has done with the video, I apologize for that.