I found some internet photos of wooden hopping kangaroo toys and worked backwards. http://www.boranupgallery.com/gifts/small-gift-ideas/lj/hopping-kangaroo/
I played around with some variations and made a working model of a kangaroo toy. The kangaroo hops really well, with two different legs for a short hop or longer hop. Then I wanted to go a step further and make some other kind of hopping animal toy.... that's when I found out that it is HARD to make even a simple mechanical toy work the way you want it to. After many rabbit body variations and different leg designs - varying center pivot point, body length, leg height etc... more than a page of trial results later, I have a hopping rabbit version that really hops. In hindsight, I learned some key factors to consider for the design of hopping toys - mainly, BALANCE and how far you deviate from your prototype design. Making a duck-bill dinosaur from the kangaroo pattern went a LOT faster than the rabbit - fewer variables to control.
Anyway, here's what I learned, may it help you design your own hopping toys faster and with less effort than I expended.
Video links for completed toys are in steps 2, 3 and 4
Note: this type of toy has small parts which could pose a CHOKING HAZARD, so not for the under-three-years-old crowd
You will need:
* wood 1/2-3/4 inch thick
* optional thin plywood (for legs) - about 1/4 inch thick
* 1/4 inch dowel
* 1/8 inch dowel or bamboo skewer
* 2 washers, center hole a bit larger than 1/4 inch (or axle size).
* scroll saw or hand coping saw
* drill press
* sand paper and files
* paint or other wood surface finish
* wood board, clip board, or book to provide the inclined plane down which the toy hops
Step 1: Inspiration
I first saw a wooden, hopping, toy Kangaroo when we were in Australia in 2008. I can't find my pictures from that trip... so I looked on the internet to find some pictures of kangaroo toys. Here is one. I'm sorry that I don't know where this came from.. it was a few years ago. (Please let me know if you know where this came from ... I'd love to attribute the photo). See this webpage for another example http://www.boranupgallery.com/gifts/small-gift-ideas/lj/hopping-kangaroo/
I kind of sketched the general shape of the pieces, smoothed them out and cut them from wood. The toy worked pretty well. I thought the back leg looked too skinny, so I tried a fatter one, which also worked. The fatter leg produces a 'shorter' hop than the original leg.