One of the simplest methods of activating a toy is to mount it on a wheeled base which has one pair of wheels fastened off center. In the case of the Hopping Kangaroo in Figure 2.9, the rear wheels are both mounted on axles which are about J in. from their true centers, so that when the toy is pulled forward an amusingly realistic hopping motion results.

The figure of the kangaroo can be jigsawed from any available plywood scrap, or scissored out of one or more layers of stout cardboard. The ears of the silhouette shown in A of Figure 2.9 are cut from tan felt and tacked on to prevent damage to tender fingers. The 3/8-in. tab (C) at the bottom of the feet is glued into a slot in the center of the base.

The latter is 5 1/2 in. long by 2 1/4 in. wide, and can be 1/2 in. thick; the one illustrated in profile B is 3/4 in. thick because there are often more scraps of this dimension available around the home. Wheels of 2-in. diameter are cut from any convenient stock and mounted between washers on nails or screws driven horizontally into the edges of the sides of the base. Both rear wheels are mounted about 1/4 in. off the true centers on holes large enough to insure against binding.

Fig. 3.9. Animated kangaroo.

It should be noted that with this type of axle mounting, unless both rear wheels are at the same point in their eccentric orbit, a waddle, rather than a hop may sometimes result. To insure a hopping movement at all times, both wheels can be fastened firmly to a revolving axle which rotates in bearings fixed to the base by any of the methods described in later toys. Sometimes the surface over which the toy is pulled is unusually smooth, in which case it may be necessary to provide traction by gluing flat elastic bands or pieces of inner tubing to the edges of the rear wheels, like tires.

Paint the kangaroo tan, the base green, the wheels red, and provide a screweye in front for the pull cord. If the young owner voices a preference for rabbits or squirrels, it should not be difficult to find a suitable magazine illustration, mark squares on it, and substitute a rabbit or squirrel silhouette for the kangaroo; or make a second toy in the same manner.