I've done a few posts about sand-powered acrobat toys. The falling sand is caught by something that looks like a water wheel, causing it to turn. The wheel is mounted on an axle, one end of which terminates in a small crank on to which an articulated acrobat figure is placed. The spinning axle causes the acrobat to do all sorts of athletic-looking moves. The Junghans acrobat clock shown here works in a very similar manner -- minus the sand, of course. This beautiful piece was restored by the mechanically multi-talented Kevin Wright.
See more restorations and original mechanical creations by Kevin Wright on his web site.