The sketch shows a suggestion for an adjustable foot operated treadle drive mechanism, with dimensions related to a typical length of a human foot.
The treadles oscillate, and the motion is transferred to a looped cord, which will, therefore, also oscillate. The drive to the rewheels (which need to move back and forth) can lead off from it (not shown).
The treadles themselves are also adjustable, so that the same movement of the driver’s feet will result in lesser or greater throw to the main drive looped cord, and this variable will allow the Chalopede to move slower and faster.