Here is a simple running robot. You can easily make it for your own. It has two C wheels made from PVC pipe driven by one single geared DC motor. It is actually hopping between the steps. See the slow motion part. Its motion is like Kangaroo.
Electrical Connection- The motor ( RPM-100) is connected with a switch in series. It is power by a 3.7V , 240mAH, Li-Po battery.
Step 1: Video Instruction
This video has shown the step by step making process of this running robot. Hope you will love making it.