repetitive impulse not working

i am trying to create a simple 3d creature that moves by pushing itself forward by force applied, like in the video below (second 46). I tried to solve this by adding an impulse/addforce on the limbs every second, but it didn’t work out as expected, since impulse/addforce were only applied once. I would also be open for another ideas on how to solve the movement problem.

My blueprint for adding force (also tried with impulse):

thanks in advance.