waspy,
the diagrams show that the device will make linear motion, not force, from the rotary motion applied. There is no net force produced by the machine, as every mass it moves is countered by a return movement.
Another thought experiment:
Take a large rocket, and fly it into a great big bag, then tie the bag shut. Will the rocket still climb?
No, the gases blown out the back of the rocket will strike the back of the bag, and produce enough momentum capture opposite the rocket thrust to make the whole rocket-bag system just stop in the air (as the expanding gases inflate the bag so very tight that it would like to explode.)
In effect, Jiff's mechanism grabs all the stuff that was accelerated backward, and by stopping it, cancels the net force.