Many things can change quickly in this business. This job started out as a body falling down a guide wire (later removed in post production) head-first into frame and into the ground. We were told that the body would travel ten maybe twelve feet, tops- from out of frame above, and down into the dirt. To really achieve the effect of burying his head deeply in the ground, we built a bungee mechanism that would trigger the instant the dummy's head hit dirt and pull the hollow rubber head all the way into the chest cavity. We didn't hear until a few days before shooting that they decided it would be more dramatic to tilt the camera up and have our dummy travel more like 200 feet down the wire into the ground. Good call, yes- this created a much more dramatic shot; it just made for more drama for our work too, to make sure we could adapt and make the changes in time. A fall from that height provides plenty of force for pushing a head into a chest cavity, so a mechanism to pull the head into the chest was no longer neccessary at all. We reversed our bungee mechanism, so instead of initiating the head collapse, our mechanism served as a shock absorber to even out the force of the impact.