Start by creating a large box with flaps sticking out of the middle. This will be used to create the trapezoidal shapes as shown above.
Above shows the approximate size of the box for the correct proportions.
Next, cut a large circle in the middle of the chest. Using bendable cardboard, line the outer rim of the hole.
Next, fill the hole up with cardboard in the design shown above. Add the shoulder pieces using bendable cardboard. The spikes are made with construction paper. Vacuum tubing as added to the front of the shoulders.
Add the exhausts to the rear of the shoulders. Attach vacuum tubing as shown above.