Introduction to Pneumatics for Home Haunting
Lesson 1
Air Cylinders
Of all components encompassing the spectrum of pneumatics in haunting applications, air cylinders are by far the most easily recognized. Air cylinders are the most commonly thought of item when regarding a pneumatic prop. The use of air cylinders in haunting is limited only by the imagination of the haunter. Applications range from a cylinder in a vertical position with a mask at the end for a simple "pop-up" to an elaborate multi-positional creature with flailing arms and rotating head. Regardless of the design, the basic principals and materials used are the same.
Let's begin with what an air cylinder is: A pneumatic linear actuator that is driven by a pressure differential in the cylinder's chambers. Compressed air is introduced into the cylinder which forces the rod contained within to either extend or retract.
A cylinder is made of several components, but we will focus on only a few. Here are some parts and terminology to get started:
Rod: the linear actuator that is housed within a cylinder.Port: orifices in the cylinder through which media (compressed air) is conveyed to achieve linear movement.In the cut away below, you can see these different components.
There are three types of cylinders most relevant to haunting applications. These cylinders are single, reverse and double acting. In single acting cylinders, air is conveyed through a single port in a cylinder. When the compressed air is removed, an internal spring returns the cylinder to its normal state. Reverse acting cylinders work in a similar way, except that instead of the spring retracting the rod when no air is applied, the spring extends the rod.
Perhaps the most common, and versatile of cylinders is the double acting cylinder. With this type, air enters a cylinder via one of two ports. The cut-away above is an example of a double acting cylinder, with the two threaded ports found on opposite ends of the chamber. If we use the cut-away as an example, we can see that air has been applied to the right port because the rod is retracted. If air was applied into the left port , the cylinder would extend. It should be noted that regardless of which port air enters, the opposite port then becomes an exhaust.
Cylinder size is measured by both its length and its bore. Bore is the inside diameter of the cylinder chamber. The larger the bore, the more air is contained within the chamber. As bore increases, so does the rod diameter of a cylinder.
Different props will require different sized cylinders. A cylinder used to move the arm of a skeleton will differ greatly from that of a cylinder used in simulating the effect of a broken elevator. To determine the proper size cylinder bore for a haunt application, we employ Pascal's Law (Force is equal to pressure being applied to a particular area).
Force = Pressure x Area
Force is proportional to pressure and area. When a cylinder is used to clamp or
press, its output force can be computed as follows: F = P x A
P = pressure (PSI (Bar) (Pascal's))
F = force (pounds (Newtons))
A = area (square inches (square meters))
Bore sizes typically range from 5/16" to 3". Stroke, (the length of the rod), is limited by bore size (smaller bore cylinders generally have limited strokes). Double acting cylinders can have long strokes, whereas single acting cylinders have short strokes due to the nature of the way they are made. Because of their internal springs, the use of long strokes in single acting cylinders is both impractical and costly.Once bore and stroke of a cylinder is determined, mounting is decided. There are no "hard and fast" rules in haunting. Something that may work in one prop may not in another prop. Here are some of the most common mounting options available.
Clevis Mount: This type of mount connects at the base of the cylinder, opposite the rod. 
These mounts allow for movement of the cylinder, such as when a cylinder needs to move in an arc to complete its stroke.Foot / Nose Mount: Attached at either end of the cylinder, these mounts offer a fixed 
hardpoint for the cylinder. They are most often used when cylinders are expected to stay in fixed position.Most cylinder rods are threaded. Some attachments for rods are as follows.
Rod End: 
Rod Clevis: 
We hope this overview was helpful.