Pneumatic cylinders are easy to make in the home workshop. They can be made in a variety of sizes for different household tasks. Homemade devices, especially plastic, should never be connected to motorized compressed air systems, or compressed air tanks. Air under pressure has explosive qualities when suddenly released from its containment and can quickly turn parts of untested cylinders into dangerous projectiles. Use a tire pump or foot pump to safely actuate the homemade cylinder.
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A Task for Each Size
Air cylinders from about an inch or smaller in diameter all the way up to four inches can be made from smooth, white PVC pipe available in the plumbing department at hardware stores and home center chains. The smaller cylinders are handy for opening or latching doors and windows. The larger ones can be used as quick clamp actuators or even to crush beverage cans. The nice part about using PVC pipe is that it comes in 10-foot lengths, so quite long cylinders can be constructed without a lot of fuss.
Select a length of PVC pipe and an end cap to fit it. Then find an end cap and two straight couplings with an outer diameter just slightly smaller than the inside of the first piece of pipe. Find the pipe size corresponding to the smaller end cap and straight couplings and purchase it too. Buy neoprene O-rings with an inner diameter equal to the outer diameter of the smaller pipe and an outer diameter equal to the inner diameter of the larger pipe. Purchase a jar of PVC pipe cement, some plastic tubing and 3/8-inch threaded tube fittings.
Remove any burrs from the smaller fittings. Install the tube fitting in the larger end cap and cement the cap onto the end of the larger pipe, which has been cut to the desired length. For the piston, the idea is to use the smaller end cap and one of the couplings to form a retaining slot for the O-ring. Cement these onto a short piece of the smaller pipe so that the gap between them just holds the thickness of the O-ring. Cement a longer section of the smaller pipe into the other side of the coupling to comprise the piston rod. After the cement is fully dry, slide the O-ring into its slot and spread petroleum jelly liberally over the entire end of the piston. Slide the piston into the cylinder and check for a good seal and smooth motion in the stroke.
Ready to Go
Connect the tubing to the cylinder and to a bicycle or camping-style foot pump. Size the cylinder so that it requires a minimum of linkage or brackets to install in your application. It may be necessary to fabricate pivots for one or both ends of the homemade pneumatic cylinder. Use a small shut-off valve to hold the cylinder in a position.