Improvised pneumatic cylinder from a bicycle pump

Compressed air can provide your animated Halloween gear with forceful, rapid linear action by activating a pneumatic cylinder.

Pneumatic cylinders can be purchased new, found used, and improvised from a variety of materials. There is occasional debate on the safest, best, and cheapest form of pneumatic cylinder.

This page shows how we built an improvised pneumatic cylinder from a bicycle pump, a technique that we used effectively on our pumpkin popup.

Warning - Don't Do This!
Basic Construction
Customization

Warning - Don't Do This!

This page is an historical note that describes an improvised pneumatic cylinder built a long time ago when we had more enthusiasm than common sense.

We now believe that only commercial pneumatic cylinders should be used for pneumatic projects, with great attention paid to the specifications and usage of the cylinders.

Basic Construction

We started with an "upright" bicycle pump, the kind where you step on the bottom to hold it down, and a T-handle sticks out the top for you to plunge up and down.

[photo] At the base of the pump is a place where the output hose screws into the base. Inside this area is a check-valve that prevents air from the bike tire from flowing backwards into the pump.

We unscrewed the hose, removed the check-valve, and replaced the hose.

With this simple modification, air forced into the base of the pump will cause the pump handle to extend.

We will further examine the anatomy of the bike pump by dissection...

[photo] The top of this pump actually unscrews.

We have already unscrewed the T handle from the top of the plunger rod.

[photo] The plunger is easily removed.

[photo] The end of the plunger has a rubber seal that fits the pump cylinder, making an airtight seal.

The spring cushions the blow when you pull the handle all the way up and hit the top of the pump.

Customization

Note that the plunger is a cylindrical metal rod. This allows the pump handle to spin around during use. When used as a pneumatic cylinder, the piston rotate freely, and if you mount something on top it might turn in the wrong direction.

For the pumpkin popup, we replaced the cylindrical metal rod with a square one, and filed a square hole in the top of the pump. This kept the pumpkin on top from spinning around and mooning the trick or treaters.

Thank you for visiting. Your comments are welcome.
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