by Scary Terry




At first glance, this is just a plain old scare crow, standing in the garden, not really doing his job, as he's surrounded by a half dozen crows. All of a sudden, his head spins around and he turns into a giant "scary crow". The surrounding crows' eyes pulsate a terrifying red glow, the Scary Crow raises into the air and thrusts itself toward the trick-or-treaters. His arms reach out as all the crows join in a chorus of scary crow sounds.

The following is a brief description of how the Scary Crow works. I'd like to thank Brad Fraley for his terrific 4 Bar Linkage Simulation Program that really saved a lot of time and effort. Also, thanks to Spirit Kanaka for suggesting Cabela's as source for plastic crow decoys.





Click here for a short video of the Scary Crow in action


The Scary Crow consists of:

  • 4 bar linkage made from 3/4" electrical conduit
  • Counter weight: cardboard tube filled with cement
  • Paper mache head attached to a rotary actuator
  • Arm mechanism: pneumatic cylinder with cable linkage
  • Electronics board: Basic Stamp 2, three ChipCorders, wireless remote receiver, power supply
  • Pneumatics board: regulator, solenoid valves
  • Lighting board: relay and pulsating circuit



Click on any of the following images for a larger view.




The 4-bar linkage consists of a pair of 2x4s in which a pair of 3/4" electrical conduit tubes pivot. I chose electrical conduit because it's fairly light weight, cheap, easy to work, readily available and strong. The linkage is extended by a pneumatic cylinder with a 10" throw. The cylinder is assisted by a 22 pound counter weight that hangs off the top tube. His total rise is about 28" and he moves forward about 18", but standing in front of him, it really has the effect of much more than that!




My wife made the head out of paper mache. It's built around a large plastic jar (Kirkland cashews) to make it easy to install on the rotary actuator (see below).



A rotary actuator is just a pneumatic cylinder that rotates. I got this one off Ebay for about $15. It has an adjustable angle of rotation, but I use it for the maximum 180 degrees. I attached the jar lid to the top of the actuator so the head will just thread on.



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last update 12/2016