This is a simple idea that was passed to me from a few people for making a simple animatronic prop that has simple turning side to side motion. It uses a electric fan, the type that moves side to side. Remove the cage around the fan, remove the bade, and then cut the metal shaft flush with the unit so that it doesnt rub or catch while spinning. In the example I was given an alien mask was used so I figured hey I have one of those so in the following pics thats what I used. For the body I used spray foam, the kind used for filling cracks and stuff, the kind I used was called "Great Stuff" Just be very careful using this and always wear rubber gloves trust me on this. Simple place you mask, or fake head over the moving part of the unit, allow room for some ventilation. Add a body of your choice and plug the unit up and turn it on...poof you have a creature that can look back and forth...price...about $40 dollars!!!!
