this program makes it all easy....

[lazz]

when working with air cylinders you can put a prop on the end of a cylinder rod and make things simple... when the rod goes up and down so does the prop.... I used to do it that way... and it works just fine with some limitations....

the first limitation is the length of the cylinder rod... you have to find LONG stroke cylinders to make things move a bunch....

second is no mechanical leverage....you only get the cylinder output....

third is stability.... it kinda sucks a little to put a ton of money or work into a prop and have it turn and point the scary mask the wrong way....

so in my opinion the easy way is to use linkage to shake and move the world.... for example... the wonderful stuff at vile things.... this guy does it ALL and well too... http://www.vilethings.com/animated_obelisk_prop.htm

as you can see in that link he does an awful lot with a simple cylinder.....but if you read his stuff you will notice he also uses a cad program ... me I use an ol four bar simulation program....in fact the one I downloaded from here.... http://www.boopack.com/software.html


the program can tell you what the lengths of the linkages need to be for different results....

I hope this helps....
if not give me a yell...

[teberle]

Nice stuff. I will be remaking my graveyard fence this year.

[alwysrit2]

The longer the air cylinder, the more expensive, at least most of the time. Another alternative is using a screen door closer. The nice thing about them is that they will automatically return to closed because of the internal spring. It is pretty simple to remove the bleed screw in the end and replace it with a 1/4" fitting. They have about an 8" throw and will handle the air preasure.
The other thing to keep in mind is that a short throw doesn't need to mean a short movement. There are lots of ways to make a 8" throw move a prop a couple of feet. Scissor Lifts are probably the most useful.
-Don

[lazz]

I have a scarecrow that uses a cylinder with a 15"stroke.... the prop travels a little under 7'....
4' up and 5' forward...

[desmo69]

Another consideration could be using the actuator for a satellite dish (C-band). Not only is it low voltage, there are switches to stop the action when you reach the end of the stroke.