Im sure someone will shoot me for suggesting this, but I was in the same boat as you a month before halloween and the way I became comfortable with how air props worked was by hacking a couple together with PVC, Door closers and sprinkler valves.
They didnt work like I was hoping, but the amount I learned was priceless and now that I figured it out with a small amount of trial and error, im now decommisioning the two props I built and am going with welded steel and commercial valves and cylinders.
You can either start the way most everyone here has with non-commercial parts and work from there (My recommendation) or you can grab a cheap bimba cylinder from ebay, I would suggest at least a 4-6'' stroke (how far it moves) and a 1 1/4'' diameter rod, a decent air valve (someone else will have to suggest one becuase im in the same boat) but I would still suggest using 1 1/4'' PVC that way you can easily adjust the linkage to get the desired effect.
Here is a quick pneumatic for beginners
http://www.wickedstone.com
**Looks like his website is down, if you would like the .ppf of the file, PM me and ill email it to you.
***I also have a couple of easy 4-bar linkage diagrams that I can email you that will help, just shoot me a PM with your email address if your interested.
Here are a few links I dug up.
http://www.scaryguys.com/slinger.htm
http://www.halloweenpropmaster.com/coffin_sit_up.htm
http://www.halloweenfear.com/Manifold.html
http://www.hauntedillinois.com/pneumatic.php
http://www.virtualplacebo.com/halloween/props/grave_jumper/index.htm
Here is a 4bar program that you can use to help design your linkage, you will have to play around with it to familiarize youself, but once you get the hang of the software, its a great thing.
http://www.boopack.com/software.html
They didnt work like I was hoping, but the amount I learned was priceless and now that I figured it out with a small amount of trial and error, im now decommisioning the two props I built and am going with welded steel and commercial valves and cylinders.
You can either start the way most everyone here has with non-commercial parts and work from there (My recommendation) or you can grab a cheap bimba cylinder from ebay, I would suggest at least a 4-6'' stroke (how far it moves) and a 1 1/4'' diameter rod, a decent air valve (someone else will have to suggest one becuase im in the same boat) but I would still suggest using 1 1/4'' PVC that way you can easily adjust the linkage to get the desired effect.
Here is a quick pneumatic for beginners
http://www.wickedstone.com
**Looks like his website is down, if you would like the .ppf of the file, PM me and ill email it to you.
***I also have a couple of easy 4-bar linkage diagrams that I can email you that will help, just shoot me a PM with your email address if your interested.
Here are a few links I dug up.
http://www.scaryguys.com/slinger.htm
http://www.halloweenpropmaster.com/coffin_sit_up.htm
http://www.halloweenfear.com/Manifold.html
http://www.hauntedillinois.com/pneumatic.php
http://www.virtualplacebo.com/halloween/props/grave_jumper/index.htm
Here is a 4bar program that you can use to help design your linkage, you will have to play around with it to familiarize youself, but once you get the hang of the software, its a great thing.
http://www.boopack.com/software.html