Beginner's Guide to Props and Pneumatics

**Weavis** · 09-22-2009,04:16 AM

Originally Posted by SkeletalRemains

Hey Weavis, that is a very cool-sounding prop! The prop that you describe can be made as simple or complex as you want it to be.

On one hand, you could connect the ghoul to the doors in such a manner that it pops out when the doors open, as you described. You can accomplish this by using 2 cylinders (one for each door) running off the same air valve, just connect both cylinders to the output of the air valve using a tee. This way you'll only have one trigger and one air valve, and based on how you build the contraption, the ghoul should retract appropriately as the doors close. Also, you can turn on a light with your same triggering mechanism. This method keeps the prop relatively cheap as you don't need a dedicated controller. Sound is another issue, I'll get to that in a minute...

The more complex way of doing this, also like what you mentioned above, is to setup the doors (2 cyls running off single air valve, or two if you're feeling spendy) in parallel from an air point of view, and use a 3rd cylinder to launch the ghoul. The only thing about this configuration is that you'll need a controller to do it, unless you are extra-crafty and creative with limit switches and stuff like that.

Ask 10 different people on this forum and you'll get 10 different answers on what kind of controller they like to use. I would recommend a picoBoo controller. Very simple to program, a little costly (like maybe $90-$100) but that's where you can bring in the sound. The picoBoo controller has built in sound (ambient for when NOT triggered, and triggered for when the prop is activated). The controller will allow you to plug in your air valves and you can trigger them in any sequence you want (in real time). This is an easy way to go. The picoBoo will allow you up to 2 outputs, one for the doors, and one for the ghoul. Just connect the light to the same output for one or the other, depending on when you want the light to come on.

There are lots of other creative low-tech ways to bring in sound: portable CD players with amplified speakers and a hacked switch to play the sounds, ISD chipcorders, loop tapes, etc. There are even threads about hacking cheap little $10 MP3 players with incredible sound quality! A whole world out there in this forum!

If this is not making much sense, let me know, I'll be happy to go into more detail on anything if you wish...

-SR

SR, everything makes sense at this time. I might get back to you when I get a little more into the building process. I think the picoBoo might be the way to go. I really appreciate your help and I'm sure I'll be talking to you again. I'll try to post pics of the build. Thanks again and keep up the good work!! Weavis

**czaaaa** · 10-15-2009,03:58 PM

Wow that nice . thanks

**Gunner** · 10-18-2009,11:42 AM

Weavis-

A couple things to think about. While the idea of using two cylinders from one valve seems the easiest, it is most likely that you will get one side of the door to open before the other. One door will be slightly heavier, a bit less mechanical advantage, a bit of wind, whatever. In order to get them to move together, you should have them timed to each other. This can be done with ropes and pulleys, shafts, sprockets, and chains, or with connected levers. It may still make sense to use two cylinders to lift the doors.

Next, to sequence the pop-up, you could work with a sequence. This would be a switch that is triggered when the doors are fully or most of the way open. Or you could work with a two channel contoller and base the actuation of the pop-up based on a time delay.

Or you could just power them both at the same time and design the pop-up so that it helps push the doors open.

Another way to do this is to spring load the doors open, and pull them shut with the last few inches of pop-up travel. When you trigger the pop-up, the first couple inches of travel allow the doors to open, and the pop-up jumps through the opening.

As SR said, ask 10 people, get 10 answers! Actually probably 15!

**shibeto** · 10-21-2009,04:20 AM

This is very cool. Thanks for your efforts

**halloweenjunkienick** · 01-21-2010,01:11 PM

Wow this is so cool, i am fifteen and are really into halloween and just starting to understand the use of pnuematics, i already knew the basics but this really really helped me understand the details. every other thing i am reading or watching only shows little sections of this but you described the whole thing perfectly, thanks soo much.

**SkeletalRemains** · 01-21-2010,09:13 PM

Thanks! That's awesome that you're only 15 years old and getting into prop building now! I know guys who just started in their 60's and wish they would have started years earlier!!

**galangrey** · 02-07-2010,03:37 PM

I made it through four years of college and never had to write anything this well done. When you know something that most people don't and you de-mystify it for them you are fulfilling the ultimate potential of your knowledge.

Also, knowing what to monetize and what to give away takes a wisdom and empathy few possess.

Thanks for such a great tutorial!