WARNING: If you are considering this project, read all Related Pages before you start!

• Block Diagram
• Pneumatic Cylinders
  • Doors
  • Beast
  • Lid
  • Claws
• Solenoid Valves
• Pressure And Flow Control
• Setup

• Related Pages

Block Diagram

Here is a block diagram of the pneumatic system, when the whole thing is completed:

On the

Please note that different types and sizes of cylinders require different amounts of air in order to operate. This can be controlled through pressure, flow rate, or both. We did some experiments to find out what pressures worked best with our assorted cylinders and no additional flow restriction.

cylinder	pressure (PSI)	comments
L. Door	20	opens, but slowly, and not all the way
L. Door	40	brisk
L. Door	30	perfect
Lid Lifter	10	looks good
Beast	40	solid, but too forceful
Beast	20	still hard
Beast	10	very nice

Notes:

• The doors are operated with improvised pneumatic cylinders from screen door closers, mostly because we had them around. We don't recommend these, an prefer real industrial cylinders. Look at how much pressure they take! It's that big, honking spring inside!

• The cylinders for the Beast and lid are industrial-strength "real" pneumatic cylinders. They are rated for over 200 PSI of pressure, but with a light load and a high pressure, the cylinder's rod will slam into the end each time you actuate it. In other words, being able to take 200 PSI static pressure is different from being slammed with 200 PSI all at once. We decided to use as low a pressure or flow as would still result in the desired effect.

Note: Most of our props use our Haunt Air Manager (HAM) assembly to control their air. This usually includes some local air storage (Green Eggs and HAM ). The Crate Beast has a lot of pneumatics in it, and deserves some local air storage, but we haven't gotten around to putting it in yet.

• open crate doors
• push out Beast
• push up lid
• thrust out claws

We used a variety of different pneumatic cylinders to do the work.

For the doors, we used improvised pneumatic cylinders from screen door closers.

Screen door closers are cheap and easy to find, but in the past we have deprecated them for reasons of safety. For this project we decided to use them anyway because (a) they were mostly contained in a big wooden crate, (b) this would be our first chance to use door closers on doors, and (c) we had some leftover.

This turned out to be a poor choice. The strong spring in the closers takes a huge amount of presure to activate.

Lesson: Don't use poor parts just because they are (a) available or (b) cheap or (c) easy to get.

Cylinder characterstics:

• improvised pneumatic cylinders from screen door closers
• one-way action, strong spring return
• body - about 9 1/2" long
• extension - 6"
• bore - about 1 1/8" diameter

Here is one of the improvised pneumatic cylinders from a screen door closer.

parts for innermost mounting of a door cylinder

innermost mounting of a door cylinder

parts for outermost mounting of a door cylinder

outermost mounting of a door cylinder

parts for a complete, mounted cylinder

a complete, mounted cylinder

This is a view of the completed pneumatic cylinders from the inside.

There was nothing really wrong with the valves themselves. They were good stuff, and we got a great deal. The problem was that they were not well matched to the task. Added problem: this model of solenoid valve is a little tricky, we had no documentation for the specific model of valve we got, and had to figure it out ourselves.

Mead LTV-120 4-way double solenoid valve, with 24 VDC coils

We have some LTV-120 technical information on our solenoid valve page.

The most important factor in using this valve is that the LTV-120 valve isn't monostable - where removing power returns it to the other resting state. This valve is bistable - it has two solenoids, each pulling it back or forth. When you remove the power, the valve stays in the position corresponding to the last solenoid energized. Thus "normally open" has no meaning. "Normal" (power off) is whatever you did last!

This also means that we need twice as many solenoid drivers as would be required by a normal monostable solenoid valve.

Note: There does exist a monostable version of this valve, the single solenoid LTV-115. But that's not what we found for $10 apiece in the surplus bins.

One board contained all of the fancy control electronics; one contained the pneumatic components and the board that drives the solenoid valves. There are only two connections between the two boards: power and a thin cable for control signals.

This is a mockup of the pneumatic board, with the major components just sitting on the piece of masonite.

This is the pressure regulator and distribution manifold on the completed pneumatic board.

Incoming air uses a pneumatic quick disconnect. Inside the crate, all pneumatic connections use one touch fittings and 1/4-inch tubing.

This shows the valves on the completed pneumatic board.

Solenoid electrical connections were simply twisted tight and covered with electrical tape.

Dennis makes some of the solenoid electrical connections to the controller board.

Some solenoid electrical connections were simply twisted tight and covered with electrical tape.

This is the completed pneumatic board.

The printed circuit board is mounted on hexagonal aluminum standoffs, threaded for #4-40 bolts. The bolts that we used have 1/4" of thread.

Test-fitting the completed pneumatic board in the crate.

• Overview of the Crate Beast.
• Effects and controller.
• The crate itself.
• Crate finish and paint.
• The Beast!
• Pneumatics. [this page]
• The Software.
• other versions of the Crate Beast.

Please visit our related pages:

• Haunting with compressed air
• solenoid valves
• Turn pressure into motion with pneumatic cylinders

Thank you for visiting. Your comments are welcome.
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