Introduction: Pneumatic Squib for On-Actor Film Blood Effects
This Instructable is derived from available Internet resources on fabricating special-effect blood-shooter devices from hand-pumped garden sprayers. It seeks mainly to minaturise the design.
This particular design grew out of a general dissatisfaction with the restrictions the garden-sprayer style of blood-shooter placed on the staging and choreography of blood effect shots.
The goal was to create a device that could replace the garden-sprayer design in all situations, and add flexibility in staging effect shots.
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Step 1: Building the Control Hose
The Control Hose carries air between the hand-held remote section of the device and the effect section of the device. It is the simplest element to construct, so we'll build it first.
The control line consists of only two unique components: the hosing and identical fittings at either end. The hosing is 1/8" OD urethane line. The fittings are 90Âº universal fittings with 10-32 threads
Clippard Parts List:
1x 1/16" internal diameter polyurethane hose.
2x Beswick Engineering MLS-1008-1-303 instead of the UT0-2
Beswick makes the smaller, square swivels with countersunk screw-heads that work just as well as the hexagonal UT0-2 fitting from Clippard, but they don't sell them individually.
Step 2: Build the Hand Held Control
The control unit allows the device to be charged with air, and holds pressure in the device until the actor triggers the effect. It is a design that was originally developed as a pilot trigger for an air cannon.
Clippard Parts List:
1x 3-way toggle valve (TV-3S)
1x Check-Valve ( I used a MCV-1BB and a short coupling 11999 - you can save a part and use a MCV-1AB)
Then, use one of the following air inlet designs
1x 1/8" barb with 10-32 threads (CT4) capped with a
1/x short piece of 1/8" ID 1/4" OD urethane hose.
A Quick Disconnect assembly made up of:
1x MJQC-VMT 10-32 threaded valve body
1x MJQC-CB4 1/8 barb quick disconnect cap
1. The check valve will have an arrow on it. If you ordered the valve with the suffix AA, screw a short coupling into the end of the valve the arrow points at. If you ordered the valve with the suffix AB, this end of the valve will already have male threads.
2. Screw the check valve into the bottom of the 3-way toggle so the arrow points towards the 3-way valve.
3. Screw either of the inlet assemblies described above into the open end of the check valve.
4. There is one remaining threaded port on the 3-way (the output)- attach your signal/control line to that port. The smaller, non-threaded opening on the 3-way is the exhaust and it should not be obstructed.
That's it - you should have something resembling the pictures from the above tutorial.
Step 3: Build the Effect Assembly
The effect unit was designed as a miniature pneumatic cannon.
Clippard Parts List:
1x 2-cubic-inch volume chamber (MAT-2.0)
1x 10-32 solid plug (11755)
1x 10-32 miniature quick exhaust valve (MEV-2)
2x 1/8" barbs with 10-32 threads (CT4)
1x 10-32 bulkhead fitting (15027)
1x short piece of 1/8" ID urethane hose.
1x long piece of 3/8" ID hose. (A foot of 3/8" hose holds 20 mL of stage blood. The squib can eject all the stage blood from 3 feet of hose, so the length of this hose will detemine how "juicy" your squib is.)
OPTION: Substitute 1 4CQ4 fitting (1/4" NPT to 1/8" Barb) for the 15027 (Bulkhead fitting) and one of the CT4 (10-32 to 1/8" barb) elements.
1. Screw the solid plug into one of the ports on the Volume Chamber.
2. Screw the quick exhaust valve into the other port on the volume chamber. There's only one male port on the QEV, so you can't get this wrong. (but for clarity, it's labelled "C")
3. One of the remaining ports on the QEV will be marked "E". This is the port you attach the effect tube to. Screw one of the 10-32 threaded 1/8" barbs into the port.
4. Attach a short piece of 1/4" OD urethane line to the barb.
5. Screw another 1/8" barb into the hexagon-shaped end of one of the 10-32 bulkhead fittings. Plug the barbed end of this fitting into the short piece of 1/4" OD line. You may remove the retaining nut and lock-washer from the bulkhead fitting - you don't need them.
6. Work about a foot of the 3/8" vinyl tubing onto the bulkhead fitting. It will be a tight fit. I used needle-nosed pliers to stretch the hose to fit the fitting.
7. Attach one end of your control line to the remaining port on the QEV - it will be marked "L"
8. Squash the unconnected end of the 3/8" tubing flat and tape it shut with a strong waterproof tape.
9. Pierce or cut a port near the taped end of the hose which will act as the nozzle through which the stage blood will be ejected.
Step 4: Using the Effect
Use of the Effect:
1. Fill the effect tube and cover the output hole with the smallest possible piece of low-tack masking tape.
2. Tape the effect under the actor's clothing in the appropriate orientation. If the tube must be oriented with the output hole higher than the quick-exhaust, I recommend pushing a plug of banana down the hose before filling it with stage-blood.
3. Dress the actor in the outer costume and pass the control module down the actor's sleeve to their hand.
4. Make a very small cut in the costume over the output hole of the effect. The smaller the hole, the more blood will stay on the actor's clothes. The larger the hole, the more blood will spray away from the actor.
5. Flip the switch towards the control line fitting and connect your air supply to the air inlet. Pressurise to between 60 and 100 PSI. (use a pump with a gauge, or a compressor with a regulator)
6. Disconnect your air supply and film the scene - the check valve will keep the squib pressurised.
7. When the actor is ready, he can flip the switch and the effect will trigger.
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