Pneumatic Squib for On-Actor Film Blood Effects

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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.

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 90º universal fittings with 10-32 threads

Clippard Parts List:
2x UT0-2
1x 1/16" internal diameter polyurethane hose.

Substitution Option:
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

Design 1
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.

Design 2
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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52 Comments

What are your thoughts on substituting http://www.clippard.com/part/MME-3PDS-W012 for the toggle switch in an instance of electronic operation?

1 reply

The flow rate on the MME-3PDS-W012 looks like it would work as a trigger valve if your looking to trigger the effect electronically, and it's less expensive than the solenoid valves I could find when I built this squib. It's fairly large (4.5"x2.5"x1.4"), so it might present some issues with concealment if you had a lot of squibs on your actor.

You'd still need a 12V, 6.5W power circuit to trigger the squib, but you can probably build something inexpensive around a 555 set up as a monostable pulse generator that would trigger the solenoid effectively.

built this rig with all the parts directly from clippard, according to your specs. this....thing....is.....awesome!!! i'm doing a live theatre show in a tiny space where someone is tied to a diner-style chair (no real place to hide contraptions) with christmas lights and gets shot in the head. the chamber and trigger are under the seat, the tube runs up the back and it splatters blood all over the refrigerator behind the actor. it's genius! and it's simple! and it's cheap! not counting shipping, i think it was $40ish, and i bought more parts than i needed. we're using the kinda pricey "reel blood" cut with almost equal part Hershey's syrup. the effect is amazing. THANK YOU for this post, Crosius! anyone else considering it, DO IT!!! so great!!

Hi, what's purpose of using a separate quick exhaust valve rather than a switch with an accessible exhaust port? Is it purely for greater flow rate?

1 reply

Partially, yes.

The miniature valves that also incorporate manual controls at that size have lower flow rates than the exhaust valve.

My other reason for using this configuration was to separate the control & the effect by a long distance, while keeping the distance from the air supply to the effect tube as short as possible.

If the effect tube was being cleared by air passing through a long tube from the switch, there would be a very different attack/decay to the effect "burst". It would start and stop less dramatically.


Hi Crosius, do you think you're able to write up a new and improved version combining what's been mentioned in the comments (e.g. daisy chain, whisker valve, schrader valve etc) with parts readily available on eBay and/or RS online? I'm in Australia and getting parts from Clippard isn't really possible.

Cheers!

1 reply

Unfortunately, I'm constrained by budget and time, so new variations on this instructable are always going to be slow.

I know Clippard has limited distribution outside of the Americas. You could try ASCO. They make similar valves and they have distributors in Australia.

 The parts are all available at Clippard's online store (www.clippard.com)

If you have a local reseller like Wainbee, you may want to have them order the parts for you.

If you can't find a local source for Clippard parts, a company by the name of Pneumadyne makes similar products.

Well, we're now in tech rehearsals for our little stage production using 8 of these marvelous devices, and I thought I would post a few "lessons learned" type tips that may be helpful for those doing stage work (as opposed to film, which can be more forgiving of "oops" moments).
1. Adding a tee fitting (Clippard # 15002-3) to move the check valve next to the cylinder and substituting a 2-way valve (Clippard # TV-2S) for the three-way valve greatly increases the concealability of the trigger.
2. We have found that using small amounts of poster-tack style removable putty adhesive to seal the hole in the effect tube (rather than the low-tack masking tape), seems to reduce premature blood leakage when the actors have to wear their loaded squib for extended periods before firing it, or when they have to move around a lot onstage before activating the effect. The effect still works perfectly with the poster-tack, as long as you don't use way too much.
3. I highly recommend purchasing extra screw plugs (Clippard # 11755, the same as used to seal the top of the air cylinder) for use as a safety. Actors can be kind of clumsy sometimes, and the last thing you want during a performance is someone accidentally triggering a squib backstage. The screw plug is used to seal the exhaust hole in the toggle valve, and prevents the squib from firing even if the toggle switch is flipped. A stagehand simply removes the plug with a screwdriver at the appropriate time to "arm" the device. You could also use a second toggle valve attached into the trigger line for this purpose, but this would increase the expense a bit. Either way, a safety of some kind is a very good idea.
Anyway, this is a great effect, and it's really giving our production a very polished and professional look. Thanks once again to Crosius for sharing it with us.

1 reply

 Blu-tac for plugging the tube is a great idea!

Also, great solution for avoiding early triggering.  Too bad it will only work with the two-way valve, though, as the three-way's exhaust isn't threaded 10-32 and the plug won't screw into it - if I wasn't using 3-ways on my squibs, I'd be using that on the next set.


Hi there, it's me again. I was just noticing that the effect assembly in the intro page picture seems a bit different than the one in the rest of the Instructable. Is that a check valve in place of the 1/8" ID hose between the quick exhaust valve and the bulkhead fitting, or just a section of tubing? Also, just out of curiosity, do you know how long the circuit will hold pressure and still fire correctly? As I mentioned in a previous comment, I'd like to use this effect in a stage production, so there could be an appreciable gap between pressuring the device and firing it (probably about 30 minutes at the absolute longest, most likely much shorter). Do you think this would be an issue? Thanks once again for a great design.

7 replies

Update on pressure retention: I have successfully discharged a squib a whole day (24 hrs) after pressurising it. You should definitely be able to keep a squib on an actor for a whole scene.

Thanks for the update. I built one last week, and after the initial "just playing with it" phase, I let it sit for about 6 hours, and it fired beautifully. Nice to know they can go up to at least 24 without losing pressure, though. I've got parts for 7 more coming in the mail next week. This is a great device, and it's going to make the show look fantastic. I've made a couple of very minor mods to your design: I put in the T (as we discussed earlier) to move the check valve closer to the cylinder, I added a push-fit splice connector to the effect tube to make it easier to fill the tube with blood and banana plugs, and I'm sealing the end of the effect tube with vinyl glue instead of tape. So far, everything works even better than advertised. I highly recommend that anyone who needs bullet hits for a film or show just go ahead and build a few of these. They work very well, and are totally worth the expense. Just do it, you won't be sorry.

Seven? Sounds like quite the bloodbath. The push-fit connector sounds like a good idea for quick reloading and quickly changing the hose lengths. Are you using something like the PQ-RU1208 from Clippard? (3/8" to 1/4" OD reducer). I'll have to try that on my next batch of squibs.

Yeah, I'll actually have nine total (including the first one I made, and an alternate version made from a CO2 bike tire inflator), and we're reloading at intermission to reuse them all in Act II. Plus several "wall splatter" effects to simulate headshots, a garroting, mouth blood packs, a slit throat, and a severed ear. Bloodbath indeed. I'm suggesting that the audience bring tarps. The push-fit splice was kind of an afterthought, but it does make reloading very convenient. It's a straight union, more like PQ-SU12. I got it from Lowe's on a whim while I was buying the vinyl tubing for the effect tube. I like the idea of a reducer, though. I think I'll try that next time. By the way, if you're ever in Statesboro GA, drop me a line. I want to buy you a beer or something.

Sounds amazing. By far the most elaborate use of these squibs that I've heard of to date.

Indeed. Funny thing is, I should really be using 15 squibs, but I had to scale back for budgetary reasons. What makes this funny is that the point of the show is about how violent, vengeful behavior is a Very Bad Thing (tm). The playwright has chosen to convey this message via an orgy of bloodshed. The really funny thing is, it works. Anyway, thanks again. I'll post some pics of the show somewhere when the time comes and send you a link so you can see what your creativity has wrought.

That's just a brass coupling with 10-32 threads at either end I had around the shop - it has the same function as the short bit of 1/8" tubing with the 1/8 barb fittings on either end, but it is less useful, since the squib is stuck in that "L" configuration. My Squib has held pressure for 10 minutes and worked fine when triggered after that time. I haven't had an application that required a longer delay, so I haven't tried longer than that. The valves and threads seal very tight at 100 psi and I cannot detect any leaks in my squib. How long a specific squib can hold pressure depends on how well the threaded connections are sealed, and how tightly the valve internals seal. If you do find that a threaded fitting is leaking (hold the pressurised squib underwater and watch for bubbles), you can use plumber's silicon tape to seal the threads. If a valve leaks, you can't do much more than exchange it, as the internals aren't serviceable. Even with a slow leak, the squib will still operate properly at pressures down to around 40-50 psi, so you might still have time to pressurise off stage (to 100 psi), wait 20 minutes and then fire a squib that still has 40 psi of pressure in it. The exception to this would be if the QEV is leaking out of the exhaust-way - that would make the stage blood "ooze" out of the squib before it was time.

So I made this following all of the directions and the chamber wont fill up...could my mini exhaust vale be faulty....it feels like only 2 psi comes out