Don't worry, these monsters are friendly...I think.
Just like those crazy arm-flailing inflatable tube men seen at outdoor events, make your own scale variant with a reused computer fan, and some multi-coloured blinking LED's. This monster is sure to brighten up any space and maybe even spook you, too.
This project uses an interchangeable thin plastic sock as the monster. You can make a few different socks and have a monster party, or you can replace the inflatable plastic sock monster with strips of fabric and create a faux fire, like this one.
The principle of air current and LED's are the same.
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Enough talk, let's inflate a monster!
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Step 1: Tools + Materials
Step 2: Some Science
Before you try this, there's a few things you need to know.
What makes the inflatable man stand tall is the rapid upward displacement of air through the sock; in this case the body of my monster. The air current blown through the sock is enough to overcome gravity acting on the sock and the piling rigidity of the fabric, giving the body a wavy-wild personality. The science to why the flailing-arm guy does his 'dance' is based on a few factors: fan displacement, height of sock (body), and fabric material used.
You need the right mix of all three of these components for your monster.
Fan data is dependent on the type of fan used, some 12V models can displace more air (CFM) than others; so not every fan may be suitable for this application.
For the nerds paying attention in the back, CFM is a Imperial measurement of air exchange.
Air Change Rate - Imperial Units
n = 60 q / V
n = air change rate per hour
q = fresh air flow through the room (Cubic Feet per Minute, cfm)
V = volume of the room (Ft2)
Air Change Rate - SI Units
n = 3600 q / V
n = air change rate per hour
q = fresh air flow through the room (m3/s)
V = volume of the room (m3)
Having a fan with a large displacement will create a more powerful air current to hold our flailing monster upright.
Height of Sock:
Consider that if the body of the flailing monster is too short, the monster won't move around so much. If the sock is too long the fan may not have enough power to lift the sock and make the monster move. Experiment with different sizes, starting from long and progressing shorter until the right height is reached, achieving a funky moving motion.
For commercial grade versions, they use rip-stop nylon, a synthetic fabric which is lightweight, strong, and resists tearing. For this scale model a thinner material was required. I chose a very thin plastic tablecloth covering from the dollar store. What you're looking for is the ability of the material to crumple when piled, meaning when you hold a piece upright and let go it should pile on the ground like a towel, not fall like a sheet of paper.
At this point we can either whip out our calculators, or we can whip out some prototypes...I choose prototypes. There's merit to working out the given equations, maximizing the output of your fan etc, but I find that applied science provide immediate satisfaction.
Let's get messy!
Step 3: Fan
Cannibalizing parts from an old desktop computer I salvaged a functional tower cooling fan and a fan finger-guard, along with some wiring cable and some other goodies which I'll use on future projects.
To maximize the output of your fan you're going to want to make sure it's clean. The donor-computer I used had not seen a cleaning in some time, spend a few minutes to clean off your components.
Step 4: Modify Hobby Box
I managed to find a wood hobby box at my local dollar store that happened to be the exact dimensions of my computer fan.
Remove the hinges and clasp from the box and set aside along with the bottom portion of the box.
Sketch out an opening on the lid of the hobby box, the opening should be smaller than the constraints of the box lid but at least as large as the fan ginger-guard that will be placed over the opening. After measuring the opening, use a large-bore drill to expose the corners of the opening. Then, use a small saw to complete the opening, using a medium sandpaper to smooth out the edges.
Step 5: Wire LEDS
For this project, I used 4 x 3V multi-coloured LED's to illuminate the inside of the monster, a 12V fan, and 12V battery to run the whole thing.
Customize your monster to your own design, remembering our friend V=I*R.
Step 6: Place LED's
With wiring completed, the LED's were installed in each corner of the hobby box lid. Point the LED's upward, angled in slightly.
Since the fabric used for the sock is translucent, the light from the LED's will bounce inside and give our monster an eerie glow.
After the LED's are installed, wire fan and attach to underside of hobby box lid.
With the main components of the build now installed in the lid we can work on the base.
Step 7: Drill Intake Openings
The base of the monster will house the switch and the battery. To allow for unrestricted air movement when in operation there will need to be air intake passages drilled into the base.
With a small drill, bore an opening for your switch.
Next, drill openings at measured increments along the bottom 4 sides of the hobby box. I would recommend more/larger openings than what's shown in this picture.
With all openings drilled, wire the battery to the switch and install both into bottom of hobby box.
Use small dabs of hot glue to hold everything in place.
Next, wire together the top and bottom halves of the hobby box.
Step 8: Finger-guard / Sock Stand
The finger guard will be attached to the top of the hobby box lid. The finger guard will protect the fan and LED's from damage, but also hold the stand that the sock will sit on during operation.
The sock will friction fit onto the stand, allowing it to be easily removed. This method of non-permanent fixture between sock and fan will allow you to make modifications to your sock (cutting it to length), and will also allow the socks to be interchangeable.
Step 9: Sock
As mentioned in Step 2, there's a few criteria to make this work. When cutting out your sock, err on the side of caution and use more sock than you anticipate using. You can reduce the length of the sock later.
Start by unfolding your plastic tablecloth (or other thin, lightweight fabric). Measure the circumference of your opening on the hobby box lid (I used the outer edge of my finger guard). Transfer this measurement onto the plastic tablecloth, adding about 5mm extra for the bonding edge.
Cut out the measured width, then cut out a long lengthwise strip. This should give you plenty of material to work with, with a consistent width.
Following the instruction on the contact cement, apply a thin veneer to the topside of one edge of the lengthwise strip, and on the bottomside of the other edge of the lengthwise strip.
When rolled over, the two surfaces will bond forming a continuous sock.
Let contact cement dry for about 10 minutes, then gently press both glued sides together and form a bond. Gently apply pressure to ensure a good bond. Let glue set for another 30 minutes.
Once dry, you should have a clean seal between the edges of the plastic, creating an airtight conduit for the air.
Step 10: Cut Sock to Length
After contact cement on sock has dried, it's time to cut the sock to the right length.
Trail and error work best here, place sock onto friction fit stand and fire up the fan. Your sock may need to be cut down in length in order to achieve maximum flail effect.
Cutting ribbons on the top of the sock will give your monster some crazy hair, and may help with the flailing effect.
Experimentation here will result in a personalized monster. If you used the same tablecloth that I did then you will have plenty of material left over to make a few variations of monster will all sorts of sock lengths.
Step 11: Wacky Waving Inflatable Arm Flailing Tube Man
I can't say for certain, but I might have been inspired by late night infomercials like this:
Step 12: Turn Out the Lights
With your sock length worked out, it's time to give your monster an identity. Using a permanent marker, draw a face onto the sock.
When you're ready, turn out the lights and fire up your wacky inflatable monster.
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