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Need practical engineering advice

Started by Crispy Apr 6, 2005 at 10:08 AM 2 replies 650+ views

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Apr 6, 2005 at 10:08 AM

Aight - this is a bit unorthodox, but I'm guessing anyone with a bit of practical thinking in the realm of engineering could possibly help me and since I'm a little short of good solutions right now, I'll just lay the whole deal out on the table. Just one note: this is for a film, so think "special effects" (but no CGI). What I want a) a balloon filled with some non-combustible (lighter-than-air gas) - the only gas of choice being helium. Based on the following description, this could be just about anything as long as it won't make the balloon drop like a dead squirrel on Valium. b) a light source inside the balloon that would leave the effect of the balloon glowing (on a dark background). c) colored lights inside the balloon that can be tuned dynamically across the entire spectrum (that is, not switched, but tuned). d) ~~the balloon to be self-sustaining~~ I already know for a fact that I can't have that since the average lift quotient for a balloon per liter is approximately 1 gram when using helium, so the average everyday balloon would lift 5 grams something, tops -> ergo a no-go. e) good, non-rigid, control over the positioning of the balloon without any wiring being visible inside, below or above the balloon. f) uniform distribution of light inside the balloon, e g no bright spots or stripes. g) a quick way to switch the balloon and fill it with a gas - that is, I need the lighting mechanism to be reusable and easy to insert to/retract from the balloon since markings on the balloons will be changing quite a few times (think: for 3 balloons, 40-60 something times per shoot day). h) a controller system for tonality and brightness. What I have a) little to no experience with electronics/practical engineering - this, however, isn't a biggie since I have some friends who'd hopefully be willing to help me out (for instance to build a controller for lamp voltages). b) proof that a set of three diodes will not do the trick because there simply isn't a diode bright enough to light up a balloon and have intensity to spare. c) hopefully sponsored access to halogen lamps (stick-shaped) of ~7 and/or ~15 cm in length and ~0.5 cm in diameter, which should be bright enough to provide the required illumination, but present other problems (read below). I haven't tested these, though. d) unverified access to a number of neutral white balloons, size unknown (I'm looking for the regular ones, such as the ones that were handed out in Mary Poppins). e) little to no funds, so buying fancy stuff is out of the question. What the problems are a) hiding the wiring: currently, I'm thinking of using three halogen lights inside three balloons, requiring six people to operate them (three to guide them and three to adjust the tonality). With the help of simple color combinatorics, I should be able to get any color I want (with moderate hue distortion, though, because halogen lamps have a freakish-looking, totally unnatural, hue). The wiring has to come out through the mouth of the balloon and at the same time remain invisible. This may be trivial or it may not be - I can't tell. I'm looking for suggestions. What I need is a non-reflective covering to wrap around the wiring so that when a spotlight hits the cables, they won't produce a specular hilight (for visiblity, think: black on black). b) dispersing the light uniformly: sticks glow in the shape of, well, sticks. I need to distribute the light uniformly across the entire inner surface of the balloon. I realize that the tips will be darker, no matter how hard I try, so that's one sacrifice I'm willing to make, but I don't want the balloon to have bright glowing sticks visible through the skin. Suggestions? c) not masking out any color range because one lamp is blocking another one. That is, I can't have the lamps grouped like this:


           o
         o   o

        top view

because the visible light would be directly dependent on the angle of the balloon with relation to the camera - ergo a no-no. I need a maximum amount of diffusion inside the balloon - is there something I could mix with the gas (if so, then how would one go about that)? d) a way to get the contraption inside and out of a balloon fast without breaking it. If I break a lamp, I'll have to pay for it and these babies cost enough for me to make baby Jesus cry (let me put it this way - 9 lamps in 3 balloons will greatly exceed the rest of the budget I have available for the entire film). e) space reserved - I had one more question, but I forgot it. I have 2 weeks to make this work, so any suggestions would be very welcome!

Extrarius

Apr 6, 2005 at 10:22 AM

Are you sure you require the light source to be inside the baloon? It seems like me a good way to do it would be to have a semi-focused light source shine on the baloon, but I guess that wouldn't work if you need the shot to include a huge area around the baloon (unless you could get it really focused). By shining on the back of the baloon, you'd probably get good diffusion and getting such a complex light setup (changing colors etc) wouldn't be as hard if you're not constrained to the volume of a baloon or the weight it can hold w/o deforming (even if you use wires, you probably don't want a baloon with corners =-).
Or, for diffusion, you could buy some of that plastic meant to be used in diffusion lighting (generally w/ the long flourescent lights) and maybe make a small box of it around the light. It might take two or three layers to get enough diffusion in such a small space, but it might work.

Eelco

Apr 6, 2005 at 10:25 AM

forget about the gas: its never going to float by itself.

just use fishing wire for the movement. simple, cheap, and quite invisible. it will probably be hard to create some sense of weightlesness though, which youre probably after.

what youd want inside the balloon are the mechanics, with some plastic diffuse lamp-bowl thingy around it, to hide everything that would otherwise be easily seen through the balloon. ideally it should consist of two halves you can click together. something like this most probably exists: dont askme where though.

for power you might be able to salvage some cellphone batteries. light, good power, and maybe you could match their specs with those of your halogen lamps, so you wont need a heavy-ass transformer.

how to get a 20cm-ish lamp bowl into a balloon: i have no fucking clue. maybe a lampoon like canvas constuction would work? maybe put a small gas cylinder inside to keep it in shape long enough to finish your take. if you use a closed balloon, be ware of warming air with all those lamps doing their thing. it might not be the effect youre after.

Crispy

Apr 6, 2005 at 6:24 PM

Extrarius: I don't exactly know what lighting equipment I will have available, but I'm sure the best there will be is a small number of hand-controlled 2-4 k spots and a number of fill lights. I know enough about lighting to say with certainty that focusing a beam of light on a floating balloon would be tricy to say the least, especially if I want to achieve a glow effect, which would suggest using a contra that would then risk falling into the lens (which, as any amateur photographer knows, would suck).

Your suggestion to make a small box/sphere around the actual light source sounds a lot more tempting, though. However, I am not really sure what the container should be made of. Giving it an elliptical or a spherical shape would sound the most logical.

Eelco:

>> just use fishing wire for the movement. simple, cheap, and quite invisible. it will probably be hard to create some sense of weightlesness though, which youre probably after.

Suspending the balloon isn't so much a problem as is hiding the three wires that go inside the balloon. I'm hoping these can be as thin as possible for the lamps to work - if then twisted together, they can hopefully be made as thin as possible...

>> for power you might be able to salvage some cellphone batteries. light, good power, and maybe you could match their specs with those of your halogen lamps, so you wont need a heavy-ass transformer.

I need a voltage controller outside of the balloon anyway, so there's no reason to try hiding the power source inside the balloon.

>> how to get a 20cm-ish lamp bowl into a balloon: i have no fucking clue. maybe a lampoon like canvas constuction would work? maybe put a small gas cylinder inside to keep it in shape long enough to finish your take. if you use a closed balloon, be ware of warming air with all those lamps doing their thing. it might not be the effect youre after.

As for the air warming up - I thought of this myself, really and I'm moderately worried - it's bound to become really hot in such a confined space. One solution would be to only have the lamps on during filming. The worst nightmare, indeed, would be a balloon blowing during the perfect take - blah. And, yes, I was thinking of using closed, inflatable balloons.

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