I’ve been wanting to take some underwater 16mm footage. I have two “danger cams” I can use. (I call them “danger cams” because they’re inexpensive enough that I wouldn’t mind putting them into situations that may result in damage.) One is an early model Bolex H16, and the other is a Krasnogork-3.
I’m thinking I can just make a box out of 1/2" plexiglass, screwing and gluing the top, bottom and back. The front plate and sides could be screwed on with rubber O-rings to provide a seal. That way I can remove them to load the camera, wind the camera, and replace (as needed) the front plexi. I think it would work, but there are a couple of technical issues I need cleared up:
[ul][li]How can I make a waterproof control so that I can activate the trigger? Some sort of rubber gasket and a rod?[/li][li]Is there a waterproof coupling so that I can attach a crank to wind the spring motor without having to surface and take off the side panel?[/li][li]Suppose I want to use my Arri 16S? Same sort of gasket-thing for the on- and off-mechanisms?[/li][li]Will I need ballast?[/li][li]Will 1/2" plexi distort the image? Should I use Lexan?[/li]How deep can I go?[/ul]
Johnny, I remember once seeing what amounted to being a very heavy ply waterproof camera bag. You might check around for one. Should be much less expensive than a housing. Not sure about depth though. Also consider whether a periscope will work for you.
I’ve always wondering about building what you are talking about but never got around to it. For the price of all those parts plus your time, you can buy one for probably just a little more like this one here. I don’t know how big your cameras are, so that case might be too big or small.
jimpatro: I’ve seen the plastic bags. The ones I’ve looked at seem to be made for specific cameras, especially video cameras. What do you mean by “periscope”? Shooting from a boat with the camera looking into a periscope? I’d like to get some shots from underwater, aiming up at a boat.
aeropl: It’s hard to say what will work and what won’t.
Here are some photos of cameras from my site. The lens on my Bolex “danger cam” is much smaller than the one in the photo. (Actually, I no longer have the pictured one.) The handgrip and pistol grip come off of the K-3, but I only have the one lens for it.
They used to make Bolex housings, but I can’t find any for sale online. Some for rent, but none for sale.
My experience shooting through plexiglas says it’s not the greatest. I suggest you get a piece and try some dry-land shots to see if you’re happy with the results.
Use a real port (Ikelite). Theirs use a compressed O-ring as a seal.
I would think that plexi would be too soft and subject to deformation - a cast acrilic might work, but I suspect a box made of sheet would fail at much over 50’ or so.
The only underwater cimema rig I’ve seen was cast metal. I have a couple of Ikelite housings for 35mm SLR - check out their site for ideas. They may make custom housings, but it would be pricey.
The Ewa-Marine “bag” I’ve got is rated for 10m.
Ballast? You won’t know until you test it, but I’d suspect you will. The Ikelite tray (handle) has a lead ballast in it.
As for fittings, I’d suggest getting a “known good” commercial housing a cannabalizing for shutter control, focus (if applicable), aperature, and maybe winding - the torque used in that operation might flex the plexi too much
Have you ever seen toy periscopes that look like a square tube with a mirror on each end? I’m just talking about building one thats a little heavier duty.
First surface mirrors of course.
Another route is to rent an underwater DV rig from a dive shop.
Do a film look in post and that should work. Cutting from surface shots to submerged footage is going to be a drastic change in look anyway so I bet intercutting film and DV won’t be that distracting.
I suppose I should start this out in a way similar to legal threads: I am an engineer, and I have designed underwater pressure vessels, but I am not your engineer, and I am not designing your pressure vessel. With that being said: Just how well this would work depends on a number of things, the most important being:
[ul][li]how large the box is,[/li][li]how you construct the box (how the edges are joined, I mean), and[/li][li]how you seal the box.[/ul][/li]The first point should be pretty intuitive: the larger your box, the more force (pressure times area) there is on the Plexiglas, and the more likely it is to break.
The second point is a little more obscure, but still pretty straightforward. Screwing into Plexiglas creates a pretty weak joint if the screws are supposed to support the Plexiglas in shear: the screws will crack through the side of the Plexiglas.
If you make a box (let’s say it’s 12X12X12), the natural way to make it would be to cut two pieces 12X12, two 13X12, and two 13X13. Assembled this way, the only thing that keeps the 12X12 pieces from imploding is the row of screws around the edge: a terrible design. A better way to make it would be to cut six pieces 12X13; this way, every side is supported by two other sides. Better yet, weld up an internal frame out of square tube steel and attach the sides to that.
The third point above relates to sealing. When you have three surfaces that come together (like at the edge of a box) it’s a real bear to seal because you don’t have a continuous gasket in all three directions. This will be almost guaranteed to leak at any reasonable depth.
I would like to suggest that, rather than making a box, you construct a cylinder. If you don’t need the vessel clear on the top and sides, use an aluminum or steel tube. Cut some square pieces of Plexiglas and hold them onto the tube with four threaded rods at the corners (outside of the tube); these can be pretty loose because water pressure will help hold the Plexiglas on. Cut some gaskets to seal between the tube and Plexiglas. This design should perform much better than a six-sided box, because the sealing issues are simpler, and, more importantly, the construction is inherently stronger. You’re not relying on screws to hold the sides on, the front and back are supported all the way around, and the cylinder is much stronger (assuming a reasonable material and thickness).
I assume you just need to push the trigger? If so, a hole with a rod through it and an O-ring should work quite well. Except… first, you need to make the rod large enough to make room for an O-ring groove. Then, remember, the water pressure will push on the rod, so you’ll need a spring or something to keep that from happening. Also, if you put the O-ring groove on the rod, you don’t have much travel before the O-ring moves through the side. Putting the O-ring in the vessel housing is better, but that’s harder to machine. You could maybe weld on a small tube, if you go to a metal housing.
Seems like you could do this the same way as the trigger: a through rod with an O-ring, and a handle to spin on the outside. Or am I missing something?
I’m sorry, I don’t know what this means.
Probably. The density of Plexiglas is near water. The question is how heavy the camera is. Water is ~62-64 lbs/ cubic foot, so you should be able to calculate the buoyancy of the air space inside and compare that to the weight of the camera.
This I don’t know. From my Googling research, it appears that Lexan is less brittle than Plexiglas (which should help the screws-tearing-themselves-out issue) and a little stronger, which seems to me a good reason to favor Lexan.
Depends a lot on construction. Assuming a 12X12X12 size, I calculate that the ends of a tube, or a box with an internal frame. will implode at about 100ft. A box with overlapping-side construction will implode at about 35 ft. A box with only screws holding the sides in will be much worse than that, and it depends on so many complex things that I’m not gonna bother calculating. Oh- realize there’s no safety factor here, so this assumes perfect construction, no additional stress risers (ahem. holes.), and a lot of luck. I wouldn’t go more than 1/3 of that depth, and a lot less than that if there is any reason the believe your personal safety would be compromised if this imploded.
Of course you can do better by getting thicker Plexiglass or reducing the size of the container.
I did think about a cylinder, since I know that they make better pressure vessels; but I was concerned about excess bouyancy. On the other hand, if I’m adding ballast anyway then I shouldn’t worry about it.
My oldest Bolex is cheaper and more reliable than the Krasnogorsk, so I think that it would be a better choice for an underwater camera. Its dimensions with a lens are approximately 9"x9"x3", which would be the (approximate) inside dimensions of the box.
I had thought of putting 1/2" plexi “frame” on the inside that would be screwed and glued to the panels. I thought this would be a good way of providing a stronger structure for the screws that hold the removable panels together. The removable panels would have a groove cut in them to accept a rubber gasket, or an O-ring if I could find one the right size and shape.
For the crank and other controls, it occurred to me that a marine supply store might have some sort of pre-made coupling; like for passing cables through a boat hull.
It would be better if I used an electric camera (hence, the reference to the Arriflex). I do have an electric motor vor the Bolex, which would add about 2" or so to the width. I have another motor that has a regulator for varying the speed. The regulator is the same width as the motor, and the same length as the camera body. Unfortunately, those old motors run on 30 volts for 24 frames per second. 36v would be better to allow some leeway on the upper end. When I used the old Bolex motor, I ran it off of six 6v lantern batteries wired in series. Very bulky. (Although it might be good for ballast!) I’m sure I could have someone make a 36v NiCd battery pack for me that would fit in the housing. Then the only control I’d need is the single pushrod. BTW: Thanks for mentioning the spring. I hadn’t thought of the water pressure pushing on the rod.
Speaking of rods: The Arri has a lever that must be puched from one direction, and it locks on. A different lever must be pushed to turn it off. The Bolex has a spring-return trigger; but care must be taken not to lock it in the “on” position. The voltage regulator does not have a lock. Anyway, if I go with an electric motor I can forget about sealing a crank.
I’ve been diving down past 100 feet, and it was cold and dark. In Southern California. Up here I won’t go that deep. Actually, until I get back into diving, I’ll be at snorkeling depths. Say 3 meters, max.
Okay, now I have a lot to think about. A cylinder does sound like the better option. I’ll have to look around to see if I can find one of the proper diameter. I don’t know how I’d cut a steel tube, keeping the ends true; but it sounds like a better design.
One more thing, about the lens port: Xema advises against using plexi for it because it will not give a good image. Then there’s the pressure problem. How about a round plate with a 2" hole in the middle? That should solve the pressure problem. What material could I use for the transparent cover, that would be strong and give a good image?
Extraneous: I’ve e-mailed Ewa-Marine to ask if they have a bag that will fit my Bolex. It would certainly be a lot cheaper and easier than making my own housing!
(Of course, I’d still like to find a purpose-made housing. They’ve got to be out there somewhere!)
Realistically, I think a good rule of thumb when thinking about construction of this housing is that you want the structure to “hold itself together” under pressure, so that the screws are primarily used to keep all the pieces in place, and not at all for withstanding the pressure. Thus frame = good.
You’re talking abut low enough pressure that I think a gasket would work fine, anyway. If you want an O-ring, you can buy O-ring cords in 50’ lengths. Just cut the length you need and join the ends with superglue. I’ve used these do-it-yourself O-rings for pressures up to 10,000 psi without leakage (with careful assembly), so you should have no problem at 3 meters.
Excellent idea. Seems like I’ve seen similar things for vacuum chambers and other applications with modest pressure differential, so you have other options if the marine supply store does not pan out.
A cylinder would definitely be easier to successfully construct. Just remember that vessels under external pressure are prone to buckling, which doesn’t happen with internal pressure. This means a cylinder that is rated to hundreds of psi for internal pressure might not suffice for your application. For example, by my calculations, a schedule 40 PVC pipe would be pretty questionable at 10 feet (although a schedule 80 pipe ought to be good to 60 ft, so that would be a possible material). Because buckling is the issue, I would lean toward a metal cylinder like steel or aluminum because metals are much stiffer than plastics, and thus more resistant to buckling. My gut feeling (sans calculations) is that any metal cylinder thick enough to afford room for a reasonable gasket is thick enough not to buckle.
I would think that if you can get a machine shop of metal supplier to cut your tube for you, the resulting cut would be straight enough. I’ve had pretty good luck with the trueness of a simple cutoff saw sawcut. No guarantees, though, and you’d have to smooth it out by hand. However, if you use a gasket (and you can, easily, at 10ft), you have a little bit of leeway in cut flatness.
Why not just use glass, then? Someone must make some nice 3" glass disks that you can fix in place with a lip around the edge.
How thick would the glass have to be? I’m also guessing that I can get a dome from an actual housing that would work. I’ll have to figure out how to attach the glass to the plate.
aeropl: I took another look at the eBay link you provided. The dimensions are too small for my cameras; but it looks like it would fit one of the cameras I’d like to get. Too bad I don’t have an extra five kilobucks lying around to get it.
How thick? Not very for the pressure. Glass is pretty strong (underwater glass spheres). Personally, if we’re talking a two or three inch disk, I’d be more worried about cracking it by bonking it into something, so I’d tend to get a thicker piece… say twice as thick as window glass. Maybe a snorkeling mask face plate would work? Is that optically good enough? If your glass piece is small enough you could probably just seal it on with some silicone caulk.
Make that optical glass (or go to ikelite’s site and find replacement “ports” (the piece through which the lens is pointed).
Cutting large-diameter tubing is something for a horizontal band saw (read: machine shop or metal seller/fabricator) do to - a milling machine to finish the ends wouldn’t be a bad idea either.
I found an actual Bolex H16 underwater camera housing. It even comes with an H16 and a 10mm lens. Should be here Wednesday.
So, I have the zodiac. I’m getting the housing. The Strait of Georgia is right outside. Now all I have to do is find my PADI and NAUI cards, get refresher training and gear, and I can film underwater!
BTW: I also picked up an underwater video housing. It’s made of an 8" Plexiglass tube and is similar in construction to the housings described in the booklet I mentioned in this thread.
