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Old Feb 21, 2011, 01:41 PM
29 rods from you in western WI
Karl B's Avatar
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control seals, camera housing

Greetings,

I have been exploring ways of obtaining underwater video using a Sony Bloggie Touch. This forum seems the closest match on RCG. If anyone has comments or suggestions, please post them.

Background:
I've used previous cameras for industrial video analysis, recording wood fabrication equipment in somewhat hostile environments. To protect the cameras within inches of high speed saw blades and flying scrap, I've made simple housings out of 1/4" lexan. Holes drilled through the case allow turning the equipment on, changing settings, and starting video. The holes were simply sealed with masking tape between uses.

When I obtained the Bloggie Touch, I realized that it should be easy enough to go one step further and waterproof the box, so that it could safely be used while boating or at the beach. There are only 3 buttons (on/off, still shot, video start/stop) that need to be controlled. The touch screen is used mainly for digital zoom and review, so I don't plan to enable it's use within the case. A transparent back is necessary for framing the shots, though.

To minimize the seals required, I designed a solid housing of HDPE with a lens window on the front and a transparent plate on the back for the view screen and access to the case.

Here is the housing, designed in Sketchup:
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Old Feb 21, 2011, 01:53 PM
29 rods from you in western WI
Karl B's Avatar
Joined Jan 2003
4,885 Posts
For controls, my first thought for a weather resistant seal was to drill a hole tight enough to slightly compress a piece of silicone fuel tubing, with a wire shaft compressed within it.

I also researched control seal designs for higher pressures. Commercially available controls are available from Ikelite, maker of underwater camera housings. Off the shelf, they're a bit large for the compact design I have, though I plan to look into them further. They consist of a hollow bolt with an external O-ring seal against the case, and an internal groove for an O-ring to seal the shaft.

Finding online guides on O-ring seal design, I came up with my own idea. I am limited in that I have access to a vertical mill, but not a lathe. A 1/4" diameter, .060 deep counterbore contains a 1/8" ID x 1/16" O-ring, and a cap plate compresses it against the shaft.

I made a simple test fixture to apply pressure to the seals and connected it to a regulated air supply.
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Last edited by Karl B; Feb 21, 2011 at 02:30 PM. Reason: added pic
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Old Feb 21, 2011, 02:02 PM
29 rods from you in western WI
Karl B's Avatar
Joined Jan 2003
4,885 Posts
I turned the regulator down to 20 psi, drizzled water over the test controls, pointed it into a rag (to contain the drill bit if the seal failed fantastically), then connected the air line to the fixture. Technically this is the reverse of the direction that the O-ring seal will be pressurized, but it is close to symmetrical in the way it acts. The fuel tube seal is fully symmetrical.

Both seals held at 20 psi, though I imagine that at pressure, repeated action of the fuel tube seal would eventually push the tube into the case. Gradually increasing pressure, the fuel tube seal started bubbling at around 40 psi. For the record, the tubing (Aerotrend standard size) was about .220 diameter unstressed, hole was .209, and the drill bit was .089. If the tubing could be contained, this would work for a weather resistant seal, but I wouldn't trust it submerged more than momentarily.

The only problem with the alloy dowel pin control shafts was how to grip them.
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Old Feb 21, 2011, 02:16 PM
29 rods from you in western WI
Karl B's Avatar
Joined Jan 2003
4,885 Posts
As built, the lens cover and rear plate are simple flat surfaces. I plan to cut a flat rubber gasket to seal them. Here is the camera inside the case. I darkened the lens port with a sharpie.

The rear plate is 1/4" lexan, while the lens port is 1/8". Does anyone know how to calculate the pressure resistance of these flat plates? I've seen everything from 1/8" thick x 3" diameter to 1/2" thick x 4" square plates used. While a thick rear plate isn't an issue, the lens port will give better results if it isn't overly thick.

To both grip the control shafts and keep them from pulling out, I drilled out small nuts to about .120, then pressed them onto the ends of the shafts. Such things are necessary when lacking a lathe to cut e-clip grooves. Because there is little clearance between the back plate and camera, the back plate was counterbored to clear the retaining nut.
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Last edited by Karl B; Feb 21, 2011 at 02:34 PM.
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Old Feb 21, 2011, 02:29 PM
29 rods from you in western WI
Karl B's Avatar
Joined Jan 2003
4,885 Posts
The controls need spring returns. They are also too long.

I shot some forgettable test video using the case of some downhill skiing at night. A big problem is reflections from the chrome plated camera case around the lens: they bounce back against the inside of the lens port, causing horrible flares in high contrast scenes.

Next steps:
I'm checking out a dive shop that sells Ikelite housings. Ikelite sells their large control shafts, which are adequately described on their website, and also a control button kit, which isn't described well. If the control button kit contains shafts and seals, I can use them without monkeying around with press-fit drilled-out nuts that protrude half an inch from the case.

Back and lens port seals: I can cut an O-ring face seal groove on the body lens port by fabricating a fly cutter of the proper width.

Lens port design: either a full-size front plate, similar to the rear, much closer to the lens, or a conical bore using a large countersink bit.
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Old Feb 22, 2011, 04:45 PM
29 rods from you in western WI
Karl B's Avatar
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Quote:
Originally Posted by Karl B View Post
full-size front plate
Some design work done today, HDPE core with 1/4 clear lexan front and back. I may try an O-ring between camera and front as a glare shield.
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Old Feb 23, 2011, 06:08 AM
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Hi Karl,

Do you have a CNC machine to make the box etc?

If you put a bit of a radius around the corners you could put an o-ring in (to seal between the box and the cover)? We do this on some of our oil filled boxes here.

http://www.sub-atlantic.co.uk/media/.../Drawing_2.pdf

Martin
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Old Feb 23, 2011, 08:24 AM
29 rods from you in western WI
Karl B's Avatar
Joined Jan 2003
4,885 Posts
Hi Martin,

No CNC, just a vertical mill. Provided the inside corners could be radiused, would catalog size O-rings be likely to fit? I wouldn't want to stretch or compress one too much, and custom seals aren't in the budget for a one-off.

While I don't anticipate personal use beyond snorkeling depth, attaching to a pole, ROV, or tether could conceivably increase the depth requirements.

Thanks for the comments,
Karl
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Old Feb 23, 2011, 09:50 AM
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Hi Karl,

I think you can buy o-ring material on a reel and there's special glue to glue the ends together.

I have one of these machines and would possibly be interested to help you if you would like? I guess doing radiused corners on a vertical mill is not that easy, but I may be wrong

http://www.cnc-step.com/englisch/htm...ter_engrav.HTM

It won't do steel, just aluminium and composites, maybe a bit of brass?

Send me a PM if this is of interest? I need a 3D model, which it looks like you have, preferably as an STL file and then I have software to calculate the CNC paths.

I'm making an ROV of my own, hence the machine.

Martin
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Old Feb 23, 2011, 01:43 PM
29 rods from you in western WI
Karl B's Avatar
Joined Jan 2003
4,885 Posts
Quote:
Originally Posted by martinjdw View Post
I think you can buy o-ring material on a reel and there's special glue to glue the ends together.
I found a kit supplier online: http://www.sealsales.com/o-rings/o-ringkits.shtml

Thanks very much for the offer. I have the core and lexan plates cut, though I haven't done the groove yet, as I don't know what thickness gasket I'll find. I'll finish this one myself, as I want to prove or disprove cut gasket sheet as an adequate seal.

BTW, I'm working in the free version of Google Sketchup, and while it's easy to master, it isn't a substitute for a real solid modeling program. The closest I could come to file compatibility is dxf. It also doesn't draw real circles and arcs, just segmented polygons.

Should the flat gasket plan fail miserably, I'll look into the o-ring kit and go from there. I actually found a DIY from a guy forming 1/4" diameter silicone rod inside vinyl tubing, though he claims it takes a week to cure. I'm surprised it cures at all. Compressed air removes the silicone, which is butt jointed easily with more silicone. I'm not sure if I want to try that route, though I could make a nearly round bead on a sheet of glass.
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Old Feb 23, 2011, 01:56 PM
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Sounds good, i'll also be interested to see how things go, keep us posted
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Old Feb 24, 2011, 02:19 PM
29 rods from you in western WI
Karl B's Avatar
Joined Jan 2003
4,885 Posts
new housing

Just missing the face gaskets. Control springs and blind holes for o-ring compression plate bolts are new this version.

I plan on buying some flat gasket material tonight (or a large innertube...) to test in the sink.
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Last edited by Karl B; Feb 24, 2011 at 02:28 PM.
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Old Feb 24, 2011, 09:44 PM
29 rods from you in western WI
Karl B's Avatar
Joined Jan 2003
4,885 Posts
Two steps forward, one step back. I drilled the back plate control holes 1/4" too far to the right.

I'm going to see if the previous back plate will fit. If not, it won't be too hard to remake.
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Old Feb 27, 2011, 03:54 PM
29 rods from you in western WI
Karl B's Avatar
Joined Jan 2003
4,885 Posts
I ordered a pack of 4.5 x 1/16" O-rings, which will fit the groove with minimal design modifications. That's why I didn't mill the grooves yet.

While I was at it, I ordered all stainless hardware. Instead of dowel pins, I'll use shoulder bolts. The head will capture the spring on the outside, with a nut on the threads inside. Since stainless 1/8 x 5/8" shoulder bolts aren't available, I jumped up to 3/16". I ordered parts long enough to replace the rear plate with 1/2" if necessary.

Funny how a few $$ here, a few there add up so fast, especially stainless bolts, nuts, springs, etc. Still cheaper than Ikelite, even if they made a housing.
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Old Mar 04, 2011, 02:03 PM
29 rods from you in western WI
Karl B's Avatar
Joined Jan 2003
4,885 Posts
The hardware is here, and version 4 is complete. Sink testing is tonight, and I'll post some shots here.

Assembly is a bit tedious, primarily getting the o-ring to lay in the gland. I plan to pack the glands with a bit of vacuum grease to help the seal as well as assembly.
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