PVC Housing: Please Evaluate My Design!

[V. G. McGillicuddy]

Hi There,
I was thinking about building a housing for a camcorder, and I would appreciate any opinions.
Here's the very simple plan:
For the main body, I will use 6" PVC pipe. The front will be a standard end cap, with a clear window (1/4" plexiglass?) for the camera to "look" out of. This window will be fastened on with small bolts and sealed with silicone.
For the rear of the housing, I will use a threaded fitting with a cleanout plug. The front edge of the threaded plug will have an o-ring to ensure (or at least, increase the chances of) a watertight seal.
I was also thinking of having a small tube protruding from the bottom with a transparent window in it, as a sort of early warning system for leaks.

The housing will have no external controls. I will power up the camera before I stick it in the housing, and turn it back off after the dive. Yeah I know, but hey, it's affordable.

Has anyone tried this type of design before? Does it work? Is there anything in particular I should watch out for? Are there any major flaws in this design? How deep do you think it will go?

Help of any kind would be most welcome.

Regards,

V. G. McG.

 

[nwbrewer]

I haven't tried this yet, but I've thought about it. Maybe after I get my canlight to no longer leak!

You may want to check out some of the threads in the DIY forum. Good info there.

Jake

 

[Nostromo]

V.G.

I think that having absolutely no outside controls would be a big help in reducing complexity and possible failure points. Overall your design seems okay. I would be most concerned with the plexi window, and it's attachment bolts. If it were me I'd forgo the bolts and try to epoxy (perhaps PVC cement would work better) the plexi directly to the PVC tube. Both the plexi and the PVC should be the thick stuff of course. Keep in mind epoxy may fog up plexi however. Some experimentation is definitely recommended. When inserting the camcorder I'd push the lens up against the plexi and keep it in place with some sort of foam against the rear, which would tighten as you screw in the cap. I would forget about the "leak detection tube". It sounds like a failure point, and if you want to check for leaks you could just turn the housing around, tip it forward and look for water that way. Besides it would make the resulting video more amusing.

As for how deep it would go, I have no idea. So much depends on your materials, and overall construction. On that note, I would HIGHLY recommend a few depth tests on the housing WITHOUT THE CAMERA in it. Who knows, it might survive well beyond any recreational depth, it might catastrophically implode at thirty feet. Who says engineering is dull anyway?

Something else to consider is how much light you have to work with. If your camcorder has a low light setting that my help, but without an auxiliary light or lights, your video quality will suffer.

As mentioned above, the DIY forum would probably have some info on this subject.

Best of luck, and have fun!
e.a.e.

 

[Nostromo]

One more thing...

There is the issue of fatigue life.

You have been warned.

e.a.e.

 

[makomike]

You can get a clear polycarbonate that can be glued(welded) onto the PVC. I have used it many time in my business building custom lights and fixtures for swimming pools. I think that might be more reliable. The polycarb can be machined as well. It comes in many form incl. 'almost' standard pipe sizes. I often used 1.25 ips. good luck

 

[diversteve]

The front will be a standard end cap, with a clear window (1/4" plexiglass?) for the camera to "look" out of. This window will be fastened on with small bolts and sealed with silicone.

For the rear of the housing, I will use a threaded fitting with a cleanout plug. The front edge of the threaded plug will have an o-ring to ensure (or at least, increase the chances of) a watertight seal.

Hi,

First of all, the "plex" needs to be thicker. Look at the Equinox website, you can see that they use thicker material. And Makomike's idea about Polycarb instead is a good one, I have an old Qwest housing and that's what they use.

I saw a similar design once, the maker used a PVC tube, with a PVC connector glued on both ends, he then squared off the inside bottom surface of the connector, cut a round piece of plex the right size for the i.d. of the opening, dropped in an o-ring and used standard draw latches to lock it all in place. Nice thing about the design is that it eliminated having to get a good seal on the mating surface of the PVC tube and the plex since the seal was on the inner flat surfaces with the o-ring in between. And more importantly it saved having to cut an accurate round groove in the plex for the o-ring.

You can get latches online or at any industrial supply house. Southco or Reid make them. (among others) However be aware that they might develop a lot of torque. If you use over-center latches, you could design it so the latch mounting screws go through the connector wall and partially into the PVC tube itself for strength.

Wouldn't having the threaded fitting take a lot longer to close? And can you apply enough torque to close it by hand w/o having to clamp the body of the housing somehow first? Especially if it's wet? Another advantage of the plex idea is that you can visually see that the o-ring is clamped uniformly. If you're threading a mating surface with an o-ring between them, I'd think there's a higher likelihood of kinking or tearing it as you tighten.

Also how will you see the viewfinder? Personally I'd use clear plex on both ends. In a flood situation - assuming a small leak - if you get the housing dry and the back open fast enough you might save the camera.

I was also thinking of having a small tube protruding from the bottom with a transparent window in it, as a sort of early warning system for leaks.

I wouldn't, it's just another potential leak point. And if it's a clear tube will you even be able to see the water inside the tube while underwater? I don't know. Plus in my experience I stay behind and slightly above my housing while filming so I'd never even see the tube.

Also you may need a place to add ballast on the bottom(lead weights) to compensate for the buoyancy of the housing. One option to consider is securing softweights in the curved space underneath your camera mounting bracket.

What about handle attachment? Some mount to the bottom.

The housing will have no external controls. I will power up the camera before I stick it in the housing, and turn it back off after the dive.

Carry the camera remote and use it to power up the camera pre-dive. You'll find that you'll have much better chances of avoiding a leak if you don't open your housing on a boat or the beach. I seal mine in my hotel room whenever possible.

If you want to add some basic controls, Ikelite sells their control rods separately.

Regarding depth, I've seen some thicker (gray?) PVC tubing at Home Depot, I don't think you'd exceed it's working pressure rating at rec. scuba depths.

As mentioned, review the DIY forum, there were a couple of threads last summer from people who did this.

my .02

 

[makomike]

Good points steve. I was a little leary of the clean out plug idea also. Cleanouts are a drain,waste,vent fitting and not rated for pressure. I have used them under pressure, but with a teflon paste. Even then half of them leak. Would need a tool to remave also. The latch idea is interesting. schedule 40 pvc I believe is rated to 140psi. 1 ATA = 14.7 psi 132feet of seawater = 5 ATA 5ATA x 14.7 = 73.5psi

Pipe is round though and I'm not a physics guy, assuming it was a schd40 cylinder I think it would be ok. Assuming the seals were rated as high. Thats alot of assumptions and I know people alot smarter than I will find all the faults that I can not.

 

[diversteve]

V.G.

I had time to do a little checking, it appears that most of the inexpensive tube-type housing mfrs' use an acrylic plastic tube, not PVC for their housings. Either 1/2" or 3/8" thick. Also they seem to universally use 1/2" cast acrylic optical grade plates for the ends. Or Polycarbonate as mentioned by MM previously.

There's probably a good reason no manufacturer uses PVC. My guess would be possible failure at pressure points between the o-ring/port and the PVC pipe itself. If it flexed even slightly, it would probably leak. I do know some of the better non-metal housings are Polyurethane, but that may be as much for it's casting properties as it's strength.

 

[JeffG]

There's probably a good reason no manufacturer uses PVC. My guess would be possible failure at pressure points between the o-ring/port and the PVC pipe itself. If it flexed even slightly, it would probably leak. I do know some of the better non-metal housings are Polyurethane, but that may be as much for it's casting properties as it's strength.

A lot of scooter bodies are made of PVC and they are good to hundreds of feet. Plus some (may not be all) Diverite canisters for their lights are made of PVC.

Using PVC is a non-issue.

 

[diversteve]

Good points steve. I was a little leary of the clean out plug idea also. Cleanouts are a drain,waste,vent fitting and not rated for pressure. I have used them under pressure, but with a teflon paste. Even then half of them leak. Would need a tool to remave also. The latch idea is interesting. schedule 40 pvc I believe is rated to 140psi. 1 ATA = 14.7 psi 132feet of seawater = 5 ATA 5ATA x 14.7 = 73.5psi

Pipe is round though and I'm not a physics guy, assuming it was a schd40 cylinder I think it would be ok. Assuming the seals were rated as high. Thats alot of assumptions and I know people alot smarter than I will find all the faults that I can not.

Mike,

I'm thinking without lights V.G. is probably going to see 1/2 that depth before the light falloff is too great.

Even in Maui... - what a sweet deal that is...I've been there 4-5 times in the last decade but can't swing moving there yet.