Pressure Pot to Test DIVE LIGHTS!

[DimitrisV]

You cut that big old tank without any support?

A friend of mine cut the cylinder on lathe and also the aluminium ring (i didn't find any othe word to describe it)
He remove 0.5 -1mm from the cylinder to take away the paint and the scratches.

How much pressure do you think those 4 latches can hold back?

I hope to hold 10bars. I haven't test it yet to 10bars bacause i need a better oring. Till now only to 2 bars
If I see that the latches cant;t hold 10bars I will replace them with stainless steel.

BR
Dimitris

[350xfire]

A friend of mine cut the cylinder on lathe and also the aluminium ring (i didn't find any othe word to describe it)
He remove 0.5 -1mm from the cylinder to take away the paint and the scratches.

I just noticed on the pics he did use a live center on the end. That's a pretty nice big lathe!

[DIWdiver]

I just noticed on the pics he did use a live center on the end.

Yes, but then he cut the end off!

[SmokedCPU]

I agree that trouble occur in shallow water.
The only recurent light trouble i got was happening in the beggening and deco of the dive, since there was only few drop in the light, for a 90min dive around 75ft. If it was occuring at depth, it would have filled the can completly

[gasdiver]

What is the wall thickness of an AL 80 after you cut the top off of it? I'm thinking about making a pressure pot out of an old AL 80 and need to know how much room I have to work with.

[350xfire]

Not a lot. I threaded my holes to 1/4"-20 and there really is no room for an oring.

[gasdiver]

Here is why I'm asking: I need to know how deep to cut the groove around the outside for my clamping blocks. I have a buddy with a large lathe who's going to face the cylinder and cut the groove.

[lucca brassi]

that design will made you some fun with nuts when you want to seal pressure pot

[350xfire]

Gasdiver, that is similar to what I did except I used a gasket and threaded 6 holes with 1/4"-20 into the thickness of the cylinder. Like Luca said, it does get tedious tightening 6 nuts. But it works.

[gasdiver]

I've got some knobs that will spin down pretty quickly. My concern is will the clamp blocks stay in the groove or slip out. I may need to put a cam band on them. If you don't mind, can you measure the wall thickness of your AL80 pressure pot? I'm assuming the wall is 1/2" and the groove I cut will be 1/3rd of that. If the wall is thicker I can cut the groove deeper and the issue of the clamp blocks slipping out becomes less. I've Googled until I'm blue in the face and I can't find the standard wall thickness of an AL80 anywhere.

[350xfire]

I've got some knobs that will spin down pretty quickly. My concern is will the clamp blocks stay in the groove or slip out. I may need to put a cam band on them. If you don't mind, can you measure the wall thickness of your AL80 pressure pot? I'm assuming the wall is 1/2" and the groove I cut will be 1/3rd of that. If the wall is thicker I can cut the groove deeper and the issue of the clamp blocks slipping out becomes less. I've Googled until I'm blue in the face and I can't find the standard wall thickness of an AL80 anywhere.

Yes, I was going to mention that, looks like those bocks may be an issue. Get a couple of hose clamps around them! I think 1/2" is about right. There is just a bit of metal left on each side of my 1/4"-20 bolts. I'll measure tonight.

[DIWdiver]

After turning the OD smooth and clean, I have exactly 1/2" left.

And why go to all the trouble to make those lid launch trigger mechanisms, er, I mean clamp blocks?

I turned the ID smooth and fit the o-ring totally inside the ID, leaving the full 1/2" for the 1/4" bolts.

I use socket head cap screws and an allen wrench. Makes fast work of driving in the screws.

[gasdiver]

Thanks DIW, that helps me a lot.

[DIWdiver]

If you really want to use bolts external to the tank OD, I would mount a permanent ring to bolt into. Much safer and easier to work with. Not that there's much energy stored in the system when pressurized (assuming you get all the air out), but the tank is somewhat elastic, as are hoses, etc, so there's enough energy there to pop the lid and make a mess, maybe even hurt you.

[SmokedCPU]

you guys are making strange plans to make complicated pots ... should make a shooting session with mine someday

i got a damn big 6'' steel pipe heavy wall, plate for flange, bottom (12x12'') and lid are .5'' steel
i dont know why, but i dont move it when its full of water... I got evrething weld and then faced the flange, and grooved for the Oring, used in pool filter ... a big one, bought 3 .... should be enought for life .... then i use 8 bolt grade8 to hold this togheter.
Hand tight is enought to bring 3 canister mag and a bottom timmer to 130psi.
Evrething is paint scuba RED, its nice, and also warn you that if you hit your legs you will remember, eventought, we fit well toghether since one year.

can somebody show me the maths to know the pressure that i should not exceed with bertha ?

[gasdiver]

If you really want to use bolts external to the tank OD, I would mount a permanent ring to bolt into. Much safer and easier to work with. Not that there's much energy stored in the system when pressurized (assuming you get all the air out), but the tank is somewhat elastic, as are hoses, etc, so there's enough energy there to pop the lid and make a mess, maybe even hurt you.

I agree with you, but my problem is that I don't have a lathe or mill big enough to make this myself. I've got some other ideas on how to simplify the design, so I'm still on the drawing board with this...

[lucca brassi]

you guys are making strange plans to make complicated pots ... should make a shooting session with mine someday

i got a damn big 6'' steel pipe heavy wall, plate for flange, bottom (12x12'') and lid are .5'' steel
i dont know why, but i dont move it when its full of water... I got evrething weld and then faced the flange, and grooved for the Oring, used in pool filter ... a big one, bought 3 .... should be enought for life .... then i use 8 bolt grade8 to hold this togheter.
Hand tight is enought to bring 3 canister mag and a bottom timmer to 130psi.
Evrething is paint scuba RED, its nice, and also warn you that if you hit your legs you will remember, eventought, we fit well toghether since one year.

can somebody show me the maths to know the pressure that i should not exceed with bertha ?

++1

[wquiles]

Guys, my apologies if this has been asked before, but can THIS Paint Pressure Tank be used for testing flashlights? The construction looks pretty strong (at least from the web site!).

Will

[DIWdiver]

It's rated to 60 psi, only 4 bar. It would certainly go somewhat higher than that, but who knows how much?

The problem is it's got a big diameter, and only four points for keeping the lid on. That puts a lot of force on each one.

[eh4]

so some of you take lights down below 130+ feet of water (60 psi paint pot for instance) ?
I can hardly imagine.
Would minimizing the quantity of gas space inside of a light or other container make it more resistant?
Say for instance if the same seal is only protecting a cc of compressible gas instead of 2 cc?

[josb]

so some of you take lights down below 130+ feet of water (60 psi paint pot for instance) ?
I can hardly imagine.
Would minimizing the quantity of gas space inside of a light or other container make it more resistant?
Say for instance if the same seal is only protecting a cc of compressible gas instead of 2 cc?

The answer on your first question is YES.
The answer on your second one is NO.

Explanation 1, yes we go sometimes deeper then the 130 feet (± 40m) but that's not only the reason to test dive lights to a bigger depth then this, you would also like to have some safety ( I like a 100% safety and I test my lights up (down) to 10 bar (100m).

Explanation 2, it doesn't matter how much air is behind your seal, 1 cc will only be faster filled then 10 cc when it starts leaking.
It's the seal that should be OK regardless of the amount of air behind it.

[wquiles]

Thank you guys. It seems the unit from HF would indeed be a good first test platform (obviously not to 10 bar!). I think I am going to get one to start playing with this stuff. I will report back when I get it

Will

[350xfire]

Will:
Yes, I brought it up before. I do think that it would be a nice simple solution to manufacturing one from scratch. For $80 you can't go wrong.

[Codiak]

Joshb,
The only thing that's 100% with water and leaks, is that the water will leak in sometime.
If I was selling a light i only guarantee it to 50% of the psi I tested it at... But for DIY test, when it leaks I'll fix it for the next dives and switch to my backup.

[josb]

Joshb,
The only thing that's 100% with water and leaks, is that the water will leak in sometime.

Yes, but depends on your maintenance.

If I was selling a light i only guarantee it to 50% of the psi I tested it at... But for DIY test, when it leaks I'll fix it for the next dives and switch to my backup.

OK, I would do the same when I would sell my lights, advertising with a 50% safety (and knowing that there is still an extra safety) but I wasn't talking about selling.
By the way of course you can buy what I build

When it leaks at your first dive OK you have to switch to your backup but ...... you did a bad job.
Once I take one of my lights down on a dive I know its OK and not leaking (exept for that one time I finished a light just a couple of days before the holiday, it was OK in the pressure pot but the sealing cap on the toggle switch started to leak after a couple of dives, now I never use toggle anymore)

[wquiles]

I am curious and wanting to learn more about testing, now that I have the HF pot on its way to me. How long do you guys leave the light in the pressurized pot before you check for leaks? 24, 48 hours? Longer?

Will

[josb]

I am curious and wanting to learn more about testing, now that I have the HF pot on its way to me. How long do you guys leave the light in the pressurized pot before you check for leaks? 24, 48 hours? Longer?

Will

If it doesn't leak in the first couple of minutes why would it start to leak after 24 hours?
I usually put it in for 30 minutes to 1 hour or so.
When I want to test a switch (for instance a piezo) I go more rapid up and down in pressure to see if I get unexpected switching happening.

[350xfire]

I do 2 hours. I recently developed a small leak on mine so I will leave it in longer and let the compressor cycle a few times.

[eh4]

Are you guys using a color changing test paper like you'll find inside of a cell phone? Seems like with all the trouble of pressure testing you wouldn't want to simply count on a visual inspection, too easy to miss a bead of water in a seam or something. Or is it the case that once you have any leak at great pressure, that it'll inevitably become a substantial leak?

[warscout2]

How much did you guys pay to have a shop build a pot? I don't have access to equipment that would be able to handle this.