43 replies to this topic

[fer_abella]

I understand the concept. I just want to know experiences, drawings, parts, schemes to add a secure, easy air lock to my homemade uw housing. I have lathes and milling machines to manufacture it.

Concept : If you lower the internal pressure of the uw housing to less than 1 bar when you are at sea level you do not need latches as atmospheric preassure replaces them to mantain close the door of the housing. When summerged, this effect continues. To open the housing you should relieve internal pressure. Think about an airtight case in an airplane. You open it in the flight, you close it, you can not open it in land if you do not use the relief valve of the case.

Advantage : With homemade uw housings, it is good this kind of locking procedure because it does not work if housing has a leak. It checks itself as watertight BEFORE entering water. Just try to open it, if it open lock is wrong.

Design : There are a lot of forms to use that design. Some are better than others. I would like to know one good one. Easy to machine if possible. I have my own design, very easy and very effective, but out there are people with more experience and i would like to learn from them.

My idea is to use

(a) a valve and an external device (a bicicle pump like thing) to extract some air from housing.
(b) a kind of sringe in the inside of housing operated from outside by a bar that you can use to decrease internal pressure and lock in place securely to mantain that low pressure.

HELP :

Do you know how works different tyoes of air locks?
Do you know how 10bar lock works in detail?
How much air do you extract from the housing using that kind of air locks?
Anything related to that will be of great help
I am sure somebody did it yet but google does not show it nor search here

Thank You

Edited by fer_abella, 20 November 2009 - 04:36 AM.

[jeremypayne]

There have been lots of threads on positive pressure ideas, but this is the first that I've read on a negative pressure housing ...

Seems a bit of an extreme length to go to avoid "latching" ... why do you hate "latches" so much?

[diver dave1]

I work in an industry where we use equipment under vacuum often. While your solution theoretically can work to some degree, the extreme effort to make it work does not justify the elimination of latches. Generally, the latches are not the weak link leading to leaks.
But, if you want to eliminate latches and you can machine your own housing - why not just have a larger sealing flange and use studs or bolts outside the O-ring? It takes longer to assemble/open but you would have no latches. BTW, if you do this, make certain to pattern the tightening to avoid stressing the seal. Since you do machine work, you likely know such patterning for bolting flanges.

Another point: Using vacuum, you can obtain a maximum pressure difference of 1 atm at the surface. Latches or bolting can provide many times that sealing pressure. A bicycle pump will not get too close to 1 atm vacuum, more likely closer to 1/2 that value.

[fer_abella]

I like the airlock system better than latches because of the use of physics to obtain 100% watertigh security.
You can not beat physics laws on that.
When nikonos V was the camera for UW photo, airlock systems were an upgrade made by some good artisans.
They did it because good reasons.
Now i understand more why it is not used widely.
People is better prepared to latches. They trust them more than physics.
For me is like using flat o-rings instead of "normal" ones.
Remember that before the use of the ones we know today, the flat model was the avalaible one.
I have manufactured some uw housings for instruments based on nuts and bolts.
10 bar use a reliable method and sell 100s of housings, i prefer theis method.
If somebody can publish photos of a real housing with airlock i will like it.
Thank you

[fer_abella]

http://www.hugyfot.c.../HugyCheck.html

It is like having a mechanical check like the one above incorporated in the design.
And that it do the locking too.
Hugy likes it too, but just to check.

[fotoscubo714]

I'm unable to post the link to the following product parts, since it would lead to an adult sexual aid website. But, these vacuum parts are used on cylindrical lexan tubes for vacuum on certain body parts (use your imagination here...LOL). With some modification they should allow to draw a vacuum inside a housing and keep it till you are finished

The two connectors can be disengaged after drawing vacuum and together with the handpump are less than $100. The electric AC-powered pump is $400.

I like the airlock system better than latches because of the use of physics to obtain 100% watertigh security.
You can not beat physics laws on that.
When nikonos V was the camera for UW photo, airlock systems were an upgrade made by some good artisans.
They did it because good reasons.
Now i understand more why it is not used widely.
People is better prepared to latches. They trust them more than physics.
For me is like using flat o-rings instead of "normal" ones.
Remember that before the use of the ones we know today, the flat model was the avalaible one.
I have manufactured some uw housings for instruments based on nuts and bolts.
10 bar use a reliable method and sell 100s of housings, i prefer theis method.
If somebody can publish photos of a real housing with airlock i will like it.
Thank you

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Edited by fotoscubo714, 22 November 2009 - 10:59 PM.

[fer_abella]

Thank you.

This is the solution i will probably build inside the housing.
It is easier than the valve type solution and more problem free.
I will use a pipe of lexar or other similar material.
Think about a 100cc ¿sringe? with a piston that can be locked at the end of its displacement, when vacuum has been formed inside housing.

But i would like to know how 10bar produces the vacuum with its air lock just to check volumes and ways of designing mechanism.

[Giles]

So rather than trust in some latches which seem to have proven themselves in various different ways and types over the years you are going to add an extra sealed attachement (read: yet another place the housing could leak)

It seems a bit odd as you would be enhancing the risk of it leaking by adding another hole in the housing.

I believe that there was an attachment for this made for ikelite housings or the like maybe about 10 years ago. I don't believe adding it made any added benefit.

[blibecap]

My Staff is currently working on this project. We hope to have a less costly alternative to the Hugyfot or Gates solution available within 6 months. You can check the website WWW.UWCameraStuff.com for details when they become available. We thought about making this a DYI project but the complexity of the electronics is more than the usual DIY person can handle. It will probably be available in kit form or self install form.

You can look at some of the research and history here. http://wetpixel.com/...showtopic=32883

Thanks

[bvanant]

I understand the concept. I just want to know experiences, drawings, parts, schemes to add a secure, easy air lock to my homemade uw housing. I have lathes and milling machines to manufacture it.

Concept : If you lower the internal pressure of the uw housing to less than 1 bar when you are at sea level you do not need latches as atmospheric preassure replaces them to mantain close the door of the housing. When summerged, this effect continues. To open the housing you should relieve internal pressure. Think about an airtight case in an airplane. You open it in the flight, you close it, you can not open it in land if you do not use the relief valve of the case.

Advantage : With homemade uw housings, it is good this kind of locking procedure because it does not work if housing has a leak. It checks itself as watertight BEFORE entering water. Just try to open it, if it open lock is wrong.

Design : There are a lot of forms to use that design. Some are better than others. I would like to know one good one. Easy to machine if possible. I have my own design, very easy and very effective, but out there are people with more experience and i would like to learn from them.

My idea is to use

(a) a valve and an external device (a bicicle pump like thing) to extract some air from housing.
(b) a kind of sringe in the inside of housing operated from outside by a bar that you can use to decrease internal pressure and lock in place securely to mantain that low pressure.

HELP :

Do you know how works different tyoes of air locks?
Do you know how 10bar lock works in detail?
How much air do you extract from the housing using that kind of air locks?
Anything related to that will be of great help
I am sure somebody did it yet but google does not show it nor search here

Thank You

If you look at the 10Bar housings, the later ones and the ones for larger cameras no longer use the airlock but rather two o-rings and a key hole latch. One problem with using no latch is that for o-rings to seal properly, you need a certain amount of compression that you might not get with a simple atmospheric pressure latch and that the system might be prone to leaking in the rinse tank where there is plenty of water but not much pressure to keep the system sealed. Seems to me that 25+ years of design of sealing systems would suggest that latches work well. I once had a Fantasea housing for a strobe that was sealed the 10bar way and I always wished it would seal with a latch. Too many ways for the system to fail.
Bill

[blibecap]

What I am working on is more of a secondary safety system. Something that would really let you know that your o-rings would most likely not leak because there are no 100% guarantees. Some people would be surprised how hard it is to seperate something held together by a little vacuum. I will publish more information once I have the exact details. I would not want to trust my housing to a vacuum seal alone but in-conjunction with a mechanical seal it would be a enhancement.

In regards to how to do this it's simple. Seal it up tight with o-rings. Have a valve/fitting of some type that you can open and close and remain sealed off.

Seal the case, open the valve, pull vacuum, close the valve, monitor the vacuum.
Make the dive or dives monitoring the vacuum.
Exit the water, release the vacuum and open the case as necessary.
Return to seal the vacuum (above)...

The fun part is the valve / fitting open and closed and sealed.
And of course Monitoring the vacuum in the whole process so you see trouble coming so you can avoid it instead of reacting afterwards.

Edited by blibecap, 23 November 2009 - 01:58 PM.

[davelew]

I've used an automobile brake bleeding kit like this one mated to the lens port (using a piece of machined aluminum with an o-ring groove and an NPT thread for a nipple to attach to the vacuum hose) to check that my housing holds a vacuum before installing a lens & port and going underwater. I usually pump the housing down to 15 inches of mercury (about 7.5 psi or 0.5 bar or 50 kPa) of vacuum, then let it sit for a minute and see if the needle moves on the vacuum gauge. The only time I had a problem was with an o-ring installed sideways on a control rod I had just worked on, and that leak took about 10 or 15 seconds to go from 15 inches of Hg to zero.

As for using vacuum instead of latches, that might work, but I would worry about telling the difference between a leaky housing held shut by o-ring friction and a housing held shut by vacuum.

[fer_abella]

The only time I had a problem was with an o-ring installed sideways on a control rod I had just worked on, and that leak took about 10 or 15 seconds to go from 15 inches of Hg to zero.

Sure your system save you from a problem. A latch is blind about that kind of probblems. Safety relies in operator and mounting. Vacuum checks the housing completely.


Very interesting the ideas of about a DIY project. More like that ?

I did not express myself completely. I will probably add a latch or two at the end.

I trust more in the vacuum than in the latches, but adding a safety latch is inexpensive and can be nice if because a bump or a crack the vacuum is gone. You should have a safety in case an oring is wrong and you lose vacuum some time after mounting housing.

I believe 10bar uses latches in part because of the answer from moderator. People is used to them and do not like new things. Perhaps your system is better, but if it is not percived as so you will not sell one. And it is not percived now.

[tdpriest]

I'm unable to post the link to the following product parts, since it would lead to an adult sexual aid website. But, these vacuum parts are used on cylindrical lexan tubes for vacuum on certain body parts (use your imagination here...LOL). With some modification they should allow to draw a vacuum inside a housing and keep it till you are finished

The two connectors can be disengaged after drawing vacuum and together with the handpump are less than $100. The electric AC-powered pump is $400.

These look like the low pressure connections used on medical equipment: designed for about 0.5 bar pressure differential. They are only sealed when connected: if the pump is removed, air enters the chamber. It is surprisingly difficult to achieve anything like a 1 bar negative pressure gradient with a vacuum pump on the surface. Even deep-water equipment is usually designed with latches or bolts: they get you through the first few metres, after which ambient pressure provides the seal. Historically, most leaks occur at or near the surface. The extra security provided by a 1 bar pressure gradient isn't that significant, so negative pressure is more a way of testing for leaks rather than locking the housing. The best way of testing for leaks is to submerge the housing...

The engineering of a negative pressure system would seem to offer far more failure modes than simple latches, so why worry? Just because the pneumatic tyre is old it doesn't suggest (to me, at least) that we should move to hovercraft or maglev vehicles!

Tim

Edited by tdpriest, 25 November 2009 - 12:44 PM.

[fotoscubo714]

These look like the low pressure connections used on medical equipment: designed for about 0.5 bar pressure differential. They are only sealed when connected: if the pump is removed, air enters the chamber.

Tim

Hey Tim,

Your above statement is incorrect.

Through my local industry connections I actually was able to get my hands on a handpump set up with connectors and small clear cylinder. The connectors can be disconnected after vacuum and the vacuum is maintained in the cylinder afterwards. I was able to draw a maximum vacuum of 650 mmHg vac (about 26 in.Hg) with the handpump. The small tube did not require many pumps, but I can see that a full housing can require too many than comfortable and perhaps practical.

I will experiment more and report if anything seems practical for our use here.

Bo

[davelew]

Hey Tim,

Your above statement is incorrect.

Through my local industry connections I actually was able to get my hands on a handpump set up with connectors and small clear cylinder. The connectors can be disconnected after vacuum and the vacuum is maintained in the cylinder afterwards. I was able to draw a maximum vacuum of 650 mmHg vac (about 26 in.Hg) with the handpump. The small tube did not require many pumps, but I can see that a full housing can require too many than comfortable and perhaps practical.

I will experiment more and report if anything seems practical for our use here.

Bo

There are many commercially available check valves for vacuum connections, for example at this site.

The problem is that most of these connectors are designed to seal a vacuum on the inside and 1 atmosphere of pressure on the outside, or lots of pressure on the inside and 1 atmosphere on the outside. They aren't designed to have 3 or 4 atmospheres more pressure on the outside than on the inside, which is the case in an underwater housing at 100 feet.

The main options I see are to either make your own one-way valve that uses external pressure to seal itself, or use a commercially available check valve and put a sealed cover over it so that sea pressure won't damage the valve. I believe Hugycheck uses the latter technique.

[JohnLiddiard]

Relying on vacuum to hold a housing together? I would never trust it. Get a small leak under water:

- With a mechanical latch, a camera has a chance of surviving the leak.

- With a vacuum latch, you loose the vacuum inside the housing and it all falls apart as you surface. The camera then has no chance of surviving.

On the second topic, Vacuum checks of seals before diving, like Hugyphot have, is a great step forward and something I would like to add as an accessory to my housings.

[blibecap]

Hi BO, Tim, Dave and others
I would again ask you to look at this thread http://wetpixel.com/...showtopic=32883 where we are discussing the same principle.

My associates and I are working on a project that will be a low cost self install somewhat DYI item that will do a vacuum test of any housing. We have looked at the Hugyphot as well as the Gates system. They both use between 6 and 10 inches of vacuum to test the housing.

They both use a check valve with a cap to seal it after pulling the vacuum. We believe that we have found a valve the will work for a reasonable cost as the Gates valve alone is about $225.

I have a electronic engineer working with me to develop the indicator system for inside the housing like the Hugyphot.

We haven't been able to locate a good, cheep, small, battery operated vacuum pump yet and have been looking at a few manual pumps. The small hand pump requires about 50 pumps to pull 10" of vacuum on a housing. We are looking at and testing other manual pumps. What are your thoughts on the KISS (Keep It Simple Stupid) idea of a manual pump? Please share any ideas on a battery operated pump that you may have.

Once we have a workable solution we will test this and make the information available here as well as our web site, http://www.UWCameraStuff.com. Our goal is to build the electronics for sale and provide the modified valve fitting as well as the rest of the parts. We also will let you know where you can obtain the off the shelf parts. Our target price is $500 or less for the complete solution.

While I don't think that a vacuum lock is a good solution but a vacuum check with a mechanical lock really sounds like a good investment protection solution.

Thanks

Edited by blibecap, 29 November 2009 - 09:37 AM.

[fotoscubo714]

We haven't been able to locate a good, cheep, small, battery operated vacuum pump yet and have been looking at a few manual pumps. The small hand pump requires about 50 pumps to pull 10" of vacuum on a housing. We are looking at and testing other manual pumps. What are your thoughts on the KISS (Keep It Simple Stupid) idea of a manual pump? Please share any ideas on a battery operated pump that you may have.

Thanks

My girlfriend has this Panasonic Pore Cleanser Model #EH2501 in her junk box. It draws 10 inch Hg/ 25cm Hg. It is a NiCad rechargable system that needs 8Hrs to recharge. I will ask her if I can rip it apart for you guys to see inside . She recalls it cost was around $40.

Edited by fotoscubo714, 29 November 2009 - 01:32 PM.

[blibecap]

Kinda cool I just don't know if it would be worth the weight and hassle of electric on a trip over a manual unit? Guess ideal situation would be really small light weight. compact and run off of 4 or less AA batteries.