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RE: [PSUBS-MAILIST] Pressure hull framing options.
Ian,
Are you getting a concrete sub?
Brian
-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org]On Behalf Of irox
Sent: Tuesday, July 22, 2008 2:27 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Pressure hull framing options.
Hi Brent,
I'm not going to discuss propane tanks, this is already done (many times!),
any thing I say is already in the archives (normal for many different people).
However, I will discuss framing issues with you. If you want to do advanced
designs like this, I would highly recommend getting a copy of:
Pressure Vessels: External Pressure Technology
by Prof Carl T. F. Ross
This will help you start to understand some of the math (reason) behind
different framing designs. It's a great book - although kind of bleeding
edge. Once you see what's going on for a simple framing solution, you'll
get an idea of how complex your is and figuring out the potential failure
modes is going to be tricky.
Note, with most H beam, it is the side of the H the contacts the pressure hull,
like with an I beam it's the top or bottom of the I attached to the hull.
First understand the general reason for stiffener like this. It's really
making that part of the hull a small diameter (small diameter means more
pressure resistance), one side of the I attaches to the hull (lots of contact
area), the long part extends into the hull attaches the hull to the inner
ring - the inner can take more pressure than the hull, hence re-enforcing
that part of the hull.
With your design, it looks like you have no plate attached to the hull,
so the legs of the H are weld straight to the hull metal. They extend
out, then before the end is a inner ring welded between the legs (the cross
bridge of the H). Before using this design over other you really need
to understand how that design is going to buckle and fail. Once you
understand how it can fail, you can do some simulation with different
designs, spacing, metals thickness, etc.. Then time to start building
some models on different scales and destroying them to verify your calculations
and research, you might have to revisit your calculations and simulations
to make some adjustments, then repeat destroying some models.
Eventually your new design will be ready to use in a manned submersible,
and providing the original research/design/work was done correctly, then
it will not fail you.
Also, how you inspect the section between the legs of your H, for
rust, leaks and the likes?
I have a feeling you can loose one of the legs from the H and just have
an L bean with the same strength instead, saving you metal, time and money.
Cheers,
Ian.
-----Original Message-----
>From: Brent Hartwig <brenthartwig@hotmail.com>
>Sent: Jul 22, 2008 3:12 PM
>To: personal_submersibles@psubs.org
>Subject: [PSUBS-MAILIST] Propane Tank Hull Options
>
>
>Hi Jon,
>
>"Regarding your second point about materials. Whether it is true or
>not, people have suggested that the time, effort, and cost required tomodify a propane tank for sub-use, is ultimately more expensive thanjust ordering the parts and starting from scratch. Perhaps that isnot strictly true from the perspective of cash-out-of-your-pocket ifthe propane tanks have cost you nothing. However, it does seem to bethe general consensus. Therefore, the issue does not appear to bewhether a modified propane tank is better/worse than a similarraw design from a performance perspective, but rather that the propanemodification is definately worse from a time/labor perspective, andcertainly from the chemical "smell" inherent in propane tanks."
>
>You make some good points Jon. Some of us have the extra time, and are willing to do the extra labor when funds are limited and we still want a reasonably safe submarine.
>
>"I'm sure you realize that once you cut the end off to install theribbing, the quality of the robot welds are immaterial since theweak link is now the the weld you made to reattach the end."
>
>Very true, but now you only have one head to attach, meaning you have one less circumference weld to worry about applying correctly. Also I have what I call a high H support ring design that if the three different basic components of each ring are cut into three sections and then the butt joints staggered, I think you could install them readily without cutting off one of the heads. The high H support ring design allows you to apply all the weld beads in relatively easy to see and work on areas, when compared to a T type stiffener being installed in a hull that has the heads already welded on. Here are some pictures of the concept I worked up some years ago. The model is I believe over kill in stiffener size and thickness, but you can see the idea in any case.
>
> http://www.frappr.com/?a=viewphoto&id=4001713&pid=10216832
>
>You can also use the angle iron configuration like on the K-250 and add horizontal pieces of angle iron between the rings for extra strength in keeping the ring from ribboning when bending, as well as seriously strengthen the hull from collapsing in an accordion fashion between the stiffener rings. Not to mention a lot of extra collision protection. But as many of you know you can't get angle stock in A516 Gr 70, (or so I'm been told) so that's why someone might want to use a the high H design.
>
>Another option might be to install a mini version of the Euronaut's stiffeners, If you can find small I or H beams.
>
>Regards,Brent Hartwig
>
>From: jonw@psubs.orgTo: personal_submersibles@psubs.orgSubject: RE: [PSUBS-MAILIST] Yunk Yard Wars Submarine BuildingDate: Tue, 22 Jul 2008 01:14:49 -0400
>
>
>
>Brent,
>
>> Can a reasonably safe ambient or wet, oil drum submarine be designed> and built? I believe there are lots of options. The Chinese oil drum> submarine builder will likely put his sub in shallow water for testing> and see he needs a lot more keel weight before he even gets into it.> He can add more weight to the wheel assemblies and/or a keel of some> sort below the hull. The RV Needlefish had the same basic metacenter> problem, and Bill found that out without ever diving it.
>
>Bill owned a very large and successful marina, and had almost unlimited
>resources available to him. Bill tested his sub by lowering it from acrane into a relatively shallow area of water used for boat launchingat the marina, so that if there were a problem he would not be in dangerof entrapment and drowning. His sub was connected to the crane at
>all times.
>
>> How many people have died in 1 ATM and/or ambient propane tank sub?
>
>I don't know, but I do know the facts surrounding a couple of engineering
>students who built what they considered a safe sub, but in which one of
>them died. The other fortunately survived the ordeal, but suffered severetrauma. I interviewed both the mother of the deceased, and thesurvivor last year. Interestingly, the day prior to the accident theyhad performed an exact similar dive in the sub without incident, andther e fore assumed that the sub was safe for shallow-depth diving.
>Funny how you can't determine the safety of a sub by the number
>of dives you perform in it. You can read about it athttp://www.psubs.org/accidents/seaker100.html
>
>
>
>> I have literature in my K-250 paperwork that has the George> Kittredge saying that you can build your whole K-250 sub out> of A-36 mild steel and be just fine. He did say how ever that> A516 Gr 70 is a great upgrade. Here is the quote.
>
>What did he say about using 55-gallon drums?
>
>
>
>> Designing a $2,000 US 1 ATM sub that anyone in the world could find> the same materials for the same price, is not likely. When one has> the need and/or desire to construct a inexpensive sub, it's not> always about getting new products cheaply, but usually about found> objects that are very cheap or even free. To build those same> objects brand new would be in many cases very expensive. I have two> used, but solid nice 500 gallon propane tanks with half hemisphere> heads that I got for free from a neighbor. Should I not use them for> a 1 ATM sub because they are not made of new A-516, they have a> little bit of rust on them, and they smell funny?
>
>You talk about cost as if safety is a constant that doesn't have tobe accounted. It's not, and has to be built into the cost of the sub.You can't base your design and fabrication on cost of materials aloneif you are serious about having expectations of diving and returningto the surface safely, consistently. At some point, you are going to
>have to assess the risk of failure associated with the design andmaterials you have chosen.
>
>Regarding your second point about materials. Whether it is true or
>not, people have suggested that the time, effort, and cost required tomodify a propane tank for sub-use, is ultimately more expensive thanjust ordering the parts and starting from scratch. Perhaps that isnot strictly true from the perspective of cash-out-of-your-pocket ifthe propane tanks have cost you nothing. However, it does seem to bethe general consensus. Therefore, the issue does not appear to bewhether a modified propane tank is better/worse than a similarraw design from a performance perspective, but rather that the propanemodification is definately worse from a time/labor perspective, andcertainly from the chemical "smell" inherent in propane tanks.
>
>
>
>> The heads are robot welded with three passes. Most of us can't weld> even close to that good. Besides I would likely have to cut one end> off to install the ribbing unless I cut the ribbing into three> sections.
>
>I'm sure you realize that once you cut the end off to install theribbing, the quality of the robot welds are immaterial since theweak link is now the the weld you made to reattach the end.
>
>
>
>> One thing that this group needs to be reminded of from time to time,> is that the synergy of experiences and combined brain power of this> global group, is incredible, if not impeded.
>
>If you are suggesting that people who have an interest in safety arean impediment to this group, then I strongly disagree with you.
>
>Jon
>
>
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