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Thread: Homemade Minisub

  1. #1
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    Homemade Minisub

    So I've been kicking around the idea of making a shallow-water minisub out of metal 55 gallon drums for a while. However, I was wondering if 3 of them welded together would have too shallow of a crush depth. Does anyone know how to calculate the crush depth of 3 standard size drums welded together in a row? Better yet, could someone do it for me? Also, I was thinking of welding one into an L shape and attaching it to the back of the sub so a second person could sit in the back, would that have much effect on the hull strength? Many thanks!

  2. #2
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    Hi Hunter, welcome to the forum. In my youth and well before I had any book learnin, I embarked upon exactly this approach. My advice to you is to make sure you have a very clear and quick avenue of escape from the rapidly crushing and contorting drums at about 15 feet water depth. At every 33 feet of depth boundary, you are adding one atmosphere of pressure which from memory is about 14.62-lbs per square inch.

    Putting that into context for you a 50-gallon drum is 23" diameter x 35" high. The surface area of that is around 3,359-square inches. Now with 14.62-lbs per square inch I will leave you to do the Math.

    A short online search on Archimedes and his "Principle," should answer most of your questions regarding (or regardless of) the shape of additional components and their willingness to crush into almost unrecognizable shapes at relatively shallow depths.

    A 50-gallon drum is designed to hold stuff in at atmospheric pressure and not to resist pressure to hold stuff out. If you are still hell bent on making a submarine, then the smaller the outer surface area the better. Make sure you have an up to date Will and maybe a Living Will in case they rescue you but not in too good a shape.
    Last edited by PinkertonD; 10-25-2011 at 09:34 AM.

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  4. #4
    Senior Engineer Marky's Avatar
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    Lightbulb

    This wouldn't be a bad size....the gov't just gonna toss it anyway.
    Attached Images Attached Images

  5. #5
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    Is it a good idea to give advice on a possibly dangerous venture like this?
    Especially when the guy doesn't have a clue.
    We shouldn't be teaching stuff like this on any forum.

  6. #6
    Administrator Kelly Bramble's Avatar
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    Quote Originally Posted by zeke View Post
    Is it a good idea to give advice on a possibly dangerous venture like this?
    Especially when the guy doesn't have a clue.
    We shouldn't be teaching stuff like this on any forum.
    Dear HunterSox, we do not recommend that you ACTUALLY get in this submarine yourself during operation. We recommend that you engineer a method to test your submarine device remotely. Should you decide to submarine around yourself, please take out a generous insurance package earmarked for the forum contributors at Engineers Edge and your loved ones.

    Thank you and please post pictures

  7. #7
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    Quote Originally Posted by Kelly Bramble View Post
    please post pictures
    Posthumously !


  8. #8
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    Didn't I see Chill Wills riding something like that once?

  9. #9
    Administrator Kelly Bramble's Avatar
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    If I ever build a submarine I would use propane tanks or thick wall steel pipe... I don't think a 55 gallon drum could take much more than 5-6 feet underwater..

  10. #10
    Project Engineer CCR5600Design's Avatar
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    No offense to any given nationality, but after seening a recent news special regarding similar watercraft manufactured in Columbia, I think it best not to encourage or support this construction endeavor.


    Ron

  11. #11
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    Hi,
    I'm a student so correct me if I'm wrong. The areas of the barrel that would get crushed in first would be along the center of each axis. (i.e, the center area of the side and the center areas of the top and bottom.
    I dont know if you're still working on that submarine, but I was reading through all these forums (i'm new here) and thought you could
    1) pressurize the submarine interior a little bit.
    2) add reinforcement on the inside with steel pipes/rebar

  12. #12
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    Hello all!
    Firstly, thanks for the advice! It's been very helpful. The sub is currently still in the design phase, although my friend and I have already bought the drums. Having taken what you said into consideration, we definitely plan to reinforce the inside of the submarine somewhat. We were thinking of just using some rebar struts placed in intervals along the interior. However, because of the size of a standard drum, the reinforcements would have to be square instead of triangular, which takes away from the strength. With that in mind, any idea on the thickness of rebar we should use, spacing, or alternatives?
    Last edited by HunterSox; 12-10-2011 at 01:23 AM.

  13. #13
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    Quote Originally Posted by CCR5600Design View Post
    No offense to any given nationality, but after seening a recent news special regarding similar watercraft manufactured in Columbia, I think it best not to encourage or support this construction endeavor.


    Ron
    Don't worry, if I was planning to transport narcotics long distances, I'd be using something a lot more reliable and roomy than 55 gallon drums :P

  14. #14
    Technical Fellow jboggs's Avatar
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    Just curious - have you ever read the story of the building and testing of the HL Hunley during the Civil War? Built from a used boiler and sank a Union ship.
    Killed three crews in the process. Fascinating.

  15. #15
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    Well, theoretically, it is possible, but three would barely fit a person, let alone life-support, and two people would only complicate things further.

  16. #16
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    Why are you even worrying about the crush depth ?

    It will take well over 400 Lbs weight to even get the drum to be pushed fully under the surface of the water.
    Unless you let water in to expel the air.

    You will have to fill the drum with water to get it to sink, proportionately.

    Then there are no questions needed about crush depth.

    You will then need to put compressed air into the drum to push the water out, to get it to float again.

  17. #17
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    Try this experiment to convince you this is a bad idea. Hook a vacuum pump to the 55 gal drum and suck a vacuum on it. A vacuum inside the drum is equivalent to the pressure at only 2 feet of water depth on the outside. Don't stand too close while preforming.

    Timelord

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