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Thread: mil-surplus drum?

  1. #1
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    mil-surplus drum?

    Didn't know where to put this so I figured if all else failed off-topic ought to work. I need a sturdy container, planning to reinforce it some and put 15-20 pounds of vacuum on it. These mil-surplus drums look tempting but I have never laid hands on one. At fifty pounds I would think it is close to twice as heavy as a typical 55 gallon drum but that is just guessing.

    Do any of you own one or have you even taken a good close look at one? I hate buying a total pig in a poke that is gonna cost me about $75 including shipping. Cheap if it works, pretty expensive if it doesn't. The idea is to quick dry turning blanks by pulling a vacuum the temperature can be low enough it doesn't break down the wood itself but still gets to the boiling point of the water in a vacuum.

    Any info much appreciated!

    Hu

    http://www.sportsmansguide.com/produ...1a9785a09690d2

  2. #2
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    heh, I was wondering if you were looking for dry storage when I first saw the post Was hoping you were doing alright with the torrents of rain down there!

    I dunno on the pressure vessel, hard to get good data on that that I'd feel real confident with, although the failure mode under compression is just exciting not terrifying.. My rough guess based on failure modes of regular 55g drums under pressure is that more than 5-8psi is going to end up with something heading towards to catastrophic failure.

    Whats the minimum amount needed to pull the moisture out I wonder..... My cousin has one of the old woodmizer units but had a lot of problems with uneven shrinkage and curing so hasn't used it in years. It was pretty huge so I can't imaging that it would have pulled that much vacuum though.

    Failure looks something like this
    Love thy neighbor, yet pull down not thy hedge.

  3. #3
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    glad to hear your still floating along hu, heard you had alot of rain down your way..
    If in Doubt, Build it Stout!
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  4. #4
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    Unless that drum has a wall thickness of 3/8" or more, I'd plan for a dramatic implosion.

    Having taught vacuum clamping and having done a few of those for demonstration purposes, I can tell you that even that thickness of a wall, depending on the outside surface area, may not be enough. Remember pounds per square inch on every single square inch of the outside of the container. Doesn't take a lot to be spectacular.
    ++++++

    Some say the land of milk and honey; others say the land of fruits and nuts. All together my sort of heaven.

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  5. #5
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    The whole vacuum thing is confusing to me to be honest. I know a fifty-five gallon drum is sucked flat fairly easily, a local power plant did that in the instrument shop as a test after somebody closed a small vent valve in a 250 gallon stainless tank. The stainless tank eventually sucked flat. The sad part of the story is that the tank had a unit built around it so a new tank had to be made, cut into quarters, put in place, and welded back together!

    However, if you look under the hood of many a sixties automobile you will find a soup can, the same can that holds 38oz of soup. This is the vacuum canister or reservoir which holds up just fine under fifteen to twenty pounds of vacuum. It is replaced by a generally ball shaped thin hard plastic reservoir in modern vehicles.

    Pounds per square inch is the story, but there is still a lot of engineering which I don't have the knowhow to do. Plus, remember a wooden vessel is subjected to quite a large total pressure without failing sometimes. One thing I wonder about is an external cladding. Many shapes are very strong as long as they maintain that shape. I wonder if sheathing the drum in four to six inches of reinforced concrete where it can't exceed the original external dimensions in any manner will keep it from collapsing? It is much harder for something to shrink in some places without a corresponding bulge in another.

    Vacuum kilns work better with short pieces since most of the moisture is boiled out of the end grain. This makes it seem much better for turning blanks than for board lumber. The end grain drying too fast is the usual issue with a blank but with a vacuum that moisture is constantly being replenished from inside the wood. I am having a lot of difficulty drying wood here, it dries too fast and cracks or two slow and molds. Three to five days drying time is just too tempting not to try to play with, especially since I have a vacuum pump and several oilless compressors that might be pressed into the same service with a drying element between the vacuum chamber and pump.


    About the floods, water came several feet above my pond dam that is over a hundred feet long. The little creek on my north and eastern border is usually less than a foot deep and maybe two to three times that wide down in a channel it has cut eight or ten feet deep. It overflowed it's banks, got somewhere between a quarter and a half mile wide, and ran about five feet deep in my lower pasture making it 12-15 feet above normal. Impressive but this lasted less than a day. The house is on a hill and I stayed high and dry. I have read about flash floods all my life, the potential of that little creek makes me understand what I read! From trickle to wide and deep enough for river tows and back down to a little more than a trickle in thirty hours.

    Hu

  6. #6
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    Hu, it's been many years since I retired but I do remember seeing those. I don't remember them being particularly thick on the walls. Which is somewhat surprising as contrary to popular belief most things military are rather heavy duty. Have to be to stand up to general military usage. Let's face it: the average private is not going to be gentle with them when told by his sergeant to go move 50 of the things. But whether they would hold up to what you are wanting to do I have no idea. I just use a kiln that I built myself and it dries everything evenly with minimum checking. I'm going to be building a new one this fall as this one is getting old and has been moved around too many times. I didn't build it to be moved around a lot. My bad.

  7. #7
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    Why not use a vacuum bag like used with bent wood and veneering? I routinely pull about 25 mm vacuum which gives over 2000 pounds per square foot pressure on the bag. But with all that vacuum, it does not seem to have a big impact on wood moisture content.
    Charlie Plesums, Austin Texas
    (Retired early to become a custom furnituremaker)
    Lots of my free advice at www.solowoodworker.com

  8. #8
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    I remember driving through someplace in Arkansas and there was an old mill up above the river with a bridge next to it. The bridge was 150' or so off of the water but had had the deck replaced at one point when the old decking had washed away!! Flash floods are bad and exciting out here in the west but you folks on the East coast sure make up in volume for the infrequency when you do get them. That amount of water in that period of time is just inconceivable here. Glad you were able to stay high and dry!

    On the vacuum drying, I've been wracking my brain trying to remember what my cousin told me and here's the short version to the best of my recollection (for whatever that's worth). As best as I can figure the vacuum drying works by dropping the boiling point of the moisture in the wood so the combination of the temperature and vacuum needs to intersect
    http://www.engineeringtoolbox.com/wa...re-d_1686.html
    That part mostly makes sense to me Also gives some guesstimates as to the desired pressures and temperatures.

    The other part is that you want to cycle the vacuum. Best as I can explain it is that the pressure drop causes the moisture to boil and come out as vapor and then the pressure rise condenses it out some so it can be extracted. As I'm recalling this was the part that caused fits to get right and ultimately why my cousin eventually quit using the vacuum kiln.

    As for pressure over an area, consider than sphere's are really strong and flat plates not so much. If you think of a small cylinder as an extruded sphere you can see where the strength comes from. As the cylinder (or sphere) gets bigger it starts to behave more like a flat plate. A bit of searching came up with the term "hoop stress" and "thin walled hoop stress" which gives the formulas for figuring the wall stress. This for expansive stress, but I think the compressive stress formulas are pretty much the same.
    https://en.wikipedia.org/wiki/Cylind...ss#Hoop_stress
    So a 20" cylinder has twice as much stress on it as a 10" cylinder.

    For a 10" cylinder with a 3/16" wall at 25 PSI
    >>> (25*10)/(2*3/16.0)
    666.6666666666666
    For a 20" cylinder with a 3/16" wall at 25 PSI
    >>> (25*20)/(2*3/16.0)
    1333.3333333333333
    For a 40" cylinder with a 3/16" wall at 25 PSI
    >>> (25*40)/(2*3/16.0)
    2666.6666666666665


    You're encase it in concrete idea would seem to naively have some merit, but unfortunately I lack the knowledge to make any useful statements on it. Best case it would act as a direct increase in the thickness of the vessels walls, although I suspect that that may not be precisely true for reasons I'm unable to coherently explain (other than muttering about the metal and concrete not being perfectly bonded). I would be a bit more cautious about pulling vacuum on it than usual in case it caused the concrete to evacuate the area at higher than desired speeds.
    Love thy neighbor, yet pull down not thy hedge.

  9. #9
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    Quote Originally Posted by Charlie Plesums View Post
    Why not use a vacuum bag like used with bent wood and veneering? I routinely pull about 25 mm vacuum which gives over 2000 pounds per square foot pressure on the bag. But with all that vacuum, it does not seem to have a big impact on wood moisture content.

    I've asked that question before - for bowls it would be hard to do without crushing them. For boards its difficult to get the moisture "migratory" - there is a kiln company out of (I think) NZ that sells a bag kiln but they use a lot of expensive high tech aluminum channel stuff to move the moisture out. There is also the problem of getting even heating (especially given how wood is a good insulator) so the heating system has to be integral to the moisture removal system (at least that I've seen). Not insoluble but more challenging than immediately obvious.

    These guys:
    http://vacutherm.com/vacuum-kiln-pro...product-lines/
    Love thy neighbor, yet pull down not thy hedge.

  10. #10
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    Quote Originally Posted by Ryan Mooney View Post
    I would be a bit more cautious about pulling vacuum on it than usual in case it caused the concrete to evacuate the area at higher than desired speeds.

    Ryan,

    No time to type more but in your usual astute way you hit on exactly my concern here!

    In another area of math, I was using my new 32" bar on my chainsaw to avoid a bunch of bending and repositioning wood. Working my way down through a jumbled pile and it was "melting" nicely. whack, I mean WHACK! A piece of limb only about an inch and a half OD bark and all and about 12-14" long came screaming out of a crevice behind the log I was cutting and made violent impact with my right leg right below the knee at roughly a real forty miles an hour. My 17.5 layer Labenville chaps with lined cordura outer weren't up to the challenge. Fortunately I was wearing Lee jeans too or my leg might have been broken. It hurt but there wasn't a lot of gore leaking anywhere and trying to take off enough clothing to see the damage seemed like a wasted effort. Pulled off everything that evening and didn't see a mark on my leg! Cool! Never underestimate Lee's. Then I ran my hand a little lower. Ouch! That big black knot wasn't there when I started this project. A day of rest and a visit to my pain doctor whom I neglected to mention the new leg pain to, and I'm good to go. Going fire up the saw before dark!

    Hu

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