Green wood to seasoned in one hour!

Discussion in 'Woodturning Discussion Forum' started by odie, Mar 8, 2010.

  1. Joe Greiner

    Joe Greiner

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    "willing"? Not exactly. But if you computed the steel plate deflection from a formula in Machinery's Handbook, you already know how. (I got the same result.) Your mission, if you agree to accept it, is to establish the Modulus of Elasticity (E) for plexiglas. As a rule of thumb, for equivalent deflections, aluminum should be about 1.5 times the steel thickness, and wood should be about 3 times.
     
  2. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Biscuit cutter

    Robert,

    While the amount of deflection of Plexiglas might be interesting, assuming that it is sufficiently thick to keep from imploding, the much more important question is what will the shearing force around the perimeter of the vacuum vessel do to the Plexiglas. I think that you might just have the equivalent of a biscuit cutter for Plexiglas.

    If you had a one foot diameter vessel and pulled a hard vacuum of 14.7 PSI, the narrow perimeter of the vessel would be pressing on the Plexiglas with a force of 1662 lbf.
     
  3. Robert Manning

    Robert Manning member

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    Hi Bill,

    I've been in the sanding doldrums for days and nights on a sculpture I'm preparing for a juried contemporary art show.

    I would guess that the acrylic would support at least 2,000 psi which is the compressive strength of soft concrete, and that the wall of those tanks is .100". The circumference is about 38" so 38 x .100 = 3.8 sq. in

    3.8 x 2,000 = 7,600 lbs.

    It would be nice to let my SCUBA friends lower the vessel to depth for a catastrophic failure test, since you can't pull a vacuum of more than 14.7 on land, but they won't dive these cold waters in CA and pretty much only dive the clear warm waters off Roatan, Honduras.

    I'm thinking one inch acrylic, but that may be a lot thicker than necessary.

    This whole project still seems a lot safer than the chainsaw motor skateboard I'm wanting.
     
  4. Joe Greiner

    Joe Greiner

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    I don't think you've found a solution for biscuit-cutting plexiglas. Large and small numbers can outwit you.

    For the construction of the carrier wharf at Diego Garcia, we used sheet-pile cofferdams with reinforced concrete caps, then 2 inches of styrofoam cushioning, topped by 3-feet-thick reinforced concrete main deck. The styrofoam has a crushing stength of one (yes 1) pound per square inch. I computed the load required to crush the styrofoam, and found it would (if it could) drive the thin sheet piles deeper into the subsurface rock, which ain't gonna happen. Our/your aircraft carriers are safe.

    One of the reasons old buildings haven't collapsed is that the builders weren't as "smart" as we are now. When in doubt, make it stout.
     
  5. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Robert, you are talking about compression, but this is a shear plus bending moment load (Check out the shear, torsional, and tensile strength numbers for concrete).

    One thing about plastics ... they are "plastic" under steady state load.

    And I will race your skateboard with my belt sander driven skateboard. I am still working out some of the kinks with feeding out the extension cords while maintaining balance in the half pipe.
     
    Last edited: Mar 14, 2010
  6. n7bsn

    n7bsn

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    Actually that's only true of the ones that survived.:D
     
  7. Robert Manning

    Robert Manning member

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    I don't think I want to go much over 15 mph, Bill.

    I once knew a cabinetmaker who used to have belt sander races in the alleyway behind his brother's cabinet shop. I think it was Porter Cable by a handle. I was up 'til 2am last night after the endless sanding watching the gas skateboards on youtube. There's just something about the sound of an occasional-use two-stroke skateboard. Does anyone make a gas powered belt sander?
     
  8. Mr. Don

    Mr. Don

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    Wood drying

    Gawd!!! Methinks all you guys would be better off getting off this site and turning wood!!! About Face!!! Gentlemen, start your lathes!!:D:D
     
  9. ebrannon

    ebrannon

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    My guess

    Maybe he has discovered a commonly available substance/powder that is highly hydroscopic that will rapidly dry a piece. Maybe silcone or Tide, or Borax, or something that you burry the piece in and can take it out essentially dry in an hour.

    Just a wild *** guess. I think he would need to have something to justify the claim otherwise it is a very short lived scheme.
     
  10. Richard Baker

    Richard Baker RIP

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    Robert, No need for your SCUBA friends to get wet. Just find a deep enough spot, hang a big a$$ weight on your vessel (so it will sink) and lower it to a depth of 30 feet. For a safety factor, better to lower it to 45 feet and let it hang there for a couple hours while you all fish. Calculations are a good start, but the proof of performance is performance.
     
  11. Robert Manning

    Robert Manning member

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    The one that got away

    That's a good idea, Richard. Maybe I could paddle out in my kayak and lower my vessel into the briny deep. Who knows, maybe I'll catch something big like this angler who told me his story at the kayak symposium in San Diego a few years ago. (You have to scroll down the page to read this interesting news story). He was towed several miles offshore. Of course the fish gets bigger every time the story is told.

    I'll bet the fishing and SCUBA diving is great at Diego Garcia.
     
  12. Joe Greiner

    Joe Greiner

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    Restricted access. Closest I ever got was NAVFAC Pearl Harbor.

    Consulting engineering is a lot like being an unwed father. Still, the best train set a boy ever had, Orson Welles notwithstanding (on his first visit to RKO studios).
     
  13. Rich Aldrich

    Rich Aldrich

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    Have you been secretly watching me?
     
  14. Roger Chandler

    Roger Chandler

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    How's the learning process going for you?

    Hi Rich,

    Your comment brought a smile :) Have you gotten any projects finished since receiving your new Jet 16/42? By the way did you get the 1.5 hp or the 2 hp model?

    How do you like it so far? I almost bought it myself before I decided on the Green Bear ;)
     
  15. pnwradar

    pnwradar

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    Some of the best bonefishing I've ever experienced. And you could wear out your arm on yellowfin & barracuda. Frankly, wasn't much else to do but fish.
     
  16. Robert Manning

    Robert Manning member

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    Rosebud
    .
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  17. Bill Boehme

    Bill Boehme Administrator Staff Member

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    While this thread has become a very interesting discussion about reduced pressure and heat to rapidly remove moisture from green wood, I think that an obvious question is being overlooked: What is the point of rapidly removing the moisture? Moisture is not the reason that wood warps and cracks -- it cracks, as Dr. Chen stated, when moisture is removed too rapidly which leads to steep moisture gradients within the interior of the wood. That translates to steep stress gradients -- for the benefit of the non-technical person, is another way of saying "warps and cracks like the dickens".

    If I were drying a roughed out green wood bowl, I don't believe that I see much difference between using a vacuum pump to remove the moisture versus laying it out in the hot summer sun in Texas. The traditional method of slow drying means that moisture gradients (and therefore internal stress gradients) are minimized.

    Dr. Chen's doctoral dissertation discussed the problem of checking when vacuum drying wood.It looks like a technique that is more suitable for producing hardwood lumber where the wood can be planed flat after drying and checking just means there is some additional waste on the ends of the boards.

    Now, for those of us fortunate enough to live in Texas, green mesquite can be turned all the way to finished size and it will be nearly dry when finished -- I have not encountered any problems with cracking and warping is minimal. If desired, it can be rough turned slightly oversized and then allowed to dry for a few days before finishing it.
     
  18. Robert Manning

    Robert Manning member

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    I am visualizing a huge difference, and I can see it working on a cellular level as if it were a motion picture in full color.
     
  19. Joe Greiner

    Joe Greiner

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    Righto. Most of the patents for enhanced drying are intended for significant production. Considering application and attorney fees in the neighborhood of US$10,000, with additional charges for periodic "maintenance" of the patent, the stakes are pretty high, and a whole big bunch of sales are necessary to make it worthwhile. Otherwise, it's just an enhancement to the resume or obituary.

    The VaTech invention (patent #6634118) includes an option of exposing the container (a black plastic bag, more or less) to sunlight as a source of heat. Some of the other ones might also, IIRC.
     
  20. charlie knighton

    charlie knighton

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    Bill, mesquite on the trail to virginia :D
     

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