• November 2025 Turning Challenge: Wall Hanging! (click here for details)
  • Congratulations to Craig Morton, People's Choice in the October 2025 Turning Challenge (click here for details)
  • Congratulations to Andy Chen for "Mesquite Vase with Polymer Clay Millefiori" being selected as Turning of the Week for November 3, 2025 (click here for details)
  • Welcome new registering member. Your username must be your real First and Last name (for example: John Doe). "Screen names" and "handles" are not allowed and your registration will be deleted if you don't use your real name. Also, do not use all caps nor all lower case.

Green wood to seasoned in one hour!

Robert - the problem issues with vacuum systems are always the seals. A vessel on the order of a propane tank may be a good start. The challenge will be getting things in and out of it, and maintaining the seals. Another approach could be to use a severed propane tank as the holding structure - unsealed, but then utilize a vacuum bagging system around the whole tank - similar to the vacuum approach that veneer applicators utilize. This would provide an easier means of mantaining seals. I am not sure that you could apply full vacuum capabilities that way, but it will be a start in the right direction. Here are a couple of links:

http://www.joewoodworker.com/veneering/welcome.htm
http://www.woodcraft.com/Catalog/ProductPage.aspx?prodid=17906

Jerry
 
Re-inventing the wheel can be a lot of fun, but an old NASA motto is "Search before research."

Patent specifications are required to describe procedures available to those "skilled in the art." That can be a nebulous restriction, but as far as I can tell, it includes you, and you, and you.

Collecting patent documents can be a lot like saving string in a ball. With some organization, it can be managed. And you can thus delegate some of the development work. Commercial limitations apply, of course.
 

Attachments

  • 34x412.jpg
    34x412.jpg
    60.8 KB · Views: 29
Joe, I'm not charting any new territory here. Vacuum kilns have been used to dry wood for decades. I feel like I have enough information to make this happen, and just need a suitable vessel. After that, it's just a matter of dialing it in as far as temperature, level of vacuum/pressure, and time. I would prefer something longer than a propane tank so I can dry short planks for my segmented work, and that is really the genesis of this endeavor. :cool2: Oh, I just thought of an idea to use the tank halves for the ends on a piece of PVC or homemade fiberglass pipe.

As for sealing, Jerry, a roll of butyl tape is standard equipment when I do vacuum veneering. It's nice to see that Joe Woodworker still has my compound curve veneered Kayak displayed in his customer gallery.
 
Last edited:
micro microwave drying

I have had good sucess drying bowls & vases via microwave. If any one is interested I willshare what I have learned!!!free!!
 
vacuum chamber

Robert- Re: your milk bottle idea. Be very careful, as even partial vacuum can cause serious implosions. I would not mess with glass, unless you can come buy an old laboratory desiccator, which often has a vacuum line port.

Take a read of the following link. http://www.hyvac.com/Other_items/Safety/implosion.htm

Jerry
 
Vacuum Kiln Drying for Woodworkers

For those that are interested there is a small book by Joshua Salesin on this subject by the title of "Vacuum Kiln Drying for Woodworkers". See http://vacuumkilndrying.com/index.html I have a copy and although I have not yet built a kiln I plan to and have been collecting parts. Lots of good information in the book, well worth the cost to me.

John
 
Robert - Yes an implosion can ricochet - off of "itself". I would not expect to be able to see any change as the wood dries. Yes, it will lose weight and may distort, but I don't think the benefit of being able to see is worth the risk. Remember the old saying about curiousity and the cat!!!

Jerry
 
steelguy said:
I would not expect to be able to see any change as the wood dries.
Click to expand...

Jerry, I wonder if I might be able to see the vapor come off and perhaps condense on the cool walls of the vessel. I'm not sure my curiosity can be contained, in this instance. I will, however, proceed with caution.
 
Robert, I have seen a few lab type bell jars on the Internet. The glass is usually around 1/2 inch thick and they have a hemispherical top. Most of them that I have seen are a bit pricey even though they are old and used. I would not consider even for a moment using something like an ordinary jug as a vacuum vessel. You do remember what happened to the curious cat? I enjoy reading your posts and would not want to read about you in the past tense.
 
Don't worry, Bill, and thanks for your informative posts as well. You are truly an asset to this forum.

Those bell jars are the perfect setup with lots of light coming in to inspect your experiment. They're probably designed to withstand a small explosion where they liftoff without breaking until it ricochets off the ceiling and then hits the concrete. Even then it would probably have to land sideways before it would shatter.:cool2:

Full vacuum is around 15 PSI and a propane tank is 12" diameter. Is there anyone out there who is willing to calculate what thickness of flat plexiglass would have a workable (minimal) deflection on the twelve inch diameter tank at only 15 PSI, assuming that the piece is evenly seated against the tank?

I know that a twenty inch diameter piece of 3/8" mild steel plate has a deflection of about 1/16" at full vacuum.

That's funny, no warning for when I slice into that propane tank with an abrasive cutoff wheel?
 
Robert Manning said:
...That's funny, no warning for when I slice into that propane tank with an abrasive cutoff wheel?
Click to expand...

The guys that make meat smokers out of the big propane (or fuel oil) tanks often fill them with soapy water before hitting them with a cutoff wheel. ;)
 
Vaughn said:
The guys that make meat smokers out of the big propane (or fuel oil) tanks often fill them with soapy water before hitting them with a cutoff wheel. ;)
Click to expand...

A friend wanted to make one into a bell... we did that very thing before wearing out several wheels cutting the bottom off

Has great tone, we hung it in the shop, then a tapped it with a hammer, sounded nice. Then he took a mighty swing... when our heads stopped hurting I took the hammer away from him
 
Robert - you certainly are determined! Don't believe that you will see vapors. You may see condensate. Depending on the type of vaccum pump you have, the water vapor may play havoc with it.

Also remember Icarus!
 
Robert Manning said:
Ralph, was that a five gallon propane tank and what was the wall thickness? Also, what diam. and width cutoff wheel?
Click to expand...

Nope, it as large, say 5 ft tall and 2 ft in dia. I don't recall the wall thickness, but we ended up using a 3inch wheel on an air-drive. Tried a bunch-o-stuff, including bi-metal blades on a "destruction" saw
 
Robert Manning said:
Full vacuum is around 15 PSI and a propane tank is 12" diameter. Is there anyone out there who is willing to calculate what thickness of flat plexiglass would have a workable (minimal) deflection on the twelve inch diameter tank at only 15 PSI, assuming that the piece is evenly seated against the tank?

I know that a twenty inch diameter piece of 3/8" mild steel plate has a deflection of about 1/16" at full vacuum.
Click to expand...

"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.
 
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.
 
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.
 
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.
 
Robert Manning said:
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.
Click to expand...

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:
Bill Boehme said:
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.
Click to expand...

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?
 
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
 
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.
 
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.
 
The one that got away

Texian said:
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.
Click to expand...

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.
 
Robert Manning said:
I'll bet the fishing and SCUBA diving is great at Diego Garcia.
Click to expand...

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).
 
steelguy said:
Guys - this method has been around for many years, in fact I have used it myself several times. The process is very straightforward and can be available to all for a few cents. The process is as follows:

1. Turn bowl to final green size and shape.
2. Stand back and admire, and ask significant other's opinion.
3. Take their suggestions and decide on small shape adjustment.
4. Make shape adjustment with coincidental, unplanned tool catch.
5. Dodge bowl as it flies off of lathe into wall behind your head.
6. Examine fractured pieces.
7. Place fractured pieces into operating shop woodstove.
8. Bowl is dry within minutes!


There was a guy about 50 years ago who advertised hat racks for a dollar in the want ads at the rear of the magazine. Everyone who sent in their dollar received a finishing nail in return!

Jerry
Click to expand...

Have you been secretly watching me?
 
How's the learning process going for you?

Rich Aldrich said:
Have you been secretly watching me?
Click to expand...

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 ;)
 
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.
 
Bill Boehme said:
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.
Click to expand...

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.
 
Bill Boehme said:
...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.
..
Click to expand...

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.
 
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
Click to expand...

Bill, mesquite on the trail to virginia :D
 

Attachments

  • mesquite pile.JPG
    mesquite pile.JPG
    102.3 KB · Views: 22
  • mesquite pickup load .JPG
    mesquite pickup load .JPG
    115.6 KB · Views: 25
  • chilsohm trail.JPG
    chilsohm trail.JPG
    110.1 KB · Views: 26
You must log in or register to reply here.
Back
Top