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Re: Windsor Chairs--was: 3X Plates and Washers on Intermediate Anchors

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Michael-

Thanks for bringing this issue up again.  

I think it is very important that everyone on this list serve understands that holes drilled in green wood will shrink (get smaller) as the wood dries.

When engineers talk nonsense in the field with contractors who have experience that (correctly) contradicts the engineers misconception, it hurts the credibility of all engineers.

cheers
Bob

On 3/3/06, Michael Hemstad <mhemstad(--nospam--at)mbjeng.com> wrote:
When wood dries and shrinks, the holes always get smaller, even the ones in Scott's chair.  Scott's chair is suffering from loose joints for several reasons:
1.  The spindles have a much higher surface area to volume ratio than the seat and thus shrink much more quickly than the seat when they dry.
2.  The holes in the seat shrink across the grain but not along the grain.  The spindles shrink in both lateral directions.
3. It's possible that when the green seat shrunk originally, wood crushing occurred.  If it happens it will happen in the seat, because Windsor seats are usually made from softer wood than the spindles.  If your chair was made by a factory in New Jersey, they may have made the seat out of thin (3/4 inch) oak instead of thick (1 1/2 inch or more) pine, in which case it's hard to say where crushing will occur, but these thinner seats always loosen up regardless of humidity changes unless nobody ever sits in them.  Properly, the seats are thick softwood.  In any event, if wood fiber crushing occurs, it exacerbates any looseness that happens upon further drying.
 
Furthermore, once the spindles or legs start to get loose, any bending or lateral force (as when you lean back in the chair on 2 legs or push away from the table) is concentrated at the ends of the embedment holes rather than being distributed linearly along the embedded length.  Thus further crushing occurs.
 
Don't confuse wood shrinkage (and subsequent hole shrinkage) with, for instance, restrained thermal expansion such as occurs when the immediate area around a hole in a piece of steel is heated and the hole gets smaller.  If the entire piece of steel was heated, the hole would get bigger.
 
Sorry, I can't help myself.  I'll bet there are about 15,000 structural engineers who are now sorry Windsor chairs ever came up.
 
Mike Hemstad
Amateur woodworker
Minneapolis, Minnesota
 
Subject: RE: 3X Plates and Washers on Intermediate Anchors
From: "Garner, Robert" < rgarner(--nospam--at)moffattnichol.com>
To: <seaint(--nospam--at)seaint.org>
 
The holes got bigger or the spindles got smaller?
-----Original Message-----
From: Haan, Scott M POA [mailto:Scott.M.Haan(--nospam--at)poa02.usace.army.mil ]=0D
Sent: Thursday, March 02, 2006 12:44 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: 3X Plates and Washers on Intermediate Anchors
I have a rocking chair that was brought up the Al-Can highway. It was
wetter
there and the spindles were tight. It is drier here - the holes got
bigger
and the spindles are falling out of the holes.=0D
-----Original Message-----
From: Chuck Ritter [mailto:riter(--nospam--at)jar.com ]=0D
Sent: Thursday, March 02, 2006 10:40 AM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: 3X Plates and Washers on Intermediate Anchors
Windsor chairmakers use dry spindles and green seats so that as the
chair
reaches equilibrium the seat will grab the spindles. Besides being
elegant in
design, Windsor style chairs are among the most durable made. Maybe a
hole
boundary wants to shrink away from the original profile, but overall, it
is
governed by bulk shrinkage. Also, given that wood pretty much doesn't
shrink
axially, the hole profile will ovalize, not shrink uniformly.
Chuck Ritter
JAR Associates, Inc

 
Michael Hemstad, P.E.
 
 
Meyer, Borgman and Johnson, Inc.
 
12 South Sixth Street
Suite 810
Minneapolis, MN 55402
(612) 338-0713 (main)
(612) 604-3621 (direct)
(612) 337-5325 (fax)
www.mbjeng.com