Lags vs. Timberloks [RE-wrenches]

[Jeff Clearwater, Village Power Design]

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Hey Matt,

That was certainly more than "Two Cents"!  Thanks for great info. 
I'll stick with lags for now.

Do folks use stainless lags?  How are they for shear strength for the 
head snapping off as opposed to lags?

Jeff C.



Matt Lafferty wrote:
>
>All:
>
>I have been through the Engineering Evaluation Process, including
>physical testing of a couple hundred pieces, with similar or perhaps the
>same fasteners as related to mounting applications.
>
>The "Pullout" is indeed strong.  They drive very well generally... At
>least for the beginning thread portions.  They are a "hardened" as
>opposed to "malleable" product. 
>
>The weekness is in the "Sheer Strength".  Heads snap off.  It is a royal
>pain when you have a headless shank sticking up above your intended
>stopping point!  Especially in a tight spot! 
>
>They are designed for Wood to Wood connections.  They have a very narrow
>shank cross-section. Their design is such that they bury the head into
>the "top piece".  One characteristic of this app that makes this
>acceptable and seldom "snaps the head off", is that the wood is soft
>enough (generally intended for timber or deck attachments) to allow them
>to do so.  When driving into seasoned wood, like those trusses and
>rafters we are attaching to, the "snap ratio" goes, well, through the
>roof! 
>
>Another difficulty encountered was "twisting out the side" and knots.
>Due to their narrow shank the heat builds rapidly as you drive it into a
>seasoned piece of wood.  This reduces some of the temper and they
>"curve" in a curly-grained piece of wood. The exposed shank is unheated
>at this point so it wants to "move over" or bend on you as you drive it.
>This caused either a Stop-and-try-to-get-it-back-out or a Snap in most
>cases.
>
>The Engineering didn't calc satisfactorily when looking at the Metal to
>Metal Sheer factor, either, by the way.
>
>As a note, when I first looked at them, my initial observation was that
>the skinny shank and small diameter of the built-in washerhead, wouldn't
>"fill up" the pre-drilled holes in a mounting foot.  This would create a
>potential for "sliding around" if the fastener was either not totally
>tight or as the roof changed due to thermodynamics.  They required
>stacking of two different washer sizes in order to adequately cover and
>secure a 3/8" hole, but still didn't address the "slipping" factor
>associated with the foot hole to shank diameter difference.
>
>I personally believe that they are an excellent product for their
>intended purpose, but not that "Oh, Boy!  I found my Dream Bolt!" for
>bolting Glass to Roofs!
>
>Two Cents!
>
>Matt Lafferty
>Universal Energies Institute
>mlafferty at universalenergies.com
>(916) 422-9772
>(916) 628-7694 Cell
>(916) 914-2247 Fax
>www.universalenergies.com
>
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-- 
~~~~~~~~~~~~~
Jeff Clearwater
Village Power Design Associates
Sustainable Energy & Water Solutions for Home & Village
http://www.villagepower.com
gosolar at villagepower.com

877-SOLARVillage
413-256-6777,  Fax 413-825-0372
61 Baker Rd
Shutesbury, MA 01072

PO Box 115
Boonville, CA 95415
707-895-9015, Fax 707-897-0024
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