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Re: [Spridgets] Fwd: Re: what does a shortblock weigh?

To: spridgets@autox.team.net
Subject: Re: [Spridgets] Fwd: Re: what does a shortblock weigh?
From: BJNoSHOV8 <bjshov8@tx.rr.com>
Date: Sat, 13 Nov 2010 16:29:36 -0600
I don't have my wood design books at home but I think a 1/4" diameter 
lag bolt is good for several hundred pounds of pullout.  If I do this I 
will use 4 of them.  I'm a licensed professional engineer so I can 
figure out the safe load capacity of this type of connection.

I installed a ceiling fan in my old house many years ago.  This was one 
of the 50 pound Hunter fans so I wanted to make sure it was properly 
attached.  The ceiling in our den had fake wood beams and I didn't want 
to connect directly to them.  I found where the actual roof joist went 
over the fake beam, and drilled a hole in the bottom of the fake beam so 
I could reach the real joist.  I used a long drill bit to drill a pilot 
hole in the rafter.  I bought a lag bolt that has lag bolt threads on 
one end and 1/4-20 machine threads on the other end, and joined it to a 
piece of 1/4" threaded rod with a sleeve nut.  I screwed this long bolt 
all the way up into the rafter.  On the bottom end of the threaded rod I 
had formed it into a hook to match the hardware normally used for that 
fan model.  After I put the long J-bolt in I hooked my screwdriver 
through the hook and picked up my weight with it.  I figured if it would 
hold my 175 pounds it would hold the 50 pound fan.

> I don't agree. Lag bolts pulling straight down are  relying on the 
> threads that's less than 1'8" bearing pulling to hold up to 300 lbs 
> and the strain of pushing it sideways. Not a good idea. Not the same 
> as holding the top of a rafter, or better bridging 3 floor joists.

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