[TheForge] Wooden Beam strength for Rigging

[Woolley]

Walt,

I'm saying beams or roof joists. They support a flat roof that sits right on 
top of them.  The span is 25' with a 6" slope over the 25' span.  Most are 
in pretty good shape.  A few have some splitting and twisting but not much 
that really concerns me.  I'm thinking 6" beam just for ease of installation 
and I really don't need to be able to lift alot of weight.  Like I said, 1/2 
ton max. but I didn't look into whether or not a 6" beam would give that to 
me. I'm just throwing that out there as a starting point.  I'd like to place 
them at 1/3 and 2/3 of total span.  Maybe bridging the two now and again to 
support something placed on or over the table which will be in the middle of 
the span.  I could easily leave at least 6" of wood under any holes I would 
make for the hangers.  What are fletch plates?  Thanks.  BTW I poured a 
footing for a gantry crane elsewhere in the shop.

Regards,
Bill Woolley


----- Original Message ----- 
From: "Walter Mullett" <wmullett at bright.net>
To: "'Sponsored by ABANA'" <theforge at mailman.qth.net>
Sent: Monday, January 30, 2006 10:05 AM
Subject: RE: [TheForge] Wooden Beam strength for Rigging


> Bill,
>
> Not enough info here.  You say the beams are 3x11.5 but you don't give 
> span
> or slope.  You also say beams and then you say rafters.  What are they?
> - Is this a sloping roof with ridge or single slope? (If you have a ridge,
> do you have collar ties on your rafters? - Over-loading a ridge rafter
> system can push out the sidewalls and sag the ridge.)
> - How far from the end of the beam/rafter do you want to hang your beam? (
> Mid-span is a worse condition than 1/4 span. )
>
> Given the above .... You really aren't talking about a lot of load.  If 
> you
> are living in a snow environment, your roof will probably support at least 
> a
> snow load of 30lb/sf.  If you can spread your load over +/- 30 sf, you 
> could
> just be replacing that load.  However, I doubt your 6" 'I' will do that.
> You can test out that by loading the beam on the ground and seeing how 
> much
> deflection it has.
>
> Your existing 3x members are probably stout enough to take up the point
> loading they will have.  My concern with these would be to make sure your
> connections are in the middle of the side of the beam.
>
> You can build it then load test it.  Wood is great because you have a
> running factor.  Unless you have some really bad flaws (knots - holes in
> wrong locations), it deflects and groans a lot before it fails.  Just 
> check
> your deflection as you add load.  If you get too much deflection, you can
> sister the joists or add fletch plates to them.
>
> Walt
>
> -----Original Message-----
> From: theforge-bounces at mailman.qth.net
> [mailto:theforge-bounces at mailman.qth.net] On Behalf Of Woolley
> Sent: Sunday, January 29, 2006 10:49 PM
> To: theforge at mailman.qth.net
> Subject: [TheForge] Wooden Beam strength for Rigging
>
> Greetings,
>
> I seem to remember a thread about beam strength a while back but don't 
> have
> any info.  I'm not sure if this is the right forum but here goes.  I want 
> to
> hang small steel I beams(6"?) under my roof joists to rig from. I'm hoping
> to get up to 1/2 ton or so capacity.  The beams measure 3x11 1/2 with no
> room above (obviously butt up to roof deck), so I have to drill to bolt
> through or lag in to hang straps down and under to support steel.  The
> joists are spaced 2 feet apart. I hope to span at least 5 or 6 of them. 
> Does
> anyone have a known reference for engineering specs on this or any 
> practical
> experience doing something similiar?  Any help would be appreciated.
>
> Regards,
> Bill Woolley
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