[TheForge] Wooden Beam strength for Rigging

[Ralph Sproul]

	Hi Bill, Sounds like your thinking on the right direction now.  Jib is
going to be a better option to trying to attach to a wooden span of that
distance.  Even a  half ton in the middle of that span is going to be risky
as it's going to take a load of steel to make it level, and with two beams
you'll need a traversing one with the trolley on it to get everywhere - so
adding three beams and a half ton load on that span is.......well, Jib is a
better thought and direction to head in.
	I've put a lot of ceiling cranes up on trusses, steel span buildings,
etc.......and this low pitch beam system your mentioning sounds like trouble
to me.

	The other option is if your close to a wall........put two posts mid floor
to run the beams on, and use a wall  for the other bearm - or run two more
posts - then hang all the steel from that transfereing all the load to the
walls and floor.  You'd probably buy two used jibs for what you'd get into
all that work and steel though.

Ralph

-----Original Message-----
From: theforge-bounces at mailman.qth.net
[mailto:theforge-bounces at mailman.qth.net]On Behalf Of Woolley
Sent: Monday, January 30, 2006 10:06 PM
To: terry l. ridder; Sponsored by ABANA
Subject: Re: [TheForge] Wooden Beam strength for Rigging



> are the individual rafters one piece or are they spliced?
> if they are spliced how are they spliced?
> do you know how the rafters are attached to the walls?
>
One piece, sitting on top of masonry walls.


> are there any support columns in the 25ft span?
> are the dimensions that you give of 3x11.5 inches close?
> the reason i ask is that a 4x12 would actually be 3.5 by 11.25 inches.
> i assume the rafters are pine.
>
>>No support columns, true dimensions 3x11.5, more than likely pine.



>> BTW I poured a footing for a gantry crane elsewhere in the shop.


I should have said jib crane. I don't think I have room for a rolling
gantry.


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