"Christopher Tidy" wrote in message
...
Steve,

Thinking about your project a little more, I would choose to alter the
design rather than trying to add a stand-off. There are simpler and
stronger designs possible, such as this for example:

http://www.hi-techedu.com/products/hfc14.htm

I had thought of that, but the vertical beam joins to the sonotube at that
point, and just sits on top. The pushing sideways and the leverage would
cause the approximately 7' vertical corner support to push off the top of
the Sonotube, or come loose where it is only nailed together. This is going
to be the point of attatchment for the lower standoff, but I will make the
bracket 18" long, and at a right angle so I can wrap the whole corner, and
attatch to post, facia, etc, and increase the distribution of whatever side
load from the flex is. I don't think it will be that much. Certainly not
as much as mounting the bottom support of a stiff leg to it.

Seen lots of stifflegs loading boats. They are really strong, but all were
mounted into humongous concrete bases.

Steve


And here are a couple of older cranes which might give you ideas:

http://www.tclayton.demon.co.uk/pics/canal/npb5.html
http://www.stroudwater.co.uk/cpsn/dudbridge%20crane.jpg

Note that both of these have a compression member which is at an angle to
the vertical. This is a nice, simple design. You just need to avoid
applying large moments to the beam as in your original proposal. In pure
compression 2" x 2" x 0.25" tubing should be fine.

The most critical part of the crane is likely to be the point at which the
top is attached to the wall. If you choose to use expanding bolts, look up
their load rating and use a good margin of safety (a factor of 10, say).
Use the right size drill and make sure the wall isn't crumbly. Should it
fail, a joint like this will not fail in a nice way.

All the best,

Chris