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Posted by mm on September 6, 2006, 1:23 am
wrote:
>Thanks. I was thinking I might just go all the way though the wall
>(drywall and all) and just have long bolts going through with big nuts
>& washers on the inside of the garage (drywall side). That way there'd
>be no chance of the fasteners pulling out.
>
>I think the load on the fasteners will not be high except for maybe in
>the winter when there's ice & snow built up... I figure if the current
>trellis can support that w/o collapsing maybe my idea is overkill...
I was building a lucite vent window (an angle piece to blow the wind
in on me when I drove) and I wanted to measure the wind strength at 70
mph to decide how strong the lucite need be. After a bit of thinking,
the obvious way was to hold a piece of lucite out the window as I
drove 70 mph. The deflection was a measure of the wind pressure (and
it was far from making an 1/8inch thick piece brake.)
The way for you to measure the force t he trellis will put on the
bolts is to go out there and push the trellis back against the wall.
My guess without seeing it is that in the summer it will take 2 or 3
pounds of pressure. With snow and ice, it might be 3 times as much.
Remember that you only have to resist the "moment" of force
perpendicular to the wall. Since gravity pulls downward, the portion
of that force that is horizontal is between small and zero.
Depending on where it rests, where the trellis rests or where the base
of the plant is, whatever is the support and pivot point of the whole
thing. Only when the trellis gets away from the wall, does the
gravity pull down, and in doing so pull to the side, since the thing
pivots at the bottom.
It's like balancing a chair on your finger. If the center of gravity
of the chair is exactly above your finger, there is no force pushing
it to the side.
>Thanks for any more feedback...
>
>Kevin
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