bob smith wrote:

"Anthony" wrote in message
8...


"bob smith" wrote in :



Hi,

I want to install two posts to hang a hammock. For aesthetic reasons I
dont want to camber them away from one another as typically
suggested. What size steel tube would I need such that deflection is
basically non-existant with a typical 1-person weight on the hammock?
(lets say 200 lbs) The posts would be 6' above ground, 4' below
ground. The hammock would hang from the top of the posts.

I was thinking 3" diameter but I'm not sure if the minimum sidewall
(1/8") would be acceptable or if I should go thicker.

What size would be equivalent to a 6x6 wood post for this application?
(ie. primarily bending strength)


www.efunda.com
look for cantilever calculations



Thanks, but that site costs money to signup (it seems they let you do 2 free
calculations first).

Also, I cant quite figure out how E and I are affected by sidewall
thickness?



--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

http://www.machines-cnc.net:81/






It's also going to depend a lot on whether you like a good solid sag in
the hammock or whether you like it tight as a fiddle string so there is
very little sag when the kids do a running jump on it. There are
several websites that deal with catenary sag and the tension applied at
the tie points for a given weight and sag. From there you can calculate
basic beam deflection using formulas in Machineries handbook or similar
based on your preference about how far the tops of the posts can deflect
under the weight.

I'd also probably fill the pipe with concrete. It will add a little
more strength against deflection and will make the posts seem less
"springy" if you choose a size on the low end of the strength scale.

Personally, I'd go fairly large and thick walled on the pipe as I think
it looks better (people perceive it as SOLID) and even when the rust
gremlins start taking over (rust never sleeps) there will be pleanty of
material there for a long time to keep things standing.

Koz