I am kicking around the idea of building a gantry crane with an
aluminum I-beam.

Last week I found a source of surplus aluminum 6061-T6 beams (10' long
by 8" high by 5" wide).

With the plan of using one for a gantry crane, what would the lifting
capacity be for a 10' beam with adequate safety factors included?

I am hoping to make this a one man assembly effort so I am looking for
ideas for an adjustable height supports.

Here are some approaches...

http://www.wallacecranes.com/ratchet.htm

http://www.spanco.com/pages/gantryaalum.php

Any other suggestions for buiiding an aluminum gantry crane?

Thanks

TMT