Originally Posted by
79pmooney
Wow! Did I see that right? A 2:1 tackle on a 4:1 tackle? 8:1 final?
I used to race 15' sailboats. I sailed my last one until it was tired enough that I didn't feel good about selling it so I stripped and junked it. I have a box of Harken and the like fittings. A few weeks ago I stretched webbing across my crawl space joists to hold insulation. Needed a block and tackle to get it tight. Found my old boom vang, a wire 2:1 pulled by a rope 4:1. Roller bearing blocks. Got a 1" piece of 1 X 4, screwed the vang to one side, a cam cleat to the other, a steel strap and the other end ot the plank, then just screwed the tang to a stud, tied a rolling hitch to the webbing and pulled. Really easy to get the webbing nice and snug, lying on my back on a stony surface. (Miserable job, but that part was fun!)
Now this block and tackle would not be up to your needed force, I;d have to settle for it pulling the real (and really strong) 2:1. 16: 1 but only about 4" take up. Good thing is that seatposts don't snap back to the original position when you slack off to shorten things up.
I'm keeping that plank, block and tackle, cleat and tang as is. Great little tool. Can't wait to use it again. (Actually I'd better! Could get expensive if I try "just seeing if I can pull my house apart".)
Ben
I only achieved 6:1 there, but the rope tension was much higher than "good practices".
And I never had to re-tension, at least not after the post had actually started moving. The rope (all one very long piece, including both blocks, the ratchet wind-up
and the bb tethering!) was highly elastic at this stress level, even the trees were flexing.
That sounds like a clever idea using webbing to "wall off" the insulation material. I shopped for a suitable material to do the same thing with my under-floor insulation so that I wouldn't be running my hair through exposed fiberglass! The materials I came up with seemed cost-prohibitive (peg-board/perf-board isn't cheap).
I could see that to much tension on too many webs might start to cause building materials, joists/studs or whatever, to move!