Towertalk
[Top] [All Lists]

Re: [TowerTalk] winch loads and tower raising fixtures

 To: towertalk@contesting.com Re: [TowerTalk] winch loads and tower raising fixtures Kevin Normoyle Tue, 23 Aug 2005 10:35:46 -0700
 ```in an old post, http://lists.contesting.com/archives//html/Towertalk/2005-06/msg00238.html I calculated the forces when raising a crankup with a ginpole at various heights. (there are three links there, one is an excel spreadsheet, others show what I analyzed) shorter ginpoles (like a raising fixture which is what, around 8' maybe) increase the forces on everything a lot. I used a 14' ginpole as a result for my lift. (I didn't have a raising fixture). I calculated assuming a direct connection to the tower (no compound pulley like on most raising fixtures). But you can divide by 2 in the right places to get the effect of a 2:1 compound pulley setup. adding weight to the top of the tower, when lifting, obviously causes a bigger effect than linearly distributing added weight across the tower. ...i.e. 300 lbs at the end of the tower, is worse than a 300lb heavier tower. Because the tower is acting like a class 3 lever, and the pull effort is closer to the fulcrum than the load is, so the 300 lbs multiplies. My calcs break the analysis in two. The weight past the tower attach point is a class 3 lever. The weight below the tower attach is a class 2 lever. I assumed the attach point height equals the ginpole height always. I assume the tower weight is linearly distributed, and simplify the analysis with an appropriate point load at the halfway points. there are two, because of the two different class 3 and class 2 lever effects). You can modify/do the calcs, but it's not out of the question to exceed a 1500 lb pulling force with a 2:1 compound pulley, with my example. (which had nothing on top of the tower). I would do the calcs with the antenna load at horizontal, even though you would install them at a slight angle. The difference can be considered design margin. I don't know the exact height of the raising fixture in question, or the height of the attach point to the tower, though. Food for thought: if you think you need stronger winch, at a certain point you need stronger cable (like 1/4"). I'm not sure what size cable was on your 1500 lb winch. The rest of the setup may be strong enough already. -kevin KE6RAD _______________________________________________ See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA. _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
 Current Thread Re: [TowerTalk] winch loads and tower raising fixtures, Kevin Normoyle <=