[TowerTalk] Advice for a 40 ft rohn 25 tiltbase tower

[Ronald Real]

----- Original Message ----- From: "Alan Wilson" <ke4nu at ke4nu.myrf.net>To: <towertalk at contesting.com>Sent: Tuesday, January 24, 2006 3:17 AMSubject: [TowerTalk] Advice for a winch for 40 ft rohn 25 tiltbase tower  > Hello, I got a 40 ft rohn 25g tower with the hinge base and I need some> recomendations on a winch to raise and lower it. I do have a tree a few> feet away which I put a pully on 20 or so ft up. I had a friend pull it> up with a 8000 lb winch mounted on the front of his truck and it worked> real slick...thanks Alan Wilson - Victor, MT Worst case is when the tower is just starting to rise off the ground.Given:tower weight = 160 lbstower CG 20 feet from baseweight of accessories at the top = 120 lbsaccessories 42' from basepulley height = 20'pulley horizontal distance behind base = 5'cable attachment point on tower = 20' from base Find:tension in the cable for tower alone, and tower plus accessories length of cable required Calculations: find moments about the hinge160 lbs x 20' = 3200 ft-lbs for tower120 lbs x 42' = 5040 ft-lbsright angle distance from cable to hinge = 12' (calcs omitted)tension in the cable for tower alone = 3200 ft-lbs/12' = 266 lbstension in the cable for tower+accessories = (3200+5040)/12 = 686 lbsdistance cable moves = 32' (calculations omitted) So you need, as a minimum, a brake winch with 686 lb capacity, and a cable length of about 40', allowing for at least one turn on the drum before tension is applied. Go to www.grainger.com and search on "brake winch" You can get the DLB 800 for $60 (+cable) or the K1550 for $84 (+cable) I think I would get the K1550. Dave Hachadorian, K6LLYuma, AZ   

What would the tension be, for this tower, if it were lowered to eight feet, on to a support? Would a backbone be necessary to prevent the tower from bowing/buckling?   

 

Ron Real, WD5CIG

Okla.