----- Original Message -----
From: "Alan Wilson" <ke4nu@ke4nu.myrf.net>
To: <towertalk@contesting.com>
Sent: Tuesday, January 24, 2006 3:17 AM
Subject: [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 lbs
tower CG 20 feet from base
weight of accessories at the top = 120 lbs
accessories 42' from base
pulley 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 hinge
160 lbs x 20' = 3200 ft-lbs for tower
120 lbs x 42' = 5040 ft-lbs
right angle distance from cable to hinge = 12' (calcs omitted)
tension in the cable for tower alone = 3200 ft-lbs/12' = 266 lbs
tension in the cable for tower+accessories = (3200+5040)/12 = 686 lbs
distance 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, K6LL
Yuma, AZ
.
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