Towertalk
[Top] [All Lists]

## [TowerTalk] winch loads and tower raising fixtures.

 To: [TowerTalk] winch loads and tower raising fixtures. "Jim Jarvis" jimjarvis@ieee.org Fri, 19 Aug 2005 13:27:53 -0400
 ```This started with Al Williams' question about winch ratings... was amplified by a mfr comment that a 1500 lb rated winch should do ok...and was commented on by Jim Lux, as follows: "And now you see why you need to ask the manufacturer why they think a 1500 pound rated winch is good enough. For instance, is there an extra pulley pass in there, so the winch cable is doubled, in which case the winch load is half the lifting load. The angle might not be 45 degrees (particularly if the far end of the tower is supported off the ground. And, the load on the cable will decrease as the tower comes up . " My questions/comments: 1) If the raising fixture isn't rated to raise the tower, why do they sell it? If you have to raise the tower to the point where the fixture CAN raise it... what good is it? How do they propose you lift the half ton load otherwise? This causes me to conclude that the fixture IS rated to lift the tower with a rated windload of antennas on top, from a horizontal position. 2) Comments about lifting angle and loads... I would analyse the problem using the center point of the tower as the lift point, just to simplify the math. 1100lbs of deadload can be assumed to locate at its center, which is N feet out from the hinge. 1100lbs x N = some # of ft. lbs. The LIFTING aspect is also multiplied by some leverage...and will net out a deadload on the winch. You need a safety margin on that...probably 30% or so. Given real dimensions, I could walk you through the calculation, taking angles into account...but I think Jim Lux already did a good job of that. In point of fact, the mfr may attach the lifting cable at a point which equals the height of the lifting fixture. Possibly below the center of the retracted tower. The loads go up quickly in that case. 3) The REAL MYSTERY...and this is outside my experience...is whether winches rated at 1500lbs are so rated because that is the safe load, or whether it's some other figure...like maximum load capability. n2ea jimjarvis@ieee.org _______________________________________________ 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 [TowerTalk] winch loads and tower raising fixtures., Jim Jarvis <= Re: [TowerTalk] winch loads and tower raising fixtures., Richard (Rick) Karlquist (N6RK)