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## Re: [TowerTalk] Question about lowering a Fold-Over tower

 To: "towertalk-request@contesting.com" Re: [TowerTalk] Question about lowering a Fold-Over tower Steve Lane Thu, 2 Feb 2012 10:27:51 -0800 mailto:towertalk@contesting.com>
 ```As I am sure you know, the forces grow quite high on the pull point as included angle of the strap approaches 0 degrees. Numbers for you to think about are: If the included angle is 60 degrees, the force on the strap is 1.15 times the force if it was a direct vertical pull. At 30 degrees, the force is 2 times vertical pull and at 5 degrees the force is 11.47 times a straight vertical pull. Steve K9SL On Thu, Feb 2, 2012 at 8:02 AM, Gary Schafer wrote: > A friend of mine did this with a small (30') tower on field day. When the > tower got down low it pulled the Jeep that it was attached to and slid the > wheels. > The tower swung out off center and crashed down. There is tremendous force > on the cable when the tower is near the ground. > > You also need side guys on the tower when raising/lowering like that. > The falling derrick is a must. > > 73 > Gary K4FMX > > > -----Original Message----- > > From: towertalk-bounces@contesting.com [mailto:towertalk- > > bounces@contesting.com] On Behalf Of Wilson Lamb > > Sent: Thursday, February 02, 2012 10:49 AM > > To: towertalk-request@contesting.com > > Subject: [TowerTalk] Question about lowering a Fold-Over tower > > > > > > Dick, > > Please don't do this until you can get some onsite help. You're looking > > for > > trouble! > > > > As that tower gets near horizontal, the compression/buckling load from > > the > > cable will be LARGE, easily enough to pull out a brace, if that's where > > you > > hook on. Who knows if your hinge hardware can take the load? It might > > be > > enough to spin the tires of your car, if on grass. > > > > Worse yet, if you get the least lateral displacement you will get the > > cable > > off to the side of the hinge/tower plane and you will then have the top > > of > > the tower trying to go sideways because of the cable pull being off > > axis! > > You can tear your hinge apart and wreck your beam in a heartbeat! > > > > The falling derick advice is right on, BUT you have to be sure the base > > of > > the derick is wide enough to provide the lateral stability you need to > > prevent the off center situation above. AND you have to secure the > > cable to > > the top of the derick so the derick can't slip on the cable and drop the > > tower as it gets low! 20' of Rohn 25, guyed to the sides, would make a > > good > > derick. > > > > There may be other problems, but this should be enough to convince you > > to > > wait for some local guidance. > > > > Good luck, > > Wilson > > W4BOH > > > > > > > > > > Hi Guys, > > I'm going to lower a 90' Heights aluminum fold over tower with my car > > tomorrow evening. I've done this before without destroying the tower > > so > > hopefully I can have another successful lowering! > > > > My question is what is the best height on the tower to attach my Nylon > > Strap for lowering the tower? > > > > A few thoughts: > > > > 1) The 90' tower folds over at ground level and has a 36" wide base. > > > > 2) In the past, I attached my nylon strap around the tower at aprx. the > > 35' level and then attach a 1/4" steel cable to the nylon strap and > > raise > > and > > lower the tower with my car. > > > > 3) I keep the top of the tower 13' off of the ground so there's room to > > attach my 24' boom Yagi to the top of the tower. Keeping the top of > > the > > tower 13' off of the ground makes it easier to lower and raise the > > tower > > with a > > vehicle than if the top of tower was on or near the ground. That said, > > with the top of the tower 13' off of the ground it's still quite touchy > > raising and lower the tower as only as a small movement in the vehicle > > makes a > > big change in the tower. > > > > So I'm looking for the best strap height to lower the tower and the > > best > > strap height for raising the tower. After using the 35' height > > before... I > > don't think that one height is the ideal height for raising and > > lowering > > the tower. Since it's easy to locate the nylon strap anywhere on the > > tower > > I'm looking for the best height for lowering and best height for > > raising. > > > > All thoughts appreciated! > > > > Thanks- > > > > Dick- K9OM > > > > > > _______________________________________________ > > > > > > > > _______________________________________________ > > TowerTalk mailing list > > TowerTalk@contesting.com > > http://lists.contesting.com/mailman/listinfo/towertalk > > _______________________________________________ > > > > _______________________________________________ > TowerTalk mailing list > TowerTalk@contesting.com > http://lists.contesting.com/mailman/listinfo/towertalk > _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```