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N4AEQ
08-31-2008, 02:55 PM
I need to decide how high up to make a fold over joint for my rohn 25. I need
something I can raise & lower by myself, I plan to put a joint of 25 in the ground abt 5 feet, if i add 1 more on top then it would be 15 foot @ the fold
over plate area.
Im trying to decide if 15 would be ok or should i go to 20'. I will be adding a
counter weight on the bottom, Im thinking of 45' tower with 5' mask to the top
and tv type rotor with vhf/uhf beam, inverted vee will be used for all HF
so the load will be low.

K9XR
08-31-2008, 04:32 PM
I need to decide how high up to make a fold over joint for my rohn 25. I need
something I can raise & lower by myself, I plan to put a joint of 25 in the ground abt 5 feet, if i add 1 more on top then it would be 15 foot @ the fold
over plate area.
Im trying to decide if 15 would be ok or should i go to 20'. I will be adding a
counter weight on the bottom, Im thinking of 45' tower with 5' mask to the top
and tv type rotor with vhf/uhf beam, inverted vee will be used for all HF
so the load will be low.

I'm not sure how you plan to build the fold-over fixture, but there are quite a few things to consider. As you probably know Rohn used to build a fold over kit for their towers (maybe they still do). As I recall they folded over near the halfway point of the total height of the tower.

I think they used to go as high as 68 feet with the fold-over option on the #25. They used a tapered tower section as a counter balance/winching arm.

The main difference between guying on this tower and regular Rohn 25 guying was that they used a 4 point guying system on the fold-over versions instead of the normal 3 point system. This allowed the guys to be placed closer to the tower. When you tilted it over you unfastened the top guys and the antennas would easily clear the bottom set of guys which were fastened at the fold over point.

I don't know if you plan to bracket the bottom to your house or if you plan to guy it, but you should probanly consider doing on or the other. At the heights and antenna load you are talking about guying the top would probably not be a big concern. There a great deal of stress on the pivot point even with a counter balance.

To answer your original question, I think you would probably want to go to at least 20' and 25' would be better for your "fixed" section.

K7MH
08-31-2008, 05:51 PM
Here are a couple of pics of the Rohn tilt over assembly if it helps. There is one locally in Roy WA. on Craigslist for sale right now.

K9XR
08-31-2008, 06:43 PM
Here are a couple of pics of the Rohn tilt over assembly if it helps. There is one locally in Roy WA. on Craigslist for sale right now.

The drawing looks about right, but I thought the arm was quite a bit bigger than that. I am almost postive that the picture shows a tower other than a Rohn 25. It may be a Rohn 45, but it may also be some sort of aluminum tower like Heights or Universal. The Arm doesn't look long enough or big enough in girth to do what the Rohn fold-over towers did. I haven't worked on one for many years, but it looks a little light duty to me.

K7MH
08-31-2008, 07:00 PM
Beats me if it is 25G or not.
The seller isn't even sure.
Craigslist ad for tiltover assembly (http://seattle.craigslist.org/tac/ele/817515590.html)

WB2WIK
08-31-2008, 07:09 PM
What's shown in the picture is not Rohn 25G.

The "idea" is about right, but the Rohn tiltover product was more substantial than that for sure; I installed half a dozen of these back in the 70s.

You need a strong foundation and four guys at the breakover point or the 25G is likely to become a couple of 12-1/2Gs. The Rohn backbone for the tiltover was a webbed structure like the tower, only formed like a sideways vee instead of a straight section.

It was a weldment, not tubing.

WB2WIK/6

WA9CWX
08-31-2008, 08:37 PM
They also used a pair of solid pieces welded on either side of a very heavy duty 'pipe' for the fold over section.

I have had both a 68' "25" and currently a 64' "45" fold over tower from Rohn.
They are quite well made, but DO require 4 guys at the fold over section.

The fold overs are just below the half way point. The cable and winch is fairly heavy duty also. It uses stainless aircraft cable, and a boat winch with a break system on the gears.

K4SAV
08-31-2008, 10:07 PM
Take a look at this:
http://www.redevices.com/rohn-foldover-25.pdf

The fold-over section is made from a modified piece of R-25 with the hinge located 2.5 ft from the bottom.

The brace for this section (Rohn calls it a boom assembly) is made from a piece of 3 inch square pipe, 0.14 inch wall, with another back brace welded to that. That additional back brace varies from 2.5 to 5 inches wide and is made from 0.125 material. This assembly, not counting the R-25 section, weighs 90 lbs.

There is a pipe attached to the bottom of the fold-over brace which provides a lever for raising and lowering it. That pipe is 11 ft long, 0.2 inch wall, and weighs 47 lbs.

The fold-over section for R-45 looks different from this.

Jerry, K4SAV

N4AEQ
08-31-2008, 10:36 PM
I was going to mount the 45' tower beside a 15' -20' tall section of rohn 25 with the foldover point on top the 20 or 15' section. It would look like a
seesaw but not exactly on center.
Im not a engineer but sometimes things work when the book says they shouldnt so I was hoping someone actually had made or seen a system like this that worked.

WB2WIK
08-31-2008, 10:45 PM
I was going to mount the 45' tower beside a 15' -20' tall section of rohn 25 with the foldover point on top the 20 or 15' section. It would look like a
seesaw but not exactly on center.
Im not a engineer but sometimes things work when the book says they shouldnt so I was hoping someone actually had made or seen a system like this that worked.

::How do you "fold over" a tower from a different tower? I don't get it. The tower that folds over has to hinge. Do you mean you intended to tilt your main tower over from its base, using a fulcrum point on a different tower?

K4SAV
08-31-2008, 10:51 PM
It doesn't sound like a good plan. Once this is standing up and you guy the top section, all the weight of the tower plus guy wire tension will be on the hinge. You need to have all that weight concentrated over the center of the section that is mounted in the ground, similar to the Rohn fold-over technique.

Jerry, K4SAV

VE1IDX
09-01-2008, 12:57 AM
I was going to mount the 45' tower beside a 15' -20' tall section of rohn 25 with the foldover point on top the 20 or 15' section. It would look like a
seesaw but not exactly on center.
Im not a engineer but sometimes things work when the book says they shouldnt so I was hoping someone actually had made or seen a system like this that worked.

That is pretty much what I plan to do in the next year or two. My plan is for a freestanding 56' Delhi tower mounted next to 20 feet of heavy steel tower that once served as an AM broadcast radiator.The two towers will be aligned face to face with the former AM tower having a hinge plate at the top which will connect to a saddle bracket affixed to the Delhi tower.When verticle the Delhi tower will be bolted to stubs in the concrete base as well as to the hinge plate and when I want to tilt it over it will be a simple matter of removing a few bolts and winding it down with a winch. I will probably have to use a temporary backstay from the top of the tower to the base but that is quite doable.Because of the power lines and layout of my tower/property I cannot simply tilt it over from the base as I do not have the room to lay over 56' of tower without encountering the service entrance to my house or trees.My method is MUCH easier to do with a freestanding tower.

WA9CWX
09-01-2008, 04:19 AM
BE carfull !

Sounds like a good plan IF the welds, and the old BC tower AND the hinge and bolts are ok.

You MUST guy the BC tower section with the hinge, NOT just from the back.

There are torque forces that amplify in even the slightest wind from the sides. Torque is NOT something towers take in stride, even short tough pieces.

VE1IDX
09-01-2008, 05:19 PM
I'm not too worried about the b'cast tower. I am very familiar with it as it came from a site I used to manage during my previous life as a broadcast engineer. It is 24 inches on a face and is made of SOLID one inch galvanized steel bar with solid 1/2 inch welded cross bracing.Each ten foot section weighs 200 pounds. It is either a Wind Turbine tower or a Trylon I'm not sure.It makes Rohn 55 look like a tinker toy set. These towers are made up on the ground for the first 100 feet and then stood up with a crane without any problems and are often erected with no guys for the last 30-40 feet. I know that the Delhi tower would fail before the b'cast tower. As for the hinge plate and saddle bracket, I am getting an engineer at work to design it for me and have the welding shop at work make it up for me. I saw this done sucessfully only one other time and my proposed installation is far heavier than the one I saw before.With proper cabling and counterweights at the bottom of the 56' tower all the b'cast tower should have to do is support the balanced weight of everything.The tiltover height will be about 15-16 feet high with about 5 feet of b'cast tower set in concrete.Rotational torque should not be a problem as it will not be raised or lowered in any kind of wind and the tower will withstand a considerable amount of torque anyway.

W5DWH
09-01-2008, 08:28 PM
So what is the advantage of hinging higher up v.s. having the hinge at ground level?

VE1IDX
09-01-2008, 10:10 PM
If I hinge it 20 feet up I gain 20 feet of horizontal space. As the part of the tower above the hinge tilts DOWN towards the power drop to the house, the part of the tower below the hinge swings UP and away from the power drop. I can drop a 56 foot tower down to the ground when the base of it is only 40 feet from the power drop. It it were hinged at the base it would require 56 feet in order to lower a 56 foot tower. If I locate the base near the top of the embankment behind the house,the lower part of the tower will swing out over the edge of the bank where it would have been impossible to locate a tower.

N4AEQ
09-02-2008, 08:06 PM
Ok, It sounds like I will skip the foldover at 20 ft up and maybe go with a
ground mounted foldover plate, there must have been a dozen for sale at the Shelby ham fest this weekend so I guess they must work ok or people wouldnt be selling them year after year? I thought there would be alot less tower stress with a pivot point 20 ft up as opposed to all the way on one end.

VE1IDX
09-02-2008, 08:36 PM
The thing about a ground mounted foldover hinge is that you MUST have a fairly substantial mast to provide the support for the tower while lowering it. That is the drawback. The good point about such a setup is that the tower is typically supported near the top by the cable and that ads support to the tower,less bending. With the swing over/ fold over system the tower itself must be able to support a substantial weight on either side of the fulcrum but requires less room to lower it to the ground. Both systems have pros and cons.

W5DWH
09-03-2008, 12:24 AM
The thing about a ground mounted foldover hinge is that you MUST have a fairly substantial mast to provide the support for the tower while lowering it. That is the drawback. The good point about such a setup is that the tower is typically supported near the top by the cable and that ads support to the tower,less bending. With the swing over/ fold over system the tower itself must be able to support a substantial weight on either side of the fulcrum but requires less room to lower it to the ground. Both systems have pros and cons.

I plan on hinging mine from the ground without using a mast. I will tie a cable on the top and then connect it to my John Deere tractor. Then lower her down. The tractor with loader and ballast in tires weighs around 12,000 lbs. Should not be a problem lowering a 50' Rohn 25G.

ZL3GSL
09-03-2008, 08:10 AM
Yes, you can lower the Rohn tower that way, and the tractor will survive that. The tower might. You might want to duck the guy wire after it breaks if you want to survive the operation. If you are very lucky you'll crumple the tower before that happens. When the wire breaks it will come at you very quickly..

DON"T DO IT.

As the triangle of tower, guy wire, and ground becomes thinner and thinner, the tension in the rope, and the compression force in the tower tend towards infinity. They don't reach infinite; something gives.

This is why you need the other jury pole (which must be guyed to keep it in a vertical plane with the tower and lowering guy).

Lucky people have lost towers, wind generators, etc, in exactly this way. Others have been killed doing it.

VE1IDX
09-03-2008, 10:30 AM
I have seen self supporting towers lowered that way but they are MUCH stronger than guyed tower especially the Rohn 25 series.I would go with the supported mast behind the tower and use a cable at the top of the tower and another in the middle to keep the tower from buckling in the middle as it nears it's end of travel near the ground.

WA7KKP
09-04-2008, 03:07 PM
I've only seen a couple of foldover towers, and in the case of 25G, I'd just leave it in one straight piece and invest in a climbing belt. It is no big thing to climb up 40-50 feet with the RIGHT safety equipment, and/or a willing ham who'd do it for less than the commercial boys.

Or invest the really big bucks in a Telex Sky Needle -- a collapsable tubular tower, complete with crow's nest at the top. But ask yourself, how often do you REALLY have to climb a tower to do antenna work? If the answer is more than a couple times, then you need to build better antennas.

Gary WA7KKP

W5JYD
11-15-2008, 08:36 PM
I need to decide how high up to make a fold over joint for my rohn 25. I need
something I can raise & lower by myself, I plan to put a joint of 25 in the ground abt 5 feet, if i add 1 more on top then it would be 15 foot @ the fold
over plate area.
Im trying to decide if 15 would be ok or should i go to 20'. I will be adding a
counter weight on the bottom, Im thinking of 45' tower with 5' mask to the top
and tv type rotor with vhf/uhf beam, inverted vee will be used for all HF
so the load will be low.

i have a home made fold over at 50ft if you send me a e mail i will send you the photoes of it is rohn 25 it will free stand at 50 ft
w5jyd Maxie w5jyd@hotmail.com

W5JYD
11-15-2008, 08:39 PM
I need to decide how high up to make a fold over joint for my rohn 25. I need
something I can raise & lower by myself, I plan to put a joint of 25 in the ground abt 5 feet, if i add 1 more on top then it would be 15 foot @ the fold
over plate area.
Im trying to decide if 15 would be ok or should i go to 20'. I will be adding a
counter weight on the bottom, Im thinking of 45' tower with 5' mask to the top
and tv type rotor with vhf/uhf beam, inverted vee will be used for all HF
so the load will be low.

w5jyd forgot it is heanged at 15foot off the ground

W4PG
11-15-2008, 11:47 PM
In case if helps anyone, attached is a picture of my US Tower foldover system, which is hinged at the base.

FWIW.

............Bob

W8JI
11-16-2008, 01:24 AM
I have a 130 foot foldover tower, here it is...

http://www.w8ji.com/images/towers/cranetractor30.jpg

Seriously, be careful with 25G. Even if you hinge it half way, which is best for load rating, you have to be very careful what you do. There is a lot of stress at the hinge point, and those legs are prtty thin.

KA0GKT
11-16-2008, 03:35 AM
Why not find a used E-Z Way RBX-50 tower. The crank-up / Fold-over design of the tower is just what you need. I know of one RBX-50 which survived the 1974 Omaha tornado (What the folks in "The Big O" call "The Big One".

At any rate, you can see how the RBX-50 was built and operates at: http://k1ypp.home.comcast.net/~k1ypp/RBX-50_Tower_Take_Down_at_K1YPP.html