In a message dated 98-03-15 14:50:31 EST, kc5ajx@hotmail.com writes:
> > I am finally geting ready to put in the base for my first tower
> >project. I have 40 ft of Rohn 25 and plan to add another 30ft to it to
> >make 70ft total height. I want to be able to fold this tower over it
> >came with a BPH25G base plate and a 19ft pole to surport the tower.
A worthwhile project. What does the "19 foot pole to support the tower"
do?
> > I feel that the 3/8 bolts on the base plate are to small to fold this
> >over safely, would the SBH25G be a better choice? or should I build a
> >stronger base plate my self? I contacted Rohn with this question and
> the
> >response I got was "We just build them we don't energineer them"
> inother
> >words they won't say.
Why re-invent the wheel? If the bolts are good enough for Rohn, they're
good enough for me.
The SBH (short base-hinged) and the BPH (base plate-hinged) do the same
thing. I personally would prefer the SBH because then you'll have the bottom
of the tower set in concrete whereas you'd have to use anchor rods with the
BPH.
Customers aren't allowed to talk to Rohn engineers.
> > My next question is about the support pole to hold the tower when I
> >fold it over. THe pole I got with the tower is 19 ft long and about 1
> >1/2" in diameter. I plan to put 2 section of pipe under this the bottom
> >section will be 3 1/2" in diameter and 5 ft in concrete the middle
> >setion will be 2 7/8" diameter. I plan to overlap them about 6" to a
> >foot so the total pole will be 5 ft in concrete and 35ft above ground
> >will this be big enough pipe and be long enough to fold over the 70 ft
> >tower with a TH6 on top or do I need to go higher or bigger with the
> >pipe? It will only have a load on it when I have to fold the tower
> over.
You'll never get an engineer to sign off on this scheme. I'm still not
clear but I think you want to have the tower hoisting line go up the 35 foot
pipe to a pulley of some sort and then out to the tower as it's laying
horizontally. I personally don't like the sound of this. My non-engineering
reaction is one of skepticism. Be advised that the forces to pick up 500 or so
pounds of horizontal deadweight 70 feet long are tremendous. Can someone
fluent in vectors pickup on this one?
> > I've been told by a local ham that this "should work" but it would be
> >best to guy the pole when I fold the tower over, so I plan to have 5
> guy
> >post to guy too, 3 for the tower and 2 for the pole.
I'll bet you a nickel that the guy that told you that wasn't an engineer.
With a guyed pole, I'll give you a definite maybe.
>> I will use the recommended 80% of the tower heigth. I beleive it
> >will be 56ft out from the tower. I plan to guy this thing at 20 40 and
> >60 ft ie every other section right or wrong?
Wrong. The Rohn book says two sets of guys up to 110 MPH. Additional
guys aren't necessary.
> Can I use the drycron rope for guys?
What, are you nuts? In case I haven't mentioned it before, the LXC Prime
Directive is "DO what the manufacturer says". Factory specs call for 3/16 inch
EHS guy cable. I think you meant dacron.
> I hate to try and figure out where to break up the wire guys
> >with insulaters and the Kelvar seems expensive but I could probably
> save
> >up enough to get the Kelvar stuff I think the brand name is Phillystran
> >isn't it?
You don't have to figure it out. Current thinking in order to have non-
resonant guy segments is in the order of 22-26 feet. I think there is a chart
in the ARRL Antenna Handbook with more info. Do your homework.
> > THe base wil be 4X4X5 ft deep is that big enough?
Considering Rohn calls for a 2x2x4 foot hole, yeah - I'd say it's
plenty. You don't have a Rohn book do you? Their five bucks from TOWER TECH.
Please purchase one.
> > Right now I have the 40ft of Rhonn 25 tower (will add 30ft more) the
> >TH6 beam and a Tailtwister rotor. future plans might include an A3WS
> for
> >the WARC bands not sure if I will try to put a forty meter beam on it
> >probably will be too much antenna on one tower.
> > AS you csn see I have been planing this for a LONG time, several
> years
> >in factand I still have lots of questions. I need suggestions from the
> >wisdom of the group as I don't plan having to redo this project. I want
> >to do it right the first time.
> > And for Steve ( sorry I can remeber your call if you want to figure
> >the wind for this area I'm in Parker county Texas).
Parker County is only a 70 MPH windspeed zone so you dodged a bullet on
that one.
What are you doing for anchors? Size, hardware, etc.?
I guess my bigger question is why do you want to hinge the tower? If it's
because you don't want to climb it, then you need to get some of your buddies
to do it or hire someone to install everything. I think you're asking for
trouble with the hinging scenario. If you get a PE (Professional Engineer)
involved and he/she signs off on it, you have my blessing. Until then, I
wouldn't do it on a bet. If everything is done to spec, the first problem
you'll have is the rotator is 6-7 years but structurally the tower will be
fine for 20 years or more.
Rick, I don't mean to pick on you but this is a classic case of amateur
"hip-pocket engineering" meaning inadequate. Congratulations at least on
seeking advice on your planned installation. I have published a little paper,
"The Ten Most Common Tower Building Mistakes" and needless to say you're
making a couple of them. When you get done, you'll have a much deeper
appreciation of this whole topic. Hopefully your installation will be properly
installed and give you decades of reliable performance.
73, Steve K7LXC
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