I have always been told that (4 foot) earth screw in anchors (Rohn) are for
very small and short towers . 20 G type.
Is this correct now a days ?
Al
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To: towertalk <towertalk@contesting.com>
Sent: Thu, Jul 10, 2014 7:39 pm
Subject: TowerTalk Digest, Vol 139, Issue 18
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Today's Topics:
1. How do bldg inspectors handle screw in earth anchors?
(Richard (Rick) Karlquist)
2. Re: How do bldg inspectors handle screw in earth anchors?
(Jim Lux)
3. Re: How do bldg inspectors handle screw in earth anchors?
(Brian Amos)
4. Re: overhead truss for 80M rotary dipole (Chuck Gerarden)
5. Re: How do bldg inspectors handle screw in earth anchors?
(Richard (Rick) Karlquist)
6. Re: How do bldg inspectors handle screw in earth anchors?
(Mickey Baker)
----------------------------------------------------------------------
Message: 1
Date: Thu, 10 Jul 2014 10:29:40 -0700
From: "Richard (Rick) Karlquist" <richard@karlquist.com>
To: towertalk@contesting.com
Subject: [TowerTalk] How do bldg inspectors handle screw in earth
anchors?
Message-ID: <53BECD84.7040802@karlquist.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Has anyone had experience getting a building permit
for a tower with screw in earth anchors? How does
it get "inspected". There is no empty hole for
the inspector to look at. Do you show him the anchor
before insertion? If you have an authorized AB
Chance installing contractor put in the anchor,
do they issue a certificate that you can show the
inspector? In a sense, this contractor is also
the engineer and building inspector all in one.
Rick N6RK
------------------------------
Message: 2
Date: Thu, 10 Jul 2014 13:21:50 -0700
From: Jim Lux <jimlux@earthlink.net>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] How do bldg inspectors handle screw in earth
anchors?
Message-ID: <53BEF5DE.8020406@earthlink.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
On 7/10/14, 10:29 AM, Richard (Rick) Karlquist wrote:
> Has anyone had experience getting a building permit
> for a tower with screw in earth anchors? How does
> it get "inspected". There is no empty hole for
> the inspector to look at. Do you show him the anchor
> before insertion? If you have an authorized AB
> Chance installing contractor put in the anchor,
> do they issue a certificate that you can show the
> inspector? In a sense, this contractor is also
> the engineer and building inspector all in one.
>
could it be more like a material and process inspection?
You have the paperwork showing you have the anchor and the mfr's
paperwork showing what its properties are.
Then you have paperwork showing you did the installation appropriately
(e.g. if you used a truck mounted drive, it gives a reading of the
torque as it drove it)
The only time I've had an "official" inspection of a structure using
screw in anchors it was for a temporary installation, and the guy came
out, looked at the plans, looked at the erected contraption, verified
that what we had built matched the plans, and said "go for it".
Granted it was in an area and application where failure would hurt
nobody but ourselves.
What do utilities do when installing poles with these anchors? I find
it hard to believe that the city sends out an inspector to watch them
plant every pole and its guys.
------------------------------
Message: 3
Date: Thu, 10 Jul 2014 16:24:39 -0600
From: Brian Amos <bamos1@gmail.com>
To: "towertalk@contesting.com" <towertalk@contesting.com>
Subject: Re: [TowerTalk] How do bldg inspectors handle screw in earth
anchors?
Message-ID:
<CAO2gF474ZEZd1saK8KY35TyC0PAtDYMyjRmcjf5ziaNBNhu7yw@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
As for the utilities usually the municipality doesn't inspect their
installations as they are self regulating. The "screw anchors" ie
"helical piers" are installed to a certain torque which the software
tells the installation contractor he must meet. As a soil engineer I
have many times had to "inspect" the installation where I watch the
pressure gauge and make sure they make it to the required pressure
(which they tell me) for each pier and then I have to send a document
to the owner stating that it complies with the design and put my stamp
on it. I'm not a big fan of that setup as I don't do the engineering
but I have to certify that it will hold up. It drives me nuts
actually. For a residential purpose I would guess that you just tell
the building official when you will be installing it and they can come
and watch. That is the only way to really inspect them.
BTW: Is this for supporting the tower? Or is it for the guys? If it's
for the tower I suspect you will need at least one per leg and it must
be a large tower to keep them at least 3 screw diameters apart to
prevent interaction. This type of support provides virtually no
lateral resistance (especially the square chance bars that have no
soil contact anywhere but the helix, they are all tension and
compression, so for guy supports they work great, but not so well for
a foundation. I suspect that the building official won't care about
inspecting screws for a guying system. They usually only care about
the foundation itself.
Brian
KF7OVD
On Thu, Jul 10, 2014 at 2:21 PM, Jim Lux <jimlux@earthlink.net> wrote:
> On 7/10/14, 10:29 AM, Richard (Rick) Karlquist wrote:
>>
>> Has anyone had experience getting a building permit
>> for a tower with screw in earth anchors? How does
>> it get "inspected". There is no empty hole for
>> the inspector to look at. Do you show him the anchor
>> before insertion? If you have an authorized AB
>> Chance installing contractor put in the anchor,
>> do they issue a certificate that you can show the
>> inspector? In a sense, this contractor is also
>> the engineer and building inspector all in one.
>>
>
> could it be more like a material and process inspection?
> You have the paperwork showing you have the anchor and the mfr's paperwork
> showing what its properties are.
> Then you have paperwork showing you did the installation appropriately (e.g.
> if you used a truck mounted drive, it gives a reading of the torque as it
> drove it)
>
>
> The only time I've had an "official" inspection of a structure using screw
> in anchors it was for a temporary installation, and the guy came out, looked
> at the plans, looked at the erected contraption, verified that what we had
> built matched the plans, and said "go for it".
>
> Granted it was in an area and application where failure would hurt nobody
> but ourselves.
>
> What do utilities do when installing poles with these anchors? I find it
> hard to believe that the city sends out an inspector to watch them plant
> every pole and its guys.
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
------------------------------
Message: 4
Date: Thu, 10 Jul 2014 18:33:12 -0500
From: Chuck Gerarden <cgerarden@atomix.com>
To: 'Markku Oksanen' <ww1c@outlook.com>
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] overhead truss for 80M rotary dipole
Message-ID:
<7eefd582140b841bfd9fb0f322cdba29f6031427@sitemail.hostway.com>
Content-Type: text/plain; charset=UTF-8
?
Markku,
Thanks for all the great information. After reading responses I think
my tubing is too small.I will also raise my truss height as suggested.
Chuck
W0DLE
----- Original Message -----
From: Markku Oksanen
To:"Grant Saviers" , "Chuck Gerarden" , "towertalk@contesting.com"
Cc:
Sent:Thu, 10 Jul 2014 07:00:43 +0000
Subject:RE: [TowerTalk] overhead truss for 80M rotary dipole
Hi
Here at south OH-land (not Ohio) a dipole like this needs to start
with 80 mm / 3 inch tubing with 3 mm walls. As tubing resistance to
bending goes with 4th power of the outer radius, any extra mm is good.
?The tube at the truss attachment is 60 mm.
Secondly, the compression (bending) caused by the truss wire
increases proportional to 1/Sin(a) (or Tan(a), for small angles these
are close) where the a is the angle between the element and the truss.
This gets very quickly very large as we move to small (Sin(a) becomes
small) angles between the element and the truss. ?So, moving the
truss higher on the tower will help. ?
I have a 100 foot home brew 80 m rotatable dipole and the truss is 3
m/10 feet above. ?Truss goes to the 40% part and the ends are
designed to stand the elements free of support. So, 40 feet out, 10
feet above means a compression force ?4 x weight seen at the truss
attachment point.
I don't know what the accepted rule of thumb would be but if a
truss-element angle of less than 15 degrees causes the weight of the
element seen by the truss to be multiplied to a compression force of
4x the weight. This would be OK if the tube would be supported so that
it can't bend under the pulling force. ?With no wind this is the
case.
For these reasons I believe there are three options: Increase of tube
stiffness (diameter) so that the tube will be straight under all wind
conditions (the part between the truss and the tower), move the truss
higher to lower truss induced compression force or more difficult, add
2 more trusses so that they are 120 degrees around the element and
prevent this bending and add more failure modes.
I would move the truss higher, there is very little reason not to
have it as high as you can (easier than changing anything else). The
truss just about only is there the support the weight of the element
and doesn't do much for sideways dynamic forces.
MarkkuWW1C/OH2RA/OG2A
> Date: Wed, 9 Jul 2014 22:36:15 -0700
> From: grants2@pacbell.net [1]
> To: cgerarden@atomix.com [2]; towertalk@contesting.com [3]
> Subject: Re: [TowerTalk] overhead truss for 80M rotary dipole
>
> I rebuilt a tired EF180C (no longer sold) which is 86' long. Many
of
> the rivets were loose and were drilled out and replaced with cross
> bolts. I particularly like W6NL's advice on connecting elements -
two
> bolts at 90 degrees which does reduce the movement in 2 planes.
> Additionally he advises two guys above, so I use Phillystran to
about
> 20' out on each element. Mine are attached to a cross arm 4' above
the
> boom and about 30" each side, about what the linear loading wires
were
> originally. It is now tuned with a Tornado variable inductor and 25
ohm
> balun for full 80m coverage < 13:1. He also recommends a down guy
to
> the mast, then the antenna is totally constrained (I don't have
one).
> W6NL's view is that updrafts are likely and wind induced
oscillations
> can also move the elements vertically as you note, so a down guy is
> important. This antenna might move to a higher more exposed tower
> position and then I will add a down guy.
>
> I also ran the original (unguyed) design through YagiMech from DX
> Engineering and that verified why there were some small bends. The
wind
> survival barely was above 70mph. With internal sleeving I was able
to
> improve that to almost 90mph. So far so good after 3 years,
although my
> wind conditions are very benign even at the 100' element height.
btw
> the tip elements are 1/4" diameter but the wind load is so small on
them
> they are not the weakest link.
>
> I think it is unlikely that an element will fail in column buckling
> before failing in bending, and you are correct that guys load the
> element in compression.
>
> Grant KZ1W
>
>
> On 7/9/2014 5:50 PM, Chuck Gerarden wrote:
> > I have had several 80 meter rotary dipoles over the years and
they
> > have failed in the same manner due to very high windsthey get
bent but
> > never actually break. I wonder if the placement of the overhead
> > element truss may cause this effect as thewind blows. The truss
is
> > pulling up on the element but as the wind blows harder, the truss
is
> > actually pulling on the element
> > at an angle other than "up" due the the wind deforming the
element.
> > The harder the wind blows, the truss pulls the element harder
into the
> > mast.
> > I am thinking the truss is too far out on the element and maybe
it
> > should be moved in closer. This changes the "pivot point"as the
wind
> > is hitting the element and the outer element area is moving more
and
> > the inner area is more stable.
> > Is there a formula or does anyone have empirical knowledge on
where
> > the best place on an element or boom the truss should attach?
Each
> > element is 41' long for a total length of 82'. The antenna is
center
> > coll loaded for resonance and fed with a25 ohm balun.
> > I of course could have 1 overhead truss and a side truss to
resist
> > horizontal forces, but I would prefer to keep it simple ifthe
> > engineering allows it. This entire problem may be the aluminum
tubing
> > is not big enough or thick enough to beginwith. The elements
start at
> > 2 1/2 inches and taper to 1/2 inch.
> > My latest solution is to use tapered 40' fiberglass poles as the
> > elements with a wires inside. With big antennas I have often had
> > better results after a wind storm since they return to their
original
> > position.
> > Anyone out there have some good engineering advice on building 80
> > meter rotary dipoles?
> > ThanksChuckW0DLE
> >
> >
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk@contesting.com [4]
> > http://lists.contesting.com/mailman/listinfo/towertalk [5]
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com [6]
> http://lists.contesting.com/mailman/listinfo/towertalk [7]
Links:
------
[1] mailto:grants2@pacbell.net
[2] mailto:cgerarden@atomix.com
[3] mailto:towertalk@contesting.com
[4] mailto:TowerTalk@contesting.com
[5] http://lists.contesting.com/mailman/listinfo/towertalk
[6] mailto:TowerTalk@contesting.com
[7] http://lists.contesting.com/mailman/listinfo/towertalk
------------------------------
Message: 5
Date: Thu, 10 Jul 2014 17:37:55 -0700
From: "Richard (Rick) Karlquist" <richard@karlquist.com>
To: Brian Amos <bamos1@gmail.com>, "towertalk@contesting.com"
<towertalk@contesting.com>
Subject: Re: [TowerTalk] How do bldg inspectors handle screw in earth
anchors?
Message-ID: <53BF31E3.2010905@karlquist.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
The screw in anchors, if used, would be for guying.
I guess you are saying that I must make the base big
enough to handle lateral force and I can't use the
guy anchors to hold the base in place. Got that.
So I have a choice of having my engineer watch
and certify and/or inviting the inspector watch
himself.
Is the pressure you are talking about the amount of
force to push the anchor in (an axial force) or the
amount of torque to turn the anchor in? With the
hand installed ones, only torque is needed. The
screw pulls itself into the ground.
Rick N6RK
On 7/10/2014 3:24 PM, Brian Amos wrote:
> As for the utilities usually the municipality doesn't inspect their
> installations as they are self regulating. The "screw anchors" ie
> "helical piers" are installed to a certain torque which the software
> tells the installation contractor he must meet. As a soil engineer I
> have many times had to "inspect" the installation where I watch the
> pressure gauge and make sure they make it to the required pressure
> (which they tell me) for each pier and then I have to send a document
> to the owner stating that it complies with the design and put my stamp
> on it. I'm not a big fan of that setup as I don't do the engineering
> but I have to certify that it will hold up. It drives me nuts
> actually. For a residential purpose I would guess that you just tell
> the building official when you will be installing it and they can come
> and watch. That is the only way to really inspect them.
>
> BTW: Is this for supporting the tower? Or is it for the guys? If it's
> for the tower I suspect you will need at least one per leg and it must
> be a large tower to keep them at least 3 screw diameters apart to
> prevent interaction. This type of support provides virtually no
> lateral resistance (especially the square chance bars that have no
> soil contact anywhere but the helix, they are all tension and
> compression, so for guy supports they work great, but not so well for
> a foundation. I suspect that the building official won't care about
> inspecting screws for a guying system. They usually only care about
> the foundation itself.
>
> Brian
> KF7OVD
>
> On Thu, Jul 10, 2014 at 2:21 PM, Jim Lux <jimlux@earthlink.net> wrote:
>> On 7/10/14, 10:29 AM, Richard (Rick) Karlquist wrote:
>>>
>>> Has anyone had experience getting a building permit
>>> for a tower with screw in earth anchors? How does
>>> it get "inspected". There is no empty hole for
>>> the inspector to look at. Do you show him the anchor
>>> before insertion? If you have an authorized AB
>>> Chance installing contractor put in the anchor,
>>> do they issue a certificate that you can show the
>>> inspector? In a sense, this contractor is also
>>> the engineer and building inspector all in one.
>>>
>>
>> could it be more like a material and process inspection?
>> You have the paperwork showing you have the anchor and the mfr's paperwork
>> showing what its properties are.
>> Then you have paperwork showing you did the installation appropriately (e.g.
>> if you used a truck mounted drive, it gives a reading of the torque as it
>> drove it)
>>
>>
>> The only time I've had an "official" inspection of a structure using screw
>> in anchors it was for a temporary installation, and the guy came out, looked
>> at the plans, looked at the erected contraption, verified that what we had
>> built matched the plans, and said "go for it".
>>
>> Granted it was in an area and application where failure would hurt nobody
>> but ourselves.
>>
>> What do utilities do when installing poles with these anchors? I find it
>> hard to believe that the city sends out an inspector to watch them plant
>> every pole and its guys.
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> 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
>
>
------------------------------
Message: 6
Date: Thu, 10 Jul 2014 20:38:46 -0400
From: Mickey Baker <fishflorida@gmail.com>
To: "Richard (Rick) Karlquist" <richard@karlquist.com>
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] How do bldg inspectors handle screw in earth
anchors?
Message-ID:
<CAOB+T5atUqODHCqW23vx3LdcH62Ess4VaZ+B5rqQDP=K8ngsRg@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
As always, it depends. Some inspectors are more thorough than others, some
municipalities have more or less stringent standards.
These type anchors are commonly used as tie downs for manufactured
buildings... like mobile homes. Typically there's a site inspection when
the structure is delivered, and the tie downs are part of the package. At
that time, they may be measured or manufacturer's tags inspected and
recorded.
After the structure is placed and the tie downs affixed, they're inspected
at the attach point. The inspector has the option to have one dug up if he
suspects funny business, but I've never seen it happen.
Contractors can get into big trouble for submitting bogus tie down
installations for inspection, not to mention liability issues.
I have a family member who owns several trailer parks, and I've seen this
process repeated many times. If you have a licensed contractor do it, you
are likely to have no problem.
73,
Mickey N4MB
On Jul 10, 2014 1:29 PM, "Richard (Rick) Karlquist" <richard@karlquist.com>
wrote:
> Has anyone had experience getting a building permit
> for a tower with screw in earth anchors? How does
> it get "inspected". There is no empty hole for
> the inspector to look at. Do you show him the anchor
> before insertion? If you have an authorized AB
> Chance installing contractor put in the anchor,
> do they issue a certificate that you can show the
> inspector? In a sense, this contractor is also
> the engineer and building inspector all in one.
>
> Rick N6RK
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
------------------------------
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