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Old August 24th 08, 12:52 AM posted to rec.radio.amateur.antenna
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Default How do you get a ground rod to 6 feet ?

On Sat, 23 Aug 2008 10:58:19 -0500, Dave Lemper wrote:

The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.

Renting a back hoe is out.
Any suggestions appreciated.
Dave WB3DWE


I would find out how local electricians do it. They have to meet code.
John Ferrell W8CCW

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Old August 24th 08, 02:53 AM posted to rec.radio.amateur.antenna
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Default How do you get a ground rod to 6 feet ?


That caliche must be something else. I've never heard of it. But I must
question either your selection of ground rod, or method of insertion.
I've sunk a number of ground rods in semi-rock.... sometimes penetrating
granite too.

We used 5/8" copper clad steel, or sometimes 3/4" copper clad steel
rods. We also used rotary impact hammers to drive the rods down.... often
right through a rock or whatever. Worked almost all the time, and did not
"mushroom" the top of the rod.

If a 3/4" pointed solid steel rod can not be driven through Caliche with
an impact hammer I can't imagine any other tool short of dynamite doing the
job.


Ed K7AAT

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Old August 24th 08, 07:59 AM posted to rec.radio.amateur.antenna
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Default How do you get a ground rod to 6 feet ?


Dave Lemper wrote in message
...
The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.

Renting a back hoe is out.
Any suggestions appreciated.
Dave WB3DWE




Here's a snippet from the state of Washington's website that quotes the NEC:

NEC 250-52 (c)(3) (1999 edition) requires that ground rods "be driven to a
depth of not less than 8 feet
(2.44m) except that, where rock bottom is encountered, the electrode shall
be driven at an oblique angle
not to exceed 45 degrees from the vertical or shall be buried in a trench
that is at least 2 ft. (762mm)
deep."

The requirement is that the rod be driven to a depth of 8 feet. If the rod
cannot be driven then there is a
choice of either driving it at a 45-degree angle or laying it in a trench
that is not less than 2 feet deep.

http://www.lni.wa.gov/tradeslicensin...ts/elc0210.pdf.

I browsed some newer discussions and found nothing newer to be at variance
with the quoted material. The current NEC is $75 if snippets won't do ya'.

http://www.nfpa.org/itemDetail.asp?c...RL=Pub licati
ons/

You need 25 ohms maximum rersistance (three-point method) to say you have a
good ground.


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Old August 24th 08, 08:36 AM posted to rec.radio.amateur.antenna
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Default How do you get a ground rod to 6 feet ?

Fred McKenzie wrote:
In article , Dave Lemper
wrote:

The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.


Dave-

Last year there was a discussion here about sinking a ground rod using
an "SDS Plus" Hammer Drill set to hammer-only. I think it was Ian
White, GM3SEK, who proposed that method.


The other point was that SDS+ bits are available up to 1.0 metres long,
so by using both rotary and hammer action you can drill a pilot hole
through most kinds of rock down to that depth.

There is also an article at
http://www.n4lcd.com/groundrod/ that proposes a slightly different
method of coupling the hammer drill to the ground rod.

The question is whether Caliche can be penetrated by such a method. Has
anyone tried it?

We don't have caliche here, by that name, but from accounts on the web
I'd doubt if it could be penetrated by hammer action alone. However, it
seems more likely that an SDS+ bit could drill through it.

Another consideration is whether or not there is moisture in the soil
below the Caliche. If not, then it might not provide a low-impedance
ground even if you could penetrate it!


That is certainly the problem at this QTH, where an earth rod drilled
and hammered into the very rocky subsoil produced a resistance of
500ohms! Long horizontal electrodes are the only kind that work at this
QTH.



--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek
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Old August 24th 08, 02:16 PM posted to rec.radio.amateur.antenna
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Default How do you get a ground rod to 6 feet ?

While I don't have any 'caliche' on my property, I am blessed with a
lot of randomly placed rock. Driving any ground rod to about 6 feet
is a guessing game more than anything else. I've found that ground
radials are more practical. Not easy, just practical. They seem to
work as well as any ground rod I've ever used (better in some
instances).
The local power company is supposed to put down ground rods for
safety. Having seen some of their methods, I'd tend to go with the
radials (ground wire attached to water pipes... PVC water pipes, great
idea huh? And, NO, I'm not kidding.)
- 'Doc



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Old August 24th 08, 02:36 PM posted to rec.radio.amateur.antenna
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Default How do you get a ground rod to 6 feet ?

On Sat, 23 Aug 2008 10:58:19 -0500, Dave Lemper wrote:

The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.

Renting a back hoe is out.
Any suggestions appreciated.
Dave WB3DWE



I have a Glen Martin ground rod driver (fashioned after a fence post
driver) that worked fine in Houston. In San Antonio, it only drives a
rod about one foot down, then muck... I ended up just driving a short
rod, mainly used as a connection post, and then I extended several
long, buried wires out from it.

bob
k5qwg
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Old August 24th 08, 05:45 PM posted to rec.radio.amateur.antenna
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Default How do you get a ground rod to 6 feet ?

I got a better ground than using a stake by doing something a little
unorthodox.

I buried an old channel 6 yagi antenna in under six inches of earth. It
made a pretty good ground. It was a lot better than a stake.

Michael


Dave Lemper wrote:
The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.

Renting a back hoe is out.
Any suggestions appreciated.
Dave WB3DWE

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Old August 24th 08, 07:58 PM posted to rec.radio.amateur.antenna
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Default How do you get a ground rod to 6 feet ?

Dave Lemper wrote in :

The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.

Renting a back hoe is out.
Any suggestions appreciated.
Dave WB3DWE



Dave,

If you truly cannot drive an electrode vertically, then you will need to
consider drilling for horizontal electrodes in trenches chased into the
rock. Drilling creates another problem, backfilling for conductivity.

Electrodes in dry rock might not be very effective.

I have had success in driving electrodes into moderately shaly ground,
and even very dry clay isn't too difficult. Pointed 19mm copper clad
steel rods or stainless steel rods are a lot easier to drive into hard
stuff than smaller sizes.

The following article shows some of the equipment that I have used
sucessfully, and likely to be more successful than using an ordinary
hammer. Machine driving does not mushroom then end of the electrode near
as much as hand hammering.

http://www.vk1od.net/post/driver.htm

Owen
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Old August 24th 08, 11:57 PM posted to rec.radio.amateur.antenna
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Default How do you get a ground rod to 6 feet ?

"Wayne" wrote in
news:[email protected]:


As a last resort I will hack a trench with a pick and lay in the rod
at a shallow angle to the surface. Would this give an adequate
ground ? I could also bond it to an outdoor brass spigot
10 yards away or even to an anchor fence in the other direction.
Dave WB3DWE

-
In my opinion the trench would be ok, but I'll leave that to the
experts on the group.

However, I remember chiseling through the caliche to be annoying, but
not that difficult with the right tools. It can be done with a
"shooter" style shovel, but that is a bit more effort. However, I
doubt if you would ever get a copper rod driven through without some
major damage to the rod.





If the soil is permiable to water, you could try another of my hack
methods. Sweat a garden hose connection onto a piece of copper tubing.
Attach a garden hose to the fitting, and point the rod down in the place
you want to sink int. Then let it rip. In my area, we have a few inches
of topsoil, than a really hard clay, then rocky clay, followed by sandy
clay/sand. It will even move some rocks out of the way. The tubing
becomes the ground rod of course.

- 73 de Mike N3LI -

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Old August 25th 08, 12:22 AM posted to rec.radio.amateur.antenna
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Default How do you get a ground rod to 6 feet ?

Ed,

"Ed" wrote in message
. 192.196...
We used 5/8" copper clad steel, or sometimes 3/4" copper clad steel
rods. We also used rotary impact hammers to drive the rods down.... often
right through a rock or whatever.


Hammer-only mode? Or "rotate & hammer" mode?

---Joel




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