Tapcon anchors nonreinforced concrete slab

I have a tripod mounted on a concrete block and an old 6 in. X 6 in. by three ft; conctrete slab the previous owner left here. The tripod holds up an aluminum pipe with an anemometer and a universal antenna. Since the area is shielded by trees about 100 ft. away, the anemometer does not give a very accurate estimate of wind speed or direction.
My fireplace chimney has a 4 in. thick slab, not reinforced, cap on the top. I am coonsidering moving the tripod to the top of the chimney cap but wonder how close to the edge would be safe to drill for the tapcon screws to hold the tripod down against the wind. We had a tornado, small one but big enough to tear the neighbors roof off and uproot some trees about 14 in. in diameter, go between my house an my neighbor's house (not the one that lost the roof). This would lift the anemometer up into \"clean\" air and make it much more accurate. The anemometer radios the speed and direction to my recording station and is powered by solar so I wouldn't have to change batteries very often. I figure 4 in. from the edge for the 1/4 X 2-3/4 in. tapcon screws. If three and a half would be OK, I could spread the tripod legs a little further apart which might be better for stability. What do you think?
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I have routinely installed the 3/16 (1/4' hex head) within an inch of edges with no problems. This is sheltered or semi sheltered locations not subject to high winds.
I see the pound in, 1/4" anchors installed within 1.5" of the edges of many porches. IMO, in 3.5" on a sound structure should present no problems.
It depends on the condition of the cap. That is a hard weather area. Generally an inch of penetration is all that is required. Do you really need 2.75" of length?
--
Colbyt
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The 4 inches in setback should be OK. A rule of thumb is to assume a 45 degree angle up from the edge so 4 inches in on a 4 inch slab should work but use the outside edge of the hole not the center - it is a good idea to have a safety factor on the 45 degree theory. You should not go closer than 4 inches to the edge.
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On Feb 28, 9:55 pm, bobcox_at_mchsi_dot snipped-for-privacy@foo.com (bobcox) wrote:

Tapcons are great in their place, but given the location you chose it would make more sense to simply drill holes where they are needed and use a two part epoxy from Abatron or similar to anchor stainless steel threaded rods in place. That way if removal is ever required it can be accomplished without butchering any part of the chimney cap. It is likely that the holding power of the SS + epoxy system will exceed the Tapcon. IIRC, the concrete panels in the Boston subway were installed in that fashion. The contractor who used the wrong epoxy (fast cure) on the Boston panels had some failures which were corrected with the proper epoxy adhesive.
Joe
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On Feb 28, 10:55 pm, bobcox_at_mchsi_dot snipped-for-privacy@foo.com (bobcox) wrote:

So how tall is this pipe that the tripod mount is holding up ?
Mounting it to the cap on the chimney might not be the best idea, have you considered mounting it with straps around the chimney itself, just the pipe, as you would an antenna mast ?
~~ Evan
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