A towering conundrum

[Opcom]

Dear Sirs,

It looks like I cannot economically put up my 56FT tower due to "caliche" being 1-2FT under the soil. For those that don't know, The caliche reserves in the Llano Estacado in Texas can be used in the manufacture of Portland cement; the caliche meets the chemical composition requirements and has been used as a principal raw material in Portland cement production in at least one Texas plant. Where the calcium carbonate content is over 80 %, caliche can also be fired and used as a source of lime in areas, which can then be used for soil stabilization.

I need to find locally a couple sections of Rohn 25 to go with the three sections I might be able to buy from the local ham club. This will make for a 50FT tower that can be guyed.

So far, the plan seems to be to dig down 2 FT to the caliche making a 4x4 hole, use a 2" or 3" rock drill to make a pattern of holes 4FT further deep in this hole, and set pieces of 1/2" or 3/4" rebar in the holes, then attach them to the cage of rebar in the 4x4x3 foundation area which will rest on the caliche rock. The foundation will be made 1 FT higher than the ground around it using a form. In the middle of this will be set the base section of the Rohn 25. The tower+base section will not be grounded through this rebar, but will later be grounded separately. This foundation is not quite enough by itself to completely secure the tower for the long term. Three guy pipes with two sets of guy cables will be used.

Since this will be done in an enclosed area of yard that is only 40x40 FT, the three guy pipes will be placed so that they are sunk 5 FT into the ground and extend 5 FT above the ground. We want to use 4" oil well drill pipe for this. We can find the pipe because any piece with a crack has tobe discarded and they go to scrap. They are made of chrome moly steel. I am not concerned about anyone wringing their neck on the guys inside my 8 FT fence. It is only me and my brother here. The closest guy pipe will be 20FT from the tower base, and the farthest one will be 28FT. This is OK for the tower's first guy at 25FT height, since the angle of the lowest guys will be about 40-45 degrees. The angle will be quite smaller as the tower  becomes taller. I may have to limit the height.

These are the tenative plans. i don't know how good the plans are, or not. It's best to ask.

What experiences do you guys have with towers, especially with guys, guy posts, and the angles of guy wires versus the stresses on them? Obviously I can reduce the angle if I strengthen the guy, up to a point, but beyond that it is of no further merit and the tower cannot be made higher.

Is there a free downloadable calculator to help with the angles of the guys and design of the site? otherwise I will have to do the excel sheet, etc.

[WQ9E]

Opcom,

I spent 3 years in Lubbock at Texas Tech and I remember the caliche well!  It was quickly explained to me why Lubbock streets flood during rains because it costs far too much too install underground road drainage.

As to your tower question, the best place to post this is on the tower talk list over at contesting.com:  http://lists.contesting.com/mailman/listinfo/Towertalk  Along with the usual internet QRN there are some people with good expertise who hang out there.  They also have very good searchable archives.

By the way, I got started building a power supply for my RBC and the RBB I got from you; hope to have it going soon.  Thanks again!

Rodger WQ9E

[Opcom]

Thanks, Please let me know how the RBB works out. I am told they sound fantastic. I had intended to use that one partly for the AM BC band.

[k4kyv]

Can't you drill holes in the "caliche" hard-pan and concrete-in re-bar to anchor the tower base and/or guy anchor pillars?

Caliche is a hardened deposit of calcium carbonate. This calcium carbonate cements together other materials, including gravel, sand, clay, and silt. It is found in aridisol and mollisol soil orders. Caliche occurs worldwide, generally in arid or semi-arid regions, including in central and western Australia, in the Kalahari Desert, in the High Plains of the western USA, and in the Sonoran Desert. Caliche is also known as hardpan, calcrete, kankar (in India), or duricrust. The term caliche is Spanish and is originally from the Latin calx, meaning lime.

Caliche is generally light colored but can range from white to light pink to reddish-brown, depending on the impurities present. It is generally found on or near the surface, but it can be found in deeper subsoil deposits as well. The layers can vary from a few inches to feet thick, and multiple layers can exist in a single location...

The best solution to (plant growing problems) is to remove the layer of caliche and replace it with a mixture of organic material and soil. The hole should be large enough to contain the plant’s mature root system and should go entirely through the caliche layer. However, when the caliche layer is thick, dig a hole large enough for the mature root system. Then, a smaller hole or holes can be dug through the remaining caliche to provide drainage.

http://en.wikipedia.org/wiki/Caliche_%28mineral%29

[Opcom]

Yes. but to anchor the tower I have would require a 5 FT deep 12" hole under each leg to be free-standing and too large a machine required for that to get into the back yard. Also, the tower I have is not intended to be guyed. With those two things stacked against me, I need an alternative. The caliche cited in your post is different from what I have. Mine is a white or yellow kind of almost rotten limestone, which turns to cement-like substance when wet. It is a mess and also it is very thick so that I have never found the end of it. My house is built on a quarry.

I can drill smaller holes in the caliche for the tower base for the guy-able tower, and also for the guy anchor pillars. I have to have some tree branches removed as well. It will be a few month's project. I'm afraid it will costa-plenty by the time it is done, even with help from the ham radio club, where the members have some tools etc.

[KB2WIG]

Doom,
I have no experience with this stuff, but, can it be jackhammered out?? The compressor hoses can be routed through the house (or around it) if you can't get a compressor back there. Ditto on the mud work.........

 klc

[Opcom]

It can be jack hammered out, however, that is alot of work, very very expensive to do, considering that it would require a 5FT deep hole 4Ft on each side, and all that rock has to come out by hand and or by vacuum. Also, the bit for the jack hammer has to be replaced periodically in such a job, and they are about $200.