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Hinge Bases, our simplest bases, provide the anchor structure for the tower, and at the same time allow the tower to be "hinged" over from the vertical to the horizontal position (and vice versa) with some external support like a crane, a strategically mounted winch, or a few strong individuals on the ground walking the tower upwards. This kind of base is ideal for owners who know that they will not be tilting their tower over very often, maybe about once a year, and can afford to hire a crew or crane to erect, and to hinge-over and back up again when necessary. Those who know they will want more frequent and immediate access to their antennas or mounted instruments may want to consider our very convenient Fold-Over-Kit systems. For more information on the functional differences between the Hinge Base and Fold Over Kits, please see this FAQ link. Here are a few pictures which show the basic process of Hinge Base installation:
Sonatube Installation Note: Although we depict the base installation with a Sonatube here as the hole form, this item is often not necessary for proper foundation installation. If there is a risk that the hole walls will cave in by the time the concrete is poured, a Sonatube may be helpful. If not, then it is actually best just to pour your concrete foundation in 'undisturbed' earth (since a hole with a sonatube form needs to be backfilled with soil or sand around the edges, this would be considered in constuction lingo as a 'disturbed' hole, and thus it also requires proper tamping or compaction of that backfill) . Most ground soil types are stable enough so that the walls will hold up for several days, without caving in. The main benefit of a 'Sonatube' is to provide the exact specified shape of the foundation and thus save on the cubic yards of concrete used. However, since a 4 ft. dia. by 12' Sonatube costs between $300 and $400, it is often an acceptable cost trade-off to simply pour 2 or 3 extra yards of concrete in a back-hoe excavated hole.
All necessary instructions, diagrams, and engineering calculations are furnished with the purchase of a Hinge Base. To choose the correct Hinge Base size, simply match your bottom tower leg diameter with the model. FULLY WELDED, NON-ADJUSTABLE VERSION (REBAR HOOKED LEGS). TABLE 2-A.
1Use lower tower section as template. HINGE BASES ON THREADED RODs (ADJUSTABLE PLUM) WITH STEEL TEMPLATES INCLUDED. TABLE 2-B.
*Sizes & amounts are approximate only--will vary per site conditions. Engineering Calcs will provide exact details on dimensions and all specs. Pre-fabbed, welded RE-BAR CAGES for your base are also available at $275 to $475, depending on the size of your base. This diagram shows a general rebar cage in footing. |
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