What's the difference between a Hinge Base and a Fold Over Kit? I have an older model tower that I bought or someone gave me without identification. How can I tell which brand it is, and whether it is one of yours?
First, if the tower is constructed of steel, it is definitely not one of our models. Our towers are constructed out of aluminum and always have been. Our section lengths have always been 8 foot in length. So, if the second-hand tower you have is in 10 ft. or other lengths, then it is not a Heights tower.
I have an old tower. Can I sink the tower section in the concrete, instead of buying a base?
No, the concrete eats aluminum and it will destroy your base. That's why we normally use steel base legs. Do not try submerging tower sections in a concrete pad.
I live in an area known for seismic (earthquake) activity. How do I factor that into my tower selection?
Please visit our Seismic page, here: SEISMIC
Should I use oxidation-prevention grease on the sleeve connections of the tower sections before assembling?
Greases and Lubricants
Even though tower structures are not dynamic moving devices, they can benefit from grease at certain key locations. Some anti-oxidation electrical type grease for aluminum may be added to the few inches of sleeve or section overlap at the tower section connection points to prevent any possible 'galvanic' fusion of the parts together many years down the line. In general, we feel this risk is very minimal on our sleeve connection. However, where a section's legs slip into a larger sized section, there may be a greater risk of those legs seizing together over a long period of time. In this case, a small amount of aluminum anti-ox grease could ease the process of removing the sections, should you ever need to disassemble and move your tower. This product can be found where electrical wiring and supplies are sold.
II. Fold Over Kits and their Actuators
The acme Screw system on your Fold-Over-Kit should always be well greased for operation, as prescribed in out Screw System installation and operation instructions. This may require you to add or redistribute the grease on your lead screw each time you operate the system. You can use a synthetic or moly-based industrial/automotive grease, which can be found at most hardware stores.
HINGE AND BASE QUESTIONS
I would like to avoid having to dig my hole any deeper than necessary. Instead of digging my base hole about 3.5 ft. wide by 7.6 ft. deep (example), can I just dig a 5' x 5' hole, since it's about the same volume of concrete?
What type of base should I purchase with my tower? A Hinged Base or a Fold-Over Kit type base? What are the differences? What's the difference between a Hinge Base and a Fold Over Kit?
Hinge Bases and Fold Over Kits
Our simplest base design is called a Hinge Base, in the sense that it allows you to hinge the tower up on two of the three legs. Oftentimes, the 'Hinge Base' is confused with the hand- or motor-operated Fold Over Kit. With a Hinge Base, two or three people should be able to 'walk' tower models up to 56' with light antenna arrays from their horizontal to vertical positions.
The Hinge clevis design which allows this to happen also is a convenient structural shape connecting the tower leg stubs to the threaded anchor bolts. So this base is functional and cost-effective at the same time, if the owner does not expect to regularly want to get to and adjust the antenna. If this is the case, we recommend our Fold Over Kits.
There probably are a couple less expensive designs to manufacture, but they would only be a few dollars less (any decent base design will cost almost as much as a tower section). Furthermore, they would not have that helpful hinge feature, which makes installation easier and usually less expensive, as well.
Footing and Rebar
Question: I would like to avoid having to dig my hole any deeper than necessary. Instead of digging my base hole about 3.5 ft. wide by 7.6 ft. deep (example), can I just dig a 5' x 5' hole, since it's about the same volume of concrete?
Answer: No, sorry, not really. Yes, it may be about the same volume of concrete, but volume or weight in the base is not the key factor. The key factor in the stability of the base is the amount of bearing resistance the base structure has in the ground in which it is planted. Giving depth to a base is like adding a extension lever to a fulcrum: it gives it mechanical advantage/potential momentum in resisting the forces trying to move or tip the base and tower over.
As one insightful engineer put it, 'If you had a superstrong, lightweight substance, like styrofoam, that would not corrode or break, you could use this as a substitute for concrete and the tower base would be almost the same size as a concrete one.' The deadweight of concrete only contributes about 5 -10% of the resisting moment in many typical tower bases; the rest is from the resisting force in the bearing surface of the hole.' This also explains why soil types are important in determining the size of the concrete pad.
Most people own property with sandy or clayey soils. Clayey soils are a little softer than sandy soils, e.g. a soil classified as some variation of 'clayey' would be considered to have a soil pressure of 100 lbs/cubic or sq. ft., while sandy soil combinations would usually have about 150 lbs./cu.ft. rating. Our bases are typically designed for 'sandy' soild types or sub-types--to be installed in clayey soil types would require us to usually increase the depth requirment by about 10-15%.
f you or your building department are concerned about the exact soil type you have, you should get a professional soil bore sample. (Sorry, we can not offer references in your area). If you are fortunate enough to live on bedrock or shale or very hard soil, then a tower base at your site may only need to be 3 or 4 ft. deep and narrow enough to fit your base legs and rebar within it's diameter.
An example of this which shows the importance of depth versus volume of concrete may be shown by looking at the base requirements of one of our very strong 80 ft. towers (the 25 sq. ft. model at the 80 mph rating). In sandy soil rated at 150 pcf, this base would need to be 10 ft. 7 inches, if the hole were drilled or excavated at 48 inch in diameter (circluar shape, with no less than 1/4" movement allowed at surface). If the base-hole's width is significantly increased to 84" diameter, then a depth of 9' 0" would still be required to resist the tower's maximum overturning moment. So a hole width increase of 36" only reduces the depth requirement by about half of that, specifically 19". This 2:1 ratio is typical if applied to most of our tower configurations.
Please visit the Footing and rebar link here for a helpful diagram: Footing and Base