Disclaimer: The photos and descriptions contained within this web page are intended to illustrate possible approaches for implementation of a tilt-over tower supported on a trailer. The author did not design or fabricate these examples, and does not infer any guidance or expertise in their fabrication or use should the reader decide to fabricate something similar themselves.
Several years ago, I was shown a homebrew installation of a fold-over tower mounted on a modified boat trailer. The owner of this fine contraption, Don/K8BB, uses it for Field Day and other types of portable operations such as in the Michigan QSO Party. A photo of Don's trailer (nicknamed "Big Yellow" because the trailer frame is painted in that color) is shown below parked in K8CC's driveway:
Barely visible beneath the tower sections and just forward of the wheels, the remnants of a Heights tilt-over tower base can be seen. The tower sits on this base, which allows it to be assembled protruding from the rear of the trailer while supported by a step ladder. To this base has been welded a piece of water pipe which extends vertically when the tower is lying down. Despite how it might appear, this pipe does not lift the tower vertical; rather it acts as a "falling derrick", supporting a wire rope cable attached to the winch seen at left in the above photo. The photo below shows the tower being raised in April 2005 at the K8MQP Michigan QSO Party operation near Indian River, MI. The lift cable is clearly seen rising from its attachment point on the tower to where it's supported by the vertical pipe, then descending to the winch.
The vertical support pipe, because its mounted on the tilt over base, moves towards horizontal as the tower tilts up. This is the essence of the "falling derrick" approach. (The interested reader is encouraged to Google "falling derrick" on the Internet to learn more about this approach, which we certainly did not invent.)
Also visible in the photo are the outriggers which stabilize the trailer and can provide attachment points for the guy wires. In the operation shown, the weather conditions were very calm, and the trailer was set up on a very stable asphalt driveway. Under these conditions guying to the outriggers proved entirely satisfactory. For more severe conditions, a set of screw in earth augers are available to extend the guying distance.
The antennas carried by the tower in this operation were its usual complement - a HyGain 203BA (3L 20M yagi), a HyGain 153BA (3L 15M yagi), and a 3L CB beam converted to 10M. Including a TR-44 rotator and mast, the tower lifts this load to a height of 56' easily.
After working with this tower trailer, I decided I wanted one of my own. I first looked at Aluma Tower http://www.alumatower.com which has a number of interesting aluminum crank-up/tilt-over products mounted on trailers but were beyond my budget, starting around $10K and increasing from there. Next was Force12, Inc. http://www.force12inc.com but the products they offered were really tilt-over masts that weren't capable of lifting the type of load I wanted (which is, essentially to be able to do what K8BB has been doing with "Big Yellow".) Finally, I looked at Glen Martin Engineering http://www.glenmartin.com who offer a new line of aluminum crank-up/tilt-over towers mounted on trailers, but again these were beyond my budget, starting around $13.5K and so my enthusiasm fizzled.
After the 2006 Michigan QSO Party, where we again used Big Yellow to raise it's complement of yagis into the sky above Cheboygan County, my interest in tower trailers was again stimulated. About this time, the local ham who built K8BB's "Big Yellow" offered to sell me it's predecessor, a smaller tower trailer nicknamed "Little Red" (again, because of the color of the paint job on the frame). Little Red was built on a smaller pontoon boat trailer and carried a smaller 40' tower (vs. Big Yellow's 56 footer) but otherwise was very similar. It also boasted a number of enhancements that Big Yellow lacked, such as a 12V powered winch and additional jacks at the rear to stabilize the trailer.
I don't have any pictures of Little Red in action since I've not had a chance to deploy it since purchased. However, the photos below (taken by its previous owner) shows it's design features; the similarity to Big Yellow is obvious.
For this trailer, a pre-built Heights tilt-over based was not available, so a homebrew equivalent was fabricated. It can be seen in line with the axle, welded atop the tubes where the outriggers are inserted.
The outriggers themselves are clearly visible in the photo above - the long square tubes protruding forward with the screw jacks visible. This is their traveling position, The vertical support pipe for the falling derrick can just barely be seen in this photo, lying horizontal longitudinally between the outriggers.
This rear quarter photo shows how the tower sections ride on the trailer during transit. These are held down with some readily available ratcheting straps and bungee cords. The tower itself consists of two 11" sections, two 14" sections, and two 18" sections, resulting in a total tower height of 48 feet. This combination of section widths allows the sections to be stored for transit in two "bundles", held down with the ratcheting straps. Masts, antenna elements and other hardware can be slipped inside the bundles and secured with bungee cords.
The two black and white boxes resembling picnic coolers are RV storage boxes used to carry the guy wires, electric winch, tools, etc.
Deploying the Tower
Once at the site, and a level location for the tower is found, the first task is to remove the tower sections, antennas, stabilizer arms, etc. from their traveling positions. The stabilizer arms are inserted into their receptacles and the screw jacks adjusted to level the trailer. The first tower section is bolted to the base, and then laid over, protruding out from the rear of the trailer. Additional sections are added; a step ladder is useful for supporting the tower during this portion of the process. When all sections are assembled, the antenna is mounted on the mast. VHF/UHF yagis are easy to install with their booms parallel to the ground while HF yagis are generally installed with their booms pointing up and the reflector resting on the ground. The biggest antenna we typically raise is the HyGain 203BA 3L 20M yagi, which has a 16' boom, so the mast has to be 8' up in the air. We've had little difficulty placing this antenna on the mast using the step ladder. Regardless of how the antenna is mounted, the rotator must be pre-aimed so that when the antenna is in the air, the control box indicates the correct direction.
Once the antennas are mounted, feedlines and the rotator cable are taped to one of the tower legs. Guy wires are attached at the joint between the first and second tower sections (from the top). The guy wire attached to the "up" tower leg is draped over the vertical "falling derrick" pipe and attached to the winch. Once everything has been double checked, the tower is slowly raised using only the winch. To lower the tower, the process is simply reversed.
As I mentioned in the disclaimer at the top of this page, I did not design or fabricate either of these trailers. I am an electrical, not a mechanical, engineer. I have worked with these trailers, and listened closely to K8BB's accounts about working with them. A certain amount of care and a healthy dose of common sense is necessary to use trailers such as these. In return, these trailers provide a large amount of functionality in portable operations, and for potentially much less expense than their commercial equivalents.
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