I discovered roof rack fatigue in July when I removed it for the car’s annual paint maintenance. I was able to find the misplaced parts from my old RhinoRack, shown here, a discontinued rack that I had not yet used for carrying a micro-tower. Its “flush mount” design may be stronger since it has more physical contact between the rack towers and its crossbars even though that contact is via plastic parts. Regardless, I’m going to try it out for a bit and see how it endures. This latest Rover setup shaves ~45 lbs from the rooftop; so, it may be a good fit! Read-on to learn how I did it.
First, some background: It’s hard to believe that I’m already on the fifth iteration of my four-band Limited Rover setup. I started with horizontal loops by M2Inc. The loops were a quick build to get me on the air for CQ’s Worldwide VHF Contest on short notice in 2022. Later, I tried a few “micro-tower” setups including a homemade setup, a Rohn micro-tower, and finally a tilt-over tower which used the shortest Rohn 25-series tower cap that I could find (shown in this photo). Each setup, although progressively lighter each time, proved to be heavier than ideal for my roof rack since internal rack components still fatigued over time. Each tower setup was well within the roof’s weight limits; however, the tall loads created excessive leverage at the rack’s mounting points. I decided to focus on weight savings.
The most obvious places to cut weight were at the tower and the Superstrut base. I think that most antenna towers are designed to support large, heavy HF antennas and are overkill for holding a few road-legal VHF antennas. I was also hung-up on carrying both loops and Yagis at the same time for some reason. I’m relatively inexperienced as a contest Rover, but I have learned enough to conclude that my operating practices don’t require both loops and Yagis on the car at the same time. I knew that I could build something lighter and less complicated. Eliminating the 25-series tower alone removed 28 lbs from the roof! However, that’s not 28 lbs of weight savings because I had to add new supports for the mast.
I use electrical metallic tubing (EMT) to support the mast. Believe it or not, the Yaesu GS-065 thrust bearing shown in this photo is at the same height as the thrust bearing atop the Rohn tower. There’s no need for a tilt-over feature since I no longer have to lift the mast over a tower to install it. The EMT and new rotator mounting plate weigh ~7 lbs. I’ve also replaced the 2-inch (OD) steel fence post mast with a 1.5-inch (ID) Schedule 80 aluminum pipe (1.9″ OD). The aluminum mast shaves about a pound even though it’s taller than its predecessor. Total weight savings so far: ~21 lbs.
My initial choice of A1200 galvanized Superstrut as a base was due to its abundance at hardware stores and my previous choice of hardware fittings. This table shows that each A1200 beam easily supports 1400 lbs with my 30-inch crossbar span before deflecting any noticeable amount. That’s OVERKILL in my setup! At 1.9 lbs per foot, my six 40-inch beams totaled 38 lbs! I considered generic aluminum “strut channel” (estimated weight allowance added in red), but I was not confident in the strength of the offerings online.
Instead, I chose B1400 “half-height” Superstrut. It weighs half that of A1200 and still supports 340 lbs per beam at 30-inches of crossbar spread. Since I no longer need a tilt-over feature, I have just five beams of various lengths for a total of 16 lbs, a savings of 22 lbs! I had to downsize some of my mounting hardware from M10 bolts to M8 and ½” bolts to ⅜” to fit the smaller channel. The smaller hardware is still stronger than required, but also cuts fastener weight in half. Don’t ask me about the actual weight savings, though; I’m not weighing my old and new fasteners! 😀
I took the weight-shaving just a little further by removing the 6m Moxon in favor of the HO Loop by M2Inc. Sure, I lost some antenna gain, but I also removed 4 lbs from the highest point of the tower. Since most 6m contest activity seems to happen on FT8, a mode that I can run in the background while driving, I’m hoping that having an omnidirectional antenna will enable me to hear stations regardless of my direction of travel. This photo shows the completed setup. The total weight savings over the entire project is 45 lbs! Admittedly, the bulk of weight savings is either right at the rack itself or within 20 inches of it. There’s still ~20 lbs above the thrust bearing which may stress the rack. We’ll see!
This photo shows my coax cable routing. Movement and flexibility as the rotator turns is very good! The new setup is surprisingly sturdy! Previous setups always had a little bit of flex, usually on the crossbars themselves. There is no movement whatsoever in this tower since the EMT attaches at the corners of the rack and braces the thrust bearing from wide angles. I’ll get a day of road testing under my belt before hitting the road for ARRL’s September VHF contest. I’ll leave the RhinoRack mounted until next summer, which should be about the time that I’d remove it for paint maintenance and another inspection. Between now and then, the Yagi setup will be mounted for contests in September, January, and June; plus, I hope to take it to exhibitions at a local hamfest in February, RARSFest in April, and Hamvention in May (fingers crossed). I’ll keep a sharp eye for small cracks or other hardware failures. If this rack fails, then I will either get a Thule rack that I’ve been watching or maybe build something custom that’s mounted through the roof like a real rack! 😉 See more notes about the new setup in the photo album below.
Topside Dieted,
Scott
