We used Diamond K540KM truck mirror-bracket antenna mounts clamped to the top seatback rail on our Tour Easy recumbents for several years, but they weren’t entirely satisfactory. The vibration from our ordinary on-road bike rides (a TE isn’t an off-road bike!) fractured the stamped-steel base after four years.
I fixed that by screwing a steel plate across the crack. It became obvious that these mounts weren’t suited to the application when the second mount failed shortly thereafter.
But we kept using them and, as you might expect, Mary’s mount failed in the middle of a 350-mile bike ride when the die-cast support dingus broke. The fresh granular metal fracture looks dead white in the picture.
I lashed the pieces together with a multitude of cable ties and we completed the mission. When I rolled our bikes into the Basement Laboratory Bike Repair Wing after returning home, the mount on my bike failed.
These mounts aren’t intended for “high vibration” applications and, it seems, bicycles produce much higher vibration than trucks. I’m certain that the frequency range is higher, although I’m not sure about the amplitude.
Obviously, it was time for something better… which meant some quality shop time. More on that tomorrow.
The Smell of Molten Projects in the Morning 
Comments
5 responses to “Commercial Mobile Antenna Mounts on a Recumbent: Failures Thereof”
[…] Having had both of our commercial antenna mounts fail, I decided to make something that could survive a direct hit. It turns out that the new mounts are utterly rigid, which means the next failure point will be either the antenna mast or its base structure. We’ve occasionally dropped the bikes and when the antenna hits something on the way down, the mount is not the thing that bends… […]
[…] More details on the homebrew mount are there and how commercial mounts fail are there. […]
[…] than the nut & washer, so most of the stress gets transmitted directly to the slab. Even in the high-vibration bicycle environment, I think there’s enough meat in there to prevent fatigue fractures. Milling bottom […]
[…] one piece at a time occasionally produced horrible compatibility problems, while showing why commercial solutions justify owning metalworking tools, PCB design software, and a 3D […]
[…] event at the Dutchess County Fairgrounds with the Mt Beacon Amateur Radio Club. This was before the Diamond antenna mounts disintegrated, […]