Archive for July 10th, 2009

Commercial Mobile Antenna Mounts on a Recumbent: Failures Thereof

Cracked Diamond K-540 bracket

Cracked Diamond K-540 bracket

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.

Antenna Bracket Repair

Antenna Bracket Repair

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.

Broken Diamond K540KM Antenna Mount

Broken Diamond K540KM Antenna Mount

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.

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