50" Curved light bar mounting brackets - to stock roof rack mounts - Whistle or Death Rattle

After my first attempt of fabricating a roof mounting bracket I quickly discovered the difference between light bar "whistle" and light bar "death rattle". When I hit 70km/hr my entire roof was vibrating hard enough that I couldn't hear my music with my windows up! I tried duct taping the cooling fins to see if the noise was from "the whistle", as I expected, it wasn't from the cooling fins. The metal I had used for the brackets was too thin at 3/16" and was vibrating excessively.
(I actually used barn door hinges from Home Depot, with a few cuts and drill holes they fit perfectly) But it wasn't meant to be.

Round 2:
I got some 1/4" steel plate from Triton, cut to size 1" x 4" - 1" x 4" - 3.5" x 4
With a few welds, a little grinding and some high heat paint, I was ready for test drive #2.
Problem solved. No "whistle" and definitely no "death rattle" even at 130+km/hr.
Stoked!

The moral of the story, if you are feeling vibration from your large roof mounted light bar, there is a good chance that it is coming from a lack of strength within the mounting brackets. I should also note that I installed a few rubber washers between the cab and mounting brackets.
For the time being I used a clear silicon to keep the wiring jammed flush into the available space along the outside of the windshield.
***I smoked out the light bar glass to keep the officers of the law "happy". When the lights are off it actually looks more like a roof rack, and with 23,000L it is still bright as hell when on.

Time to test it out.
Thanks for reading.

 

Interesting read. I bought the relentless fab mounts and I have a whistle but no rattle. I've been trying various techniques to eliminate the whistle with no luck. I've tried the autozone edge trim and tape. Starting to wonder if it was a poorly designed light bar. But now maybe the whistle is coming from the mounts themselves. How should I test this theory?

 

Thanks! I'll start by saying that I'm faaarrr from a professional. For me, I reached my hand out my window to feel what was vibrating, I could very clearly feel the mounting brackets vibrating. Also, the sound I was getting was not a whistle, it was definitely a strong rattle/vibration that I could hear and feel when I put my hand on the roof of my cab while driving 60+.

My process:

• rule out cooling fins with duct tape, or packing with foam.
• rule out all the mounting hardware - check its tight, but not too tight.
• rule out the mounting interface by adding rubber washers
• rule out the shape of the mounting bracket by covering any cut outs or holes in the metal with duct tape

The base of my bar sits approx. 1.5" above my roof. There is so much that I don't understand about wind dynamics that could be at play from scenario to scenario. Perhaps measure how thick your mounting bracket metal is. . . I'm at 1/4" with no bends.
Let me know how it goes, good luck bud!