Crafting a Sheetmetal Bracket Text and Photos by // Lead Instructor Joe Padula
reatly underused material in car audio fabrication, sheetmetal is probably one of the best materials to create OEM quality brackets and mounts. In a recent installation, I was presented with a high-end car needing a remote-mounted radar detector. The goal was a stealthy install with no permanent modifications to the vehicle. In this type of installation, the radar receiver is mounted behind the grille or front bumper fascia. Unfortunately, this particular car offered no location that was optimum for stealth, proper signal reception and mounting depth. I came up with an innovative solution by using the properties of sheet metal.
1. In this picture we can see that the antenna for the Radar detector is deeper than the available clearance between the grille and radiator
3. The first step in the process is to take careful measurements of the opening and the antenna.
2. But by orienting it vertically, it fits perfectly. Unfortunately, the antenna needs to have its receiving end pointed towards the signal. We will use the reflectivity of sheet metal to radar to our advantage by creating a combination mount / reflector.
4. Next, the measurements are transferred onto office-supply poster board with drafting tools. The idea is to create a full-size template of the bracket before going to the metal. It should end up looking a little like the paper airplane templates we used to have when we were kids. Basically, I laid out a “U”-shaped channel that cradled the antenna with tabs on the side for mounting. I also included an extra piece on top that would end up being bent at a 45-degree angle to deflect the radar signal down into the antenna. The mounting-hole positions were also marked out at this time. Solid lines indicate areas to cut, dotted lines are those along which we’ll bend the sheetmetal.
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5 & 5A. The paper template was carefully cut out and folded into the shape of the finished bracket and test-fitted to the car.
6 & 6A. Next, the template was positioned on top of a piece of 16ga. galvanized sheetmetal. If you have trouble finding it locally, check with air conditioning contractors, as they typically use it in fabricating A/C ductwork. Trace the outline with a sharp scribe or sharpie marker.
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7 & 7A. Cut out the sheetmetal using an air nibbler, air shears or tin snips. I like to use the air nibbler to make a cut close to the line and finish with tin snips for a clean edge. An air nibbler is an indispensible tool for working with sheetmetal. It will cut a perfectly clean line following straights and curves as easily as scissors through paper. The big advantage of the nibbler is that it will not distort the metal when cutting large pieces like tin snips can. Models are available powered by air, electricity or even as an attachment to your drill, but the air-powered versions are the most compact and convenient to use. They can be found through outlets like Harbor Freight or online for less than a hundred dollars.
8. The metal must next be bent into its finished shape. The proper tool for the job is called a sheetmetal brake, also available at places like Harbor Freight, but for this small project, a bench vise and small hammer sufficed.
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10. The finished antenna mount was secure, professional and stealthy.
The Source: 9 & 9A. The reflector was carefully bent to a precise 45-degree angle using a drafting angle, the antenna was mounted to the bracket and the bracket was mounted to the car using existing holes.
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