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3D Printed Solutions for Magnetic Loop Antenna

3d printed solutions

Have you ever tried to attach a nut inside a small diameter tube? How about a one-of-a-kind mounting bracket? 3D printed solutions are magic. 

Recently, I was struggling to attach a flat solder lug to a round tube. An easy approach would be to use a screw terminal. But I found it really hard to hold a small nut in place on the inside of a very small diameter tube. My tube is ½ inch aluminum core PEX inside a small enclosure.

After removing the outer plastic layer and drilling a hole, I was trying to hold a nut in place while tightening a screw down. Ideally, this should provide me with a good connection between a copper wire and an aluminum tube. But there just wasn’t room to get my hand in the box, or my finger inside the small tube to hold the nut steady.

I tried tweezers but the nut kept slipping off. I tried some glue stick to hold the nut in place, but that was no good, either.

Finally, I had the idea to capture the nut inside a small 3/8 inch cylinder. My thought was that the inside of the tube would then automatically hold the nut in place while I screwed down. It worked perfectly first time. You will notice the capture cylinder also includes a small extrusion to indicate direction and provide grip when installing.

Most CAD software allows you to create a six sided polygon (hexagon) properly sized for capturing a nut. My innovation was figuring out how to insert a nut to be captured on a curved rather than flat surface. As the screw turns, it tightens against the inner surface of the tube, while the plastic capture walls prevent it from turning.

3D Printed Solutions – Fence Mounting Bracket

Next up was a custom mounting bracket for my wideband loop antenna.

3d printed solutions

My antenna mount is a 3 foot length of 1½ inch ABS pipe, typically used for waste water. I wanted to attach this to my chain link fence. The fence post and ABS pipe have diameters of 48 and 48.3 mm, respectively. Using CAD, I designed three brackets to grip these pipes and be held together by two 3″ stainless steel bolts. A pair of these brackets holds the antenna mount firmly in place.

If I had a wood fence, I could have designed the fence bracket to be screwed into a fence post. Same idea.

These 3D printed solutions for my loop antenna were fabricated with PLA filament with 15% infill. My total cost of printing these was probably around $5. If I could have purchased right-sized brackets, they might have been cheaper. But since they did not otherwise exist, that’s a moot point.

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