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DIY Drone Strobe and Remote ID Mounting Bracket
Once I received my Dronetag Beacon Remote ID (RID) module, I started thinking about ways that I could mount it on my Autel EVO II Pro drone at the same time as the anti-collision strobe light that the FAA requires me to use when flying my drone at night or during civil twilight.
It wasn't any kind of emergency because I don't fly during those times very often, and Remote ID wasn't mandatory yet anyway. So I spent the next couple of weeks looking for a material that would be lightweight, strong, and easy to work with.
I settled on polycarbonate because in addition to possessing all of those qualities, it also can be bent without heating. It's not obvious from the pictures, but there actually are slight bends in the mount to hold the strobe and the RID module horizontally while conforming to the slight curve in the surface of the drone where it's mounted.
How I Chose the Mounting Location and Design
When choosing a spot to mount anything on your drone, it's important to consider several factors:
- It has to clear the propellers and any other moving parts.
- It should be far enough way from the GPS and WiFi antennas not to interfere with them.
- Although in this case the weight is trivial, it should be as close to the drone's longitudinal and lateral centers of gravity as possible.
- It should be non-metallic to avoid interfering with the GPS and remote-control signals.
The location in the picture was one of two possibilities. The other was aft of the position in the picture between the two top-facing obstacle-avoidance centers, and was my backup location if the RID module interfered with the drone's GPS or WiFi (which I'm confident that it doesn't based on extensive testing).
The reason I chose the outrigger design (where the bracket sticks out on both sides) was because the Dronetag works best when it has a clear view of both the sky (for the GPS) and the ground (for the Bluetooth signal back to the operator). The strobe doesn't care about either of those things; but for the sake of balance, I decided to make the mount symmetrical and mount one device on each side.
The reason the mount is notched on the rear is to clear the obstacle avoidance sensor just aft of it.
I made the mount out of a polycarbonate replacement lens for a welding or grinding helmet. This is the outer protective lens that goes over the inner lens, which usually is darkened in the case of a welding helmet. They come in various materials; so if you're going to duplicate my project, make sure the one you buy is polycarbonate, not glass or some other material.
The mount is attached using one-inch-wide heavy-duty Velcro.
Some other materials I considered, but decided against, included:
- Wood. Rejected because it would have provided extra surface preparation and coating to assure good adhesion of the Velcro.
- Acrylic. Rejected because it's more brittle, harder to cut, requires heat for bending, and is hard to find in small sizes.
- Metal. Rejected because it could interfere with the compass or radio signals.
In the end, the polycarbonate was the only material that checked all my boxes.
The Tools and Procedure
I laid out the pattern on the polycarbonate using a combination square and an ultra fine point marker pen. I left the protective film on until the very end; so I was marking the film, not the polycarbonate itself.
I had to notch the back to clear the obstacle avoidance center on the drone while providing adequate mounting surface for the two devices. I did this by using heavy-duty shop scissors to cut the basic shape. An X-Acto knife can also be used if your drone's design requires unusually-shaped cuts.
I also had to put a bit of a curve in the top to conform to the curve on the drone and get a good fit with the Velcro. Then I had to bend the two outriggers up slightly so they would be horizontal when the mount was attached to the drone. I made the bends using an improvised modeler's bending brake.
Unlike most other thermoplastics, polycarbonate doesn't need to be heated when you bend it. It does have a lot of springback, however. You'll have to bend it past the angle that you actually want because it will try to return to its shape after you release the bending brake. It takes some trial and error to get the right angle without exceeding it. Fortunately, the polycarbonate I used for this project is very inexpensive; so if I had to start over again with a new piece, it wouldn't have broken the bank.
Once the device is in its final shape, smooth the edges and round the corners using a modeler's file to prevent cutting your hands when you handle the mount. It also makes for a more-professional appearance.
A Few Considerations When Attaching Something to Your Drone
Whenever you attach something to a drone, you have to consider the following factors:
- Location. You need to avoid interfering with propellers, control surfaces, and GPS and radio antennas.
- Weight and balance. Make sure to check the manufacturer's specs to determine how much additional weight your drone can safely carry. You also should locate it as close to the center of gravity as possible. On fixed-wing drones (and some copter drones), you may have to do some weight-and-balance calculations to make sure that you're still within gross weight and CG limits.
- Parasitic drag. Any protuberance on your drone will increase drag. This may reduce maximum speed, reduce battery life, or make the drone harder to hover or maneuver in strong winds.
- Battery life. Any additional weight and drag will reduce your battery life. Though the loss is unlikely to be significant with something as small and lightweight as strobes and RID modules, be on alert for reduced flight time after making any additions.
If you have any doubts about whether a modification you're planning for your drone is safe, seek the advice of more-experienced people before making any changes to your drone. You can also ask the drone's manufacturer for their advice.
Finally, do thorough flight testing in a safe place after making any modifications or additions to your drone. You may experience slightly different handling characteristics than what you're used to. You want to find out in a safe venue.
Revised July 3, 2023