Thursday, September 26, 2013

QUADframe/3DR uBlox GPS Mount

elevated GPS mount

The hexacopter I am building is based on the APM 2.6 flight control system.  That system uses a uBlox GPS module for autopilot capabilities.  Most professional multirotor helicopters have the GPS unit mounted on a rod above the airframe.  For ultimate accuracy the GPS unit must have an unobstructed view of the GPS satellites and be far from any electrical interference from the flight control system and motors; hence the elevated mounting.

Unfortunately, neither QUADframe nor 3D Robotics makes such a mount.  There are some kits on the market but I didn't feel like spending the money or waiting for shipping.  So I decided to make one.  I found some fiberglass rod that I salvaged from a broken umbrella; just the right diameter and stiffness.  I decided to use some rivet nuts to affix the rod to the frame plate and GPS housing.

GPS dissasembled and drilled for rivet nut

I disassembled the plastic GPS housing and used a 5/16" brad point bit to drill a hole in the base of the housing.  I had to drill the hole off center to avoid hitting any of the circuitry.

8-32 rivet nut installed in GPS case

I crimped the 8-32 rivet nut into place.

upper frame plate drilled for rivet nut

8-32 rivet nut installed

I did the same to the frame plate.  The location of the hole in the frame plate was dictated by the length of the GPS wires.  It needed to be relatively close the the APM unit.

fiberglass rod with thread

I settled on a 5" length for the rod.  I cut it to length with an abrasive wheel on my Dremel and threaded the ends of the rod to 8-32.  As expected, the threads didn't hold too well so I secured the rod in the inserts with epoxy.  Once it set, I reassembled the GPS module.


Now the GPS unit is mounted well above any obstructions or interference.  I'll have to wait until everything is assembled until we know just how clean and accurate the GPS signal is.  Fingers crossed!

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