Under The Hood – 3DR SOLO – Part 2
Continuing from my last post “Under The Hood – 3DR SOLO – Part I, I will begin taking you through the steps I took to disassemble my SOLO. To begin remove the battery pack from the SOLO. Underneath there a four phillips-head screws. Using a basic screw driver these four screws can be easily removed. When disassembling there is no right or wrong way. Everything is learned by trial and error. The most important thing is you don’t break it! Proceeding cautiously will go along way to ensuring you’ll be able to fly again.
At this point you’ll be scratching your head trying to figure out why the battery tray can’t be removed and is still attached at the front. It’s at this point you need to take a timeout and carefully plan your next move. The black GPS cover has to come off somehow. The first time can be slightly difficult, however once you figure out the technique it becomes second nature. This is the procedure that worked for me:
- Use two hands to firmly grip both sides of the cover. The picture shows a one handed grip, but two hands work best.
- Firmly pinch both sides of the cover and push forward. It helps to have dry hands here. It will be tight, but you’ll be able to snap the cover off.
With the battery tray removed we now get our first look at the main control board. All drones will have a board similar to this. Here is where all the various components (gimbal, ESCs, motors, flight controller) interface with each other. At this point unless you are wearing a grounding strap do not touch any of the surface mounted components. They are fragile and susceptible to ESD (electrostatic discharge). If you fry one of these components, it will be very hard to solder in a new one. For an EDS event to occur it doesn’t take much off a shock. In many cases you won’t even notice. For many drones the main board layout will be different. Let’s see what we can identify on this board:
- Upper right corner – main power connector
- J1 – Connected to the power supply
- J2 – Compass
- J4 – Motor 3 ESC controller
- J5 – GPS
- J6 – Motor 1 ESC controller
- J7 – Motor 2 ESC controller
- J8 – Motor 4 ESC controller
- Gimbal data cable can be seen soldered to 8 different pads.
- All four motor power cables (red/black) are soldered to the main board.
At this point we need to remove some other components to free up the main board for removal. I will start with the gimbal. The gimbal performs a very important function for our drones. It stabilizes the video from external forces. A 3 axis gimbal will have motors controlling the x, y, and z axes with input from the gimbal’s IMU (Inertial Measurement Unit). On my SOLO I didn’t have the gimbal, but instead the camera mounting bracket. The removal of these items will be the same regardless if you have the gimbal or bracket. Before you turn the drone over remove the 4 propellers.
Turn the copter over and remove three screws from the gimbal. You will be able to loosen the screws but not remove them completely from the gimbal. They are being retained by a lock washer. However with them completely loosened you can eventually remove the gimbal.
3D Robotics are the first to come up with a removable motor pod. Brushless motors are definitely a drone maintenance item. If one goes out, your drone goes down. It’s very important you replace these motors periodically. Recommendations are after every 150 flight hours. Continuing with the disassembly let’s remove the four motors. Using a flathead screwdriver pry off the LED covers. With the covers removed you can see the LEDs themselves along with four more screws.
With all the motor screws removed flip the drone over. Each motor can now be gently lifted out of the arms. The two power cables just slide out from each other. The controller cable can be disconnected. Use a flathead screw driver to pry the cable off. Do not pull directly on the wires themselves. You may pull one out of it’s connector.
How cool is this! Each motor pod is it’s own subassembly. This subassembly includes both the motor and the ESC (electronic speed controller). The ESC performs the very important job of taking input from the flight controller and varying the rotational speed of the motor. Since our motors are fixed pitch (props do not change pitch) the only way to induce movement of the drone is for the flight controller to change the speed of the motors independently. Drone dynamics will be covered in another post. But for now keep in mind the ESCs contain some very important circuitry. With the motors removed you can inspect the solder joints for the 3 motor power cables (red, black, blue) on the ESC. One of my preventative maintenance items I perform after every 10 flight hours is to check all solder connections. Note which motors go to which arms when all 4 are removed. Motors on a drone are arranged in pairs. Each pair spins clockwise (CW) or counter clockwise (CCW). It’s okay to switch motors between like spinning pairs. With the motors removed we can now proceed in removing the main board. Please join me for my next post where we’ll finally get to see the all important flight controller. This piece is the brains of the whole operation.