HobbyKing CP-7 Retracting Drone Landing Gear: Build, Bench Test, Install, Flight Test & Fail


Introduction: HobbyKing CP-7 Retracting Drone Landing Gear: Build, Bench Test, Install, Flight Test & Fail

  • As more drone flyers with a particular interest in aerial photography are moving to gimbals which can rotate 360 degrees then it is important to get the landing gear out of the field of view. The CP-7's are a budget set of retracting legs which worked fine once a faulty motor had been replaced. You can buy them from HobbyKing.
  • This video is intended as an easy reference/reminder. Some screens may change too quickly to see all the detail, so you might have to use 'Pause'. Here's the Menu:
  • 00.12 – What’s in the box; 01.12 – Build #1: Standard (recommended) setup; 02.34 – Build #1 Bench Test; 02.50 – Build #2: Quick workaround to fit the landing gear on an Aliencopter Bee 470 Cruachan to conduct a flight test; 03.32 – Build #2 Bench Test; 03.46 – Flight Test Part 1; 04.07 - Flight Test #2: Landing Gear Fail; 04.29 – Build #3: Provide a separate power supply to the Landing Gear; 04.45 – Build #3: Bench Test.
  • Notes on the Landing Gear: Motor mounts are pre-built; Weight = 305g (Including the plastic bags...); No instructions as such, just specifications and photographs; T-joints on the landing gear are pre-fitted and very solid. Landing gear and struts are aluminium; Struts are pre-drilled top and bottom for bolting to motors and landing gear; Motors are described by HobbyKing as 'Servoless'; They are delivered already attached to removable glass fibre mounts; Contains a glass fibre/composite (battery?) tray and servo lead loom to operate and power both motors via a single Rx channel; Includes 30mm, 10mm & 6mm steel bolts and 22mm hollow aluminium spacers. In this test whilst both motors were working using the provided servo loom, however, they were not synchronised, with one motor slower in one direction and prone to ‘stuttering’. This ‘stuttering’ leg managed to stick in the 'up' position during the Flight Test... ...fortunately, because this was just to test the landing gear we had left the original legs in place and did not have to crash land... Once landed, we eventually got the landing gear to work after many flicks of the switch, but the 'stuttering' remained so we went back to the bench and tested with a separate power feed dedicated to the landing gear... HobbyKing agreed to send a replacement Landing Gear Set with no fuss after seeing the video of the landing gear stuck in flight. They provided a first class customer service experience, but please note you will need to provide a video to show the fault otherwise you will enter an endless debate...
  • HobbyKing Specification for the Landing Gear: Leg size: 10 x 240mm (L) 10 x 140mm (W); Size: 273mm (L) x 240mm (W) x 190mm (H); Leg base: 270 x 240 x 185mm; Weight: 300g; Max Model Weight: 7kg. Base Specification: Diameter of Axle shaft: 8mm; Axis Size: 20mm; Operating Voltage: 4.8V~6V; Speed: 5V: 4 second /65 degree, 6V: 3.5 second /65 degree; Torque: 5V: 3kg/cm, 6V: 3kg/cm; Amps: 5V no loading: 40mA with loading: 120mA/6V no loading: 50mA with loading: 150mA; Weight: 66g each; Size: 66 x 23.5 x 27.5mm (LxWxH).
  • Specification for the Aliencopter Bee 470 Cruachan Drone: Based on the extremely robust Aliencopter Bee 470 folding carbon fibre frame, metal spacers are used throughout for enhanced rigidity. 10x4.5" carbon fibre propellers are driven by HP2814-910kv motors and controlled by 40A High Voltage SimonK ESC's. These provide up to ~1500g of thrust per corner. The Flight Controller is an Arducopter APM 2.6 providing the option for remote or autonomous flight (using Mission Planner). A 32 channel, 600mw 5.8 GHz transmitter for video signal to goggles or monitor as standard as is a 433 MHz telemetry transmitter to allow wireless control/ Mission Planning/ programming/ monitoring using a laptop/ smartphone/ tablet. 12V power is supplied from the onboard UBEC for accessories and the gimbal. Servo plugs are used for 12V and Video-out Transmitter. The arms fold by simply removing the thumb-screws. The legs also fold and lock in place.



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