Hello and happy new year.
I decided that I wanted to have retractable landing gear on my hexacopter, but I didn't want to pay the full price for a ready made set (£50/$80). With all the parts I gathered, it came to about £12/$18, so that's quite a saving to be made.
I made a write up article to help others to make their own in hope that we can begin to develop the Ardupilot to enable automatic retracting landing gear like on the DJI systems A2 flight controller. I hope that Droidplanner will have a dedicated button to enable/disable auto landing gear, and also to set the altitude trigger, using either the barometer or gps or optical flow sensors. If anyone has undertaken this suggestion already, i'd be grateful for some links posted in the comments.
Many thanks and happy flying
Tutorial Link: http://dalybulge.blogspot.co.uk/