RETRACTS!!

Warning: This mod will void your warranty and is for experts only. Proceed at your own risk.

Introduction

If you read my post on Dumb Legs (which is a pre-requisite for this project), you must have been able to guess this was going to be the next project. I needed to take this on because launching and landing my VR Copter was just too dangerous without landing gear. 

This mod is for experts only, requires a full teardown and soldering to a pin on the 60-pin pixhawk connector and printing 3D printed parts so make sure you have the resources before buying parts.

1. Print Pillow Blocks

The first step of this obviously to procure all of the parts. Included with the retracts will be two y-cables that are necessary to use, and you need to clean and print the included 3D part which is a pillow block that connects the new legs to the body.

2. Teardown Solo

Follow the instructions in Solo Teardown to remove the innards from the body. 

3. Cut Hole in Solo

You will find that under all of the legs there are holes to let antennas through, except for one. Using a dremel, carefully open up a small hole similar size to the ones in the other leg mounting locations.

3. Tap into PixHawk 2 (FMU CH2)

This is where things get real tricky, we need to tap into FMU CH2 on the PixHawk 2 connector. Find your friend who is really good at soldering small things, buy them a 6-pack and tell them they cannot drink it until they solder a small wire to this pin for you. Use the images to make sure you are looking at the connector from the correct side.

After the wire is soldered in place, you need to knock down the lip on the PixHawk 2 so that the wire can come out from under PixHawk.

4. Solder Y-Cable

Included with the two sets of retracts, are two Y-Cables that need to be combined and then soldered onto the main board. In my case I was lucky enough to have another connector, so I could add a connector between the main board and my newly created super-Y-cable.

This is how the super-y-cable needs to connect

Red = Power = connects to main board (image below)

Brown = Ground = connects to main board (image below)

Yellow = Signal = connects to FMU CH2 from Pixhawk

5. Route Cables & Mount Blocks

If you have made it here, you are past the tough part! Wohoo!! Now you begin to reassemble Solo ensuring that you can route the cables through the holes where the legs mount and then again through the blocks. Mount the blocks in place with the same screws used for the legs.

When finished, build Solo back up. I'm assuming if you can do this mod, you can rebuild Solo.

Connect Servos

Connect servos and install onto pillow blocks using some M3x10mm screws and nuts.

Turn on Landing Gear in APM

The hardware section of this mod is complete!! You did it! Now you need to tell Solo it has retracts! Luckily this is all supported in Arducopter and you can change some settings using APM Planner.

To do this, you must connect to Solo using APM Planner. To do this:

• Turn on Solo and connect to the wi-fi with your computer.
• Once connected, open APM planner and click "connect" in the upper right corner.
• Navigate to Config/Tuning tab
• Set CH7_OPT to Landing Gear
• Set LGR_SERVO_RTRACT to 2000
• Set LGR_SERVO_DEPLOY to 1000

Discover CH7 Easter Egg

So now you are wondering, how to I set CH7 to low and high? Well luckily I found out that there is a little easter egg in the controller that will change CH7 to low and high! (I cheated and asked the guy who wrote the code for the controller.)

To Retract (set CH7 to low): Hold Pause Button

To Deploy (set CH7 to high): Press Pause Botton Once

Resize Legs (optional)

The legs as the arrive are a bit long, if you want to shorten them to be the length of the standard legs so it will fit in the backpack you need to remove 1.75" from the legs. 

Further, if you want little feet (like the image below) you will want to remove the leg, cut it down to the bend (0.75"), then cut another 1" off of the opposite straight side and then install it back into the servo.