I have a long history of being involved with R/C planes and helicopters and moving into drones is a natural extension of that. However, until recently I had little exposure to quad copters and I had the opportunity to see them fly at a drone meet. I got interested in them and decided to build my own instead of buying something off the shelf. The goal for the project was to develop a central motor variable pitch quad copter. The purpose of the variable pitch is to increase the flight envelope which allows things such as inverted flight as well as faster response to things like wind. The benefits of this were well documented in the work that MIT did and a video of some of that can be seen here http://youtu.be/VIkqqVr_u9U. The second portion of this project is to centralize the motor. The purpose of this is to get the heavy motor off of the ends of the quad to further reduce inertia and increase response rate. It also allows the user to gear down the motor to swing a larger prop at slower RPM. This increases the total prop area and reduces the disc loading which makes the quad more efficient. It is also my hope that the mechanical systems will be lighter than the motor/ESC setup which will reduce the overall weight. The downside to all of this is the added mechanical complexity and increased cost of components.

The design effort started with a traditional X configuration with a central spur gear that ran the power to pulleys. This design did work but it was REALLY noisy and had so many gears that it robbed efficiency. The support blocks were made from 3D printed nylon which I had done at shapeways. The gears were RC car parts and the variable pitch system was from a small RC plane system. I used an APM for the flight controller. This is version 1 and it can be seen flying here https://www.youtube.com/watch?v=ZrD4gScApQk.

A lot was learned from this design and we quickly moved to version 2 which is nearing completion. Version 2 features a more efficient and much quieter drive train as well as a V-tail configuration. The official reason for the V-tail configuration is that it has better yaw control but secretly the reason is that it just looks cool!