I have been building a variable pitch tricopter and wanted to share my results so far.

Basically - I chose a tri and not a quad, because the tri geometry is the same as a traditional heli 120 deg swash plate. Since I can't write a firmware on my own, I wanted to use an off the self solution.

I used a home made simple frame

3 e-flite park 370 hollow shaft motors with their variable pitch props

3 castle ESCs that I had laying around.

Here is a video of the tri on a table

http://www.youtube.com/watch?v=XI_8KCJyjcA

Here is a list of my various attempts

1. radio programed as 120 deg swash and used airplane stabilizer - worked but not great
2. used a commercial heli flybarless system - it flew , but could not set gains low enough
3. used my ardupilot mega - with traditional heli firmware - worked, but could not remove oscillations
4. I retried the APM with heli firmware and reduced the swash upper and lower limits to 1400 to 1550 and lowered rate p to 0.8 and stabilize p to 3.5 no I term and stabilize D of 0,07

 This allowed me to fly and hover, but very touchy

Check out the video above - and now I need suggestions .

I think one point is I need to redesign the pitch servo so that I use more of the servo throw, but mechanically reduce the movement - I have lost a lot of resolution using such a narrow pitch range in mission planner

suggestions welcome

Al