After more than a year of design and development, I've built version 2 of the iQuad custom tilt-rotor quadcopter which is capable of achieving high forward speed by tilting its rotors forward in flight. After several days of flight testing and tuning, I was able to achieve stable hover and incredibly fast forward flight. Near the middle of the video, you can see the iQuad hitting a top speed of 53.3 miles per hour on the third flight of the day! This was achieved with a 40 degree forward tilt of the rotors.
For stability control, I'm using an APM 2.5+ and a modified version of the 3.0.1 arducopter firmware. Big thanks to R_Lefebvre and Gary McCray for convincing me to switch to the 3.0 version and other suggestions. To support tilt-rotors, I created a new body configuration, which adds servo control and does the proper mixing of the pitch, roll and yaw inputs depending on rotor tilt. I also added logging for the tilt input and servo angles, which was very helpful for debugging some initial stability problems. For the final phase of the project, I'm planning to add four wings that will wrap around the metal arms (and maybe some tail-fins), to allow a full transition to forward flight.
Here's another video of me having some fun with the iQuad. Near the middle of the video you can see the iQuad hovering in place while tilting forward/back.
Hi Hollis, sorry for the extremely slow reply. Haven't been too active in diydrones recently. To answer your question, I did make the wing design, but it was too heavy and hard to control. I also made a couple of other variants, but the tilt-rotor quad in the video was by far the fastest and most fun to fly. It seems there are a bunch of copy-cat projects making similar tilt-rotors now too. How is your project going?
I'm working on a tilt-rotor counter-rotating octo with wings optimized for tandem orientation (so that the engines will be inline similar to your craft). The airframe is full CF and sits on a 2m x 2m footprint. It utilizes horizontal and vertical stabilizers instead of the fins mentioned earlier in this thread. I'd be grateful for any help you could provide code-wise or pointing me in the right direction for programming arducopter for VTOL planes. I'm not sure how your wing design is going but it could be insightful to trade notes.
Not planning to sell, but if enough people are interested, maybe =)
With regards to servos, I am using Hitec mini servos. The main consideration for me was small size and weight, and the ability to calibrate the end-points of the servos. The torque seems good enough, and they're also super-reliable. I haven't had any stripped gears even with some minor crashes.
Nice little thing you going on there. I was wondering what's the torque rating for the servos you are using, and how did you came to choose that rating?
Keep on the good work!
Selling them in the future?...
I got most of the stuff from servocity. The shafts are 5/8", aluminum. Carbon fiber would work, but probably not save a lot of weight. Most of the added weight is in the tilt mechanism, landing gear, motor mounts, etc... The tubes are surprisingly light (about 15 grams each).
Fantastic job on the tilt rotor. I'm working on something similar. I'm curious as to where you got the shaft bearings and motor mounts, and the size of the shaft the motors are mounted too. They almost look like stainless steel, but I'm guessing they're aluminum. I'm curious as to why not carbon fiber tubes for the shafts.
My off-the-cuff opinion on that would be that it's less efficient to fly that way, and will also produce higher vibration. These rigid propeller systems are not well designed for high speed flight with an airflow perpendicular to the propeller disk.
Is there any reason why one doesnt simply put a prop or edf on the back and have it push the copter about with the facing down props doing the lifting ?
Stan, I think tilting up slightly may actually be better because the whole quad can act as a lifting body. Most flight time probably in forward flight, but stability is my main concern (over flight time). Luckily my design makes swapping the arms pretty easy, so I might actually try with both symmetric and asymmetric wings and see which works better.
Scott, I think raising the rear would help, but it would probably have to be substantially higher to make a difference. Plus, I'm already kind of locked into a design with the front and back being in a line. The propwash doesn't seem to be a huge deal after I shifted the CG slightly forward. I was thinking in the future I could also try using slightly smaller props on the front motors.