Multi-rotors: Aerial Filming
The "Perfect" Aerial Platform
By: Eric Monroe (Shadow74)
I have seen this topic discussed many times across several different forums. While there is more than one way to "skin a cat" the following is a collection of things that I have learned first-hand in my successes and failures with multi-rotors.
My 2 cents…..
(okay its probably more like 10 cents) :)
Achieving this happens with quite a few things going on at once. First and foremost (from what I have found) you have to start with a stable copter. You can have the most awesome mount in the world and with the wrong copter you are still gonna get the typical bumpy/shaky/jello Youtube crap when it comes to your footage. Start with a good copter. One copter that I believe fits this category (as far as one that can be purchased from a company) is the Cinestar Revolution by Quadrocopter. They make a Cinestar 6 and 8 with optional GPS, position hold, and the best 3 axis gyro stabilized gimbal (IMHO) that I have ever seen. These machines are state of the art, and have the power to carry everything from a GoPro up to a RED EPIC cinema camera. Here is a video featuring this setup:
(Enjoy because this is STELLAR piloting/camera work....Tabb is one of the best in the business)
The Cinestar copters, are unfortunately currently out of my price range. Ranging anywhere from $8,000 to over $15,000 depending on options. Since I still want to produce quality aerial video I set out to invent my own platform. (admittedly however, with all the R/D I have put into doing this I could have probably bought a Cinestar 6 and been done with it.)
Here are some pics of a few copters that I have designed, re-designed.....and then redesigned again. :)
A few things I have learned about obtaining great footage:
The copter cannot have a small footprint. A Gaui 330 for example is just too small. So are most of the out-of-the-box copters.
Here is the copter that I started with:
Most of what I have learned early-on about aerial filming came from flying this little guy. In a near-perfect dead calm situation I was able to gather a handful of nice shots, add the slightest wind and the footage was not usable. The small footprint and lack of mass just makes things that much more difficult in terms of flying characteristics.
The heavier your multi-rotor is (within reason) the better and more rock solid that they seem to fly....problem then is powering it for more than 4-5 minutes. For filming, I will no longer fly anything setup to fly with a 3-cell. Of course I am not saying that it can't be done, however if you build a machine that is meant to carry anything more than a GoPro forget it. My latest quad design (the angry bird) measures 38" from motor to motor, weighs 6 1/2 lbs, flys the Cinestar's motors swinging 14x4.7 props and is powered by a 50C 5-6 cell lipo. This machine will carry a GoPro for close to 15 minutes. For GoPro only machines you can make a 3 cell system work, but you will get WAY more power and flight time if you go with at least a 4-cell setup. FPV Manuals sells a Delrin version of David W's tri-copter and advertises 28 minute flights with a GoPro using two 3300mah 4S lipos running in parallel. It is not the prettiest machine to look at IMHO, it has wooden arms etc. but flies for a LONG time which FPV guys love....still a bit too lightweight for filming.
The more rigid the frame, the better footage you will get. This is because fewer vibrations are able to transfer throughout the copter frame itself. I discovered this when I built my first big quad using metal arms. I built another duplicate frame using wood arms and it was full of vibrations that are not present in my metal armed version.
Prop balancing is an art.....one that you MUST not only get "good" at, but AMAZING at. I have spent as long as 30+ minutes a piece precision balancing my props for my multi-rotors. You have to static balance not only the blades, but also the center hubs…..then dynamic balance after that. Prop balancing is CRITICAL to good footage. Balancing the motors is also extremely important. Precision takes patience……but yields fantastic end results. When everything is balanced properly, fewer vibrations make it to the camera and the flight controller. The gyros on a multi-rotor flight controller are extremely sensitive. The fewer vibes that make it to the controller, the smoother and more stable your flying/filming experience will be.
Enough about copters…….let's talk camera mounts:
Once you have a nice WIDE copter platform to carry your camera, mounting it to the copter is next. (Would be nice if cameras just flew themselves….that would save us all a lot of hassle.) I have experienced that keeping the weight that you are carrying in line with the forward flying plane of the aircraft keeps it from penduluming the copter around and making it "pitchy" when it flies. A number of pilots mount their cameras (especially the larger ones) under the copter. This can make your copter fly goofy at high speeds. In a hover it is usually not too bad, but there will be times where you will need to accelerate to follow a boat or a motorcycle and when transitioning from fast forward flight back to a hover the weight hanging underneath wants to keep going forward causing the nose of the copter to pitch up. When using a camera with a wide angle lens like a GoPro Hero, hanging it underneath will most often times cause the landing gear, the props and the boom arms to show up in your shot. Putting the camera out on a boom up front and counterbalancing with the battery(s) in the back keeps everything in line and gets the camera out front where it can do what its supposed to…….capture great footage.
There are 2 things to do about vibration.....minimize what the copter is creating through a rigid frame, proper balancing of props etc. and then dealing with the inevitable vibrations that are left over. Vibrations (from what I have experienced through trial and error) must have a path to travel. Minimizing the contact point between your camera boom and the copter helps tremendously to deal with existing vibrations. Once the few existing vibrations manage to get through that point and travel out the boom, the next step is up the risers to the secondary camera boom. Most all of them dissipate before reaching the secondary boom.
If you do choose to mount your camera under the copter, make sure that the measurement from motor to motor is significantly larger than the distance from the top of your copter to the bottom of your camera mount. If the latter distance is the same or greater than the motor to motor measurement you will have an extremely unstable machine and a crash waiting to happen.
Some of my work:
Here are two videos that I put together using my multi-rotor designs. The first is filmed entirely with the GoPro Hero and the second with a Canon 5D MK2 HD-DSLR camera. Enjoy!
An additional 2 cents……. :)
Multi-rotors have fast became my favorite machines to fly. I have designed and flown several and have had an absolute blast learning how to tweak these amazing machines for gathering awesome aerial video. I can honestly say that my feet are firmly planted in this area of flying and I am looking forward to the continual growth of multi-rotors in the R/C world. Sharing each of our experiences whether positive or negative helps everyone. Make sure to post on the forums! Happy flying!
Multi-rotors FTW! :)
Eric Monroe (Shadow74)