I have several Pixhawk-based multicopters, ranging from 6" to 13" props. I love the tunability, the feedback information and the feature set.
However when I go to 15" props, I chicken-out and go with a proprietary controller (i.e. an A2).
Based on what we know about 3.2 (assuming release version… I wouldn’t put a beta on a valuable vehicle), is it time to take the plunge and put a Pixhawk on my next 15"-18" build?
Is there anything I should know/do/be aware of before making the jump to APM on a larger (15"+) craft?
As much as I truly love autotune (it’s amazing, IMO), I wouldn’t trust it on a big octo with an expensive gimbal attached. I’ll probably use a small dumbell for testing and just dial it in through CH6.
I’ve been seriously impressed with Pixhawk. I have a little 6" prop 2300kv Octo all the way to a 13" 700kv Quad. They both work great, but the real benefit it being able to sort through the flight logs and figure out what’s going right and wrong.
I guess my only fear is the unknown. I’m looking at an octo frame that can take 18" props and while I’m not looking to load it down that heavily, I’d like to load it with batteries and go for long video runs.
On an unrelated note, I need to find about eight of those waterbuoys (currently sold out) so if my new bird hits the drink, I can at least fish-out the frame and reuse that and the motors (I’ll use U-series, which are supposedly waterproof). They’re little water-activated gadgets that inflate and support up to 1kg weight each.
Can anyone else think of anything I should consider in using a Pixhawk with 18" props?
If you’re going to be a bear, why not be a Grizzly? Should I just build a quad with huge (i.e. 25+") props? Is that even better or is it worth the hassle to have some motor redundancy?
If you’re going to be a bear, why not be a Grizzly? Should I just build a quad with huge (i.e. 25+") props? Is that even better or is it worth the hassle to have some motor redundancy?[/quote]
Depends what you plan to carry and where you’re gonna fly. My new project is a V-tail (not v-frame) X8 in the 90cm (or bigger) class.
[ul][li]Big, because I want to use big props and slow motors for endurance[/li]
[li]X8 for redundancy[/li]
[li]V-Tail for agility[/li][/ul]
I’m trying to find a good compromise here between endurance and reliability.
If you plan to do serious videography, you should rather go for something with smaller props and faster motors and plan it a bit bigger so it can carry more batteries. Reason is that the combo slow motor/large props is much more likely to produce low freq vibrations which won’t bother the Pixhawk but will let your video look like you wiggled the tilt all the time.
All great input – thank you. I too have considered a fairly large X8.
If I’m doing an octo with 18" props, any wild guess on what my initial PID settings should be? I know this is an absolute shot in the dark, but I figure this thing will be about 6kg-7kg stripped (no camera or any other amenities) and even fully loaded will be less than 16kg. The motors will be size 5008 @ 340kV.