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Discussion in 'Cinestar 8' started by Steve Maller, Jan 3, 2014.
Sounds good. Converting my flat over now too as the Dual FC forces my battery plate up 20mm
Latest update (Feb 27 2015)
After the crash a few months ago, I've been reluctant to get this bird back in the air. I wanted to work on my skills and make sure I didn't run into a similar problem as last time (which I attribute to pilot error), as well as make sure any damage to the copter was addressed. I spent a lot of time flying my smaller copters and testing this copter on the bench and in the park.
But I encountered a problem (mentioned in this thread I think) where the copter was experiencing something best described as a "pendulum" effect when flying. After extensive investigation, including several emails exchanged with Holger Buss of Mikrokopter, I took a close look at how my Flight Control board was mounted. I had changed it because the standoffs I was using broke in the crash (good shock absorption!). But I think I had a substandard configuration of them which might have been causing a bit of movement in the MK stack (which I have all in the center, unlike the standard Cinestar configuration of the Navi and GPS on boom 1). Anyway, the addition of the SmartOSD board only made it worse. So I re-did all the standoffs and snugged the boards a little closer together with shorter standoffs, and I am cautiously optimistic that this may have solved my problem. I flew her today in a really strong wind (15mph+) and she never felt out of control in both manual (mainly) and Position Hold (for just 10-15 seconds). Here's an edited flight video in case you care to watch. I was just doing some simple maneuvers to make sure that the oscillations didn't recur.
Looks like you may have some variable rate time dilation happening, there Steve.
Or were you tweaking the playback rate?
I call it "Benny Hill" mode.
More like "Fanny Hill" Mode.
That's great that you think you fixed it. I would love to see some before and after pictures of what it was setup versus what its like now. If nothing else it would helpful for documentation for others. My question is this though: Why would it only start doing that right after a crash when you flew with the standoff's like that for over a year with hundreds of flights on it?
When I had the crash last year, the standoffs I was using broke (good shock absorbers!) so I had to re-do them, and I didn't have the 35mm ones I used so I used a 25mm and a 10mm, then used the vibration isolators. I need the extra height, as the 25mm ones don't quite clear the cooling fins of the Double Quadro board. But in butting together those three things (two nylon standoffs and the rubber isolators) I think they lacked the structural integrity of a two-piece setup on each corner. That, combined with the fact that I'm using the SmartOSD board now (I didn't use to use it) and the "tower" in the center of the copter probably had a small amount of play. And that (according to Holger) might have been enough to set up a resonance or feedback look in the gyros.
All I know now is that I flew her this morning with the MōVI on board and she was rock solid. What a relief!
(I wonder if Instagram videos can be embedded in here?)
Looks like you've solved the problem, Steve.
You can, as you have discovered, embed Instagram, but the playback is crappy....lots of hesitation....doesn't really show that you've solved the problem. (Of course, this could be the fact that Portland might in an Internet backwater without decent bandwidth, or that Comcast hasn't got the message about net neutrality.... )
Hey Steve, I'm looking to build a VERY similar build. Would yo go 4014's if you live at 5400ft or stick with the 4012's? Anything over 15min would be fantastic. Running M5 GH4 (maybe C100 or 5d) 2x 16,000mah
That will not make much difference if you move over 4014XF. With 16" prop, 4014 might generate less thrust since it's 380KV versus 400KV of 4014.
If you plan to use C100, which is a heavy camera, I would recommend you to go with 4014XF+18" props. This way, you will be on the safe side.
Or, buy Steve's machine which is listed on the forum. Once you use 17" props on them, you will have plenty of power there.
First of all, I could save you a LOT of trouble by just shipping you my copter! It'll cost you a LOT less than sourcing everything from scratch and accounting for the dozens (hundreds?) of hours required to get these things dialed in.
Secondly, I'd think twice about 2x16A batteries. I fly with 2x10A and get great performance.
I don't have any experience flying at altitude although 5000' or so doesn't make a huge difference from what I've heard.
Thanks Steve! How soon could you ship?
Steve got a quick question for you where you using stock settings for your set-up?
After i rebuild my x8 i am thinking it was underpowered, The Heavylift QuadrocopterLLC flat turned into a x8 just dont have the power to carry a 5dmkIII with m5. After i retested it was running at 60% hover. So I have bought the same kde motors and 16 inch propellers as your build. Now its pretty much the same set-up as yours was.
Just wanted to know if your tweaked any PID settings before i get myself into trouble again
Jason, typically the same motors from a flat 8 to an X-8 will resulting in 15+% result in overall thrust/lift capacity.
to be clear, what Gary's saying is that you'll LOSE 15% of your thrust
I used most of the stock MK settings. For the mixer I used 64 for the upper motors and 67 for the lowers. I played around with the dynamic stability depending on payload and wind, but that was more of a "feel" thing depending on how I wanted it to fly. It also depends on your CoG and how long your booms are, what gimbal and camera you're using, etc.
Ok thanks steve and Gary I knew about the LOSE 15% of thrust loss when making x8!! should of just bought bigger motors and props to start with! at least i have lots of spares for the flat 8 now
I really like the x8 handles in the wind and fast decents i am now waiting for parts to rebuild again it never ends hahaha
Good luck! Let us know if we can help in any way.
Hey steve did you have to cut and resolder all those kde motor wires? there super long there goes half a day!!
I hover throttle was about 50%-55% with the mk5diii and radian gimbal and 16inch props
I had my first flight yesterday went well i had a issue with in gps i think its because of the massive bundle of wires strapped under the fc. I got a external compass also which i think will help my cause
I replaced only the bullets at the end of the motor wires, not the wires themselves. I like the larger Castle 4mm bullets.
What kind of GPS problem did you have? I placed the GPS and Navi boards on top of the Flight control board, as Holger does in the MK copters.