Chris,
Your mapping helicopter, is that camera hard mounted? Just some ball dampeners? Or a gimbal?
Getting away with a hard mount or just a simple ball dampener setup seems like it would be an ideal route for something like mapping provided it causes no ill effects as weight could be kept low.
Ive just been kind of running some numbers for weight vs power available. I have some Wh/Kg figures for some packs i use and 4-7s 5000mah LiHv packs at 3800grams, shooting for 1300rpm would likely yeild a decent flight time?
Unfortunately ill likely never get great times using the heavy gimbal so its go up, get it done in 12-15 minutes, then land and swap packs, but things look alot better on paper for an 800 with a light camera setup for mapping and also the inherent effeciences of forward flight i usually dont get to use with the gimbal.
Gas makes good sense on paper for its proven long flight times, but then i have to carry fuel, tune and maintain, clean the grime off everything and deal with the vibes that come with gas. I built a high amp charging case a couple years ago i either plug in at home or run off a honda eu2000 in the field, so ive been spoiled by 20-30 min charging for 6 5000mah 6s packs and the general ease of electric once properly set up with enough packs and a good charging solution. I definitely want a nitro for a number of reasons, but for mapping id like to make electric work as im already invested in it heavily, provided i can get the flight times i need for a site.?
I guess i should focus on the task at hand and get the videography helicopter tuned and working again before i delve too deep into something else⌠just thinking out loud. 
I wanted to get some more flights in with it today, but alas mother nature had 25-30mph winds with higher gusts in store for today so that dident happen. It was just starting to feel like a helicopter again and not a drunk bumble bee. Just itching to try to get all the gains higher and play with the ATC_ANG_PIT_P⌠Hopefully weather is better tomorrow.
Tim
Tim, itâs just hard mounted but some rubber washers on the mount. I got a gimbal for it - a two-axis Walkera G2D. But those rubber jello balls give out at 45 mph and it end up dangling by the safety strap and wires. It donât need it anyway, as the only reason I thought it needed it was to adjust pitch. But thereâs no need to adjust pitch. Just set it static so the camera points straight down and it works very well.
Youâd have to experiment to see if your helicopter would fly at 1,300 rpm ok. I donât know. When you start talking about 3.8kg of batteries, thatâs well over a gallon of fuel. Thatâs why I find it hard to get very excited about electrics bigger than 600 class.
Chris,
Thanks for the info on the camera setup! And to electrics, yeah i dunno. I have no idea the longevity ill get with a light mapping setup. Ill have to keep playing with pack voltage vs capaciry vs weight. It might turn out i can get away with 12,000 mah 7s lihv at 4.35 volts and hit 30 min after adding in forward flight effeciences? Thats the fun part i guess, thinking of ideas or solutions to a problem, and acting on them and gathering data. Which soon enough ill have some. Wouldent be hard to simulate a mapping camera with some dead weight attached to the skids etc,l. Then i can prove, or disprove my theory without spending alot of time on a platform for mapping and go a different route, ergo a gasser, if need be.
Tim
Okay,
So I went high with the headspeed⌠Too high, had to back way off the P gain as it was oscillating. Brought it down and dropped the headspeed to probably 100rpm or so higher than it was throughout initial testing. The pitch bob is in fact mostly gone now. I gain is at .29, D is at .0009 and Pback down to .06 but I will try to bring it back up a bit higher again. Also added a bit more VFF, just a few points. With the added headspeed and VFF along with the I gain it is really starting to feel better.
Bill, BTW increasing the IMAX was exactly what it needed on the tail. Seems to hold better and hunt less.
Tim
So i saw what happens with too much VFF. Backed off it a bit, split pitch and roll P gain and have D at .001. Dont know what the data will look like but it felt pretty good. I rocked it back and forth, forward and back pretty hard trying to get some bad behaviors and couldent. Almost time to try some FFF and banked corners at a bigger field. I hope anywaysâŚ
Tim
Tim,
You would probably be ok incrementing the D gain in 0.0005 increments. Iâm not sure how you were doing it before.
You may want to look at your RCOU 4 parameter in the log file and see what your average value is in a hover. If it is pretty far from 1500 then you may want to mechanically adjust that bias out. So the RCOU 4 will be closer to 1500. My only concern is if you are using more than 50% of your servo throw in a hover then you could run out of control throw.
Bill, I re-centered the tail pwm and added a bit of mechanical pitch to get the tail stable in a hover. It seems to hold very well now, and has a pretty smooth response and judging by the look of the tail rotor in flight its not using too much throw to hold it in place?
I just put in quite a few flights and its finally starting to feel quite good. I have a video I will upload later of me trying to tease out instabilities and such. Itâs remarkably better than it was yesterday. The slight headspeed bump has helped a lot as well. Iâll attach my current parameters I just landed with after the best feeling flight yet.
Thanks,
Tim
Video of my last test flight. Sorry about the crazy camera work, my 9 year old was âdoing it like in the moviesâ so he says. Lol, whatever it takes to get another generation into helis⌠It was really starting to feel good though.
Tim
Just a thought, i wonder if having RC_SPEED at 333HZ is affecting anything in a negative fasion? Ergo, potential source of ossicilations? Or is that not a factor? My P gain is much lower than i thought I would get to, but that being said, the heli is starting to feel more locked in and has far fewer small ossicilations or negative tendencies in general. I looked at the logs and requested vs actual rates are getting much more symbiotic looking vs when i first started looking at them if that means anything?
Tim
First of all, thanks to all you guys for this thread. I got my PH2 and I wanted to set it up for heli. I had a bunch of questions which are already answered in this thread. Here is my setup, yet to be bench tested. This is 450 Trex clone. I am still in the process of gathering courage to fly it considering it the beta SW. I also have a spare FBL head. So I plan to fly both FlyBar/FBL using the same heli. This is an excellent opportunity to see how the parameters change from from FBL to FlyBar when everything else (servo, weight., etc) is same. Update about it to follow soon.
Tim, I think all setting the servo refresh rate faster does is make the servos use more power. I donât think youâll see any difference setting it back to 125, except your servo battery will last a few seconds longer.
Your helicopter is looking much better now. I just checked in on this thread and Iâll have to get up to speed on your latest params and logs.
Youâre starting to end up with what it took me several weeks to get ârightâ as far as your rate settings.
Just for your info, you can set these to tune your stabilize collective curve
IM_STAB_COL_1,0
IM_STAB_COL_2,400
IM_STAB_COL_3,600
IM_STAB_COL_4,1000
The 1 param sets the bottom of the collective, #2 sets it at about the 40% stick postion, #3 at about the 60% stick position, and #4 is the max. The idea is to get it to hover at mid-stick and the closer you set #2 and #3 together, the flatter the collective curve is at mid-stick in stabilize flight mode. Itâs a good idea to get it to hover at mid-stick, otherwise when you switch to the Altitude controlled modes youâre going to get a big jump in collective pitch and the helicopter will either go up down quite quickly.
I just noticed those were still set to the defaults, so thought Iâd mention that.
Sunit, thatâs a pretty tall looking helicopter. Seems to me thatâs one of the downsides of the PH2.1 is the amount of room it takes up on the carrrier board. Itâll be fun to see your 450 fly with a PH2.1!
Chris,
I asked about the RC_SPEED parameter because i had just recently read a thread where someone had set up the tail at 333 on a Pixhaw, the. Switched to 125 and it ossicilated/wagged.? I dident look into it too far and even if I did, I do not have the skill yet to pick apart the logs and parameters to see if something else changed too? For the moment, ill probably just leave it where it sits as its finally starting to feel good in the airâŚ
Thankfully just bumping the headspeed up a tad helped alot with pitch issues! Good call! I get much longer flight times at lower headspeeds, which translates into a lot more tuning per set of packs, so i really wanted it to work at 1250-1300. Iâd say its at 14-1450ish, ive got to throw an FrSky RPM sensor on it and just get it over with alreadyâŚ
As to the hover position, i remember seeing Rob set that in a video. At the time i figured I would leave it at a linear curve as thats what i was used to from all my 3D helicopters so at least during the initial flights and tuning it felt farmiliar.
Now im starting to get to the point where i want it to feel more like a UAS set up for videography, so I couldent agree more with your sentiment on changing it! I appreciate your in depth description of the parameters as well as what can happen when its not adjusted that way when switching to guided flight modes. If today is as nice as they say, ill hopefully get to play around with that and get it flattened out at mid stick, remove some of the negative pitch and hopefully eliminate the jump in collective you speak of when i finally try a gps or barometer based flight mode.
I will say, im scared to death to try loiter or similar mode. ive been watching the GPS portion of the logs for anomalies, and havent seen any yet, but putting an 800 in ths hands of a flight controller scares me just a bit. Lol
Im hoping i can get rid of that little tiny bit of wobble when im beating it up jabbing cyclic fore/aft and port/starboard today. Although the P gain is quite low, it seems to fly good at this point. It was quite âgustyâ with the wind during the day yesterday and the helicopter seemed to take it well and it dident set off any ossicilations. It did float up and down a bit with the gusts, but i attribute that to the lower headspeed vs the low disk loading at the moment combined with the very touchy collective i have set at the moment. Im sure with a gimbal hanging off it adding substantial disk loading to the mix it will be a different story. Before with the gimbal and camera gear it handled wind quite well. Just hung there like a rock in the sky, way less balooning than the octa copter, which is why i cant wait to see loiter in action. The octa copter will be officially obsolete if this system im building works as i want it to. 
Tim
I forgot to ask, if the helicopter feels good to me in stabilize, it should be good in loiter correct? Im still not ready to attempt it as i have to research the mode alot more, but im just starting the process of educating myself on the next step.
Tim