800E heli 3 blade fbl Head pixhawk cant stop it oscillating

Thank you, but I am sure the opposite is true ! I have zero experience with DD-tail, could you please tell me more about it ? Do you use it because of reliability - do you put it on your next heli as well ? What about efficiency ? Can you please tell me more about Motor, ESC, battery size etc. ?

Hi Heli flyers. Usually I stay right in the background but today I am happy to see a little movement and colour at the Trad.Helicopter posts. Here 2 more photos to show both Helis with their Scorpion tail motors.
Markus I was reading a lot about it before I started to experiment with DD-tail. I mentioned earlier I have my Helis mainly for cameras. You can afford more weight at the back and the DD-tail makes the main motor and Tail independent. I do not want to rely on the FW to control the tail motor. Both Helis have 2 Castle Heli ESC,s who have one of the best govern rpm control. The pixhawk knows from the setting there is a DD-tail with variable pitch. The channel 8 signal for the main motor is split with a y-cable to each ESC. The tail ESC does not has the red wire connection. After testing I look at the logs from the ESC,s to get the info of temperature, rpm, amps battery voltage. My ratio for rpm is the factory recommendation. For the TR700 with the present motor and pinion is 1:4.73. This is working perfectly and I will not go back to torque tube. Also less vibration. But again if you want to have a not so heavy Helicopter this is the wrong way

to go.

Hi Markus
Finally got a small hover with your set up WHOOOOOO adjusted ACCEL_Z_P = 0.35

But had very little control what do i do next do i increase the ch6 Rate_Rll,Pit up until i get a oscillation so what do i need to look for

By the way THANK YOU so much for your assistance I’ve been working on this Heli for months and getting nowhere.
Will need to buy you a beer
Cheers
Kevin
From the first step of a very long ladder

Hi Fred
That looks amazing
Got my first little hover today but not very locked in using 3.3.3FW with Markus help well pleased to be taking the first step on the long ladder
Thank you all so much its been months and now a little win.
Cheers
Kevin

Hi Fred,

looks cool :-). What type is the Scorpion for the tail ? What battery size do you use for the tail ?
What is your opinion regarding 2-blade vs. 3-blade on the main rotor ?

Hi Kevin,

Finally got a small hover with your set up WHOOOOOO adjusted ACCEL_Z_P = 0.35

sorry I am lost. Which option did you choose ? Pixhawk 1 with 3.3.3 on default settings and ACCEL_Z_P=0.35 from my post #7 ?
Was the hover without oscillations ?
Please post your parameter file, I can tell you more after looking at your file.

Off topic question, why three blades instead two? someone have a comparison? thanks

Hi the reason i’m using 3 blades is to run a head speed of 1150RPM and have a very efficent long flying platform
no 3D just purely UAV and mission flying and hey they just look Great

I moved from 2 blades to 4 blades to get better performance like Kevin and probably more similar to why Fred switched to 3 blades. It sounds like Fred had increased the weight of his 700 series heli quite a bit above what they usually weigh. I changed a nitro heli to an electric powered heli and went from a flying weight of 7 lbs to 10 lbs. For a 600 series Heli this caused some issues mainly when approaching to a hover where the aircraft would require a lot of collective to arrest its descent (settling with power). So to improve this I did a trade off between number of blades, blade length and rotor speed which all play an important part to performance. I went from two 600mm blades at 1800 RPM to four 550 mm blades at 1600 RPM. I don’t have my problem with approach to hover and I still require about the same power for hover.

Hi Bill. You have explained it as I have experienced my weight increase of the TR700. But I hope there is a light at the end of the tunnel. Elon Musk,s batteries. I am in a process to work out if those TITAN Li-Ion packs are suitable for my application. That would reduce the Lipo Battery weight of my TR700 by half. Now 3.4 kg total of all Lipos on board. If it works with the TITAN Li-Ion the TR700 will weight 7.55Kg instead 9.25Kg with the heaviest of my cameras on board. Hopefully we have better battery options on the market soon.

Hi Markus.
The RJX has a Scorpion SII 3008 1220KV. Shaft replaced with a 6mm main shaft from a TR450 Heli. The TR700 has a Scorpion HK 4015 - 1450 KV. Shaft replaced with a 8mm main shaft of the RJX 500. This shaft is reduced to 6mm on a Leith to fit the Align tail pitch slider. I have tried all sorts of options different motors, coupling the shafts. It just does.t work without having a long one peace shaft with the pitch slider fitting on it. I have tried even a long titanium shaft because there is not a 6mm long enough shaft around as a spare from all models spare parts . You do not have a lot of motor options because of the shaft problem. Than you have to play around with the Lipos to get the right motor rpm. Here are the Castle Heli ESC.s the best option I believe.
The result for the RJX is that I am using for the tail motor a 3S 3300mAh battery. Don,t forget the COG has changed you might have to use a heavier Battery what you would like.
The result for the TR700 tail motor is a 2S 8000mAh battery.
The RJX has plenty left for a second flight. The TR700 has the same discharged as the 12S Main motor batteries.
There is so much involved it took me month between the change and flying again. But I am patient and take my time. I would not fly with the TR700 what I have not tried with the RJX 520. My RJX 500 had a crash because the motor cable connection from the ESC came unplugged in flight. Since than I do not use plugs to the tail motor any-more. The cables are soldered on and hidden in the tail boom. I do not have a 3 blade head for the RJX.
It is definitely not a simple change and should be considered very carefully. But I love the final result now with both Helis.

Hi Markus
Here is my params file i could get the heli off the ground but the delay on response was woeful so i did not do a lot more the thought is best for you to have a look at these files.
Cheers
Kevin

markus first flight param list.param (9.2 KB)

Hi Kevin,

some settings are not as usual, therefore please try this:

  1. setup your TX with a Dual rate switch, low = 50% high=100%, Expo about 30% or whatever you like.

  2. check Radio Calibration using high rates, left and right o.k., nose down gives lower numbers, collective up gives higher numbers, endpoints reasonable …

  3. for early testing setup your mode switch for Acro, Stabilize and AltHold. Later you can change to PosHold, RTL, etc.

  4. set STB_PIT = 4.5 and STB_RLL = 4.5 (back to default) play with these values later.

  5. do the following setup in Acro mode, ACRO_TRAINER = 0 and high=100% rates on your TX, UNPLUG the motor and arm the heli (you need servo output)

  6. you are using RATE_PIT_I = 0 and RATE_RLL_I = 0, that doesn’t really work for flying ! But now you want to make your setup, therefore keep this setting and set RATE_PIT_P = 0 and RATE_RLL_P = 0 and keep RATE_PIT_D = 0 and RATE_RLL_D = 0.
    Set RATE_PIT_FF = 0 and RATE_RLL_FF = 0. Now if you move your cyclic stick(s) nothing happens (yaw should work)
    The P-part + the I-part + D-part + FF-part = 0 therefore no movement.
    The FF-parameter is the direct pilot input (no control loop feedback, therefore no oscillations). Depending on your taste you can put more weight on the PID-loop or more on the direct pilot input.
    I prefer to fly RC_FEEL = 100 and use more weight on the pilot input part.
    To do this raise your RATE_PIT_FF and RATE_RLL_FF until you measure more than +/-8° on the blades. Now lower H_CYC_MAX to get 6° to 8° depending on your taste.
    Now lower RATE_PIT_FF and RATE_RLL_FF until you measure about 75% (or less depending on your taste) of this value, which would be 4.5° to 6°.
    You should have now a reasonable swash movement (you are in helis since 35 years, you know how it should look)
    Set RATE_PIT_P = 0.02 and RATE_RLL_P = 0.02 and RATE_PIT_I = 0.5 and RATE_RLL_I = 0.5 (P and I on default) and keep RATE_PIT_D = 0 and RATE_RLL_D = 0

  7. your H_COL_MAX = 1650 and H_COL_MIN = 1400 doesn’t look right to me. Check your collective range, it should be at least +/-10°, I use +/-12°. In case your tail can’t hold the +/-12°, go lower, but not less then +/-10°. It would be better to get longer or more blades on the tail, as low rpm flying usually needs it anyhow.

  8. you didn’t setup the tail limits ? They are still on default, please check.

  9. check stick direction and move heli around all axis to check for correct counter action

  10. use low dual rate setting and carefully try the heli in Acro mode, ACRO_TRAINER = 0. If not enough control, try high dual rate. In case the heli oscillates try ACCEL_Z_P = 0.3
    The heli should be flyable now, far from perfect, but no severe problem.

  11. in Acro mode, ACRO_TRAINER = 0, if everything seems o.k., start channel 6 tuning. Start with TUNE = 4 and set reasonable limits. Watch out if you use Extended Tuning page, it might change some settings. Be careful tuning I, be very careful tuning P and be VERY, VERY careful tuning D parameters.
    Keep in mind that the heli is sensible to air density. If you tune the heli in cold air at sea level to the limit, it will oscillate like hell in warm air on a mountain.

If Acro mode, ACRO_TRAINER = 0 setup is perfect for you, check Stabilize stick movements and counter action.

Kevin,
I think part of the reason why the response feels delayed is due to the large deadzone in the pitch and roll. I know I found that to be troublesome especially flying in acro. I suggest you set RC1_DZ and RC2_DZ to 5 or less. I think mine is set to 2. The exponential will then help provide a more shallow gradient initially.

Here is a nice article about PID: SAS_MHWJUN13_daves.pdf (1.5 MB)

RCx_DZ compensates for inaccuracy of your TX and RX channels. If you have the same trim value in hot and cold wheather you should lower it a lot. If it is too low it will be like constant input and confuse the PID loop.
RCxDZ = 30 and a sensitive setup will feel like nothing is happening around the center and usually the pilot is overcompensating.
Using a modern quality receiver RCxDZ = 5 should be no problem.

Hi Markus
Firstly thanks for all your help it is really very much appreciated

Not sure on what you mean “Start with TUNE = 4 and set reasonable limits
i have adjusted all prams as suggested going to have a hover in the morning
Pitch range now 11.9 +/-
swash is 5.5 degrees
The tail did not need any adjustment from default it was perfect travel and center amazing but i had to have win some where.
have attached the current Param file for you to have a look at if you get time .

Markus params 111216.param (9.2 KB)

Cheers
Kevin

Hi Bill
I have adjusted those DZ to 5 so hopefully with the hover in the morning all will be OK fingers crossed
Starting to get a small understanding of whats going on in the FC and how it all works.

Big thanks to all the you guys in the forum and your valuable advise

Cheers
Kevin

Hi Kevin,

there are only two parameters changed compared to your last file, RATE_PIT_P and RATE_RLL_P back to default. Either you sended me a wrong file or my bad English is the problem or you think you changed parameters, but you didn’t really do it.

I have adjusted those DZ to 5

No, DZ is still at 30 in your file ! Go to ‘Full Parameter List’, type RC1_DZ in the ‘Search’ field and change the value to 5 AND click ‘Write Params’, now click ‘Refresh Params’ and check if you have 5. Same for the other parameters (you can change many parameters and save them with one click on ‘Write Params’.

DO NOT FLY using this setup !

Hi Markus
Thanks for that i spent hours changing it all but it has not save to the FC sorry for that ill do it all again in the morning and get back to you thank you for checking once again

Best Regards Kevin

In ‘Full Parameter List’ go to TUNE and set it = 4 to do channel 6 tuning on RATE_PIT_P and RATE_RLL_P. The default value is 0.020. You take the default value for the lower border, that is TUNE_LOW = 20 (1 = 1000, 0.1 = 100, 0.01 = 10, 0.001 = 1). Depending on the sensitivity of your channel 6 knob and your patience you choose the upper limit i.e. 3 times higher, in this case 0.060, which translates to TUNE_HIGH = 60.
The USB plug isn’t made to last forever, it is much more comfortable to use the telemetry link.

Thanks for that i spent hours changing it all but it has not save to the FC sorry for that ill do it all again in the morning and get back to you thank you for checking once again

Please understand that YOU have to check EVERYTHING, it is your heli not mine :wink: