1. If you would like to get rid of these banners and the ads within the posts, all you have to do is sign up and they will go away!
  2. Hey Guest, are you here looking for the PDF Plans? They are located in the store in the tab above, but you must be signed in to access that part of the site. It only takes a second to sign up!
Hey Guest, I see you are not signed up on our forum yet. Did you know Registration is FREE and is only a couple clicks away? You can even sign in from Facebook, Twitter or Google+ for your convenience! So what are you waiting for, CLICK HERE to join in on the conversation!

600 Tail Kick On Punch Out Goblin 570

Discussion in 'Helicopters' started by murankar, Oct 1, 2017.

  1. murankar

    murankar Moderator Staff Member

    Blog Posts:
    9
    Joined:
    Dec 4, 2011
    Messages:
    7,677
    Likes Received:
    307
    Trophy Points:
    83
    Occupation:
    Soldier
    Location:
    Mentor, Ohio
    Here is the current issue as of this writting.
    On punch out my tail kicks to the right or nose left. How I found this problem or should I say what motivated me to fix the issue was because I decided retune the heli. What I had done was zeroed out the auto trim in the NEO via the VCnotrol. I set the tail, aileron and elevator back to zero. This feature is basically the sub trim to the VBAR. Mikado has designed the VBAR to adjust auto adjust so the pilot can speed up the tuning. Well unfortunately this system is not perfect by any means but it does get really (and I mean really) close. After my re-auto trim flight I landed and shut off the auto trim right as I throttle holded. This system will keep changing the numbers even after you landed (the not so perfect part).

    Once the heli was landed and ready I hovered it again. While I still had drift it was not nearly as bad as it was. So I opened up the screen on the VControl that handles the sub trim and left it open and hvered the 570. As I found the drift I dialed in the sub trim poionts at a time till the 570 was damned near flying with out thumbs.

    My next feat was to see if the heli would tilt front or back on punch out and bam, tail kick. As of right now there is not tilting but I still need to test a thing or two. I also set my head and tail gains to the knobs and adjusted those and still no improvements.

    Hardware:
    Scorpion Motor, Hobbywing 100a HV esc, Vbar Neo on Neo Governor

    Now to solve the issue:

    I had this problem righ after building the kit. When I first built the kit I setup the governor on the esc and had active freewheeling turned on. All I did was increase the tail acceleration and that solved the kick.

    Now I am using the Neo governor and the issue is back. I have went and adjusted the tail acceleration and played with all the gains to no avail.

    hypothesis:

    What I think to be the issue is with the active freewheeling. I wont know for sure till I can get out and fly again. From what I have learned is hat active freewheeling does not play well with heli linear thrttle and external governors. I have also learned that active freewheeling is only needed when throttle output is going to be operating in a wide range. This range is about 30% or more through out the flight. Since I am running on a governor and throttle PWM will be fairly consistant I dont really need this feaure.

    I have heard that active freewheeeling is for running lower throttle outputs (below 50% PWM). While this could still be true I am finding that it is primarly used to help the MOSFETs run cooler by smoothing out the duty cycles of the FETs due to wide throttle ranges.

    Bear in mind I am not an electronics engineer and the info I have is from other sources and is my interpritations of said informaiton.
     
    Last edited: Oct 1, 2017


  2. Smoggie

    Smoggie I Support Rc-Help! Rc-Help Supporter

    Blog Posts:
    0
    Joined:
    Dec 14, 2015
    Messages:
    2,106
    Likes Received:
    76
    Trophy Points:
    58
    Location:
    Aberdeen, UK
    Active freewheeling makes the ESC more efficient at any throttle setting below 100%. I've noticed measurable flight time increases between AFW off and on, about 20 or 30 seconds typically.. So i'd not disable it unless you really have to. I really dont see how AFW could cause tail kick? I use it on all my helis and it's never caused an issue on any of them.

    FWIW PWM frequency is always constant, it's whatever frequency you set it at in the ESC. The 'Duty Cycle' varies with throttle opening but using governor doesnt make duty cycle constant, in fact it's the opposite, running governor means the actual throttle opening varies constantly and over a wide range as load on the rotors changes and the ESC adjusts throttle to maintain constant RPM under this changing load.

    Getting tail kick dialled out is usually just a matter or optimising the tail gain and if necessary the 'collective pre-comp'. (I'm assuming mechanically everything is good and that you have set the tail travel to give all available movement of the pitch slider in both directions?)
    • First thing is to keep increasing tail gain until you notice the onset of fast tail oscillation during pitch pumps and/or fast forward flight. Once you reach that point you know where your maximum gain is so just back it down a few points so there is no more fast oscillation.
    • If after optimising tail gain there is still sign of tail kick to the right (nose left) on pitch pumps increase the 'collective pre-comp' value until the kick is gone. (if the tail actually kicks left as opposed to right decrease pre-comp)
    For best results you need to go through this process for each different headspeed that you fly at, higher headspeeds will need lower gain and usually lower pre-comp.

    This has worked for me 100% effectively on all my helis and most of them run Vbar.
     
  3. murankar

    murankar Moderator Staff Member

    Blog Posts:
    9
    Joined:
    Dec 4, 2011
    Messages:
    7,677
    Likes Received:
    307
    Trophy Points:
    83
    Occupation:
    Soldier
    Location:
    Mentor, Ohio
    This is an issue that hobby wing knows about. Their solution is to turn off afw while in heli linear throttle, which is the external governor mode. Again I have not been out to test this as of yet.

    I have set the pee comp to 70 and it still kicks. Tail main gain has been as high as 90. Head gain is at 90 and my head speed is set to 2200 till I find what is causing the kick.

    When I had this on the hobby wing governor the tail pre comp with afw on solved the issue. I was in gov store mode when I did it.

    Mechanically it's as close as I can get everything and I was over the top with getting everything dead on. Plus there is no binding.


    My question to you is are you running internal or external gov? If external what mode are you in? Heli linear or airplane?
     
    Last edited: Oct 1, 2017
  4. Smoggie

    Smoggie I Support Rc-Help! Rc-Help Supporter

    Blog Posts:
    0
    Joined:
    Dec 14, 2015
    Messages:
    2,106
    Likes Received:
    76
    Trophy Points:
    58
    Location:
    Aberdeen, UK
    I have to admit that I've not used the FBL governor with the HW ESC, I always just use the internal HW governor. I've read a little about the issues between the Vbar gov and the HW ESC and also heard a wide range of opinions about what causes it and how to fix it. Personally i just avoid the problem by using the HW internal governor.

    It will be interesting to hear if disabling AFW helps.

    PS.. having the tail gain as high as 90 without the tail oscillating tends to point to some mechanical issue. Maybe you arent getting all available travel on the pitch slider? Or maybe a smaller tail pulley would be better for the headspeeds you are flying at. The stock setup on Goblins tends to be optimised for hardcore 3D headspeed so a smaller tail pulley can make the tail work much better at 'normal' headspeeds. Just slightly more tail RPM can work wonders, this was what fixed sloppy tail hold on my Goblin 770 and on the 630. Using slightly bigger tail blades has a similar effect.
     
  5. murankar

    murankar Moderator Staff Member

    Blog Posts:
    9
    Joined:
    Dec 4, 2011
    Messages:
    7,677
    Likes Received:
    307
    Trophy Points:
    83
    Occupation:
    Soldier
    Location:
    Mentor, Ohio
    As for the tail gain, I did not have any shakes or wags with the gain that high.

    Just to make it known, yes the hobby wing governor is a great governor out of the box. It works just fine for 99% of the pilots out there.

    I had the 570 on the internal at first. It was very easy to set up. The only thing I did not like was not knowing the actual headspeed on the display. For what ever reason the VControl was not able to display that info. So I switched to the Neo. Now I can set my headspeed based on actual speed and not on PWM output.

    Down side is the dreaded tail kick. Hopefully I can get out today and see if I can test the theory out.
     
  6. Smoggie

    Smoggie I Support Rc-Help! Rc-Help Supporter

    Blog Posts:
    0
    Joined:
    Dec 14, 2015
    Messages:
    2,106
    Likes Received:
    76
    Trophy Points:
    58
    Location:
    Aberdeen, UK
    It 'should' with be possible with HW V4 ESCs to get an RPM signal from the ESC into the FBL telemetry, it needs the latest firmware though. Personally I never worry about what the precise RPM is, i just set it up by how it 'feels' to fly and dont get too concerned about the actual RPM number. I guess it's interesting to know the number but how it flies is far more important.

    Please report back on if disabling AFW makes a difference, but do watch out for a drop in flight time or deeper battery discharge for the same flight time.
     
  7. murankar

    murankar Moderator Staff Member

    Blog Posts:
    9
    Joined:
    Dec 4, 2011
    Messages:
    7,677
    Likes Received:
    307
    Trophy Points:
    83
    Occupation:
    Soldier
    Location:
    Mentor, Ohio
    Yes it has one. For ever reason in the headspeed screen it does not show actual headspeed. I tried everything I could in the vcontrol to get it to display. I finally gave up and switched
     
  8. Tony

    Tony Administrator Staff Member

    Blog Posts:
    10
    Joined:
    Feb 21, 2011
    Messages:
    31,873
    Likes Received:
    1,205
    Trophy Points:
    113
  9. murankar

    murankar Moderator Staff Member

    Blog Posts:
    9
    Joined:
    Dec 4, 2011
    Messages:
    7,677
    Likes Received:
    307
    Trophy Points:
    83
    Occupation:
    Soldier
    Location:
    Mentor, Ohio
    I did not get a chance to get out today. I did however update all the hobbywing stuff the PC software, prog box and ESC.

    Now my ESC is the Platinum 100A pro HV V3 and I found out tonight that Active freewheeling is no longer an option on this ESC. Time to dig in and see wha is up.
     
  10. Smoggie

    Smoggie I Support Rc-Help! Rc-Help Supporter

    Blog Posts:
    0
    Joined:
    Dec 14, 2015
    Messages:
    2,106
    Likes Received:
    76
    Trophy Points:
    58
    Location:
    Aberdeen, UK
    Uri,

    That's right, Active Freewheel is only on the Platinum V4 ESC's. It was never a feature on the V3, they don't have the hardware to support it. Your problem must be elsewhere.
     
  11. murankar

    murankar Moderator Staff Member

    Blog Posts:
    9
    Joined:
    Dec 4, 2011
    Messages:
    7,677
    Likes Received:
    307
    Trophy Points:
    83
    Occupation:
    Soldier
    Location:
    Mentor, Ohio
    As of today I have reduced the tail kick. Now it's very slight.

    First I raised the gov gain in the Neo from 40 to 55. Then I reduced the tail acceleration from 70 back to 40. Increased the tail P gain to 65 and I gain to 35.

    The biggest difference was increasing the governor gain. I still fiddle around with acceleration a bit but I think it's fine for now.

    I am also continuing with the trim adjustments. I think I got it as dialed in as I can get it. Hover is hands off with no wind. I am thinking about adjusting the I gain in the head just a few points.
     
  12. Tony

    Tony Administrator Staff Member

    Blog Posts:
    10
    Joined:
    Feb 21, 2011
    Messages:
    31,873
    Likes Received:
    1,205
    Trophy Points:
    113
    That is fantastic URI!
     
  13. murankar

    murankar Moderator Staff Member

    Blog Posts:
    9
    Joined:
    Dec 4, 2011
    Messages:
    7,677
    Likes Received:
    307
    Trophy Points:
    83
    Occupation:
    Soldier
    Location:
    Mentor, Ohio
    Finally getting this thing dialed the way it should have been a year ago.
     
  14. D.O.G.

    D.O.G. Well-Known Member Goblin 380 Supporter

    Blog Posts:
    0
    Joined:
    Jul 9, 2013
    Messages:
    2,009
    Likes Received:
    47
    Trophy Points:
    48
    Gender:
    Male
    Occupation:
    Disable
    Location:
    Inverness,Florida
    The main thing it's dialed in the way you want :) Nice going URI and now a video of your tame bird in action Lol. Good luck on future flights.
     
  15. Smoggie

    Smoggie I Support Rc-Help! Rc-Help Supporter

    Blog Posts:
    0
    Joined:
    Dec 14, 2015
    Messages:
    2,106
    Likes Received:
    76
    Trophy Points:
    58
    Location:
    Aberdeen, UK
    Uri, Good that you are making progress but i think that the root of the problem may be quite simple.
    Have you changed these settings previously? Reason i ask is the default settings are P = 80 and I =60
    ScreenHunter_29 Oct. 11 18.29.jpg

    So by having these values lower than default you will be lowering tail gyro gain and making the tail hold weaker, which is most likely the cause of the problems. These values work in conjunction with the master tail gain value but if you have them set low your tail hold will be weak regardless of what you have master gain set at in the Tx.
     
  16. murankar

    murankar Moderator Staff Member

    Blog Posts:
    9
    Joined:
    Dec 4, 2011
    Messages:
    7,677
    Likes Received:
    307
    Trophy Points:
    83
    Occupation:
    Soldier
    Location:
    Mentor, Ohio
    I actually realized I posted the wrong numbers on my final flight. I went up about 15 points from stock p and I gains.

    On my last pack I was flying nose in towards myself and doing right turns, or turning left based on my perspective and heard tail jitter from a high main gain. Adjusted that down about 5 points and the jitter was gone.

    It still has some kick but not like it did.
     
  17. Smoggie

    Smoggie I Support Rc-Help! Rc-Help Supporter

    Blog Posts:
    0
    Joined:
    Dec 14, 2015
    Messages:
    2,106
    Likes Received:
    76
    Trophy Points:
    58
    Location:
    Aberdeen, UK
    That's good Uri, at least if you notice the onset of a little tail wag then you know where your limit is. Increasing collective pre-comp will get rid of any remaining slight kick, it's very effective.
     
  18. murankar

    murankar Moderator Staff Member

    Blog Posts:
    9
    Joined:
    Dec 4, 2011
    Messages:
    7,677
    Likes Received:
    307
    Trophy Points:
    83
    Occupation:
    Soldier
    Location:
    Mentor, Ohio
    I believe my tail acceleration is back at 40 still. I would have to try and do a 15 point incremental increase to see if that works.
     

Share This Page