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    Tricopter

    Hi, sorry but i am new to this place actually. i have some problems trying to do my tricopter actually. hopefully someone who has done it can provide suggestions to solve them!

    I'm using the following equipment for my tricopter:

    1 X Futaba GY240 AVCS Gyro (for yawing control)
    3 X Tahmazo ER 2208/1100 brushless motors (for lift)
    3 X Tahmazo Pro.C Max 3018-3s ESCs (1 connected to each motor)
    1 X Futaba 7C TX with RX
    1 X Tahmazo 26000mAh, 3-cell Li-Po battery
    3 X Hobby King 401B AVCS Digital Head Lock Gyro
    1 X yaw servo
    2 X 10X4.7 puller blades
    1 X 10X4.7 pusher blade


    i used 120 degree CCPM (HR3) for the TX. the motors are connected to channels 1,2,6 while the gain for the motor's gyro are connected to channel 5. The yaw gyro uses manual gain though and it controls the yaw servo using channel 4.

    i put 2 puller and 1 pusher blade for the motors, cos i thought there might be some torque due to blade motion and setting the puller and pusher blades to rotate at different directions will somewhat reduce the net torque though.


    When i tried to power it up and fly, apparently one side of the arms have a higher rpm than the 2 others. As a result, it will tend to flop when the throttle is turned higher.

    I tried to use swash settings to control. it's helpful but cannot totally eradicate the problem. Sorry for asking, but can anyhow explain what the swash setting is for in the tricopter use?

    I tried trimming the controls also but somewhat it cannot totally solve the problem. the rpm outputs for the 3 motors can be almost the same after trimming but then the throttle stick is pushed higher, it drifts to one side then lopsides again, probably due to higher rpm for one of the motors also.

    Has anyone experienced the same thing also? Hope someone can provide me with some expertise! Thanks!


    #2
    I have no experience in tricopter...but there are some of the settings u are using appeared to be not right in my personal opinion:
    Since it is 120Degree apart tricopter, it is like normal eCCPM 120Degree swash plate.

    That mean, the movement of the tricopter behave similar to swash plate.
    Now, since it is eCCPM120, you cannot just use gyro and control it. The way I look at it, it is like trying to use gyro to stabilize eCCPM120 swash plate type of flybarless heli.

    Assume it is like using gyro to stabilize flybarless heli for eCCP120Degree swash plate, then u need either:
    1. Those flybarless avionics devices like SK360 or SK720 or VBar.
    2. Normal gyro (as what u are using) BUT using eCCPM120 mixer electronics instead.

    For #2, your TX is configured as mCCPM type and then the gyro will stabilize it by controlling the individual channel. Then the o/p is fed into the eCCPM120Mixer. The o/p then goes to your motor/servo instead.

    Again, I might be wrong because I do not have tricopter experience. I just use helicopter point of view instead because the way I look at it, it is similar to heli's swash plate movement.

    SH

    Comment


      #3
      could i get this right:

      all motors are facing the same direction, but two turn in the same direction while the other is opposite?

      i assume the props are all mounted correctly and in the proper direction of rotation?

      in this case what i can guess is that the props are not 100% identical. you could try measuring the thrust from all props running at the same rpm and i doubt you'll get the same amount from the pusher and puller.

      in any case, i'm not sure if the concept of a tricopter is even sound? note that beyond dual rotors the next step up is a quad rotor. so while two rotors cancel themselves out, there is a torque from a rotor that goes entirely un-compensated
      JR 9x
      Raptor 50 SE
      Raptor 90 3D
      Mini-Titan


      Superb machine!

      Piper Warrior 2 Pa-28-161
      Lycoming O-320-D3G 160HP

      Pilatus PC-21
      Pratt & Whitney PT6A-64B 1600SHP

      Comment


        #4
        I do a quick search in the internet and found this (see below). Maybe you can follow what they do.

        Upon further look at your picture and the one I found on the internet, it looks like the control do not follow helicopter swash plate movement at all. To stabilize the heli, you do not tilt the triangle...but tilt the rotor (in this case, propeller) instead. To yaw, you tilt the rear rotor/propeller instead. Thus, the center/triangle base remain stable flat. With that, U can use gyro on each triangle axis or motor/propeller axis and u do not require eCCPM mixer.

        Because of this design, The way I look at this, 2 frontal motor need to spin on slightly slower RPM than the rear. 2 frontal maybe spin in the same rotation and the rear will spin in opposite direction to counteract. The tail/rear need to spin faster than the frontal 2 motor.

        U can put one more gyro at the center to conteract the yaw...and use it to increase/decrease the 3 motor instead (due to inconsistent governor or inconsistent propeller). U can use V-Tail mixer in it.


        Comment


          #5
          Hi brandon,

          yup. 2 are rotating in the same direction while the other is in the counter direction. I thought it was the motor direction that was wrong, that's why there's extra/ less lift on one of the motors but upon verifying, the problem persists still.

          not sure if the tricopter concept is sound. do anyone understand how the torque thing is settled? seems like there will be a net torque but the video from the first link posted by Super Hornet (sorry dunno your name!) shows that there's no torque at all.

          Hi Super Hornet,

          i followed that site's method actually. I suppose the CCPM is to control the 3 motors at the same time to produce rolling and pitching effect while moving it front and back. but i don't really understand what swash settings are for in a normal heli.

          if the front 2 rotors rotate slower than the back, will it cause the whole thing to flip over?

          Comment


            #6
            I trying to think in physics or logical point of view here.

            Lets say both from rotor spin in the same rotation and the rear spin at opposite direction, and lets say all 3 motors spin at the same RPM. Assume all 3 propeller is the same, then your craft will go in a yaw direction because one motor (rear) cannot cancel off 2 motor's torque.

            So, to counteract this yaw problem, 2 possible solution to this:
            1. Two frontal motor spin slightly slower and rear spin faster. The overall torque may able to cancel off each other. By doing so, u might want to shift the Center of Gravity a bit to the front (that is, tail slightly heavier).
            2. All 3 motor spin at the same RPM and the CoG is at the center. This configuration might end up craft in the yaw state. So, to counteract it, tilt the rear motor slightly opposite the direction it tilt. Take example, if craft is doing yaw in clockwise direction (seen from top). Then tilt the tail to slightly facing right side. The lifting power from the rear can then compensate or trying to turn the craft counterclockwise.

            SH

            Comment


              #7
              Hi SH,

              shall try out ur method and also find out the thrust from each prop also.

              thanks!

              -beanlee999-

              Comment


                #8
                beanlee99, you might want to contact pang (heliguru) as I've seen him build one similar to yours and got it to fly.
                Beastx installed and flying ...

                [SIGPIC][/SIGPIC]

                Comment


                  #9
                  i see, the one that was posted uses the third prop as a quasi tail rotor. the rear motor is able to tilt in the direction counter to torque. there must be some other compensation being done by the gyro because as the prop tilts its thrust line changes relative to the vertical
                  JR 9x
                  Raptor 50 SE
                  Raptor 90 3D
                  Mini-Titan


                  Superb machine!

                  Piper Warrior 2 Pa-28-161
                  Lycoming O-320-D3G 160HP

                  Pilatus PC-21
                  Pratt & Whitney PT6A-64B 1600SHP

                  Comment


                    #10
                    I must say the tricopter concept works. I have built and flew a smaller tricopter using similar 401B gyros with Towerpro motors (840 KV) and HBK SS 18 A ESC.

                    From what I can tell from the pics, you are nearly there.
                    I am a fan of ---------'s, so not I am not sure about your Tahmazo motor/
                    ESC setup. Given the variations within the electronics and motor hardwares, you would not expect the 3 motors to run at same speed. Plus there is a gyro along the way. Try to calibrate your ESC's end points with all the electronics in place.

                    Most ESC's don't operate on the full 1-2ms signal pulse range for zero to full throttle. If you have servo travel at full on on both sides, you may need to reduce their ranges individually so that that motor speed can be controlled across the entire stick movement. HK's ESCs only need +25%/-25% and Castle Creation's ESC about +40%/-40%. You will have less 'jumpy' craft.

                    A quick and dirty method which I find quite effective.
                    - Remove all the props, place said tricopter on a stable surface,(so that no gyro movement would unsettle the motors).
                    - disconnect the power links to the other two motor (hopefully you have them in bullet connectors).
                    - apply power and advance the throttle stick, adjust the each ESC's lower end pts, so that all motors can start to move at same throttle stick position, of course you have to do this individually).
                    - do the same at the full throttle, (some ESCs have a fully lighted LED to indicate full throttle position, with ESCs like mine, I used auditory sensors - my ears, to hear that the motor speed can go no faster).
                    ( if your tx has multipoint curves on per channel, you could also adjust the mid-points too at a powered hover)

                    Worthy notes,
                    - some ESCs would not arm if the lower end point is set too high. (déjà vu – i.e
                    going 'separates' with Honey Bee FP's tail motor).
                    - some Gyro's have a significant offset to the operating pt. established by the tx/rcx.
                    - a lower KV's motor to swing a larger prop will have gentler speed range
                    for smoother control. (where did you get the counter pitched 10x4.7)

                    Hence, the finding the right ESC/Gyro combo is key to a tricopter's success.

                    I found the cheapies from HK to be good enough as prove of concept for my
                    small tricopter below. I have managed to house most of the electronics in an
                    uncomitted fuse of a small glider, it helps in orientation when in the air.

                    It would still be flying had it not being the cheap tail #@!?& ESC that decided shut down early when the two front motor was at full bore. It back-flipped all the way down and broke the two front pine 'prongs'. If I am to repair it, I think I will have break-ways front prongs or/and some sort of wings to allow it to glide when things goes wrong in the air.

                    This early 'retirement' have force an early start of a two-tilt rotor craft attempt, much along the line of Avatar's Scorpion. I have since encountered the need of a good performace vtail mixers and Gyro's with long 'decay' time. I heard some PIC micro controller implement is necessary. Any recommendations ? More on this later.

                    When do fly BTW?. I am 'on-off-loner'. I fly, when the mood takes me, early mornings in Old Holland Road and Woodsland (since banned). Please know if I can be of any help to you.

                    Sirod.

                    Comment


                      #11
                      Hi Sirod,

                      what combo do u recommend then and how to choose the best combo? hahas.

                      Anyway, could it be due to the transmitter/gyro combination also? heard that the transmitter got its own signal frequencies also. i'm using the futaba 7c transmitter.

                      Thanks

                      beanlee999

                      Comment


                        #12
                        BL,

                        The difference between your tricopter and mine is I used the TowerPro 2410-9 outrunner and the ‘Simplest’ 18 A ESC combo from the well know mail order house near Singapore.

                        As far as I know, there are not much issues between the make/model/frequencies used of transmitters and gyros.

                        Having you checked with your original build information source about the suitability of the Tahmazo Motor/ESC combo with 401B gyro ?

                        Why don’t you make another go at finding out why your Tricopter flipped to one side whenever go on throttle up. Perhaps, as pointed out earlier, you need to carefully calibrate the ESCs. What about the Gyros gain setting? Are they on HH or rate mode.
                        Sometime we overlook even simple things like prop direction and rotation.

                        Try to get the tricopter on a stable level hover first.
                        You could concern yourself with countering rotational torque (yaw) later. From experience, controlling yaw is the least of the problems. In fact, even with all 3 rotors turning in same direction, the tricopter could still fly, with a slight tilt. If set up correctly, the tilting tail rotor offers similar counter torque as in helicopter with a single main rotor.

                        ‘I sense impatience, grasshopper, sometimes it is the journey and not the destination that is important’ (sic). Sorry about this philosophy shit,, my point is why are you in a hurry to get to the end product?. Do not be hasty in abandoning your original setup and investment. Make it a learning experience.


                        Sirod

                        Comment


                          #13
                          I'm a tricopter flyer too.

                          Yes like Sirod said, its probably the HH vs rate mode that's screwing up your tricopter.

                          Leave the CCPM mix alone.

                          And as for the CCW/CW, you can put whichever prop anywhere it doesn't matter.
                          Mine are all CCW, it only means the tricopter tilts more in a hover.

                          Comment


                            #14
                            The fact that you used three similar motors and escs, the rpms should not differ much. Its definitely the HH vs rate mode problem.

                            Comment


                              #15
                              Beanlee,

                              I relooked you pics,. Judging by each gyro’s slightly larger base, laying on their sides, I think your front gyros orientation are reversed. You should, viewing from the top, rotate them (theta) 180 degrees. The tail gyro orientation is correct. Unless, your 401Bs have reverse switch (mine do not ) the gyros should be orientated towards each other in a ring fashion – daisy cup.

                              You could do a ‘flip’ test to check if the gyros are orientated correctly. Throttle up, slowly with one propped arm at a time please, at partial throttle position when sufficient speed is reached, tilt the propped arm down, you should sense an increase in motor speed and fighting back to keep it up on the down stroke. Conversely, on the up stroke, the motor speed would slowed down.

                              As suggested by Etman and I, check again if your gyros are at rate mode.

                              Caution, if you have to do this at home, when the gyro is set too high, it could flip back onto your face, - wear eye/face protection if you can. Don’t ask me how I know.

                              Now enjoy..

                              Sirod.

                              Comment

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