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Thread: MPX FOX FPV TWIN BOOM PUSHER

  1. #1
    FPVdicted egosession's Avatar
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    MPX FOX FPV TWIN BOOM PUSHER

    Multiplex FOX FPV Twin Boom Pusher

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    Aircraft: 2 x MPX FOX gliders
    Reinforcement: 6x1mm CFK in wing, 3x1mm CFK + balsa in elevator, 3x1mm in fusalage
    Dimensions: 700mm wingspan, 500mm lenght, ca 220 gramm

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    Motor: Dualsky XM2812CA-27
    Prop: 7 x 3.8
    ESC: Roxxy BL-Control 710
    Batt: 2S 800mAh
    Servos: 3 x 5g
    RC RX: Rex 5 Channel 40mhz

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    FPV
    Cam: RC-TECH TX41
    TX: Included in CAM, 2.4ghz, 10mw
    Antenna: sort of very simpel dipol, not sure though
    RX: Fatshark with Dipol 5dbi and homemade Cloverleaf

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    It flies very nice. I didnt expect that with the weight of over 200gramms. I m sorry that I dont have a video. I m working on that

    I got a problem with the reception of the FPV though. The camera has an attached small 2.4ghz 10mw transmitter with a simpel wire antenna. I did the first FPV flight with my Fatshark RX and a 5dbi rubber ducky or dipol antenna. The reception was very bad in the turns and also 50 meters away. I was flying in a living area in a park. Probably alot of wireless stuff around.

    I did made a cloverleaf antenna for the second flight (thanks for the manual IBcrazy) and the reception got better... with better I mean still a lot of strips in the picture, but enough room between the strips to see where I m flying to. There are also strips when both antenna are straight and more than 15 meters away from each other.

    The plan is to replace the simpel wire antenna on the TX with a Vee, helix or cloverleaf. But I m not sure about the attachement of the ground/reflector. I will post some pics on the next post.


    A other issue I have and I would like to discusse with you is the trailing edge of the wing and rudder. On the MPX FOX they are really big for a TE. The reson why they are that big could be that they are less critical on damages or because to introduce some drag to prevent it to get to fast. Because the MPX FOX is a non rc glider and is made for throwing around.

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    The big question is now: should I trimm them to get a nice smooth airflow. Or shold I leave it, because it flies okey. But will it fly even better with trimmed TE? I know, its not a big deal, but I m intrested in your opinion.
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  2. #2
    FPVdicted egosession's Avatar
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    Antenna

    This is the RX which is glued on the back of the camera. You see on the back on the curcuit board a sort of metal housing. I m not sure if that housing is made only to attache the stepdown thing or if its the reflector for the simpel wire antenna.

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    I m really not exactly sure about how the antenna works without a ground wire? Because I would like to solder a Vee or a cloverleaf antenna on. If that housing is a reflector/groundwire do I have to remove it?

    A other Antenna I would like to test is this one:

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    This is a 0dbi helix, from here. I got one, but with the wrong sma connector. I dont want to destroy it and would like to build one. But I couldnt find a some information about sutch a small helix antenna. If someone knows the diameter that would be perfect!

    Here are some pictures of my homemade cloverleaf antenna:

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    Last edited by egosession; 18th June 2011 at 10:45 PM.
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  3. #3
    I Like Waffles... SENTRY's Avatar
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    VERY creative. I like to choose planes that aren't popular or are different. KUDOS!! Any details on the 5dbi antenna you use on your FS gogs?
    "I Like Waffles" : FPVLab on Facebook and FPVLab on Twitter

  4. #4
    FPVdicted egosession's Avatar
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    Its a simpel dipol antenna. Looks exactly like a normal 3dbi dipol antenna. It just has 5 dbi. This antenna was in the set with the FS gogs.
    Last edited by egosession; 18th June 2011 at 10:52 PM.
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  5. #5
    FPVdicted egosession's Avatar
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    Open Helix antenna

    Yesterday I could open the cap of my 0dbi Helix antenna:

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    Now I can rebuild it. But I m not sure where the ground goes... or just leave that out?

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    After I couldnt get a answer about the simpel wire antenna on my little camera (see pics above) I decided to solder a dipol on it. Today I will go and fly again at the same spot. I will see if it helps. And I will take my external RX with me, to see if the fatshark RX is weak against ext. rx's. Also the cp 8dbi patch (factory made) will be involved.

    Here the pic of the dipol on my little cam:

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    FPV killed my bank account

  6. #6
    Very cool Fox!
    I may have to copy that.

    Your question....

    The big question is now: should I trimm them to get a nice smooth airflow. Or shold I leave it, because it flies okey. But will it fly even better with trimmed TE? I know, its not a big deal, but I m intrested in your opinion.
    You may see a very *slight* improvement from trimming the trailing edges. It should reduce drag a tiny bit if you trim it.
    In Russia you don't fly plane.... Plane flys you

  7. #7
    FPVdicted egosession's Avatar
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    Thanks! Its really a good flyer. I was yesterday on the field and it flew perfect. And I had a lot of crashes, it survives a lot of beating. I had to take it out of trees (10 meters high), without damage. I guess it helps that the booms and the elevator are just pushed together without glue. It can move and absorb the crashenergie.

    I finally found the solution for the bad transmission... I had the wrong RX. I had to take the same RX that was coming with the cam/TX. I thought it just needs the same frequenzy, but sometimes it needs the right RX. With the right RX, I had wonderfull flights. Low, fast, alot of fun.
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  8. #8
    Engineer for Jesus Christ IBCrazy's Avatar
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    Sweet plane! Gotta love the dual boom pushers and your's is incredible! Ditch that helical antenna, though. It will only cause frustration. It's not a circularly polarized antenna. It's actually a linear antenna.

    -Alex
    If it is broken, fix it. if it isn't broken, I'll soon fix that.

    videoaerialsystems.com - Performance video piloting

  9. #9
    Where do you have the C/G balance point?

    Thanks!
    In Russia you don't fly plane.... Plane flys you

  10. #10
    FPVdicted egosession's Avatar
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    I measured the c/g on the normal uncutted fox, it balanced at 40mm. And in the internet I read about 35 - 40mm c/g on the normal fox.

    The twin boom pusher flies with the c/g at 33mm. I got a 6x1mm CFK flat rod at 30mm, then the servocable running at 33mm to the middle fuselage (You see them on the pics, thats my c/g point). But I got the feeling mine is tailheavy (and still flying good ) So I would go with 35 - 40mm for the first try. Very important is, that the elevator needs uptrimm. about 3mm at the TE.

    An other thing is and hard to see in the pics, my elevator consists out of 4 pieces to get the space between the booms. I got a APC slowfly 7x4.8 on it. So ca 8" between the booms. Its kinda hard to explain with my english... The cutted away right and left pieces are glued at the inner left and right. Aligned the 4 pieces at the LE and trimmed the TE.
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