front swash goes down when increasing pitch

[ch53e]

ok, now what am I doing wrong. I am using the stock constants from Joe all the other stick movements move the servo's in the right direction. But when I increase the left stick to increase pitch, the rear goes up and the front goes down. I am using a JR 10X radio, please don't tell me to sell the radio and buy a Futaba.

also, I started a new Social Group for Twinn Rexx tandems. That way we could ask questions and get answers quicker.
John

[Gra55h0pper]

Hi John,

A couple of things to check...
- make sure the gyros are both in rate mode for now
- double (or triple) check the wiring between the Rx and the Tx2, e.g. make sure the pitch input to the TH2 is really connected to the pitch channel on the Rx. See http://www.tech-mp.com/th-2_support.htm and http://www.tech-mp.com/Twinn_Rexx_docs/TR_WD.PDF.
- the Tx should be set to *not* do any CCPM mixing as it's done by the TH2. This means that every cyclic function (aileron, elevator, pitch) only affects *one* channel as transmitted. Most transmitters have a function which displays the channels as transmitted. If you give pitch inputs only *one* channel should change value
- check the values of constants 10 and 18. DCP should be controlled by CH5 through constant 18.
- check constants 11 and 12 also, to make sure the elevator servo is at the programmed at the right position relative to the swash plate (both at 6 o'clock)

Doublecheck that all other functions are indeed OK:
- right/left aileron needs to cause both swashes to tilt to the right/left
- up/down elevator needs to cause both swashes to tilt forward/aft and the front one up/down and the rear one down/up (just a little bit)
- right/left rudder needs to cause the front swash to tilt right/left and the rear swash left/right

Let us know what you find out.

[Gra55h0pper]

BTW: no need to buy a Futaba... :D

[ch53e]

Since I didn't have a speed control at the time, I miss counted the slots in my rx. I had the black wire in the 5th slot ( actually the 6th, pitch) and had the yellow in the 4th (actually the 5th, gear). Now that they are in the correct slots, the swashes are moving properly.

I checked the gyro's and they are moving the swashes properly when I move the model.

I've been flying heli's successfully for 13 years. Had a Cricket back in 82 and couldn't hover it to save my life. I teach setup, check over machines, test fly and teach flying at my field. I wish one of you were within a day's drive to check over what I'm doing. I guess you all are helping me .. just long distance.

I really appreciate all your help.

John

[ch53e]

Glad to be able to keep my JR :thumbup:

I figured that would have been the first response from a Futaba user.:)

Thanks again

John

[v22chap]

I find that something new and really radically different always flusters even the best pilots ... and tandems are all of that ...but I find that read and re read the instructions and double ,triple check all connections usually will take care of most problems ... but it is nice to be able to pick from us guys that have done the same thing already .....
I must confess that I hooked up the 401 to the yaw axis to do an experiment and ended up changing things around enough to get the Ch 5 into the elevator on the RX and the elevator into the ch5 gyro .. thus the gyro was augmenting the elevator not the DCP ... it flew ..but was really pitchy in forward flight:arggg:
Stuff happens ...and especially if you have more than 2 or 3 birds to try and remember everything on. :hug:

[Gra55h0pper]

Stuff happens ...and especially if you have more than 2 or 3 birds to try and remember everything on. :hug:

I agree! Did you know the Twinn-Rexx will actually hover (well, sort of) with the front blades mounted upside down? Please don't ask how I know... :oops: :D

[Gra55h0pper]

John -

Cool!!! Sounds like it won't be long before another Twinn-Rexx will take to the skies! :D
Take your time on the mechanical setup though. Although it's not necessarily difficult, I found it pays off to spend more time on it as compared to a single rotor heli, on a twin you cannot apply Tx subtrim for each rotor individually. See Joe's manual and my tips on:
http://www.helifreak.com/showpost.php?p=519054&postcount=13

D'ya have any pics of your progress? Will you be installing a fuselage?

-H0pper

[ch53e]

I'm still attaching components and cleaning up wiring. Then I'll completely go thru the mechanics and programming to make sure everything is where it should be. The ESC is connected and programmed and the heads spin. This is going to be fun. I am going to get a fuselage for it and I too want to paint a civilian scheme. I'm going for the British Airways transport look.

Here are a few pictures. I have more in my album or you can see them in the Twinn Rexx Group I started.