V-Tail as CCPM 120 Mixer

[Super-Hornet]

Recently I got myself 2 pieces of V-Tail mixer. It is from SHS and it is unbranded.

I did a test to see whether is it possible to use for CCPM 120Degree configuration.

Result:
Yes but not really good. By connecting them up with one channel i/p from V-Tail mixer is then cascaded with the o/p of another mixer. You have to try around to get the correct combination to achieve it. The 3 i/p (2 from one mixer and 1 from another mixer) is then connected to Aileron, Elevator and Pitch channels (Lets call them A, E, and P)

The ATV (or End Point) of A, E and P require to tune down to like less than 50% on both end.

The draw back of such cascading configuration is that the timing or servo travel for all channel maybe almost the same. With that, for 120Degre CCPM, the heli will experiencing collective up/down when u do Elevator movement. The problem may be able to solve by tweaking around the ATV for all A, E and P instead. If not, maybe use "programming mix" instead.

The other disadvantage of using such combination is that the V-Tail mixer that I use somehow not compatible to Futaba GY240 gyro. I suspect the GY240 o/p or i/p frequency is either higher or lower than the standard signal from RX.

You can use the above method as a "poor human" (politically correct term) configuration to control CCPM 120Degre heli.

For CCPM 90Degree heli, it may work better.

(Sorry! No picture to show the connection)

SHornet

[pilot_bear]

interesting, have some questions.

1. why do you need 2 vtail to control a 120 ccpm ?
assuming that vtail is used for the roll effect, 1 ch can be use for the pitch (fwd/backward)

2. how do you control the pitch of the blade ?
because according to the vtail function, if one servo goes up , the other down.

[Super-Hornet]

1. why do you need 2 vtail to control a 120 ccpm ?

Why need 2 V-Tail? Well, Total of cyclic servo for 120D is 3. The o/p of 1 V-Tail is 2. In CCPM, at any point of time, minimum of 2 servos move at the same time and according what cyclic and collective u apply, normally 2 servos move at opposite at each other. When doing aileron, 2 servo move in opposite each other but when in elevator movement, that 2 servos move in the same direction but the 3rd servo move in opposite of the 2 servos. Then when u apply collective (which is pitch), all 3 servos move in the same direction. Using 1 V-Tail only, I don't think u can achieve it.

2. how do you control the pitch of the blade ?

Same as the above explaination. That is why u cascade 2 V-Tail so u can
have 3 i/p signal. The 3rd i/p signal is use for pitch.


SHornet

[Super-Hornet]

Here is the picture that I drawn for the CCPM mixer.

[pilot_bear]

oic, thanks for the explanation, with the diagram, its easiler to understand now.