"Wag" on AP ship. to much payload?

[petter268]

I use stock motor, stock ESC and stock servos and gyro on my T-rex 600 ESP with PS1 2XPT mount. For me, it looks like the tail servo and gyro cant hold the tail because its to much payload to hold on to. If you understand me right. Is the stock Align servo and gyro to "bad" for this payload?

[PhotoShip One]

With a heavy payload you will require more collective pitch on the main blades. More pitch = greater torque. Greater torque = greater anti-torque and as such will require more authority from the tail rotor.

Two ways around this are

1) increase tail rotor speed

2) increase tail rotor diameter

option 1 is not always available and is dependent on the helicopter design. Some helicopters allow for a speedup tail gear/pulley. Some do not

option 2 is easily handled by any helicopter provided there is enough clearance from the main blades.

I would say for a quick fix, try some 10mm longer tail blades if you have proper clearance from the main blades.

[petter268]

so you suggest I try some T-rex 700E tail blades?

[denizcan]

what do you mean by "hold"? I tested 5 kg payload and the tail was holding.. if we are talking about wag, welcome to Align's world that is full of surprises..

[petter268]

Its not wag when I have the mount and payload off. Atleast not as I have noticed. I looks like the tail cant handle the extra payload. Because after a turn, it can start wagging. Because now the tail need to hold the heli + the payload.

[OneSkidShort]

I had pretty much the same thing happen on my Logo. Changed the tail blades to slightly bigger and all problems were solved. Less work for tail blades, smoother the operation.

[petter268]

What tail rotor do you recommend?

105 mm?

[OneSkidShort]

I'm using 105's

[onlocation]

Are you using the align 780 gyro?

Do you have another gyro you can test before you buy new tail blades? We really like the Spartan Quark.

[petter268]

Hmm, I dont have another gyro. I will try to get 105 mm blades

[daruq7]

Would multi blade tail rotor help? Would that work the same way as increasing the diameter?

[SteamEngine]

If you are flying in governor mode you might have a slightly excitable governor if you have too high a rate of rpm tracking (throttle response speed). Test this by reverting to end point mode (not governor) and see if your wag goes away. If it does, either fly that way or adjust your governor setting to standard or medium response speed.

The fact that the tail wags is proof that the tail rotor has enough authority. You do not need to change the rotor diameter. Its a conflict between the response of the tail servo and the governor speed servo. You have to intervene in that conflict to stop the wag. I assume you have tried reducing the tail gain already. Have a go at the governor.

[hareedy]

i have the ps1 2xpt mounted on my logo 600 3d with the 95 mm tail blades
i had all sorts of vibration u might think of
it all went away when i used 600 size semi symmetrical blades and there was no wag using the 550d
but when i used my 5d markII i started getting slow wags
so i stretched the logo in to 600 se and i used 700 size blades and a 105 mm tail blades and then the slow tail wags started appearing again after a few tweaks on the vbar settings i managed to get less wag but still it aint good enough to take descent aerial video shot
i am still working on it
i will try the 115 mm tail blades and c whats gonna happen
i will update you
good luck
one more thing try to keep the camera mount and battery as close as possible to the main shaft
cheers
Zidan

[SteamEngine]

The helicopter is a resonant system when something vibrates and oscillations and wags appear. Any resonant system can be disturbed by altering something mechanical. What usually happens is the the resonant frequency changes. If the new resonant frequency is not excited by the operating head speed or whatever, the bobbles or wags subside. That's OK and a perfectly practical way of getting rid of them. However, the servos are active devices that inject energy into the system and also introduce phase lags. All helicopters have a head speed regulation system of some kind, whether running in 'governor' mode or not. The tail gyro and the head speed controller interact with each other. Mainly the HS affects the tail control as opposed to the other way round.

In control theory terms if the system gain is more than 1 and there is a phase shift of 180 degrees in the controller/s, the system must oscillate; i.e. bob or wag. It is difficult to express the gain and phase shift in our model helicopters in classic control theory terms but it leads to an understanding of what might work and what probably wont. With governors we don't have any information as to weather they hunt or have a serious phase shift but if there is a conflict that results in wag it is probably more effective to try and attack the set-up of the ESC /governor and the tail servo than to mechanically rearrange the mechanics of the helicopter. That is why I suggest altering the gain of the ESC, flying in direct mode, and reducing the gain of the tail servo.

We talk a lot about tail servo gain. We don't talk much about ESC set-up except how that might avoid the ESC from catching fire. I am waiting for Castle to come back with some input about their ESCs and the potential for them to hunt if set up aggressively. They have already said that their observation is that many are set up by users with a macho attitude and with too much gain and get the wags.