Tail Blade Pitch Question

[Rhumba555]

I have an HDX300 that I am building (still) and am in the final testing and adjustment phase and I have a question.

I watched the Finless videos and don't recall seeing this. Since the main rotor is spinning and causing the tail to spin opposite, don't we want to have the tail pitch slightly offset to counteract the main rotor torque even when the heli is just sitting on the ground. I hope I'm explaining this right. Here's an example:

If the tail blade pitch is set to zero (middle of the tail pitch slider travel) and I spin up the rotor, the tail pitch has to adjust just to hold the tail still, which means that it has already used some of it's travel to hold the tail, then when more main rotor speed/pitch is applied, the tail blade pitch adjusts again to counteract the new torque effect using even more travel. Am I right? In other words, when the heli is in a stable hover, the tail pitch is not at zero, is it? Is this why pirouettes are faster in one direction than the other? Please help me out here as I've ordered the CNC tail system for my heli to replace the plastic POS that I thought I could get away with but it broke, and I need to know how to set-up the tail pitch when the heli is at rest. Thanks guys and sorry for the long post.

[PaulW]

Hi, You are right but in modern radio / helicopter combinations the Gyro takes care of compensating for the Torque of the main rotor.
Heading lock gyros log the neutral position of the servo during the first few seconds after switch on and use this position to maintain the position of the helicopter in yaw. Most computer radio transmitters have a rotation feature which allows tail pitch to increase as the throttle/collective is increased and I can't say for other gyros but My gyro specificaly states that this feature should be turned off when using the gyro

[Rhumba555]

Ok, but I'm curious about the setup. Do I set the blades at zero pitch at servo neutral or do I offset them a few degrees to help maintain the travel volume on both sides of center?

Thanks again.

[PaulW]

Piccy's in my T-Rex 600 manual show the slider beig positioned in the middle of its travel range when the servo is at neutral . On my Walkera the tail is showing zero pitch at this point (haven't put the tail rotor assembly on the T-Rex so don't know what, if any the pitch will be on the tail blades)

[pchavis]

Just came across this and you may already found the answer but I was told you need about 3 degrees when setting the heli up. But Im a newbie.

[Pinecone]

With a heading hold gyro you want to make sure you have maximum travel available. Since the lower end gyros only have one limit setting you set the tail pitch slider in the center of travel and don't worry aobut the tail pitch.

With a higher end gyro with separate left and right limit adjustment, you could set the tail pitch for neutral to be the hover point, but with a good headinghold gyro, there is really no point in doing so. The gyro will set the tail where it needs to be.

[BarracudaHockey]

The answer is......................(insert drum roll)...............it depends!

"Proper" setup is where the tail servo is 90 degrees to the linkage when the tail blades are correct for a hover, usually 3 or 4 degrees pitch. This makes the gyro not work as hard and allows the use of the natural positve expo (futaba speak) around center of a round servo output to its advantage. To achieve this you hover the helicopter in rate mode and adjust the linkage for no drift then set the limit of the gyro for no binding in either direction. Yes this will sacrafice some throw in one direction. No it wont matter because the side with more throw needs it because its fighting torque and the side with less throw is just letting torque take over and do its thing.

Now....in the real world life isn't always perfect and the fact is that most small electrics dont have sufficent throw or good control system geometry design in the tail to cope with asymetric pitch throw and a gyro that can't set individual end points. The solution is a compromise and involves setting the tail pitch slider in the middle of its throw while the servo arm is 90 degrees to the rod, with the most limit you can get on the gyro and this usually means 0 degrees pitch, and letting heading hold do its thing. The disadvantage is rate mode is a thing of the past and the gyro/servo are working harder but for the smaller electrics its the best we can do.