oldfart
Elite Veteran
Location: Vancouver, Canada
My Posts This: Topic Forum | Tail rotor responseHi Payton,
The MYTH of not having enough T/R throw in ANY helicopter to perform a fast piro in either direction is one that I often have to debunk (demonstrate) at fun flys that I attend.....even to some very experienced pilots who have never flown a heli without a gyro.
If you are not getting the tail rotor yaw rate (in any direction) from any heli on the market today it will not be a result of the T/R design but rather the Servo/Gyro/TX set up.
Proof would be to fly any heli (I have done this on most models n the market today) without a gyro and you will find that it will piro in both directions fast enough to scare the $hit out of most flyers!!!
The piro rate is directly related to what is put between this natural piro rate and what you have now....the gyro stabalizing system. The phenomenon you are describing is usually a result of a gyro/servo/TX combination that is not optimized.
How to optimize?
a) First plug your servo DIRECTLY into the RX and turn the Radio on insuring there are no mixes or sub trims operating and that the Rudder ATV in ALL conditions are set to 100/100.
b) Now install the servo arm so that it sits 90 degrees to the pushrod, in the middle of its travel. Now when you move the rudder stick from center to full right it should move the arm in as much of an arc as it will from center stick to full left. Now we are sure that the servo will be operating from a linear mechanical setting.
c) Now install the gyro into the circuit. If you are running a HH gyro that does not have "end point" adjustments then you must insure there is no binding at the end of travel (left & right) by attaching the ball joint on the servo arm at a point out from center that will not allow it to bind. (The rudder ATV in heading hold IS NOT an endpoint adjustment with the Gyro in the circuit. This is what many people still believe....and what causes most of the problems.) If you have one that does have end point adjustment, then you can use a longer arm and use the gyro's end point adjustment feature to adjust for no binding at either end of travel.
d) Now go and do the initial tail rotor hover trim of the heli in the yaw rate mode and trim for no yaw by MECHANICALLY adjusting the length of the tail rotor control rod. DO NOT use the TX's rudder trim lever or sub trim as this will later have an adverse effect on the HH trim (it will drift in HH).
e) Now you hover in the HH mode and trim ELECTRONICALLY by using the RX trim lever or sub trim.
f) Now optimize your gain settings (this may initially have to be roughly set during the first hover if the tail wags) in both modes. Increase until the tail starts to wag then back off a few points. If you use a different rotor speed for different modes, then set this for the maximum rotor speed that will be used.
Now try a pirouette in the HH mode moving your stick a bit to the left or right for the first few, increasing the stick movement until you are full left or full right. If you want a slower rate, you can decrease the rudder ATV's, if you want more piro rate you can increase rudder ATV until you have maxed them out (140/140 with Futaba, 150/150 with JR). By then you should be getting a pretty fast piro rate. Of course because this is all set to optimize the piro rate in the HH mode, the rate in the Yaw rate mode will be compromised. Why? Because to optmize the gain in the Yaw rate mode, the gyro will take away max servo movement in the air. To regain it one would have to "overdrive" the servo using a longer arm which on gyros without "end point" adjustments, this cannot be done without causing binding in the HH mode.
So befor you change anything be sure that you have your system set up to optimize it. You may just save yourself some money.
Phil |
Certainly that is a good tip, as is using a punch to get it out.
