Gregor99
Elite Veteran
Location: Western Wa
| Don't say just get a Trex!
Loved that comment. Ya know if post this in the Trex forum they's say "should have got a futaba gyro"
Anyway, to answer the question, I've had a bad case of the bounce on my HBK2 a number of times. In my rearch and study of the state of my tail I found a few contributors.
Slop in the linkage - Disconnect the tail linkage at the servo or the slider arm. First move it throughout the range to make sure its smooth. Next hold the tail blades, then push and pull on the arm. In my case I found the pivot screw for the linkage arm backed out a tiny bit. But just enough to cause add a little slop to the slider movement. Also, if any roughness or lack of smoothness was found find and address that as well.
Servo response/mechanical abilities slower than gyro response - From Spartan help page
http://www.spartan-rc.com/support.php item 11
| Quote |
| Let's imagine a car driving at high speed when suddenly the driver needs to do an emergency stop. From the moment such decision is made until the car has come to a stop, the car has continued to travel due to the reaction time required to hit the break and the time required for the car to decelerate. A similar effect happens to a helicopter that yaws fast when suddenly the pilot returns the rudder stick to neutral, thus command the gyro to stop the helicopter. Time is required for the servo to respond as well as to decelerate the tail. Depending on the servo speed and the mechanical capabilities of the heli the combined deceleration distance may vary from a few centimeters which is hardly perceivable by the human eye to several centimetres. However, unlike the car example, the gyro remembers where the tail was the moment that the stick was returned to neutral. Thus as soon as the helicopter stops the gyro will continue driving back to that point. This appears as a bouncy stop. Bouncy stops can very easily be fixed using the Deceleration Profile adjustment via the PC, PDA or detachable LCD. Effectively, this adjustment tells the ds760 how rapidly to decelerate the tail with the aim of keeping this task within the mechanical capabilities of your helicopter. You also also adjust the CW/CCW stop gains which control the responsiveness of the gyro during stops.
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Servo arm offsetting From CSM (an uncommon gyro)
| Quote |
| Some helicopter tail linkage geometries give somewhat asymmetric response to tail pushrod movement with much more rapid changes in pitch occurring one way than the other. In these cases the servo throw to cover the full pitch range may be greater one way than the other. The SL720 has independent travel adjustments for the two directions to accommodate these differences. In some machines more symmetrical handling characteristics may be obtained if the servo arm is rotated around one or even two splines on the servo shaft so that it is no longer at right angles to the pushrod when the servo is centred. A change in the pushrod length will be needed to restore the 8 degrees of pitch with the servo centred. With the servo arm offset in the correct direction the servo throws will be more equal. Remember that the travel limits will need re-adjusting after this process to ensure the full tail pitch range is available.
Adjusting the Stop quality
At the initial installation you will have made sure that the servo travel limits are set so the tail pitch each way is limited only by the mechanical limits of the linkage. You will also have carried out the Quick-trim procedure and adjusted the gyro gain to the maximum that gives no wagging. Now assess the quality of the left and right stops from fast pirouettes (i.e. full stick). Note if the stops are sharp enough for your flying style and see if there is a marked difference between the two stops noting which stop is the softer. If you are trying to obtain fast stops you will find, beyond a certain point, that increasing the gyro gain has only a marginal effect on stop speed. This is because the available tail rotor authority dominates stop times from fast pirouettes. If, having optimised the gain, the stops are softer than you require you will need to increase the power of the tail rotor. Since you will already be using the maximum pitch range available increase in the tail blade length should be made. A small increase in tail blade length can make a large increase in the available thrust of the tail rotor. Longer tail blades increase the mechanical gain of the tail system so an adjustment to the gyro gain may be needed.
In many cases only one of the stops is soft. Check that the mode 0 trim is acceptable and repeat Quick-trim if needed before re-assessing the difference between the stops. A lack of tail-rotor pitch one way (usually in the leftward direction) is quite common. This shows up in slower entry into left pirouettes and slower stops from right pirouettes and can be especially noticeable with governed engine systems in low G manoeuvres (e.g. stall turns). We find that good tail performance is obtained with 45 degrees of right tail pitch and 35 degrees of left tail pitch. In extreme cases it may be necessary to increase the tail blade length until the soft stop becomes acceptable. Prevent the faster stop becoming excessively hard by a small reduction in the travel adjustment for the appropriate pitch direction.Generally this will be all that is required to obtain matched stops from all speeds. However if stops from more modest speeds of about 180 deg./s show some left-right imbalance then these can be matched by use of the stop tracking controls via the PC interface
The left and right hand stops are not equal. Stops from right hand turns are slow but clean while left hand stops are bouncy.- The mechanical tail trim needs setting correctly. Carry out the procedure in the Quick-trim section of this manual and reassess. If you still have problems, try reducing one servo travel as follows: - if bouncy when stopping left turns, reduce the right pitch travel limit and vice versa.
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Canton MO backyard flying club
West Coast Chapter |
bet they really wondered what I was doing out there holding that remote.
