CSM 400 w/ Futaba 7C
Gyro How-to
last updated 1-2-2006

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  Connect the 'Rud In' plug on the gyro to channel 4 on the receiver. Next run the 'Servo' wire to the plug of the rudder servo. Next run the 'Gain' wire to channel 5 on the receiver.
  Mount the Gyro on the back plate behind the main shaft. Use the mounting tape that comes with the gyro. Apply one strip on the left and one on the right of the bottom of the gyro. Make sure you clean both mounting surfaces so the tape sticks good.
  Before we continue it helps to understand the characteristics of heading hold gyros. They all have to initailize. This one takes about 5 seconds. Don't move the helicopter during the first 5 seconds after you turn it on.
Common misconception of all heading hold gyros Another thing that a lot of people don't understand is that the rudder travel adjust (ATV's / EPA's) does not adjust how far the servo moves. You cannot use this to prevent linkage binding. This adjustment only effects how fast the tail moves (your pirouette rate).
radio setup For this setup we will make switch 'B' to control the gyro mode. To do this you need to get in the menu system by holding the 'Mode' button down for one second. This gets you in the basic menu then press 'Mode' once to get to the advanced menu. Use the jog wheel to get to the 'GYRO' function. Use the down button (by the jog wheel) to get to the second page of gyro options. At the very top set 'GYRO' to 'ON'. Next set 'SW' to 'B' and set the 'MODE' to 'GY'.
Use the up button to get back to the first page and set 'UP' to 'A90'. Set 'DN' to 'N90'.
zero out anything that would effect the rudder In the advanced menu go to 'REVO' and set to 'INH'.
zero center position Go to the 'SUB-TRIM' menu and set 'CH:4 RUD' and 'CH:5 GER' to 0.
Also make sure the trims are centered.
set pirouette speed Go to the 'E. POINT' menu and set 'CH:4'. Hold the rudder stick to the left and set the value to 70%, hold the rudder stick to the right and set it to 80%. This will set how fast the helicopter rotates. You may want it faster or slower so change the value appropiately. Note that the left and right values are different. The helicopter will naturally spin faster to the left due to the direction of torque so to get the rotation rates close to the same you will need to set the right side higher.
  First make sure the 'B' switch (the front switch on the top/left) is flipped up. Next disconnect the rudder link from the servo. Turn on the receiver. Wait 5 seconds for the gyro to initialize. It may or may not initialize correctly depending on where the gyro channel reverse setting is set in the radio. Remember the gyro has to start up in HH (Heading Hold) mode. Continue with the next step to determine if it's in the right mode.
set to start up in HH Move the rudder stick to the right, then back to center, if the rudder servo does the same then you are in normal mode which is wrong. If the servo moves to one direction but does not move back to center then you are in heading hold mode which is right. If you ended up in normal mode then go to the 'REVERSE' menu and change channel 5. Then turn off the receiver and then back on and let the gyro initialize in heading hold mode.
set to normal mode Now that you have the gyro initialized correctly, flip the 'B' switch. This will make the gyro go into standard rate mode.
servo direction Check the servo direction. Move the rudder stick to the right and watch the servo arm. It should move the servo clockwise which thereby should pull the rudder control link forward. This will make the nose of the helicopter rotate to the right. If not, then go to the 'REVERSE' menu and change channel 4.

With the rudder link disconnected from the servo. The first thing to do is make the link slide as free as possible. Adjust the guides to acheive the least resistance. I added a slight bent to the front section of the rod as you can see if you click on the photo to the left. I did this so as to stop the resistance the rod had on the first frame guide due to being pulled down to the servo. I also used a JR Ball link resizing tool to remove unecessary resistance from the ball links. Once you get the link as free from resistance as you can, turn on the radio and receiver. Wait 5 seconds for the gyro to initialize. Set the rudder servo arm so that it points straight up with the rudder stick and rudder trim centered. The best position for tail centering is to adjust the rudder link so that you have 4.5mm between the pitch slider and the tail rotor casing with the collective stick centered up/down and left/right. Check that the front link is centered with the servo arm. If it's not, turn the link clockwise to move it toward the back or counter clockwise to move it forward. Once the center of the ball link matches with the center of the arm and you have the 4.5mm at the tail slider, then you can move to the next step.
Set back to HH Now that you're done with that, you need to flip the 'B' switch back to heading hold mode.
Install the ball on the servo arm Mount the ball on the rudder servo arm so that it is 14mm from the center of the screw that holds the arm to the servo.
CSM400 auto setup mode With the helicopter off, turn it on and before the gyro initializes, toggle the 'B' switch a couple of times. The gyro will verify setup mode by moving the rudder servo back and forth a couple of times before going to center. During this time make sure the rudder trim is centered and you do not move the rudder stick. The gyro is remembering center position at this point. Now to set the gyro reversing you first check that the yellow "REV" LED turns on and off as you move the rudder stick full left and full right. Now move the rudder stick to the left and release it back to the middle. This will set the gyro direction. Toggle the 'B' switch to move to the next step. The gyro will 'zip' the servo back and forth in acknowledgement and again park the servo in the middle. The next step is to set the travel limits. After you just got through toggling the 'B' switch you should have noticed the rudder servo moved all the way to the first travel limit. Use the rudder stick to adjust this position. Toggle the 'B' switch and now set the other side of the travel limit the same way. Toggle the 'B' switch again and you should see the rudder servo move back and forth twice then go to center. The auto setup is now complete. For the setup changes to take effect you have to turn the helicopter off then back on.
Flying adjustments To get the tail to move faster or slower, adjust the rudder channel travel. Go to the 'E. POINT' menu and set 'RUD' left and right. A higher value will make the heli pirouette faster and a lower value will make the tail slower.
If you the tail wags in a hover then decrease the gain. Go to the 'GYRO' menu and decrease the value of the up rate if wagging in HH or down rate if wagging in standard rate mode.
Symptom Cause
Gain values have to be set low to stop any tail wagging. 1. The helicopter is out of balance. Vibration is the cause of low gain settings. Check the blades, check for bent main shaft, spindle shaft, tail shaft, out of balance tail blades, etc.
2. I found that a sticky clutch caused me to have to turn down my gain by 20%. Check the
engine/start shaft alignment and look for a broke shoe.
3. The ball on the rudder servo is too far away from the center.
HH doesn't hold good 1. The RPM's should be 1850 to 1950 for 3D flight. It's also important that your engine is running good. If your engine loads up a lot then you won't be able to keep a consistent RPM. Remember that a few hundred rpm drop on the head is several hundred rpm drop on the tail.