Non-heading hold Gyro How-to
|In general the gyro goes between the receiver
and the rudder servo. By this I mean the gyro will
connect to channel 4 (or whatever the rudder channel is
on you receiver) and then the rudder servo will connect
to the gyro. I will provide a few examples to help you
figure it out for your gyro: RC Vision 2000 - the plug
labeled 'RX' goes to channel 4 on the receiver and the
rudder servo plugs into the connector on the gyro labeled
'servo', CSM 400 - connect the 'Rud In' to channel 4 and
'Servo' to the rudder servo. Futaba GY401 - connect the
male plug with 3 wires into channel 4 on the receiver and
the female plug to the rudder servo.
Now your gyro will have anywhere from one to three additional connectors. These 'other' connectors are gain, hh select, pc interface. Most of the time you will just have one additional connector. This is used to control the gain and selects heading hold or not. This will be plugged into the receiver. The channel you plug it into will depend on the radio. Most of the time it will be plugged into channel 5 (the gear channel). If your radio has a gyro function in the menu then it is usually connected to channel 5. BTW: There is a misprint in the Futaba 8U Super manual, you do connect to channel 5. Often times JR upper end radios use Aux2, but you will need to look in the manual to find out. If you are not sure just email me the radio you have and I will let you know. For radios without a gyro menu, you still connect to channel 5 then will use the ATV for channel 5 to control the gain.
Note: I mentioned two more 'other' connectors. One you will find on the higher end JR gyros like the 550, 5000, 6000, etc. They decided instead of using one connector to adjust gain and select the mode (heading hold or not), they decided they wanted two. This does give you twice the precision for gain, but do you really need it??? Personnally I don't like using up a spare channel just for this. Plus the radio setup gets more complicated :-(
The second 'other' connector is a PC interface. This is mostly for CSM gyros. It allows you to adjust several internal settings.
Note: If you are connecting a Futaba plug into another brand receiver then in most cases you have to remove the flat 'key' on the side to the plug.
|Mount the Gyro on the back plate behind the main shaft. Use the double sided foam tape that came with the gyro. Some gyros use thick foam and others use thin. It all depends on if the gyro has internal dampening. If you put too much dampening this can cause a resonance problem.|
|Before we continue it helps to understand the characteristics of heading holds gyros. You will notice in non-heading hold mode that your rudder stick only moves the servo for the first 75% to the right and the first 25% or so to the left. The servo does not move when the stick is past these positions. Another thing to remember is that all heading hold gyros have to initailize. Some take up to 9 seconds. Don't move the helicopter during this time. Most gyros will let you know it's finished by moving the servo just a little bit one way then back.|
|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||Disconnect the rudder link from the servo. Turn on the radio and receiver. Wait for the gyro to initialize. It will move the rudder servo a little to let you know it's ready.|
|zero center position||In the radio, set the servo centering to zero (CNT=rd6000, SubTrim=JR radios). Make sure the trims are centered.|
|zero revolution mixing||Find this function in your radio and zero out the up and down (and any other) points. This will cause problems with the way a heading hold gyro works.|
|set limits to 100%||Set the rudder end limits (EPA=rd6000, ATV=JR radios) to 60% both directions|
|dual rates to 100%||Set the Dual rates to 100%|
|set gain||Set the channel you are using for remote gain. If you have a gyro menu then you will set it there, otherwise you have to go to the menu for servo end limits (travel adjust). The concept is to use the end points to not only choose between HH or Normal, but also to adjust the gain in each mode. For example if your end point range is from -100 to +100 then a value of 60 would put the gyro in normal mode with 60% gain. If you set the other side to -60 then it would make the gyro operate in heading hold at 60% gain. If your end point range is from 0% to 100% then a value of 80 would be 60% gain in normal mode and 20 would be 60% gain in HH.|
|set to normal mode||Move the rudder stick to the right, then back to center, if the servo does the same then you are in normal mode. If the servo moves to one direction but does not move back to center then you are in heading hold mode. If your switches are in the right place for normal mode, but the gyro is in heading hold then you can go to the channel reversing menu and change the direction of the channel you use for gyro gain (usually 5).|
|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 channel reverse menu on your radio and change the direction or channel 4.|
|gyro direction||Rotate the helicopter so the nose goes to the left and watch the rudder servo. The servo needs to rotate clockwise. If not, then flip the reverse switch located on the back of the gyro sensor box.|
|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 for the gyro to initialize. It will move the rudder servo a little to let you know it's ready. 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.|
|Hold the tail rotor stick full right and pull the control rod all the way forward. Note: The servo will only move during the first 75% of stick movement. This does not mean something is wrong, this is the way it was designed. Hold the link over the servo arm to see which hole it will align with and install the ball in that hole. Often times around 10mm from the center works the best. You want to use the one that is furthest from center that does not allow the servo to mechanically bind. After you mount the ball, confirm that it does not try to pull the link further than it can mechanically go either right or left. Now you can snap the link on the ball.|
Adjust the rudder link so the helicopter does not rotate at hover.
You want to increase the gain until you see the nose of the helicopter wag (oscillate back and forth), then back off the gain. That will be the highest you can set the gain.
|Gain values for Normal and HH are low.||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 electronic boards inside the sensor box could be vibrating. Use small rubber foam pieces inside to cushion the circuit boards.
4. 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.|