CCPM interaction on XP7202
10-26-2007, 01:58 PM
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CCPM interaction on XP7202
Hi Danny
I'm setting up a 3-servo 120 degree CCPM system on my 7202. I made it work and all the links are at 90 degrees, the servo arms centered, and the swashplate is level with the collective at 50% travel. I had to use a little subtrim on pitch, aileron and more on Aux1 and make some minor pushrod adjustments to get the servo arms and swash perfectly level. Using the end points for the individual channels, I also have the swash perfectly level at 0% and 100% collective travel.
The problem is at the 25% and 75% positions aprox. There is some interaction at these points and I can't figure out how to get rid of it. I can lower the collective all the way and slowly raise and see the swash start out level, then tilt a little, after that level out at 50%, then tilt a little, then level out again at 100%.
How do I adjust those in-between points? I tried using the programmable mixing, but I can't isolate just those channels. To explain, the two rear servos are on the the AILERON and AUX 1 (Pitch) channels. The swash tilts a little to the right, so I don´t know if any mix (I have in use two) could fix the problem.
I ´ve used 3 4721 servos on swashplate. Then I replaced the servos for 3 new DS8231.
But he problem is the same.
Any suggestions on how to fix this?
Gabriel
I'm setting up a 3-servo 120 degree CCPM system on my 7202. I made it work and all the links are at 90 degrees, the servo arms centered, and the swashplate is level with the collective at 50% travel. I had to use a little subtrim on pitch, aileron and more on Aux1 and make some minor pushrod adjustments to get the servo arms and swash perfectly level. Using the end points for the individual channels, I also have the swash perfectly level at 0% and 100% collective travel.
The problem is at the 25% and 75% positions aprox. There is some interaction at these points and I can't figure out how to get rid of it. I can lower the collective all the way and slowly raise and see the swash start out level, then tilt a little, after that level out at 50%, then tilt a little, then level out again at 100%.
How do I adjust those in-between points? I tried using the programmable mixing, but I can't isolate just those channels. To explain, the two rear servos are on the the AILERON and AUX 1 (Pitch) channels. The swash tilts a little to the right, so I don´t know if any mix (I have in use two) could fix the problem.
I ´ve used 3 4721 servos on swashplate. Then I replaced the servos for 3 new DS8231.
But he problem is the same.
Any suggestions on how to fix this?
Gabriel
10-29-2007, 09:08 AM
#2
RE: CCPM interaction on XP7202
It is likely a combination of differences in servos and the differences in sub trim. Idealy sub trim should be zero. Try to find a servo arm that will center at 90 degrees without the use of sub trim (arms will be different from arm to arm, and if you use a full servo arm, try turning the arm 180 degrees.) If the geometry is different between the servos, there are slight servo differences etc, it can cause what you are seeing.
