Servo calibration issues
While setting up the flaps on a current warbird project I found that at full flap deployment there was quite a large descrepancy in the flap angles between the two.
I double checked to insure that I was using the same hole in both of the control horns and both servo arms as well as the arms were indexed at the same position with the flaps retracted. Both are identical in the set-up.
This led me to double check the ailerons and I found that, again with symetrical set-ups, both travelled the same to the down side but one travels 1/8" more than the other to the up side.
I am using Futaba 3004 sevos, Specktrum Dx7 system, each servo pair on a single channel with a standard "Y" cord, no reversers, chokes, limiters, slowdowns or other in-line accessories. The trim and subtrim on both channels in question is null and the reversing function is "normal".
Is it common that servos of the same type have such differences in the calibration? Is there a pot that can be adjusted internally to address the calibration? Being analog, I don't think they can be programmed. What, if any, are the options; short of going dual channel and using sub trim(which I don't have the an extra channel for anyway) or using some type of in-line limiter/adjuster, which I really don't care for?
Maybe grab a dozen servos and measure them to try to "match" a couple of pair?
The flaps can be evened out mechanically by using different index positions and different holes on the arm but the ailerons aren't going to be "fixed" that way because it's just the CCW rotation on one servo that is out of wack with the other.
Thanks!