2-servo elevator
08-15-2002 | 04:25 PM
#1
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2-servo elevator
Is it possilble to adjust 2 servos enough to gain an elevator control that you cannot detect deflection differences in the air?
Here is the gist of my challenge:
I'm setting up a Cap with dual elevator servos. I connected one to channel 2 and the other to channel 7. I am using a Futaba 9C TX, a Hitec Supreme 8-channel RX, and dual HS-425s.
The 2 servos are mounted in the fuselage on either side of the rudder servo and the control arms point to the fuselage sides. Clearance between them and the rudder servo would make changing their directions very difficult and because of this I'm virtually forced to mix the channels instead of y-connecting them. This of course means that when I set the MIX up between elevator and channel 7 I have to reverse the direction of channel 7 in relationship to the elevator channel.
I've done this and my problem is I'm getting a significant difference between the 2 elevator deflections (difference will definetely effect the trim of the airplane). The push rods cross each other in the fuselage, they are of a nyrod design with a carbon arrow shaft as the sleeve -- virtually no side flexing, and they are virtually identical in size. Right now I'm attributing the deflection difference to the servo deflections.
Here's the rub: Neutral for both servos are not currently 90 degrees to the servo case. They actually point slightly aft of 90 degrees to the case. If I was to modify the clevis' so that they both are exactly 90 degrees to the case will I elliminate the deflection difference or is the difference due to one servo going in one direction and the other going in the reverse?
Is there anything I can do with the 9C programming that would help to even out the deflection of these 2 servos? They aren't digital so I know I can't program their deadpans. Can I expect the servos to be close enough in deflection angles and rates to be able to just adjust the center points? Will the HS-425s hold their centers well enough?
I'm asking these questions but am not standing still -- I will be modifying the clevises to make them both 90 degrees to the servo case. I will also refine the adjustment to get as close as I can to neutral on both servos without using the subtrims. Since I also own the Hitec servo programmer I will verify that the pulse widths between channel 2 and 7 are the same. Unfortunately, since these are analog servos I won't be able to adjust their deadpan.
If I was able to y-connect these servos (one would have to be electrically reversed) would I gain an advantage over PMIXING 2 channels?
I have 4 brand new JR 537s. Someone with experience with both the JR 537s and the Hitec 425s please tell me if the JRs are more precise.
Here is the gist of my challenge:
I'm setting up a Cap with dual elevator servos. I connected one to channel 2 and the other to channel 7. I am using a Futaba 9C TX, a Hitec Supreme 8-channel RX, and dual HS-425s.
The 2 servos are mounted in the fuselage on either side of the rudder servo and the control arms point to the fuselage sides. Clearance between them and the rudder servo would make changing their directions very difficult and because of this I'm virtually forced to mix the channels instead of y-connecting them. This of course means that when I set the MIX up between elevator and channel 7 I have to reverse the direction of channel 7 in relationship to the elevator channel.
I've done this and my problem is I'm getting a significant difference between the 2 elevator deflections (difference will definetely effect the trim of the airplane). The push rods cross each other in the fuselage, they are of a nyrod design with a carbon arrow shaft as the sleeve -- virtually no side flexing, and they are virtually identical in size. Right now I'm attributing the deflection difference to the servo deflections.
Here's the rub: Neutral for both servos are not currently 90 degrees to the servo case. They actually point slightly aft of 90 degrees to the case. If I was to modify the clevis' so that they both are exactly 90 degrees to the case will I elliminate the deflection difference or is the difference due to one servo going in one direction and the other going in the reverse?
Is there anything I can do with the 9C programming that would help to even out the deflection of these 2 servos? They aren't digital so I know I can't program their deadpans. Can I expect the servos to be close enough in deflection angles and rates to be able to just adjust the center points? Will the HS-425s hold their centers well enough?
I'm asking these questions but am not standing still -- I will be modifying the clevises to make them both 90 degrees to the servo case. I will also refine the adjustment to get as close as I can to neutral on both servos without using the subtrims. Since I also own the Hitec servo programmer I will verify that the pulse widths between channel 2 and 7 are the same. Unfortunately, since these are analog servos I won't be able to adjust their deadpan.
If I was able to y-connect these servos (one would have to be electrically reversed) would I gain an advantage over PMIXING 2 channels?
I have 4 brand new JR 537s. Someone with experience with both the JR 537s and the Hitec 425s please tell me if the JRs are more precise.
08-15-2002 | 09:19 PM
#2
2-servo elevator
On my 9Z and before that 8U Txs, I used the Ailevator function to do what you are trying to do.. I think they go on 2 & 5. Once I got over the all the features of Ailevator and turned off the elevator/flap mixing, it works like a charm. On my 9Z I can adjust each surface for neutral and travel - I think the 8U did the same - I would assume the 9C can do it just as well. Give it a try and you won't have to try to figure out all the stuff you are trying to figure out on your own.
Dan
Dan
