Bozwth

My Feedback: (3)

Is it preferable to operate twin elevator servos with separate channels or a single channel? I had them hooked up with a y harness at first and then changed it over to separate channels because I thought it would be a better way to go, but they seemed to have actuated more in unison when they were operated with the single channel. What is the preferred way to go?

Bozwth

rjmdubois

I try to avoid Y cables. All the current to both servos passes trough one single connector, increasing voltage drop - more critical if you are using high performance servos. Also you loose some advantages of the computer radio, like subtrims or end-points adjustments.

That's just my opinion

Highflight

My Feedback: (4)

It's always better to have each half on it's own channel, HOWEVER, for that to be an advantage, you have to have a radio that will allow you the fine tuned control of each channel and servo.
For example, you can have a situation where the two different servos aren't exactly centered or not exactly synced correctly. In that case, you'd want to calibrate them together with something like the servo calibrator device from Hitec, or better yet, use a transmitter that offers servo calibration features within it like the MPX EVO (in it, you can adjust servos using 5-point curves, center, and end points).
If you're using a basic radio without any calibration capabilities, then a Y-harness might be the best way to go if you work real hard getting the mechanical linkages right to get the servos working together.
Then there's always that little doohickey that connects between your RX and the twin servos that also allows some adjustment, but if you're going to spend the extra money anyway, I'd say you're better off putting that money into a more capable radio.

Highflight

Bozwth

My Feedback: (3)

I just upgraded to the Futaba 9CAP transmitter and am using Hitec HS-5645 digitals. I guess I need to get ahold of a Hitec programmer. Unless my new transmitter will do the job.

Bozwth

Highflight

My Feedback: (4)

I don't believe the 9C has the capability to adjust two servos together while the 9Z does.

You'll probably be happier getting something like this http://www.futaba-rc.com/radioaccys/futm4155.html because you get instant, observable response with how the servos are adjusted.

Highflight

Henry_90lx

With the 9C you just need to set the sub trim for each servo so that they are both centered then go in to the end points and make it so each servo stops in the same place.

I like the benifit of two elevator servos because you can use them as elevons. My Ultra stick uses dual elevator servos and with the flaps coupled to the rons and elevons it rolls like mad.

Henry

smokingcrater

the 9c CAN do dual elevators without messing with the subtrims for each. Just set up a mix that does aux to elevator, and then make sure trim and link are both active. I have two planes that use dual elevator, I also mix the elevators into aileron roll.

Henry_90lx

Yes that is true, I was just mentioning the sub trims because every now and then I hook up a servo that just wont center quite right and I have found that a quick couple of clicks in the sub trim menu fixes all

Henry

hilleyja

My Feedback: (3)

To get the elevator travels as close as you can without a Hitec Programmer, 1st manually set up each control surface so that your TX Subtrims for both channels are as close as possible to ZERO. You can then set each servo to the same extends and be almost assured they are fairly synchronized. Then just setup the 9C TX for AILEVATOR and set the airlons to 0%. I do find that synchronization starts to fall off when you get to the maximum throws.

Bozwth

My Feedback: (3)

Thats what I've done so far. I'll try to get my hands on a Hitec Programmer to get the synchronization better.

mulligan

You should be aware that using separate channels means one servo (the slave) will lag the other (the master) by a quite small fraction of time. If response time is very important, then use a "Y." Voltage drop may be an issue, but of course just as in the case you use many servos, you might consider using a separate battery for your servos anyway. If response time is not an issue (and the lag won't be noticable unless you're performing aerobatics at a very high level), then the flexibility of two channles is nice, as you can trim them separately electronically, etc.

Henry_90lx

I would think that you would not be able to notice the lag unless you had it hooked up to some kind of test equipment. With the speed that microprocessors send information both servos would receive the movement information almost simultaneously.

hilleyja

My Feedback: (3)

The lag you are referring to would be negligible to the point of being virtually undetectable. Each control signal is in the micro second range, i.e., one servo gets the signal a few micro seconds after the other -- you'll need an expensive oscilliscope to show the lag. That wisp of cross wind at .25 mph would be a hurricane compared to the effect a micro-second lag would have.

What you didn't point out is that if you went with a 'Y' you would have to reverse one of the servos, potentially adding some lag to the servo response in its own right. If you tried to reverse it manually with your linkage you will have a difficult time matching the opposite servo's geometry, again a potential lag.

mulligan

Yeah, the servo reversing requirement with a "Y" has already been mentioned. In my case, I reverse the servo within the servo (chaning motor and pot leads), so there is no delay. If you use a reversing circuit between the receiver and the servo, then you would be adding a delay.

In any case, you are right to empasize what I said earlier- the delay will be very, very small.