Twin Elevator Servo problem, help.
 

Im having problems with my elevator servos on my u can do. Its been there from the start but as I improve and try to clean up my maneuvers its beginning to get in the way. Maybe this stuff is just the nature of the beast when dealing with 2 elevator servos I dunno, Heres the deal.

I have 3001 Futabe servos on my elevators.
I have worked really hard to get the servo arms centered and setup exactly alike on the servo itself. I have got my pushrods tuned up so that I have no subtrim and perfectly centered elevator halves. All of the pushrods have no play, no bind, everything fits up nicely.
In the neutral position everythng looks right.

Problem 1.
When I begin to feed in elevator up or down the servos travel at different speeds to the desired elevator input. One actually travels faster than the other.

Problem 2.
Plus they may or may not matchup at various points in the travel between neutral and full up/down. So unless I am at full up/down the halves may be off by as much as 1/4"+. But at full throw they match on high rate.

Problem 3.
I have the high rate elevator throws lined up perfectly at the endpoints, but when I switch to low rates the two elevator surfaces do not match up at the low rate endpoint. In other words one has traveled further than the other.

What is going on here? I am going nuts. Especially the fact that 1 servo seems to actually be significantly faster than the other. I think the EP issue can be worked out on the 9Z but not on the 9C when dealing with endpoints at 2 different rates. Help..

RE: Twin Elevator Servo problem, help.
 

Your 9C should have a twin elevator mix already. Are you using that?
Another thing to look at is where the control horns (on the surface) are located. If they are not exactly the same distance from the hinge line the problems you describe will appear.

Let us know.

RE: Twin Elevator Servo problem, help.
 

Geffon,
I am using that mix on my 9C, Ailvator function connected to channels 2 and 8 and set at 100% on both elevators to get full travel. Both control horns are the same distance from the centrline of the hinge and the same distance from the fuselage. ALso the holes on the control horn are exactly above the point where the hinge and elevator surface meet. Im sure I am doing SOMETHING wrong, I cant figure out what it is.. I even rehinged my elevators to get the alignment EXACTLY right, but no improvement.

RE: Twin Elevator Servo problem, help.
 

It is most likely then a difference in servo output even though they are the same specs..
Can you try some different servos or try another 3001 to see if that matches any better?

RE: Twin Elevator Servo problem, help.
 

Hmm, maybe so. Is that a common problem? I am old to U Control but new to RC so Im learning about servos. Im also going to switch to carbon fiber pushrod assemblies to see if I can get the slop down to nil . I am using Z Bends and they are nice and tight but I want to try to eliminate any possible mechanical problems..
Thanks for the input.

RE: Twin Elevator Servo problem, help.
 

I agree that it may be a servo problem. I would try switching to two entirely different servos (maybe the aileron servos). If that fixes it, one of your servos is bad or, at least, out of alignment.

Going to better quality sevos might help, but even the low-end Futaba's are usually decent.

Leonard

RE: Twin Elevator Servo problem, help.
 

Sounds like a servo problem to me too. Is one of the servos older than the other one? Errr, maybe one of the servos has a slightly messed up wire (which is not allowing it to get all of its potential voltage). The damage might or might not be visable.

What kind of speed difference are we talking about here? If its a lot you might be able to place both of them side by side (with no linkage connected) and see if you can tell the difference. That would eliminate most of your mechanical problems if you could tell the difference.

RE: Twin Elevator Servo problem, help.
 

No the servos are both new, got them at about the same time and they probably have about 75 flights on them . I am going to try swapping out servos and see what that does.

RE: Twin Elevator Servo problem, help.
 

This is a function of the servo/receiver and transmitter. My recommendation is to reduce the throw to balance the deflection up and down. Many people set up 3D flows and then dial in 40% rate reduction and 60% expo. If oyu reduce the movement of the elevator mechanically with 100% rate and the expo you need, it should be be less noticable. Going to digitals also reduces this difference in deflection.

RE: Twin Elevator Servo problem, help.
 

What about one of those matchbox things? I think thats what they are called, but i know they are supposed to match servo travels and everything, even centeing. I havent used this and am not familiar with it, i think it may only be used for digital servos anyways, but i'm not sure. thought i would through that out there.

sean

RE: Twin Elevator Servo problem, help.
 

OK,
Changed out the servos. Didnt help.
Went from Z Bend connections to carbon fiber pushrods with threaded clevis couplers on both ends to eliminate all play whatsoever, mechanically adjusted everything out to level with no trim or subtrim. I even moved one of my control horns so that they are TOTALLY exactly in the same locations on the control surfaces.

Still have something really weird going on, no matter what the endpoint is set at on high or low rate, at 90% up elevator input on the stick the right elevator is full up,,,, the left elevator is at about 75-80% of its endpoint. The last 10% of up elevator gets the left elevator up the rest of the way so that with full up on the stick the elevators match. In a nutshell the 2 halves move at different ratios but eventually get to the same endpoint.

Geist,
Is this something I just have to live with unless I buy digital servos? Is this is typical for all planes with dual servos and ailevator function??
If I go back to a Y harness will that do it? I dont use the ailevator function for anything except standard setup of these two elevator servos.

Everyone Thanks a million for the input.

RE: Twin Elevator Servo problem, help.
 

Try a matchbox, equalizer, or the FUTABA thing(dont know what it is called). I have the 10X and still had problems doing twin elevators!!!

Just fuss around and it will get done soon...it just takes some time. I do not know what those servos are, but try to use more thna standard servos if possible. See ya

Dan

RE: Twin Elevator Servo problem, help.
 

Hey

There's two thing that I could see that is wrong...

1st: Maybe a function on your transmittre is wrong, wo to be sure, create a new airplane on your transmiter and enable two elvator mixing and you will see... If it's not that, the only thing I could see is:

2: One of your servos is broken or not center correctly, try to disconnect your rod on the arms and try the two servos and see... If the are wrong, see your local dealer and talk with im... One of your servo may be broken so...


That's my opinion, and I never ad that my problem(im using Jr X378 and 8103)...

Hope this gonna help...


Thanks



MaVeRiCk_048

RE: Twin Elevator Servo problem, help.
 

try disocnnecting the two servos and switch the channels they are on. the left one will go on the right ones channel and vice versa. Then see if the problem switches with the servos. if the other side has the problem, then you know its your radio setup, if the same servo is still leading then you know its the servos. get what i am saying? if not then i will try and explain more.....just flip flop your connectors basically...

sean

RE: Twin Elevator Servo problem, help.
 

1. Call Futaba service and run it past them. The know the 9C a bit better than the guys here.

2. Go through the menus and switch assignment screens and turn off every switch and mix that you do not use

I use an Airtronics Stylus. It has servo speed adjustments...does the 9C have that? If so check it and make sure both elev. are set the same.

There is no reason for this to be happening. There are tons of guy at my field that have the 9C and fly with every configuration in the book with no problems....Call Futaba/Great Planes.

RE: Twin Elevator Servo problem, help.
 

Try this

Make a p-mix that has channel 2 as the master and any empty channel that your not using (like channel 5) as the slave.
Set up amounts to 100% both ways, and then move the right elevator servo (I assume you have the right side of the plane on your main channels) connection from channel 2 of your reciever to channel 5
Know try and see if they move the same.

One other thing, if the subtrim to one servo is set past zero (-47 for example) and the other is at zero you will have to even them out to let's say -27 and +27. Then you go back and set up your linkages to even everything back to normal.

The 9c manual states something on page 32 that I always wondered about, and is the reason i think that you and many others I know are having a problem with there twin elevator setups using the ailivator function or making up two mixes yourself.

They state "Ranges from 0% (no servo movement at all) to 140%. At a 100% setting, the throw of the servo is approximately 40° for channels 1-4 and approximately 55° for channels 5-8.•

RE: Twin Elevator Servo problem, help.
 

One other thing to note. This problem only shows itself when setting up planes with a lot of throw like you do with 3d planes.

RE: Twin Elevator Servo problem, help.
 

Im not sure about the servo speed adjustment on the 9C. As far as I can see in my manual there isnt anything on it.
I did swap the aileron servos and elevator servos to see if it was a servo problem. No difference. The servos are working perfectly now that they are driving the ailerons and the elevators are still acting up. Like I said I even switched to the best carbon fiber linkages and couplings I could get my hands on today and they are PERFECTLY aligned mechanically.
I think Im going to call futaba and see what they say.

Thanks a milion for all the input, suggestions are still welcome and I will let you know what Futaba says. [8D]

PS
Sal I caught your reply just before I posted this. Im going to read your post more carefully and see what you mean. I will let you know what comes of it.

Also you are right, the throws dont get out of square on low rates at all if I set my endpoints on low rate. (Which royally screws up the high rate)
AND on high rates both surfaces move together until you get out to about maybe 25 degrees. At 30 degrees things get really out of line until full throw, which is where the endpoint kicks in.

One more thing sal,
When I changed to Carbon Fiber today I set my linkages to where I am dead center and neutral elevator with no subtrim or trim whatsoever. I will have to adjust the up trim once I am in the air.

RE: Twin Elevator Servo problem, help.
 

Sal
Holy Crap.
I just went back and read that quote on page 32 in context. If that is so then there is really no way to get the travel squared up because by design the servos are shooting for 2 different places that are 15 degrees apart. Maybe the 9C isnt designed to handle high angle throws like the 3D planes use?[:o]

RE: Twin Elevator Servo problem, help.
 

Then try adding the mix i suggested. Even though channel 5 will imitate channel 2 , it will still move the same distance as channels 6,7 and 8 by desighn. I did this to my hangar nine edge and my Pizza box which both had 50 degrees of throw.
Just my .2 cents

RE: Twin Elevator Servo problem, help.
 

Not to be negative... But, my money is on servo quality.

It sounds like you are doing everything correctly but you are fighting yourself with your servos.
There is a reason they are only $19.99 new.

My best advice is upgrade the servos slightly and I bet your problems will go away.

RE: Twin Elevator Servo problem, help.
 

Let us know what futaba has to say about this. I would like to know about the 40% vers 55% too. I have been using expensive digital servos with the same problem. Have tried all the combos with frustating resultes. Mike

RE: Twin Elevator Servo problem, help.
 

test

RE: Twin Elevator Servo problem, help.
 

I called futaba about this back in may of 2003. I walk them through step by step and they still said they didnt see the problem with there 9C. Yet 4 to 5 other fliers at the fields I frequent had ran into the same problem with there big planes setting up for 3d.
If there is something I'm missing I really wish someone would jump in and hand out some more advice. I'm getting tired of reprograming Mixes on friends planes.

RE: Twin Elevator Servo problem, help.
 

Called Futaba and got some info.
Also, I have been fishing for a few days, came home took it off the charger.
I called Futaba and we played with it for about 20 minutes while I was on the phone and surfaces moved together just as they should.

[&o]
Then, they began to mess up again. Looked at my Voltwatch and it had just dropped to the 3rd light in the green. Im recharging and we will see if power is the issue, I hope it is that is an easy fix...