Hello guys, I have a Goldberg Sukhoi that I'm trying to get the dual elevator servos set up. Un fortunally my Airtronics VG6000 radio will not allow you to adjust or reverse the servos independently. I had Airtronics reverse the throw on one servo for me and put them in the plane. After setting zero the low rate on both servos were perfect at 1 inch travel up and down. On high rates one servo was perfect at 2 inches up and down but the other was 2 1/4 up and 1 3/4 down. Is this something I am going to haft to live with and if so how much is this going to effect the performance of the plane. Any help will sure be appreciated. Have a good day everyone.

Yes it will affect performance. Get a servo synch. Its called a matchbox by JR: http://www.horizonhobby.com/Shop/ByC...ProdID=JRPA900

can't you adjust the endpoint?

If your really looking for precision--then garacy is right on the money.

You could also get an Equalizer from www.smart-fly.com. Same thing as a Matchbox--but a little cheaper.

Are your control linkages both set up the same way? Same length on the pushrods? Control horns adjusted to match each other?

Just a few things to look for.

But, definetly, get a Matchbox if you can't work it out. It's the only way to get any precision out of a dual elevator setup when you don't have a radio that will mix it for you.

(editd four speling[:-])

Thanks guys It sounds as if the matchbox is the way to go. Everything is identical on both sides, the same length control rods and both horns are set the same. Someone at work suggested to take the servo horn on the one with 2 1/4 up and 1 3/4 down and move the horn a couple of teeth on the servo to balance it out. Do you think this would work. I honestly believe that when Airtronocs took this servo appart and reversed it caused some of the problem.

Edge,
I had this problem on a flap setup. I had to go to a second channel on the receiver to set up separately. If you suspect the servo is not PERFECT, don't use it. I used a repaired servo and I will never do that again. School of hard knocks!![:@][sm=thumbdown.gif]

Before you spend all that money you may want to look at this.

This is what I use on all my warbirds and 3D planes and I have never had a problem yet.

It has an adjustment pot on it so you can zero the control surfaces out and it also allows you to just plug and play..and for under $10.00 you can't beat it. Dont mess with adjusting one servo as some one at your work suggested. Just get this and be done.
Expert Brand and the model number is exra325


http://www.e-clec-tech.com/seres.html

This link shows thew price as $19.99, but my local hobby store sells it for about $9.00.

Good luck.

Tom

Lib,
I don't think you can set the servos independantly with a reversing "Y" harness.[:-]

Trust me, this harness and the associated pot does the trick.
The pot has a screw adjustment that allows you to equalize the control surfaces and reverses the servo's so you get the desired effect.

The reversing Y will only reverse the servo. For elevator you need something more sophisticated, either mixing or one of the Matchbox/Equalizer gedgets.

I have not yet tried the Equalizer, but I have used both mixing and the JR Matchbox. Both work very well. The nice feature of the Matchbox is you use just 1 channel for up to 4 servos, whereas mixing requires a separate channel for each side. The Matchbox allows you to change reversing, adjust the center and the end points individually for each servo with them all on the same channel. The Matchbox also has a port for external battery hook-up. All of this results in a fairly steep price, $79.99 if you buy 1 and $55 is you buy a pair. The Equalizer has a 2-servo version that runs about $50, as I recall.

Hmmm, so I guess I am just imagining that this is working on my planes.

Like I said good luck, spend away.

The reversing "Y" that Liberator indicated does allow you to adjust the end points of the servo it reverses to match the other. It's pretty much a single channel Matchbox & consequently much less expensive. I have used them myself & they work very well.

Lib,
Does that pot adjust them both at the same time or just the reversed servo? I've never used one.

One stays centered and the pot "knows" which one to adjust to equalize the elevators.

The only problem I had with it at first was that the pot wants to wander a little as you put stuff in the fuse and button things up. So I drilled a small hole in the side of the fuse and centered the pot so I could make the adjustment with the wing on. Problem solved nicely.

Good mounting idea! [sm=thumbup.gif]

Hello Garcay, Using the JR Matchbox do you set the radio up in a nutral position { End point at zero, servo centering at 0 } and use the settings on the matchbox to adjust both servos? And how does the dual rate on the radio play into this.

Set up your servos as you normally would on the radio (I am going to assume that the servos are identical except that one is reversed). Set your dual rates as you normally would. Then fine tune on the matchbox. If your servos are matched at neutral but skew at full throw in either direction, something is wrong with your servo. If your setup is a mirror image from one servo to the other and the geometries are matched, the matchbox would line up the servos and would continue to deliver equal proportion to both sides. There is no reason why the servos would not reach the identical end-point. [:'(] The only thing you could do is change the end point at the matchbox for the one servo if you could not do it at the radio. You could have even reversed the servo at the matchbox.[sm=thumbup.gif]

The reversing Y won't give you the precision you need.

I've explained this probably 10 times here on RCU--seems noone is listening.

For the 11th time:

A servo will NEVER travel the same amount in BOTH directions.

For instance:
When you pull up elevator--lets say the servo travels clockwise 55* (degrees)
When you push down elevator--it's NOT gonna move 55* counter-clockwise--it's gonna travel 50* or maybe 45*---but NOT 55*

This is true of ALL servos from EVERY manufacturer. From the cheapest Blue Bird--too the highest quality biggest turbo 2000 digital from JR.

NO servo will travel the same amount in BOTH directions. PERIOD.

So:
You slap a reversing Y on one of your elevator servos and then center them up with the pot.
Looks good right?

Take a look at your elevatos when you pull up elevator.
HMMMMMMM--thats funny. The left side goes up 1" and the right side only goes up 3/4"
Whats up with that?

Thats because the left side servo is traveling 55* (for arguments sake) and the right side is only going 45*

NOW--push DOWN elevator:
HMMMMMMMMMM--same thing--ONLY REVERSED!!!!!!!!!!!!!
The left side goes down 3/4" (45*) and the right side goes down 1" (55*)

The servos are reversed--and they are NOT traveling the same amount.

One is going 55* (left elevator) clockwise and the other is going only 45* (right elevator) clockwise. Then you push the stick the other direction----and BOOM--the the left one now travels 45* counter-clockwise and the right one travels 55* counter-clockwise

You get differential throws in the elevators. Eveytime you pull back--the plane corkcrews to the left. And everytime you push down--the plane corkscrews to the right. Thats why you can't pull back and do a nice round loop without it spiraling away from you or snapping out on the top of the loop. It's not that your plane is doing a high speed snap. It's because your elevators aren't adjusted to track with each other throughout the full range of travel.

If you think I'm full of sh*t then try this:

Put a nice long servo arm on a servo. ANY servo.

Now hook it up to an receiver and push the stick in one direction. Note the amount of travel in that direction.

Now push the stick the other way. WHOOOOAAAAA!!!!!!!!!!!!--it don't move the same amount does it?????????????

Thats because the servo will NEVER travel the same amount in both directions unless you set the ENDPOINTS with the TX or a Matchbox.

So when you reverse a servo and center it with the pot--you are indeed reversing the servo.

BUT--and here's the kicker---YOU HAVE NO WAY TO ADJUST THE ENDPOINTS.

You need to be able to adjust the endpoints of BOTH servos INDEPENDANTLY if you want the elevators to move together and be synchronized throughout the full range of travel.

You can't do that with a reversing Y. You can only adjust the center point.

Reversing Y's don't work if you really want any kind of precision. If you don't care about precision--and your flying a Cub--then, most certainly, buy the reversing Y and be happy. Or maybe your not even a good enough pilot to notice that a plane can spiral towards you or away from you in a loop. Maybe you can't figure out why everytime you pull back and point the plane straight up that you also have to add in some aileron to correct it because it started to corkscrew when you hogged back on the elevator.

If thats the kind of pilot you are--then by all means--save yourself $30 and buy a reversing Y. You'll never know the difference.

If you WANT precision and you want to fly aerobatics--then buy a Matchbox or an Equalizer. If you want your plane to track straight when your pulling a loop--------or if your even a good enough pilot to notice that a plane will spiral away from you in a loop with poorly set up elevators---the you should get the Matchbox.

Thanks Garcay, Maybe Santa will bring me a new radio for Xmas that can perform all these functions. But for now I am going to order the matchbox. Have a good day.

Sorry to butt in, but I have a questioned about y-harness used for dual elevators. Can you use them and what is the difference between the y-harness and the reversing y-harness besides the obvious the reversing action? I have a Goldberg Tiger 2 and I have to used dual elevators because the dowel rod that connects the elevators halves got fueled soaked. So I split the elevators halves and ran a pushrod for the second elevator servo. The problem I have is there is no room in the tiger to have the servos pointing at each other to use the reversing y-harness so I opted to use the y-harness. What problems could I run into? The elevators halves seem to be moving the same distance, but it is hard to tell. Should I purchase this from [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXANF2&P=0]Futaba[/link]? I am using a 7CAP from futaba.

Thanks in advance!!

I guess the problem is that although your right about the difference, I am not seeing them be that far off. At least not so far off that I notice it on my 3D plane. If you are flying pattern then you may...I guess...maybe...see some twist on an elevator throw that knockes the plane off course.

If your telling me that you are seeing that big of difference in your aircraft, I'll believe you, I just never have seen that much difference to matter. Of course I am also not flying large scale IMAC or anything like that.

Manny,
I assume you mean that in the servo tray, the servos are so close together that the servo arms can't be pointing at each other. If so, forget the reversing harness. Use the standard "Y" and have the servos travel in the same orientation(both clockwise and counterclockwise). Just flip one arm over (no, the servo teeth don't let the arms line up exactly either, but thats OK) and adjust the 2nd push rod until both elevators are equal. Then tighten the pushrod connector whether its an EZ, clevis or ball joint. The servos are traveling in the same direction and so should the elevators. You can adjust for rates and end point equally.

RC is right. If you don't have a computer radio to adjust from a separate channel, you have to get a matchbox or equalizer if you want the precision. This is especially true if you bottom out your servo throw in one of your dual rates. [:@]

Look, what I said was, and I think Rcpilet is saying the same thing, if you are setting up a sport plane and don't care all that much about precision and don't want to spend the money, by all means get a reversing Y.

I used to mix all my multiple control surfaces, but after discovering the Matchbox, I am using it. It just does much, much more than just reversing and a cursory setting of the amount of movement that the reversing Y does. I use them on most of my twins and a triple. The triple was so easy to set the throttles, it was hard to believe. I set the center one as normal, then blipped the outboards in with the Matchbox. Done. I am getting ready to set up a Harrier 3D .46 and will be using one on elevator.

As RC electronics gets more and more sophisticated, we are getting a larger difference in the top end and low end equipment and also in the additional equipment available. Are digital servos necessary? No, but I like them, especially on rudder for the holding power. Is a Matchbox necessary? No, but it certainly makes dual elevators or twin engines easy to set-up and many people will say that it or something like it is required for multiple digital servos on the same surface. It gets down to your personal preference in precision and what you want to spend on the hobby.