JasonSU78

I am a rookie builder trying to assemble a U Can Do 60. I am totally stumped by the elevator setup though. I am using a Futaba 6EXA with 3004 servos through a regular Y-harness. I got the elevator setup mechanically centered, but then when I go to full deflection with the radio, one side goes higher than the other. And then on the down side the one that was low on the high side goes lower than the other. I cannot figure out how to get the same throw out of it. Theres nearly a 1/2 inch difference.
I tried switching servos, and adjusting the pushrod location on the control horn to no avail. I even called Great Planes/Futaba for assistance and they were stumped.

If anyone can assist me I would be forever grateful. This silly little problem has brought my project to a halt.

Flyboy Dave

My Feedback: (21)

Does it use a single servo for the elevator with two push rods,
one for each side of the split elevator ?

Dave.

bhole74

It is supposed to have a servo for each half. Personally, I would save a servo and set it up that way.

JasonSU78

Its currently set up with 2 servos, one on each side of the fuse. thats what the directions called for.

If I wanted to use one servo, how would it be setup?

JasonSU78

How would I set it up that way, the fuselage would be in the way, and I am not really sure how one servo would control two surfaces?

And would I need to get a higher torque servo?

Thanks for the help.

Flyboy Dave

My Feedback: (21)

Stay with what you have now. It sounds like the servos are not "paired",
or working the same. Recheck the linkages and make sure everything is
the same.

FBD.

Tall Paul

There's a couple ways to install the servos and servo arms for dual elevators.
The optimum way is to mount the servos in the cabin, on a conventional servo tray, and hook up each pushrod on the same side of the servos.
Back in the tail, as in the U-Can-Do, the conventional method results in precisely what you've gotten, unequal travel between the halves.
The best cure for this is use an electronic Y-harness which electrically reverses one servo. Then both wil move the same..
The picture shows some of the possibilities..
The second version can use a conventional Y-harness.

ZebraOne

My Feedback: (8)

Several things can go wrong
! Are the control horns mount EXACTLY the same on the elev.halves? Control holes must be even with the hinge line.
2 Are both serco shafts located to the rear or the front?
3 Most servo arms are marked to allow for correct spline location and centering. Check 'em.

Getting a dual control splitter with an adjustment pot for centering will most likely help cure most all if all the above is correct.
Above all don't give up... Find an Elmer ar someone to help. Most RC,ers love helping out new folks
Zebra
AMA129570

Kaos Rulz

Is it an "Elmer", or is it a "Huckleberry"? Guess it depends on what part of the country you're from.

ZebraOne

My Feedback: (8)

Ed

Sorry for the elmer.. It's a phrase that us hams used to describe a mentor for
a newcomer to ham radio.
Zebra
AMA129570
KE6OKM

Kaos Rulz

No Problem. I wasn't digging at ya.

CRFlyer

I just finished up a U-can-do 60 and I used a reversing y to hook up the two elevator servo's. Had no trouble at all, and the travel is the same for each half.

Flyboy Dave

My Feedback: (21)

With a computer radio....you can slave a servo to the elevator servo, and
then reverse the slaved one.

Dave.

JasonSU78

Thank you all so much for the wealth of good ideas. I ended up slaving the flap channel to the elevator and worked the programming to get the same throw. That fixed that problem, now I just have to remember to never touch the flap control!

Hopefully that will be it for the big problems. Another couple hours and it will be done! I can't wait to see her in the air!

Thanks,
Jason

By the way, I couldn't find a reversing Y, where would you get one of those?

Flyboy Dave

My Feedback: (21)

I think Cermark still sells them. They were needed in some circumstances with
the old radios....but not much call for them now with the computer stuff.

FBD.

CRFlyer

There are a number of them out on the market. I have this one made by futaba and seems to be more expensive than the others, but it works well and has a nice centering control.

[link]http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXANF2&P=7[/link]

JasonSU78

Ahh, I simple looked up reversing Y harness!

Again gentleman thanks for all the help. I'll probably just go with the mix I have set in for now and see how she flies.

Villa

It sounds to me like a straight geometry problem. When the servos are in neutral, the angular location of each arm must be the same. The horns on the elevator must be in the same location relative to each other and the longitudinal axis of the plane. If you look carefully at the Futaba servo arms you will see letters (a, b, c, I don't remember this well) on the arms. I believe ( I do not recall reading this in the Futaba manual so I may be making this up) the letters describe slight differences in the angular orientation of the arm to the center mounting spline of the servo arm to the servo. Work with those letters to make very small angular adjustments in the location of the servo arm. Sorry if this is a bit confusing. Anyone else have comments on the letters on the multible arm Futaba servo arms?

Flyboy Dave

My Feedback: (21)

Yes....they are numbered 1-4, or 1-6, depending on how many arms it has.
Using the arm with the same number on each servo will....in theory give the
same position or alignment. However, the servos do not always center exactly
the same....to the arm can be change to a different number to make small
changes in the alignment.

This is a throw-back to the old....non computer radios. Now these small
adjustments can be made electronically with the sub-trims on the radio.

FBD.

TexasAirBoss

My Feedback: (22)

There is one more problem you might face with dual elevator servos and that is speed. They can be hooked up perfectly. The end points can match exactly. And yet the speed at which the servos travel may be different. There are devices on the market that insure the servos travel at the same speed. It might not sound important, but on some planes it turns out to be very noticeable. You'll just have to try it out and see.