equalizing elevator and rudder travel
 

I am just about finished setting up my Multiplex Fun Cub mated to a Spektrum DX61 TX and a Spektrum AR6210 receiver. My problem is the travel on the elevator and rudder is out of whack. The elevator has twice as much down movement as up movement and the rudder has twice as much left as it does right. I can't do anymore with the servos, horns etc. Can I get the two control surfaces equalized by programming the transmitter. If the answer is yes how fo I do it? Thanks for your help.

Yes you can (at least up to a point), but you shouldn't!

There has got to be some mechanical reason for the unbalance. Can you post pictures of the servo arm and control horn?

Terry

check your other post :) (about flaps) you need to set the travel to the same value in both directions (up/down, left/right) and make sure the sub trims are at zero.

OK AMA. Sorry about posting this same question twice.

Well I got the travel where I want it but I must have done it the hard way and the wrong way. For example the elevator travel is set at: up 125% and down 2%. It works . The travel is minimal as suggested in the Fun Cub manual if the plane is to used as a trainer but something must be wrong to have to do it this way. Also the dual rate switches don't work. The travel is the same in both settings. What am I doing wrong? I just adjusted the end point trave percentages until I got the travel I wanted.

That is normally indicative of setting up your linkages incorrectly.

It may be that you did not center the servo arm with the TX before setting up your linkages. That results in grossly unequal travel as you have, and are correcting via the radio.

Set the transmitter to it's defaults, and adjust the arms and linkages so you get equal travel of the elevator without resorting to changes via your transmitter.

You need to set up the dual rate for each switch position. Default is both at 100% so they will be both the same until you change one.

Don't know about the DX6, but my DX7 has dual rate and expo on the same menu.

Terry

Hi, stlmstr.. :)
http://www.rcuniverse.com/forum/begi...-receiver.html
I did mention there are several other things to zero out, besides just setting the end points :)
(sub trim, redo the mechanical setup, etc. you also have to set the dual rate switches up in order for them to do anything, but I would leave them disabled, you'll want to focus on flying the airplane, not looking for switches :) )

I decided to just fly it like it is for a little while. The travel on each control is exactly where it is supposed to be for training purposes. When I get to the point I want to increase the travel and fly at say an intermediate level then I will go back in and set everything up again the right way. I was able to set up dual rates but took your advice and disabled them for now. I will turn them back on when I am ready to experiment with more manuverability. I took the Fun Cub off in my front yard and set it right back down until I can get to the flying field. I gave it full up elevator , very little power with flaps down and it left the ground about 10 or 12 feet from where it started. it was flying at a very slow speed so I don't anticipate any problems at this level of manuverability. thanks for all the advice . I will put it to good use when I reconfigure everything..

If it goes up, comes down, and it's all in one piece-that's 99% of the battle.

As far as that last 1% goes, it's similar to the 80/20 rule. 80% of the benefit, for 20% of the work/ 20% of the benefit for 80% of the work. For airplanes it seems more like 90, or 95%. That last little bit to take it to that "ultimate" level seems very difficult and time consuming.

You got it up; got it down; it's still in one piece. Sounds like a good day.

There must be a mechanical setup problem with your linkages. As you compensated with the travel % in your Tx, it is possible that the throw could have an unequal "time laps" to get to the endtravel positions. Not sure if that would be a problem in your application, just a heads up. V.

Hi!
You cannot fly a plane with just 2% of travel...!!!
Remember to have a good flying plane it's vital that you first mechanicly trim the plane...not do the trimming with your transmitter.

Then set the transmitter up so you have 100% travel or more on all channels! That's the second most important step to follow.

No to trimmuing!
To mechanicly trim a plane you have to remember that the servoarms must be aligned 90 degrees with the push rods to equal travel in both directions.
Secondly! To avoid flimsy flying surfaces (that can develope into flutter) you allways have to use as short servoarms as possible and to use as long rudder/elevator arms as possible! That's the general rule for all airplanes!

Then you fly the plane!

If you arnt't satiesfied with how the plane behaves after the first flight,conntact a friend ho does know how to set it up for you.
Many times the Cof G has to be changed and also the servo travel in the transmitter, but remember never ever trim it out with the transmitter the first thing you do!!!!

JAKA I thought some more about your post. Although the airplane will fly like it is I am going to get in touch with the product support people at Hobby Zone and get them to help me set up the travel properly. They helped me set up the flaps when I was struggling with that. There isn't anyone around here who can help. I bought the transmitter and 2 receivers from them and they will help me out. Might as well get it right now before I start flying it. You were right.

After talking to the Hobby Zone problem we identified my Rudd and Elev setup problems. The control rods that came built into the Fun Cub are too short so you can't center the servo control arms. Thats why I am having so much difficulty setting up the Rudder and Elevator travel. I looked around but so far can't find any replacement control rods. Anybody have any idea where I can find control rods for the Multiplex Fun Cub? I thought about chaging the holes that the rods connect in to but after looking at them I don't think it would make that much difference. Which holes in the servo arms and control horns would give me the most length out of the control rods?

I wouldn't change the hole bc it would change the trows + as you've said it wouldn't change the length much anyways.

One option is to move the servo aft to shorten the distance to the horn or second is to replace the pushrod itself. If you move the servo, recheck the CG.

I found a place where I can get a couple of new , longer control rods so I will just replace them.

JUST to make sure you haven't missed something...
IF you were to remove the two servos, rotate them 180 degrees each and re-install, would that make the control rods fit better?
(if you look at the top of the servo's, you'll notice the output arm is closer to one end of the servo than the other)