leedees

I am using the JR 11X on a new build. What are the effects of using a sub trim setting of say 200 when your servo is set on high resolution with 120 degrees of travel? (max travel is 180 degrees at low resolution servo setting). I have a linkage issue that needs this much sub trim to center my servo. Am I causing myself any problems?

woodie

As long as you don't have any binding issues with the servo rotating then it shouldn't be an issue. Sub-Trim does not affect end point adjustments and AFR, it only moves the center timing for the servo. Having said that, it sounds like you have a geometry problem if you have to get that far 'off center' with sub trim to center your control surface. Can't you just move one spline on the output arm and get much closer to center? Or, you linkage is the wrong length.

Also, if JR has an unequal number of splines on the output shaft, sometimes rotating the output wheel or arms 180 degrees will get you much closer to what you need physically. If it is an even number of splines, then rotating the servo arm/wheel will do no good.

Woodie

Rafael23cc

My Feedback: (6)

I was going to suggest rotating the arm, but then I saw that he is using a subtrim value of 200. Since I do not know how the new 11X works I refrained from comment. On my 9303 or my 10X a value of 200 would be extreme, and would probably be messing with the overall travel of the servo. But then again, he mentioned a 180 degree max travel servo and 120 degrees normal travel. I do not have that kind of servos in my toolbox.

Rafael

leedees

Woodie,

Many thanks for your reply. That was exactly what I needed to know.

You have identified the problem correctly, my pushrod is about 3/8 inch too short for the servo location etc. And I have taken advantage of the spline offset where lever is mounted on the output shaft. The 200 points off center on the 11X is equal to 100 points on a 1024 resolution radio.

It's a beautiful pushrod supplied in the ARF by Aeroworks, it's just cut and threaded the wrong size. They are aware of the issue but the solution they offered was not suitable. Otherwise an outstanding kit.

MinnFlyer

My Feedback: (4)

If the pushrod is too short by 3/8", rotating the servo by that much is not a good idea - and even if you did, you're much better off moving the arm than adjusting the trim that much.

If this is a "Nyrod" type pushrod, you can just cut it anywhere and re-join the two pieces with a piece of threaded rod leaving a 3/8" gap between the two pieces.

carrellh

I would be very tempted to buy a new pushrod.
In my mind I see the geometry of moving the arm on the splines creating a situation where you have more travel one way than the other. Some of that can be "programmed out" but it still seems bad.

Carrell

MinnFlyer

My Feedback: (4)

Carrel is absolutely correct about the geometry, but a new pushrod is not necessary. The joint shown above will work just fine - I have done it on many occasions.

1bwana1

If it is on a single surface like a rudder it not going to cause a lot of problems. But if it is on a surface that is mated to another surface like aileron, or elevator it is likely to cause issues with travel not matching throughout the range. I would just buy a new pushrod, and set the plane up right. Pushrods are cheap.

Skaluf

MinnFlyer,

You can't use this type of Nyrod system on a large aircraft like he is talking about. These aircraft use solid 4-40 (or larger) rods or turnbuckles for pushrods.

S

leedees

Here's pics of the difference in servo arm position of no sub trim with the amount of sub trim needed to make the elevators fair at center timing. This is a 1.20 size Aeroworks Yak 54. Pic on the left is with sub trim dialed in and pic on the right is 0 sub trim center.

fizzwater2

My Feedback: (61)

so take the servo arm off, set the sub trim to zero, put the arm back on the closest set of splines that will minimize your sub trim. It looks like there ought to be a set closer than that which takes such a large amount of sub trim.

leedees

Fizzwater2, I apparently suffer from drain bamage. Once I looked at the pics that became obvious to me as well. It did get it much closer, one side virtually no sub trim and the other 73, no doubt due to an odd number of splines.

I have several plausible excuses... late night coffee drinking building, I was a teenager in the sixties, it is so hot in south Florida we can't reason. I also reminded myself I had to rotate the servos from stock position of the output shaft being at the rear to being at the front trying to accommodate a pushrod that was initially too long and from that position no amount of servo arm adjustment would work and I guess I had removed that solution from the list of possibilities.

I appreciate everyone's help. At the very least, I now know a lot more about digital servos.

fizzwater2

My Feedback: (61)

LOL - love all the excuses! I resemble a lot of those..

Enjoy that new plane, as long as it's not too hot out!

StevL

A word of caution programming the 11x.

If you use "Flapperon" with two servos (one each wing) be sure to go into flap set up and set the "Land" value to "0" if you do not intend to have 100% throw on your flap setting (or set it to the value you want). I'm not sure why it defaults to 100%.

Also, do not "Inhibit" the flap switch or you will lose trim on your left aileron when set up as flapperon. Only the right aileron (aileron channel) will trim

Best way to use two servos in the wings and not deal with all this is to "Mate" the Aileron channel to another Aux channel.

You may have already found this small programming error.

Cheers,
Steve

leedees

Steve, thank you for the heads up. I have not yet setup any aileron servos and that could be a real pita problem to sort out. I wonder if they will remedy this with a software upgrade.

MinnFlyer

My Feedback: (4)

Sorry, I was thinking they were Nyrod. My partner just cut a Nyrod too short on an AeroWorks Cessna the other night and that's how we fixed it.
If it is a solid metal rod, you can do something similar by cutting the rod and soldering a brass sleeve over the cut to extend it

StevL

[ul][*] Set your sub trim to 0.[*] Attach the servo arm as close to 90 degrees as possible. (all metal gear servos need a dab of loctite or other thread lock)[*] Use the sub trim to set your servo arm 90 degrees.[*] Now use the turnbuckle push rod to mechanically set the flight surface to dead neutral. (may need a different length push rod)[*] Use travel, expo, etc. to fine tune your set up and to acheive the deflection you desire.
[/ul]

You can program that servo too with a HiTec programmer. No need in this application, the radio will do it all.

Cheers,
Steve

daven

My Feedback: (1)

Looking at that picture, why don't you turn the servo around so the arm is closer to the surface?

leedees

Dave,

That was the stock way to install, however with the output shaft at the rear the problem was reversed to a greater degree. The pushrod was longer than all adjustments could accommodate. With the servos in the stock position the factory recommended cutting off about 1/4 inch of thread and screwing the pushrod deep into the ball joint. I didn't like the idea of pushing unthreaded pushrod into the ball joints. They also agreed putting the output shaft towards the front would work. Very decent guys to work with at Aeroworks btw.

Rafael23cc

My Feedback: (6)

One more question....

How can you have subtrim on one side and no subtrim on the other? Are we talking about two servos here? One on each side of the fuselage? Am I missing something here? Or are you talking about travel adjust instead of subtrim?

Confused......

Rafael

StevL

He has to have two servos, one on each elevator half. They usually do vary, you don't mount them exactly the same and flipping the servo over makes the splines line up a little different.

Program each side separately, takes about 5 minutes or so.

Steve

leedees

Rafael,

That's correct, there are two servos, one on each side of the fuse for each elevator half. They are both mounted with the output shaft towards the front. There is sub trim required on the one side because there are an odd number of splines on the output shaft so when you flip the servo arm to the other side of the servo the result isn't exactly 180 degrees.

The travel adjust will be pretty close to the same for each side.

That spline count was new information to me and is compliments of Woodie's post early in this thread.

Steve just said it all better and shorter.

Rafael23cc

My Feedback: (6)

Thanks for the clarification. That makes sense now. As you can see from my avatar, I'm a heli guy but always wanted to dab into the giant scale airplanes. I finally got a couple on my workbench and I'm accumulating components to put them together.

Rafael