Electric Aileron Trim spring tesnsion?

[dreed]

Hi all, I had to pull my seat pans this weekend to fix a bad BNC and installed the springs/safety wire to my already installed aileron trim servo.

Nothing in OP19/instructions were super clear on the amount of pre-tesnsion so I put both springs in just slight tension when the sticks were neutral, but now think I may have under tensioned them, and they should have just a little tension when in their most "relaxed" position (stick deflected far left/right).

Curious to see others thoughts, or if anyone has a measurement of the lengths of safety wire they ended up with when all said and done or maybe even used a gauge to measure the tension.

Thanks in advance!

 

[N890GF]

I recently installed mine as well, I don't have the numbers, but am also curious. Maybe you can share a picture of your setup with the safety wire installed? Here is a pic of my in-progress setup, you can see the springs and safety wire. I'd estimate about ~3 inches of safety wire, I'm not sure.

 

[dreed]

Thanks George! I have significantly less tension (more safety wire) than you do. I didn't snap a pic, but I think a buddy did. I think I'll be pulling the pans to adjust a little bit and take snap before I do and post it.

Thanks again-

 

[lr172]

Mine is set up with VERY little tension on both springs when motor arm and sticks are both centered. The goal is for one side to be tensioned and the other slack once the arm is off center. If that is not enough to get it under control, then you need to work on addressing a heavy wing.

 

[rvbuilder2002]

I usually adjust the springs so that with the stick and trim system at neutral there is about a quarter inch of stretch on the springs.

 

[dreed]

Thanks All-

I am probably a little less that 1/4" of pull when centered. I may tighten them up just a little but sounds like i am close.

As far as the need - I installed the servo when building. I've been flying for about 2 years now, and a little over 200 hours and the plane flies/trims out beautifully.

 

[planenutz]

When adjusting the tension on my RV-6 aileron trim springs I found that doing it by feel was not particularly accurate and when I thought I had it right, the springs were loose and sagging when the ailerons were at full deflection while full opposite trim was applied. This seemed like a bad idea for an aerobatic aircraft so I adjusted the tension so there was no sag at all.

To clarify - with the servo moved across to full deflection in one direction, move the stick to full deflection the opposite way and lock it up so there is almost no tension on the spring, but so that it is not loose and saggy. Repeat on the opposite side. In this way you'll have the same amount of tension on the springs and the trim will be sensitive enough in flight, without losing any "feel" due to the spring tension.

At first you might feel you have too much tension on there however its unlikely to be the case if you're using the springs supplied by Vans. More importantly though, done in this way the springs are not able to get hung up on anything they shouldn't when in flight.

 

[snoop9erdog]

Leave system disconnected?

Not intending to hijack this thread, but I'm genuinely curious. I have a buddy that recently finished a 7. He said that with a Garmin 2 axis Autopilot and 507 controller........he never touched this spring trim system. Does it add unnecessary friction to the control system? Could it be left un installed?

How many wish they have never installed this? If installed do you use the spring trim system? Is my question or suggestion a bad one? That's fine, but why? Could there be a legitimate argument to not install or will the OEM prevail simply because it's part of the design?

Above comments for the manual spring trim system. Apologize if it doesn't apply to electric trim

 

[wirejock]

Trim Spring

I just installed mine per plan. Plans say to move the servo arm all the way to the left stop. Which is actually full right trim. Place the stick in full left forward position and secure the spring with slight tension. Repeat the other side.

There's quite a bit of tension to move the stick. I don't like it. It would get tiring hand flying.

I prefer Scott's tension set up quoted below. I think I will center the trim servo configuration in the HDX and finish the tensioning during the final rigging per Scott.

I usually adjust the springs so that with the stick and trim system at neutral there is about a quarter inch of stretch on the springs.

Any ideas welcome.

 

[gasman]

I recently installed mine as well, I don't have the numbers, but am also curious. Maybe you can share a picture of your setup with the safety wire installed? Here is a pic of my in-progress setup, you can see the springs and safety wire. I'd estimate about ~3 inches of safety wire, I'm not sure.

View attachment 45980

I know you are not flying yet, but just to be safe, place a piece of blue (or whatever) masking tape on that loose nut that connects the elevator pushrod. You don't want to forget to tighten it.

 

[D-Dubya]

I think some are missing the point of how this type trim system is designed to work. First off, yes, you have to have the springs installed--assuming you plan on moving the ailerons in flight. The springs allow for stick movement while applying a little "nudge" to the stick in whichever way you've called for trim.

Secondly, this type spring applies a force that's linear with deflection. As Scott stated, center the servo up and install the springs with an equal amount of spring deflection on each side. There should always be some tension in the spring, even when the trim servo is all the way to one side or the other. It should never be completely slack.

And yes, it's simple--but it works. These planes are so well balanced (if built correctly) that it takes very little force on the stick to deflect the ailerons. You will not need to strong-arm the stick to overcome the spring force. In fact, you won't even notice the spring force when you're flying.

 

[lr172]

I

Secondly, this type spring applies a force that's linear with deflection. As Scott stated, center the servo up and install the springs with an equal amount of spring deflection on each side. There should always be some tension in the spring, even when the trim servo is all the way to one side or the other. It should never be completely slack.

.

If you install it as scott and I suggested, any significant deflection of the aileron WILL cause one of the springs to lose all tension and is completely slack and droop. Very important that the builder carefully observe this behavior and insure there is nothing nearby for this slack spring/wire arrangement to get hung up on.

If you do it as wirejock did, you avoid the slack issue, but get a REALLY stiff aileron movement. Your build, your choice.

 

[wirejock]

Spring tension

If you install it as scott and I suggested, any significant deflection of the aileron WILL cause one of the springs to lose all tension and is completely slack and droop. Very important that the builder carefully observe this behavior and insure there is nothing nearby for this slack spring/wire arrangement to get hung up on.

If you do it as wirejock did, you avoid the slack issue, but get a REALLY stiff aileron movement. Your build, your choice.

That makes sense. I will expirement with the tension till I get a happy place with no slack. Right now it feels like a gorilla has to fly it and the wings aren't mounted.
Yes, I know. They need to be adjusted during final rigging.

 

[jcarne]

I don't have too many pics for that one but I believe I installed them to just barely have any tension when fully deflected. I don't like the idea of slacked springs catching on something. Keep in mind when you are flying there is generally really small control deflections.