Paul Eastham

Paul Eastham

Well Known Member
I did my best to follow the instructions -- both springs somewhat taut with everything neutral -- but what I ended up with doesn't seem right.

I noticed that if I set the trim completely over to one side, then move the sticks the same direction, one spring assembly goes very limp and the other very taut. It's a longshot, but it seems like the spring could fall off (it's only held on with a loose ring on the end of the spring) or get kinked or otherwise screwed up.

This can't be right, can it? But removing more slack would really stretch out the spring in certain positions...?

20070315_IMG_4528.JPG
 
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Need more stretch...

I made the springs 'somewhat taught' in the least stretched position. So in the position shown in your picture, I made that spring slightly extended. When you do this, both springs are quite extended in the neutral positon, but that's the way springs are supposed to work. In fact, when I move the stick to it's extremes, the spring pulls the lever back and forth a bit and the ribs flex without the covers in place. Without that pre-tension, I don't think the trim would be very effective.
 
I'm not flying yet, but I doubt you'll ever have the trim cranked all the way to one side as you show in the picture. Plus if you don't have the ailerons hooked up yet, remember that they'll restrict the movement of the stick.

On a related note, I got my aileron trim all hooked up so it was working well. Then I hooked up the wing push rods including the autopilot servo. Now the stick no longer centers from the pull of the springs. Is that a problem?
 
Just installed my trim last weekend

I just installed my trim last weekend and though I am not flying yet I believe I set it up correctly.

The distance between the trim arm and the spring is very close to 1". This is seems to work as advertised, a slight pre-load on the one spring when the stick is moved to the extreme.
 
I am going to put the electric trim in the center with the biased springs like I did on my 6-A. I see that my new bracket already has a horn on it that I had to build last time. Good news!

Would any of you folks out there have a picture of the aileron trim servo mount using the biased springs? If so, I would really appreciate some pictures.

If you would prefer, please e-mail direct [email protected]

Thanks
 
Late reply...

I'm sure you guys are way past this topic now, but for anyone looking for answers I'm going to reply anyway! I just did my aileron trim today and I got the same result (limp spring on the starboard side) as Paul did.

I looked closely at the diagram and I think I know why this happened (well, besides the fact that it's NOT done right). The plans don't clearly tell you that the pivot lever is supposed to be centered above the elevator pushrod when the servo is in the neutral position. I mistakenly assumed that when everything was neutral the lever would point straight ahead...so I went ahead and drilled the holes for the servo, but too far aft.

Moving the servo forward would've pushed the lever more to the right (centered over the elevator pushrod), and both springs would require the same length of safety wire to make the stick forces even.

I think there are a couple fixes to this: Remove the servo and re-drill the mounting holes slightly forward to put the lever in the "real" neutral position. Second option would be to built some slightly longer arms that attach the servo-arm to the lever. I think that would be hard, so I'm going to just redrill the servo mounting holes.
 
DGlaeser said:
I didn't use safety wire to connect the springs to the lever. I used metal model airplane clevises - easier to attach and adjust compared to safety wire (for me anyway).
Click to expand...
I did the same thing - here are my photos for anyone who cares to see them:

20070528_trim1.jpg
20070528_trim2.jpg


I plan to solder the clevises shut to keep them from letting go of the springs.

Hey, what do you know, RV's really are like big R/C models! :)

mcb
 
Paul Eastham said:
This can't be right, can it? But removing more slack would really stretch out the spring in certain positions...?
Click to expand...
No, it's not right. Remove the slack...springs are meant to be stretched. You don't want this stuff jingle-janglin around in there. A jammed control system can really ruin your day.
 
OK, my turn....

[URL=http://imageshack.us][/URL]


When I move the trim servo arm, the force is not strong enough to move my control sticks. Should there be tension on the control sticks at the base or should they move loosely? I'm wondering if maybe the attach bushings are too tight. I can move them by hand, of course.
 
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