On all my planes the servo arm push the linkage for up elevator. On my yellow f15 however it seems to pull, I'm not really comfortable with the setup...is it safe?, Is there a setup that will pull that is safer than the traditional rod and clasp set up?
Any help, links or pics would be appreciated.
Thanks
Kevin

Kevin, I would rather pull to go up any day, that is the strongest the control rod can be!

I built the YA F15 one of the first kits 4 years ago. Built per spec, and from what I understand the airplane is still flying, I sold it a couple of years ago.

Sean, it's not the rod i was worried about it was the Threads on the rods constantly beig pulled on.
Thanks
kevin

In roughly 20,000 turbine powered flights I have witnessed, and roughly 100 jet crashes I have witnessed:

Not one single time have I ever heard or seen of the threads on a linkage failing.

But if you are still concerned, let me know and I'll come up with a solution you can live with.

It would be nice to have options, thanks for the oppurtunity to pick you brain by the way.
Kevin

I use this: http://www2.towerhobbies.com/cgi-bin/WTI0001P?&I=LXK079

and this: http://www2.towerhobbies.com/cgi-bin/WTI0001P?&I=LXWH35

On 4-40 threaded rod.

I didn't use to use a nut on the metal clevis, because once the threaded rod is into the plastic of the kwik lock, it can't rotate, thus no need for the nut on the metal clevis.

However, over time I have noticed that all metal clevis are not the same! Some are not perfect fit for 4-40. So I have started putting the nut on only to keep the clevis straight, not because I'm afraid of anything failing.

When I take off I go to full power, and I only come off when I land, so this slop free setup has been done on probably 20 of my jets, and never had a failure of control surface.

Mileage may very, but that's what I do.

One more thing, I use the metal clevis at the servo horn. It fits better going through slots in servo holders etc.

awesome dude thanks!!! coincidentally that's my exact setup, guess I'm just a little paranoid sometimes. I just would hate to have a plane go in because of part failure.
Should have it flying by the end of the month.
Thanks again
Kevin

If you are worried about thread failure I would silver solder the clevises onto the rods. Just remember that you are excreting a pushing and pulling force on the threads with up and down movement of the control surface.

It really does not matter if you have to push or pull to achieve up elevator as long as you get the correct surface deflection with the correct stick input.


Alan

Alan, there have been reported failures of silver solder, most notably Kenny Falconer's twin powered F-18 loss. To each his own, and I get that, but, man, I don't think I would go there.........

And on "push or pull" some of my 4-40 threaded rod have a piece of brass tubing slid over it, and pinned in between the nut on the metal clevis, and the plastic of the kwik lock. Will not bend ever. That is in particular on my "push" for up elevator. On the pull, it really is not neccessary unless you are going to do a lot of outside loops.

Of course this also has a lot to do with distance of the rod. All mine are under three inches a most are under 1.5. Very very strong at that length.

I believe the issue has more to do with long term vibration and deterioration of the threads. A jam nut behind the threaded clevis is good or loctite is OK. Some people solder the thread clevis onto the threaded rod as ultimate security. Don't run a threaded clevis on a threaded rod without using something that will prevent thread damage from vibration. Thanks, Aman