PDA

View Full Version : TREX - Can't Adjust -12/+10 Setup Pitch


qb7ops
10-11-2006, 02:55 PM
My Trex SE CF decided to take a suicide dive (on its own accord of course) leaving me to replace a few parts. Nothing exceptional; the spindle, main rotors, flybar, and boom. When rebuilding I checked to make sure nothing else was bent or broken. I follow the Finless videos for my rebuilds; particularly "CCPM Part 2".

The swashplate (microheli) is balanced and flat at 50% throttle. At full positive throttle the block sits just a hair below the head. At full negative is doesn't hit the collar or frame.

With the flybar level:
1. The control levers are level and even (ball and opposite screw)
2. Links from control lever arms to the seesaw are both same length.
3. The seesaw mixer arms are level with the flybar cage.
4. The blade grip links have been slightly adjusted to get o% pitch at center throttle.

With respect to the TX (Futaba T9CHP Super) endpoints at 100% both sides, all trim is 0; swash AFR settings all at 50%; sub trims have been adjusted for servo centering. For setup, the TX throttle and pitch curve settings are at default (0 25 50 75 100).

With the exception of checking CCPM interaction, I have followed the CCMP Part 2 video as best possible. I also reviewed the other applicable videos in case something else might apply.

At 50% throttle the pitch on both main rotors was 0%. But I ended up with -12 pitch at full negative and +10 pitch at full positive throttle. I started from scratch 3 times re-checking links, etc, and still cannot get an even 10/10 or 11/11 rotor pitch at both negative and positive; still -12/+10. Adjusting the Swash AFR pitch did not help at this point in setup.

Excuse the long-winded explanation of my problem, but I wanted to make sure whoever read this understood what I did, or did not do.

Anyone suggest a simple correction, or something I may have overlooked?

Seeker
10-11-2006, 03:48 PM
Once you get the mechanical set up complete (sounds like you have), use the pitch curve on the radio to dial the proper pitch through the range of the stick that you're looking for.

For instance with a -12/+10 mechanical setup your curve may end up (for idle up) at 13,35,58,79,100 to get you to -10/+10 rather than keeping the curve at 0,25,50,75,100 (just an example here)

ClayK
10-11-2006, 03:58 PM
Sounds like some control rods are off. You should be able to get +/- 11

qb7ops
10-11-2006, 04:05 PM
Appreciate the input Paul. The last time I mechanically setup I had a perfect -10/+10 not having yet adjusted the pitch curves. I just had to reduce the swash AFR pitch setting down to 47 or so. Thereafter I setup of the throttle and pitch curves on the TX for flight. As Bob says in his video, if you dont get an even pitch (his example -11/+11) in the mechanical setup, you did something wrong.

Maybe I just go lucky before, but I do believe I am either missing a step or neglecte to adjust something properly. I wil see if I get any further input then try your solution.

Thanks again!

Bayou Talker
10-11-2006, 11:15 PM
Measure the travel of the swash plate from center stick position to both ends. It sounds like it is moving more to one direction than the other. If it is, and the servo arms are centered, then adjust the links to the swash plate until the travel is the same in both directions. Then the swash plate will be centered. After that, it is a matter of adjusting the linkages from the swash up to the blade grips to center everything else up. That should take care of the problem.

qb7ops
10-12-2006, 06:18 PM
Well, I think I got it beat and now have -10/+10 on the mechanical pitch setup. The control rods were off, but collectively, and I moved all links down a few notches; except the links on the blade grips.

I wasn't sure how to measure the travel of the swashplate without take the head apart, so I did not do as Cliff suggested. However, he was right in that the travel of the swashplate is not even; there is more travel down than up. From a novice standpoint, it looked like the 3 servos moved a greater distance down than up even though they are centered. After putting around a lot of time into resolving this, I think I will wait until a pro can look at it the swash travel hands on. I'M REALLY TIRED NOW!! :D

Thanks all for your input; much appreciated!

Bayou Talker
10-12-2006, 07:25 PM
I am glad to hear that you got it working. To measure the swash travel as I suggested, just use a short ruler and hold it next to the swashplate parallel to the main shaft and simply measure the travel. It would be easier if the head were removed but you should be able to get close enough with the head on.

qb7ops
10-14-2006, 12:13 PM
Roger that Cliff. I will give it a try. Sandstorms are keeping me inside right now, so a good time to tinker around. Thanks!