SCREW CCPM !!! I'm going to HDE.

[thedude0901]

** RANT ON **

I've spent the past 3 days of my life trying to get the CCPM interactions out of my Trex and I'm no closer now than when I started. I've watched the Finless video so many times that I've memorized the dialoge but I'm still not getting it. Maybe I'm just stupid or missing something, but It's just not working out for me. :arggg: :arggg:

Here's a list of the crap I can't fix:
1. Moving the trottle from 0% - 100% causes the paddles to go from several degrees negative to several degrees positive in both elevator and aileron positions. :bomb:

2. The best I can do is +10 -8 on one blade and +8 -8 on the other blade. I still don't understand how I pulled that off. :arggg:

AAAAAARRRRRRRRRRGGGGGGGGG !!!!!!!!!

Yea, it's great that with CCPM all 3 servos move the swash but is that really necessary for a bird this small? I'm using 3 HS-65MG servos on 6v with 30 in/oz torque. Is 90 in/oz torque really necessary for a noob learning to hover?

I've had this thing on the bench for almost 2 weeks and I want to fly it instead of tweaking it !

** RANT OFF **

I feel better now.

I'd still like to give a special thanks to Finless for all of his hard work and time he put into those videos. It's people like him that keep the hobby going. :)

Best Regards,
The Dude

[Jermo]

:) NEVER GIVE UP!

I'll send you my XL HDE frame if you are that intent on it. You can send me yours if you want.
Jermo

[Jermo]

re: PM, you're better off just working out the interactions from the CCPM1 and CCPM2 video's finless has up. To use my HDE frame you'd need another servo AND an HDE swash.

posted to help anyone else reading the thread.
Jermo

[vera]

So I guess you wore out the swash AFR.

Well, my 2-cents worth is simply to recheck the mechanics and make sure you have 90 degrees between arm and rod. Unfortunately, the rod moves according to the cosine of the angle, which is pretty linear at small angles, but that goes down the drain at larger angles. The rate of change of all 3 rods need to be very much the same throughout collective movement and that can't happen unless all 3 servos meet their rods at the same angle (with zero elevetaor/alieron).

If I was at the point of shooting the heli, I'd set the trims and subtrims to zero, make all 3 AFR inputs the same, set the pitch curve at points 2, 3, and 4 all to 50% and set the collective TX stick to somewhere near half, and then check the mechanics and get 90 deg on the servos and bellcranks.

Perhaps you already know, but just to be sure let me remind you that different arms on the servo wheel will line up differently. The number of different alignments is (N/2)+1, where N is the number of arms. So a 4-arm servo wheel will have (4/2)+1=3 different alignments, depending on which arm you use. So if you don't have 90 deg between arm and rod try a different arm. After running out of arms, use the arm that gets you the closest and then resort to subtrim. Try to get the bellcranks to meet their rods to the servo at 90 deg also, or at least be the same angle for all 3. And of course if you change the rod length to get the 90 then that will mess with the swash levelness.... so then you have to mess with the rods to the swash to re level it. Then restore points 2-4 on the pitch curve and try again. If that still failed then I'd be trying to see which servo is out of step.


Is 90 in/oz torque really necessary


I think 50 would be plenty.

CCPM is a nice idea but it's particularly sensitive to the mechanical setup.

[Taffey]

To use my HDE frame you'd need another servo AND an HDE swash.

posted to help anyone else reading the thread.
Jermo

I may be missing something obvious, but don't the HDE and CDE versions of the T-Rex use the same number of servos? The HDE uses 4 (1 for elevator, 1 for aileron, 1 for collective, 1 for rudder), and the CDE also uses 4 (3 direct to swash, 1 for rudder).

Right?

I know the HDE and CDE swashes are different, as you mentioned, but the servo count should be the same.

[Jermo]

my mistake. you are correct.
Jermo

[kingair200]

hey dude,
i just re-built mine, it took me a little while to figure it out too, but i did. if you want, pm me and i'll give you the scoop for mine and maybe it'll get yours close enough were you can set it up from there.
regards
dave :mrgreen:

[mezz303]

I could never fully get rid of ccpm interactions with the HS65mg's and decided a while ago that I didnt care!
Intrestingly tho I have just built a new SE with JR 385 Digital servos all round the cyclic and there is absolutely zero ccpm interactions. (no exageration)!!! The heli feels almost robotic in the air as well. They are about $5 more than HS65's here in Australia and not metal geared however upgrade gears should be available soon. They are my new servo of choice!

[hoot]

When I had the JR DS281 servos in my Trex I was replacing gears after EVERY crash. Then I bought the Hitec Hs65mg's when they first came out.

These little workhorses have been through hell and back and still have not damaged them. I am not having any interaction issues but then I do have the power of the 12Z which has neat little features for taking out interaction like servo speed control, swash mix, swash mixing rate and linkage compensation. These are things people don't know exist in these higher end radios when they poo-poo on you for having things you "don't need".

[mezz303]

I too love my HS65's, I'm not suggesting anybody replace them. I am still using them and as you said hoot they are very tough however I have shredded a few of the karbonite gear versions so the difference in durability (fairly obviously) lies only in the metal gears. I still beleive you would have a better servo thats just as tough in the 385's if only they would bring out the metal gears! I'm using both at the moment on 2 different helis. Incidently the 281's have been discontinued and replaced by the 385's which are faster and have more tourque. :D