Pitch problem on v120do2s and 7e

Ok I have a 7e running deviation. All is good during non motor setup.meaning basic setup of heli with main disconnected.
Problem:when I check the pitch,it looks fine at upper and mid(zero pitch),but it goes WAY LOW on bottom! Blades hit boom if it were running! I'm drawing a total blank here.ive been out of the hobby awhile so bear with me!

Hi,

you really have to measure / math calculate the max positive pitch.
If this is fine for you e.g ~12 degree positive pitch and at middle stick you got 0 degree (zero) pitch then you would want to do this:

Use pitch channel "Servo Travel Adjust" (Scale-) to lower the min pitch to something < 100%.

You would want to have positive and negative pitch to be the same.

First goal is to care about zero degree pitch at middle stick by mechanically adjusting this.

The V120d02s works as a bigger 450 CP.

You can either adjust all three (servo) mechnical push rods to the swash plate for the swash plate middle position on the main shaft

AND

you can tune the top head push rods from the swash plate to the top head to adjust both blade trackings / 0-degree pitch (on "master" blade)


Go from the BOTTOM to the TOP.
- 90 degree servo arms to the push rods (IMHO not to the main shaft on the V120D02s, at least not on my Xtreme V120 frame)
[- electronial sub-trim of servos to fine tune 90 degree for all three cyclic servos within the FBL - Walkera FBL won't let you do this]
- middle the swashplate on main shaft for equal positive and negative pitch path
- zero pitch when pitch stick is in the middle (you have to have a linear pitch curve with 0% in the middle on the -100-...-0...+100 scale) as best mechnical as you can
- fine tune zero pitch by using sub-trim on pitch channel
- properly adjust max positive and negative degree pitch by tuning on pitch channel servo travel adjust

So if zero + positive pitch (scale+) is kinda fine on your setup you only would need to tweak for adjusting negative travel adjust (scale-) on pitch channel (CH6 / Cyclic3 in my DSMx advanced mixer setup).

Thomas

Ok so basically my problem is on bottom end as my mech setup it perfect at mid and high
My curves are like you said. BUT I think the travel range is what's doing it.
Also I haven't checked it physically yet till I'm home. But if that's NOT it, then I'll start over following your directions.thanx Thomas !

Yes, that will be the fastest solution to adjust Scale- / min travel adjust.
Electronically scaling down the pitch in one direction is far easier than having to (mechanically) max out servo travels.
Good luck!


Actually I see no real benefit trying to mechanically middle the swash plate on the main shaft by turning all 3 cyclic push rods and having to re-adjust the top push rods for 0-degree pitch and blade tracking.

I would only do the "mechnical hard way" by restarting from zero if you see that the max negative or max positive pitch is too far away from ~12 degree pitch and going over >100% travel adjust may not actually solve that.
The swash plate way would then be really off in one direction / too far away from the middle position on the main shaft.

Or if you maybe notice that you run off the top push rods (not enough length in or out) and you get to the ends for trying to adjust for 0-degree pitch on the master blade or you fail to re-adjust blade tracking by the slave blade because both blades are too much off.


Remembering that you can electronically tune sub-trim and travel adjust on the pitch channel even on FBL systems in your transmitter firmware setup (even when the FBL does not support it - many FBL's do that) is IMHO a very nice "workaround" which I learned from Blade NanoCPX FBL pitch setup (that FBL does not support adjusting pitch internally too).


There are even some (FBL) helis (e.g NanoCPX, MCPX, Blade 130X, etc.) which do not even support adjusting the top head push rods for blade tracking / 0-degree (zero) pitch because the push rods are of fixed length.
So you actually would have to mechanically adjust for 0-degree (zero) pitch by moving the swash plate up/down on the main shaft.


Both pitch travel limits where off on my NanoCPx too.

I decided to move the swash plate more into the middle of the main shaft because
- 0-degree pitch was way too off (too much sub-trim needed)
- positive pitch was mechanically adjusted at factory to too much (~18-19 degree) positive pitch
- mechanically too less negative pitch

Thomas

I had same problem with nano cpx.
Turns out it was setting in TX. I always setup my heli's the "hardway" I'm old school which is why I over thought my problem!! Lol
Well all's good so far indoors static testing.
Today(if wind not bad) we fly!! Thanx a million
Thomas!!