3G and poor cyclic/elevator response

[paulsouthport]

Evening all

I put a 3G system on my Pro a few weeks back but weather has prevented me from really trying any proper flying with it.

Today I did get out. I'm finding that, when I give it rapid positive collective the tail pitches down, nose up. It's quite unpleasant. Gentle collective doesn't seem to display this.

The head is new and all tight (in the right places), servos are all new MD933

Anyone have any ideas?

cheers
Paul

[vinny155]

hey paul,have you levelled the swashplate at the top end of travel,you have to do this with the 3g whereas you dont with the vbar,i better read the manual on this one,my memory fails me

[paulsouthport]

Hi Vinny

Yes, I was quite anal about the setup on this. It's odd, it feels like the elevator servo is moving later than the rest, but catches up at the end!

[vinny155]

what way have you got the 3g mounted,sometimes they need to be strapped down,other times they dont,i have never played with the cyclic gain on any of mine,im currently running 3g on my 500 and it is seriously locked in,i love it,i would try strapping it down/unstrapping it first and have a go

[paulsouthport]

Nice one, I'll try that.
It's mounted on a single align pad, worth doubling up?

[tourerjim]

Your best bet is default the TX & start again as I had same fault best to use swash levelling tool not only for levelling swash plate but to also check you've got no interaction between top & bottom of the swash.

[vinny155]

its a bit of trial and error with this paul,try a variation until its right,strapped/unstrapped 1pad 2pads,i ended up using a strap on one 500,strapped really tight on a pad with zero movement,on another no strap,i could wiggle the unit with little force but thats the way the unit flew right

[paulsouthport]

Thanks very much Jim and Vinny - I'll try both those suggestions and give it another go. At least it's not just me!

[coolice]

Hey.

This little quirk of the 3G is exagerated on the smaller 450 models and can be mixed out by adjusting the collective pitch compensate slider within the 3G's PC software program. Having said this there is more than one slider which can and does effect the way in which the 450 handles colelctive pitch inputs, you will find that it is not a mis-levelled swashplate at the extreme's of travel but the 3G's settings effecting it's ability to maintain a level fuselage with quick collective changes.
I would imagine that if you make slower changes the pitching of the nose is less pronounced.

Out of interest what main blades are you running? As the weight and distribution of it's weight is more critical on a 450 I found.
Also what firmware?

First of all I would suggest trying my settings file for the 3G runnign V2.1 firmware attached, you can load then up in the PC program to view slider positions before writing to your model.

Also, do not level your swashplate at the extreme's of travel using your transmitter ATV's as you would on a normal flybarred setup. You must leave your ATV's at 100% travel either side of centre and this is mentioned in the 3G's instruction manual, if these are altered it mess's up the system..
If you have some differences in the swashplates level at the very extreme's of pitch range, it will most probably be generated by not having the servo arms perfectly level at mid stick, as doing so changes the arc of which the control ball moves in compared to the other two servos connected to the swash.

I found that a single Align foam pad worked the best, with a velcro strap going lightly over the top so as not to remove the pads vibration absorbtion but just steady the top of the 3G sensor case to stop any rocking in aggressive flight.
.

[paulsouthport]

Hi Coolice.
I'm running your settings but am on V3 of the 3G software. Would you say 2.1 is better?
My ATV's are at 100 and the swash leveller confirms level swash throughout, so the pitch compensation looks like a possibility. As you say, slow pootling about shows no strange behaviour, just during rapid positive pitch input.

Blades are Align 325D 3G blades, the head is the newer single piece Pro FBL head, albeit on the older Pro.

[tourerjim]

Thanks very much Jim and Vinny - I'll try both those suggestions and give it another go. At least it's not just me!

Forgot to mention the gyro unit needs to be as near as poss to main shaft, you may find it will fit on the bottom frame tray

[paulsouthport]

Forgot to mention the gyro unit needs to be as near as poss to main shaft, you may find it will fit on the bottom frame tray

That's interesting, so you mean on the bottom plate below the main shaft? Should fit there no problem.

[tourerjim]

That's interesting, so you mean on the bottom plate below the main shaft? Should fit there no problem.

Yep directly under main shaft if you can get it to there.

[coolice]

Hi Coolice.
I'm running your settings but am on V3 of the 3G software. Would you say 2.1 is better?
My ATV's are at 100 and the swash leveller confirms level swash throughout, so the pitch compensation looks like a possibility. As you say, slow pootling about shows no strange behaviour, just during rapid positive pitch input.

Blades are Align 325D 3G blades, the head is the newer single piece Pro FBL head, albeit on the older Pro.

Hey Paul.

Yeah, I tried V3 for a short time but found I could not get my machines flying as good on the cyclic feel as I could on V2.1. I tried all manner of software changes, but to no avail. The tail felt a little better on V3, but the loss in cyclic performance was too great for me to warrent stickign with V3 so I downgraded back to V2.1.
If you can I would go back to V2.1, that is my personal recommendation and my settings are geared towards V2.1 over V3. I think I do have the V3 settings I was making, but as I didn't get the model flying as well as I did on V2.1 I stopped refining them.

Ah, the 325 3G's are great on the model and is what I stuck to when they were eventually released so you'll be fine with these.

With sensor location, ideally the tail gyro has always been said to work best directly under the main shaft as that is the point at which the model yaws around. But the cyclic gyros, especially the rolls would be better located along the centre line of the boom assuming the model rolls axially around the boom.

I think location with respect to vibration levels plays more of a part in the sensors performance over location due to movement in flight within reason of course.
.

[paulsouthport]

Thanks very much for that - I'll downgrade it to 2.1 and try again. It's really not very confidence inspiring as it is!

cheers
Paul