TREX 450 Sport with Align 3G Cyclic question - RC Groups
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Nov 06, 2010, 07:34 PM
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TREX 450 Sport with Align 3G Cyclic question

I've a 450 sport which I recently upgraded to flybar less with the 3G unit. I also did the same with a 250 which works superbly, but I think I may have a problem with the 450 and I was looking for some advice from anyone that has done the same.

I have set it up exactly as per the instructions and incidentally it also has the latest V2.1 software. Once it is up into a hover it is as though it is very reluctant to alter cyclic. This is highly noticable if something like a breeze causes it to tilt slightly. For example if it tilts back and I apply forward cycle then it is as though nothing is happening until suddenly it pitches forward, as you may imagine this is leading to over correction. The same happens in all cyclic directions. It is acting almost as though there is a dead band around centre stick and when you push it further it kicks in. I will say here it isn't an uncontrollable pitch forward (or other direction) just a not moving until the stick has deflected so far type of pitch forward. Unfortunately it is hard to explain.

Whilst my initial though was that the gains may be too high I'm not getting any nodding and in any case I'd have expected it to react to the initial disturbance if that was the case. Though I admit I haven't tried changing the gains.

My second thought was that perhaps it is now just a lot more sensitive to cyclic then in the flybar configuration. And because I'm not used to that level of sensitivity I'm over controlling. When I introduce some expo (I haven't be flying with expo previously) the effect does seem to be reduced so this may be the reason but there again it could just be masking the real reason.

My third thought was to wonder if the servos are up to it, they are standard DS410M on cyclic but again I think they would have shown more problems in holding a hover if they couldn't handle the loads.

Can anyone offer any advice, I love it on the 250 but it is making me a bit wary of flying the 450.
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Nov 06, 2010, 11:16 PM
Registered User
The swash mix might be to low. I was thinking of expo at first. It does have a built in expo setting that you need the computer link to change.
Not like I ever got a 3g to fly really good in a hover.
Nov 07, 2010, 08:48 AM
Redjestird Youser
SidewaysLS4's Avatar
I'd try turning off the expo in the radio, put 1 in the 3G expo field, turn on the switch and change the 3G cyclic pitch motion delay to 70 or 80, and tune the response to the stick via your radio's dual rates. Also, the 3G does get kind of lurchy if the total gains are too high, maybe try turning them down also.
Nov 07, 2010, 08:51 AM
Registered User
Many thanks for the reply.

Swashplate cyclic mix is 54% (9 degrees) on a DX7 with 44% (12 degrees) on pitch. I have the computer link and the expo setting for both aileron/elevator is set at 2 and I current have about 30% set on the DX7 for both.

As the swash mix is as per the manual at 9 degrees (I can't do 3D just developing my hover skills) are you thinking that the command rate in the computer link may need reducing so that the swash AFR can be increased providing more descrete steps thus greater resolution?
Nov 07, 2010, 09:00 AM
Registered User
SidewaysLS4, lurchy is a good description of what it seems like I'll try adjusting them down. How does the cyclic pitch motion delay change behaviour, I was reading the note associated with it but it isn't very forthcoming on what exactly it does.
Nov 07, 2010, 04:58 PM
Registered User
I've tried turning down the total gain and this seems to have helped though it still seems to think about it before responding to control movements.
Nov 07, 2010, 08:49 PM
Love my scale Whirlybirds
Keyrigger's Avatar
Although the swashplate is directly connected to the grip arms, make sure that the links are snug but not binding. Also check that the linkages on the servos are very free to move as well. They may cause a delayed response to the input you give them. Also, make sure that the grips move free as the wind and that there is no binding of their movement. Just a couple of thoughts. Take care.

Nov 07, 2010, 11:01 PM
Redjestird Youser
SidewaysLS4's Avatar
You know, I forgot to mention the control rate for A & E also. Since youre not 3D'ing it (I'm coming from a scale model type flying style myself), I'd also try control rates around 40 to make it less frisky. This way you can get rid of some of that 30% expo in the radio, I never could get it to feel right with expo.

Cyclic pitch motion delay is kind of like heavy flybar paddles, in that commands wont translate into a 'right now' rotation, it will gradually start rotating. I know your trying to chase down a delay issue, but give it a shot anyway with less radio expo. A lower control rate along with motion delay might give you the toned down feel you are after without the delay issues you are experiencing.

I also have 70 on the Hiller and 50 on the Bell in the Misc setting tab. I kind of just pulled those numbers out of a hat in the process of playing with it, but I liked the change it gave.
Nov 08, 2010, 03:26 AM
Registered User
Originally Posted by Zaragon
---- are you thinking that the command rate in the computer link may need reducing so that the swash AFR can be increased providing more descrete steps thus greater resolution?
Yes, that is what I was getting at. If the swash mix is to low, you lower the resolution. I had better results increasing the swash mix (after setting travel limits on the 3G), then lowering the control rate in the gyro to a comfortable speed.
Nov 08, 2010, 12:57 PM
Registered User
Thanks for the replies. Hopefully the next time the rain stops over a lunch time I'll give the suggestions a try.

Any other thoughts are also welcome.
Nov 14, 2010, 12:32 PM
Registered User
The rain held off today so I've been able to experiment a little with the settings, one at a time to see the effect.

I tried turning on the Cyclic Pitch Motion Delay and it isn't what I need to fix this, or perhaps it would be if the rest of the setup was correct. Whilst it does what SidewaysLS4 was suggesting the problem is that it only seems to do so in respond to user input. So if a gust of breeze has the heli tipped and hareing towards a tree my control response is slowed and delayed. What it isn't doing is stabilising the heli. So if I could get the system to compensate for the original outside force then this setting would be useful.

At present I have the total gain compensate turned down to 40 (from 50) and the hiller rate turned up from 60 to 70. Though I needed ssome more expo in the TX to stop me over correcting. It seems to be getting better and seems to be reducing the lurching/sticky effect but there is still a long way to go. What I find interesting is that the 250 with 3G fitted out of the box is significantly more stable and I have better control of than the 450 and I definitely have more fun with it at the moment.

Hopefully there will be some more fine weather this week for some more experimentation
What I seem to be trying to achieve is a high level of self stability against external forces which the flybar provides normally but with quite a sensitive and quick response to cyclic command that would previously have been slowed and tempered by the flybar.
Nov 14, 2010, 06:22 PM
Redjestird Youser
SidewaysLS4's Avatar
Where is your lock gain at?
Nov 16, 2010, 02:42 PM
Registered User
Both aileron and elevator are set at 70 which is the original setting. At the moment I'm not yet at the stage of a fast (or any forward flight).

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