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Old Sep 10, 2012, 04:14 PM
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Servo Mixing

Hi Guys

I need some help. I have been flying my RPG for a short while with help from a friend. I have managed to go solo which is a great achievement but I am struggling with servo mixing. My model uses two servos linked together the same as you would do for a Delta. My radio is a Futaba 10CG. The programme I use is Elevon Mixing which I am told is the right programme to use. The problem is when you tilt the blades back for take off, you lose an awful lot of blade movement to the right, which is fine when it is windy but as many of you would know, if you don't get the blades up to speed, it takes off and kicks to the left. That is when you need full right movement to counter act it. Same as you would if you put in right aileron. Have any of you come across this problem and how have you solved it? The guys from Futaba in the UK tell me that is how the programming is whether you are flying a Delta, a Gyro. You just have to live with it. Please help?
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Old Sep 10, 2012, 04:50 PM
It was a GLITCH! Honestly!
SafeLandings's Avatar
Stourport on Severn ,Worcestershire, United Kingdom
Joined Dec 2007
4,868 Posts
Hi John,
Sounds to me like you need to go through your programme and check that your throws on elevator and aileron are set at maximum when set in elevon mode. You may well have your elevator set at 100% and aileron at say 120%, this will cause the problem you have described.
The other thing may well be that your ATV has been adjusted one way rather than adjusting a rod. Always best to have the servo output arms horizontal and do set the lengths of your control arms rather than adjusting through the transmitter.


Hope this helps?


Regards

Rich
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Old Sep 11, 2012, 01:04 PM
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Up State New York , USA
Joined Mar 2009
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John:

I think Rich is right and I would like to maybe say the same thing but explain what I found only today.
I got to the field with my crane fly only to find your same situation , more travel back and less forward , and more travel left and less travel right. At first I thought I needed to set end point adj. but they were all set at 125 percent in all directions so after scratching my head I noticed that when I had my last flight and had her all dialed in my trim travel on the elevator was all up and my aileron was all right. Follow me so far? With the trim set like that it gave me less travel on the stick in those directions. Now I had to take a mental note on what the head looked like , recenter the trims with the transmiter and move the pushrods by turning the cleves in or out to get that same head position. DID I LOOSE YOU ? I know I got lost trying to put it down on paper. Now my head is back to the dialed in position and the trims are centered on the transmitter and I have equal in both directions in both elevator and aileron.

Wow I got a headache and need a nap, hope this helped Bill
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Old Sep 11, 2012, 02:53 PM
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Hi Rich and Bill

There is certainly something weird going on with the mixing. Sunday afternoon I had the model on the garden table. Set all the trims, end points, everything back to the default setting. Set the servo arms up in the middle, played around with the control rod lengths as Richard suggests, getting everything where it should be without any electronic mixing to give me a good starting point, so I was already thinking what you were saying Richard, but not knowing really why. Anyway, I then set it in Evelon Mix and lo and behold if you were to put full right aileron on, and then pull back on the stick you can physically see that you are losing probably 30% of your right aileron movement. The people in Futaba in the UK say that this is unavoidable whether you are flying a delta or a giro, you will lose some movement due to the mixing, but I know what you mean Bill you can play around with the trims, end points and get some real strange effects. So I will try and see if I can make the same thing happen as you tried. My friend Tim is flying a hump back at the moment with separate servos for aileron and elevator which makes things damned easy. Got to get this damned thing sorted as I have a Gyro One to fly very soon and has the same head mixing.

Regards

John
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Old Sep 11, 2012, 07:01 PM
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Elizabeth South Australia 5113
Joined Nov 2005
1,785 Posts
G'day John
This is an issue that I have noticed myself......but it has never caused any problem.....I am using a JR system and there is always a "floating" movement when the controlls are being used.......one side starts it's travel just a little before the other and the heads on all my models ''sway " a little......But as the head is always under some kind of load.......in flight ...all is good........It may be a Futaba "thing"...........
Happy Landings
Chris...........
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Old Sep 12, 2012, 11:56 AM
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USA, CA, San Jose
Joined Dec 2007
855 Posts
I'd like to help John but I need to ask some diagnostic questions.

1) Do you start your setups with 100% travel or all the travel the Tx will allow i.e. 125%-150%.

2) It sounds like you've double checked all your mechanical geometry. All stick trims 0, end points max, same holes in servo arms and control horns, servo arms centered or at least identical for each side (some differential can be mechanically achieved by setting servo arm one or two splines off center)

3) Check that any Tx differentials are cleared for both channels, exponentials are the same or cleared for both channels. Are tx subtrims cleared or identical?

4) Are you using a preset mix or a custom mix setting? Custom mixes can be a problem if the master/slave settings are not correct.

5) Are you actually setting the throws to use full travel or do you reduce throws with endpoint adjustments. Does the problem exist if only using 50% stick travels?

You may find your fix while checking these things however, my guess is that this only happens at max travels. That is one of the idiosyncrocies of the mix programming. The Tx computer will downgrade throws of a mixed servo to allow stick trim adjustment room. You'd probably find the throw of the elevator is reduced some too but it's less noticeable. If you make your initial mechanical setups with more throw than you need and then reduce the throws with end points adjustments, you may find the problem goes away.

One disclaimer I have is that I have been using JR equipment for a long time and only somewhat familiar with Futaba. I have trained many students that use Futaba and have had to become familiar with some of the functions, but not all of the advanced ones.

I hope this helps,

Don
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