#%*@ing computer Tx programming

I have a pretty good handle on radio programming, or so I thought. I've used a Futaba 8U Super for several years and just bought a 9C Super (which
is much easier to program). I've used the mixing capabilities to clean up my knife edge flight, counter the pitch affects of deployed flaps, etc..
But setting up the throttles on a twin has frustrated me. When I set up a twin on my 8U, I couldn't get the mix to work properly and ended up using "throttle needle mixing" to get the two throttles to work CLOSE to in unison. I just tried it with my 9C and couldn't get it to work properly.
I used a simple, linear mix with Channel 3 the master and Channel 8 the slave. I nulled the control for Channel 8 in the Aux channel menu. In the program mix 1 menu, I have 100% on both the arrow-up and arrow-down boxes. "Link" is off and "Trim" is on. 0% offset.
The end-point, sub-trim and trim settings for both channels are untouched at 100%. I haven't set up any idle down or throttle cut yet; they are default at "inhibited".
The slaved throttle moves in unison with the master until about 75% throttle, when it stops while the Channel 3 throttle continues to open. This is the same problem I ran into when I set up a twin on the 8U. There is no information in either manual regarding this. The Don Edberg Futaba 8U book and the Futaba 9C website FAQ didn't mention it either.
Am I overlooking something?
I may very well dream about smashing both radios with a big hammer tonight as I sleep. :-)
Thanks for any advice, desmobob
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On 2006-09-17 04:23:49 +0200, "Robert Scott"

Hello,
I'm a 9C user,
I had a look at the 9C manual and 9C User's Guide (by Annmarie Cross).
First, servos travel are different (+- 40 for channel 1 to 4 and +-55 for channel 5 to 8). Look at the END POINT Page.
For the 2 engine throttle setup you need, I think is better to slave one of the auxiliary channels to the Throttle one. I would not rely on idle mixing. If needed, use the end point adjustment on the slaved channel to have the right travel (idle and full power).
Have a look at the Futaba FAQ web page. There are some undocumented tips.
I have a two servos (airbrake setup on the throttle channel of my 9C but I'm not sure if I use a Mix or Y cord for that purpose). I will check later and keep you in touch.
Hope to help you,
MLB
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On 2006-09-17 04:23:49 +0200, "Robert Scott"

Hello,
Here is an update:
On my Airbrake setup, I use two servos and two channels.
Master is Throttle, Slave is Gear (No Use on that aircraft - Flying Wing glider Cortina).
Mix rate is +100/-100, Offset is 50% Mix ON, Link ON?, Trim ON, SW Stk Throttle, Posi NULL.
End points are Throttle 105/105, Gear 105/100 to adjust servo travel
Bye,
MLB
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Here is a link for an advanced two engines setup. Not quick and dirty but quite tricky...
http://www.futaba-rc.com/faq/faq-9c-q511.html
Have a nice flight,
MLB
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Thanks for your help, MLB.
Good flying, desmobob
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I got a response from Futaba Service.... setting the Offset to 50% has the throttle and slave in unison for full travel now. But now, I can't get the Idle Down and Throttle Cut to work on the slave channel. I have the Link set to On.... still no go.
I should have bought a JR!
Good flying, desmobob
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I heard from Futaba Service again (they are quick).
"Unfortunately both of those functions will only work on the master channel."
If you're going to be setting up multi-engine models, you may want to skip the Futaba 9C Super. I spent $400 on a computer radio and have to use a Y-harness on the throttles so I can have throttle cut and idle down on both engines. :-(
Good flying, desmobob
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Just a thought. I've seen this done with float planes to enhance on the water steering. Try connecting your throttle servos to 2 aux channels and slaving both to the throttle channel. You should also be able to program a mix with rudder if required to give differential thrust. I am working on a twin and will be trying this with my 9C soon.

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| I heard from Futaba Service again (they are quick). | | "Unfortunately both of those functions will only work on the master | channel." | | If you're going to be setting up multi-engine models, you may want to skip | the Futaba 9C Super. I spent $400 on a computer radio and have to use a | Y-harness on the throttles so I can have throttle cut and idle down on both | engines. :-(
You could get your basic V-tail/Elevon/flaperon _hardware_ mixer ($15 or so) and put it in your plane, with your throttle channel as the input that adjusts both engines equally, and another channel as the input that adjusts them unequally.
Then your throttle cut and idle down would still work, and you could adjust them seperately via your other channel.
--
Doug McLaren, snipped-for-privacy@frenzied.us
`Sir, I protest! I am NOT a merry man!' --Worf, ST:TNG
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wrote:

Doug,
That's an interesting and clever idea. I think I'll pass though.... although those units are pretty straightforward, getting linkages to the two throttles would be mighty interesting, indeed! (Maybe not too bad using flex cables....)
I stuck a Y-harness on Channel Three and did the fine-tuning on the linkages to get them nicely in synch. I'm done messing with setting up twin throttles for this season! I have a Wing Mfg. A-26 Invader kit in the shop that I hope to build this winter. I'll be motivated to mess with twin throttle set-up again in the Spring if I get it built.
Good flying, desmobob
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| > You could get your basic V-tail/Elevon/flaperon _hardware_ mixer ($15 | > or so) and put it in your plane, with your throttle channel as the | > input that adjusts both engines equally, and another channel as the | > input that adjusts them unequally. | > | > Then your throttle cut and idle down would still work, and you could | > adjust them seperately via your other channel. | | That's an interesting and clever idea. I think I'll pass though.... | although those units are pretty straightforward, getting linkages to the two | throttles would be mighty interesting, indeed! (Maybe not too bad using | flex cables....)
Linkages? No ...
Something like this is what I was referring to --
http://www.combatwings.com/catalog/product_info.php?cPath2&products_id "7&osCsid40dbe4a3bdd9dbc970027f38535d3c http://www.bill-tek.com/Elevon.htm http://www.californiasailplanes.com/digimix.html
perhaps you're thinking of those setups where one servo moves another servo back and forth, and that servo is what's connected to the control surfaces? That would work, but the modern electronic mixers would be easier -- pretty much trivial to install.
Perhaps I shouldn't have said _hardware_ ... I meant hardware as in a piece of eqipment you put into your plane, as opposed to programming you do in your TX.
--
Doug McLaren, snipped-for-privacy@frenzied.us
He was deeply in love. When she spoke, he thought he heard bells, as
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Indeed.... "hardware" was the word that threw me off -- it doesn't take much! I was picturing the old mechanical type mixers. "Mechanical" was the word I was thinking when I was looking at "hardware."
The mixers you linked to would make the project much easier, for sure.
If I try it, I'll let you know how it works.
Thanks again, desmobob
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