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Old 05-05-2014, 04:34 AM   #1
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Default Differential thrust mixing with an Airtronics RD8000

I have an Airtronics RD8000 and a RDS8000 that I would like to use for a differential thrust project. I've tried mixing throttle as the master and rudder as the slave and visa/versa to no avail. If anyone has and ideas it would be greatly appreciated. I also have a Tactic Ttx650 I could use also. I am making a twin rotor heli., kinda like the scorpion ship in Avatar, and have the fore/aft and aileron setup Ok. I would like to have the ability to slip it side to side. It will rotate on its center and fly backwards and forward but would like it to drift sideways in a hover like a heli. Thanks!
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Old 06-04-2014, 06:59 PM   #2
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You might try asking this in one of the Heli forums since no one has responded in this forum.

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Old 06-05-2014, 05:09 PM   #3
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Probably, I've even asked 3 radio mfg's and no response from them too. The only radio the my work with out a mixer is the taranis and maybe the DX6 or 8
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Old 06-05-2014, 05:44 PM   #4
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The mix should be possible... it may take some experimenting.

I've never used Airtronics so I'm not sure of its mix priorities....

I have done differential throttles with Futaba, Hitec, Polks (Tracker III) and Spektrum DX-18

If doing just 2 channels to mix for differential thrust I'd use rudder and ythrottle channels. User programmable mix rudder to throttle and throttle to rudder at 100% and check the result. You might have to hold significant rudder to get the throttles to arm the ESCs.... fix by adjusting endpoint/ATV for the throttle channel.

The point is... TRY. Take the props off and just keep adjusting the mixes until the throttles respond the way you want them to.

I had a radio maker say their radio could not do CCPM... I made it work and sent them the info on how to do it. (actually it was easy including "Idle up", autorotation and acro modes)
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Old 06-05-2014, 06:03 PM   #5
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fhhuber,

Thanks for jumping in. I have never worked with multiple motors much less diff thrust. And I don't know his radios so I am useless on this one.

Not even sure how you would approach this.

Each motor needs its own ESC.
Each motor needs to be on its own channel
You would have to mix the two channels to the throttle

Now you need a way to vary the throttle position on each channel independently of the throttle stick.

Sounds like some complex mixing that would need a bunch of user mixes.

I would bet my 9C Super could do it but not sure of the logic I would need to make it work. And that is the issue, the logic of the command/mix structure.

Maybe if one motor was slaved to the left rudder channel and one was slaved on the right with center being 100% throttle.

Then mix them both to throttle as a variable offset. This would bring them up together.

That would be a minimum of 4 user mixes though I am not sure if that would work.

Left and right would slow one motor down.

Not sure that would work but that seems to be the logic path I would explore.

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Old 06-15-2014, 04:01 AM   #6
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I've seen that there is a simple plug-in mixer for about $8 that I can use. It's for a V tail but it can be used for thro/rudder mixing.
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Old 06-15-2014, 04:45 AM   #7
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Some radios this is EXTREMELY easy...

I haven't found a 6+ channel computer radio that had to resort to using a mixer between RX and ESCs.

It took me about 1 minute to get the mix set up first time I tried it on the DX-18. Polks Tracker took 2 minutes because I had to use 2 bi-directional mixes.

Futaba 8UAP it took 5 minutes because that was the first time I tried differential thrust.

Unfortunately I don't have access to a RD8000. I bet I could have it figured out in under 5 minutes.

************

Remove the props

Get both throttle working correctly on a Y to throttle channel.

Select a second channel for one ESC... mix to the throttle channel and make that work correctly.

Mix rudder to throttle. Get that to respond correctly

Mix rudder to the second throttle channel. It should just be +/- reversed values to the first rudder-throttle mix since when the one motor increases power due to rudder the other should decrease power.

***********

Approach it logically and break it down into several small problems. Solve one at a time.
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Old 06-17-2014, 12:43 AM   #8
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Ok, will try that on the TTX650 and the RD8000 or the RDS8000
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