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Kill switch on a twin

Old 05-20-2024, 03:24 PM
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Default Kill switch on a twin

Can anybody help?
I have tried to configure the "throttle cut" function on my Spektrum Tx (a DX7S and a DX18) but all I manage to do is cut one of the two. The one plugged in to the 'thro' socket cuts just fine but the other channel keeps running merrily.
And that's a bit pointless. Dangerous even, a trap for the unwary if you think you've disabled the throttle and accidentally knock the stick.
So what programming trick will make the slave motor cut along with the other?
I need them on separate channels by the way so that I can mix them individually.
Old 05-21-2024, 03:53 AM
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Moved from classifieds to radio section
Old 05-21-2024, 10:21 AM
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Go to the second page of channel assignment. Assign your second aux throttle channel to be ​​​​​throttle . Throttle cut should then work on channel 1 and the aux channel you assign throttle.

Last edited by A. J. Clark; 05-21-2024 at 10:27 AM.
Old 05-22-2024, 12:17 PM
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Originally Posted by A. J. Clark
Go to the second page of channel assignment. Assign your second aux throttle channel to be ​​​​​throttle . Throttle cut should then work on channel 1 and the aux channel you assign throttle.
I think I tried that and it didn't work. Throttle cut still only cut the ch1 motor.
I use a couple of mixers that mix some rudder as master into the throttles such that left rudder opens up the right engine and vice versa. Maybe I can't do both?
I'll need to start from scratch and try again.
Old 05-23-2024, 04:41 AM
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Throttle cut should override all other functions.
Old 05-23-2024, 10:31 AM
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redneck throttle cut;

a rubber band around the throttle stick and pulled around the bottom of the TX.

looks jicky, but effectively keeps the throttle stick from being bumped to any other position.
Old 05-27-2024, 01:40 AM
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Originally Posted by A. J. Clark
Throttle cut should override all other functions.
You are quite right! On the DX18 there was a second page that I missed and now the throttle cut does indeed cut both, like on a Y-lead.
Trouble is, now I can't mix rudder into the throttle for taxying (it's a waterplane).
On twins I used to mix left rudder into the right throttle to rev up the right engine a little to make it turn left. And another mixer advanced the left engine with right rudder. But now both are tied together I don't have differential throttle.
I am sure it can be done, but I don't know how. Any ideas?
Old 05-28-2024, 03:55 AM
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You can get much better help if you just export your model and attach the file. Do that so we can see exactly what you're doing, and then we can provide you with detailed instructions.

Basically, you need one mix to copy throttle to a new channel, two mixes for rudder-to-throttle for differential thrust, and another mix to provide throttle kill on the second channel. Or a DX20, which has multi-engine support.

Andy
Old 05-28-2024, 10:40 AM
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finally, a "cost effective" solution for the man...
Old 05-29-2024, 01:24 PM
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Originally Posted by AndyKunz
You can get much better help if you just export your model and attach the file. Do that so we can see exactly what you're doing, and then we can provide you with detailed instructions.
Basically, you need one mix to copy throttle to a new channel, two mixes for rudder-to-throttle for differential thrust, and another mix to provide throttle kill on the second channel. Or a DX20, which has multi-engine support.Andy
"another mix to provide throttle kill on the second channel."
That sounds like a plan. I'll try that when I get home (on holiday at the moment). Should work on the DX7X as well!
Many thanks.
Alasdair
Old 06-09-2024, 12:43 AM
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Finally managed it.
That bit "another mix to provide throttle kill on the second channel" sounded so simple but I spent hours trying without success. Then a clubmate put me onto this video on Youtube, which explains it easily, with screenshots.
youtube.com/watch?v=v7x1hEMfgZw&t=654s
It needs one mix THR to AX2 with rates 100/100 offset 0, always ON, to link the second motor.
Then the second mix THR to AX2 with rates -100/ 0 offset -100 which is activated by the cutoff switch. Seems to work on the DX7S as well as the DX18.
[why is there a big blank space in my post where there ought to be the url of the youtube video?]
[how do I post a clickable link to the video? It was there in the 'preview']

Last edited by alasdair; 06-09-2024 at 12:52 AM.

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