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Old 07-16-2010, 10:08 AM   #1
1996celt4
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Default How do you stop a nitro engine ?

I have learned a lot here and appreciate the help. I do not belong to a flying club so much of my knowledge is coming from you guys.

Like the title says, once the engine is running how do I stop it. I thought of two ways. Tell me if they make any sense or are dangerous:

1. Put my throttle stick all the way back. Then go into my subtrim for the throttle and push or move the servo arm to a negative value. This way the only way to start the engine would be to move the throttle stick a little forward. Then to kill the engine I would bring the stick all the way back to 0. My only negative on this is if I am flying I focus on watching the heli and not the Tx. If I mistakenly pull the stick too far back it will kill the engine in flight.

2. Zero out the throttle using the subtrim so the engine will start and run with the stick all the way back. Then fly and land the heli and when I want to kill the engine go into my subtrim like I did in step 1 and set it to a negative value forcing the servo to choke the engine.

Thanks,

Bob
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Old 07-16-2010, 10:41 AM   #2
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Most newer computerized radios have a "throttle-cut" option, which you can bind to a momentary switch. That way full down stick is idle, and when you hold down that momentary switch it will move the throttle fully closed to kill the engine. If your radio doesn't have an option like this, I would just set it up to idle at full stick down and then after you land, bump the trim down until the engine dies. Or just set it up that way and kill the engine manually by pinching the fuel line after it spools down.
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Old 07-16-2010, 10:52 AM   #3
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Bob,

You should set the throttle linkage and range so that idle occurs at low stick and center throttle trim. Leave sub trim alone.

When you start the motor, generally a few click of up throttle trim is necessary for a fast idle. When you land and are ready to shut the motor off, just go to low stick and give down throttle trim until the motor shuts off.

Good luck.
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Old 07-16-2010, 11:02 AM   #4
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When you set up the travel limits of the throttle servo, set the idle position with the throttle trim centered. That way low stick is idle in normal flight mode. Then bringing the throttle trim down while at low stick will close the throttle and kill the engine.

Search around for throttle setup threads. There are even some Finless Bob videos on the subject (look in the Trex 600N build series for example).
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Old 07-16-2010, 11:07 AM   #5
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Look here: http://www.helifreak.com/showthread.php?t=115887

And here: http://www.helifreak.com/showthread.php?t=41514 See step 13
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Old 07-16-2010, 12:34 PM   #6
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Thanks folks for all the input and the links

Bob
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Old 07-16-2010, 12:42 PM   #7
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If you have an engine that just won't quit, stop the blades and pinch the rubber exhaust extender. It will stop much quicker than shutting off the fuel.
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Old 07-17-2010, 12:41 PM   #8
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Quote:
Originally Posted by fastflyer20 View Post
If you have an engine that just won't quit, stop the blades and pinch the rubber exhaust extender. It will stop much quicker than shutting off the fuel.

Good to know for an emergency shut down. Thanks. Right now I am using the throttle trim to kill the engine. I know it it is not instantaneous but it works. I have a DX7 and will try to set up a throttle cut .

Bob
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Old 07-17-2010, 12:52 PM   #9
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Quote:
Originally Posted by 1996celt4 View Post
Good to know for an emergency shut down. Thanks. Right now I am using the throttle trim to kill the engine. I know it it is not instantaneous but it works. I have a DX7 and will try to set up a throttle cut .

Bob
I'm using the same method as I don't have a throttle "cut" set up yet.
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Old 07-17-2010, 09:29 PM   #10
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Set all my nitro powered flying stuff, both planks & helis, to have their engines running at a stable, mid-idle speed when the throttle stick is fully down and the trim is at the mid point of its travel.

Full cut-off is set for when the throttle trim is moved all the way down. Just requires a little bit of time and effort to set it up physically in the first place. Including backing the drum rotation stop screw (if the cardie has one) out far enough that it can't stop the throttle's drum from rotating to where it can completely shut off all the incoming air and fuel supply, with a drop of 'lock tight' to make sure it stays in that position.

The 'fine tuning' of this set-up has always been done using the throttle channels end point travel adjustment -always worked for me with using JR radios over the last 30 years and with nitro engines from .15 size clear up to my somewhat larger 160 nitro burning 2 strokes. :-)
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