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Gas Powered Thoughts Advice for Gas Helicopter Success from Carey Shurley |
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07-27-2011, 08:45 PM | #1 (permalink) |
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Join Date: Apr 2004
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The Throttle Return Spring - Do I Need This or Not?
If you've flown gas helicopters for a while you know that if you've got a lot of vibration in the model, you're going to see a higher failure rate on the throttle servo.
Why?
This is different from virtually all glow powered models. Few if any of them have a spring return on the throttle butterfly. If the servo fails or the link pops off, it will likely stay where it is. I've been asked about whether or not to "de-spring" the throttle butterfly for a gas powered helicopter. You can see it here: Throttle Return Spring Location my advice is to leave the spring on to maintain its use as spring loading the butterfly shaft against the circlip on the end opposite the spring but to unload its tension so that the throttle butterfly moves freely and stays in any position. All you have to do to unload it is to take a small screwdriver and flip this little spring end off of this retaining ledge and it will no longer keep tension What keeps tension on the spring?.........This! My reasoning for doing this is three fold:
These days I'm using digital coreless servos and I recently had a throttle servo failure where the servo totally failed and just stopped working. In this case I had not yet removed the spring tension on the carb spring. Because the servo outright failed, it lost power and no longer held its position. As a result, the carb shut itself. Fortunately I was in a position that I could get the model on the ground undamaged. So is this a good thing or not? Well it depends, there's no one right answer here. I was just hovering so it didn’t matter. If the model had been in a nose down funnel, I suspect it would be broke bad. If you spend most of your flying time fairly high, this won't matter much. If it closes the throttle you'll have time to recover and auto-rotate. If you do a lot of low altitude radical manuevers and the throttle closes suddenly, you'll get to show everybody your extraordinary recovery skills! One clear advantage of leaving it on would be evident if you crash the model and pop off the throttle linkage. With the spring, the throttle closes and it just lays there. Without the spring, who knows............chicken dance anyone? The Bottom Line:
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Carey Shurley Proprietor - Gas Powered Helicopters Last edited by carey shurley; 08-06-2011 at 11:43 AM.. |
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07-28-2011, 09:07 PM | #2 (permalink) |
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Join Date: Oct 2006
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Carey,
I'm certainly not looking a gift horse in the mouth as I really appreciate all this little tips that most of us would have to learn the hard way, were it not for you beating us to the punch . That being said, I wonder if added slop in the throttle servo gear train would really matter, if one were to leave the spring in place and under tension. Would the spring not 'take up' the slop in the linkage/gear train? Your thoughts? |
07-29-2011, 05:14 AM | #3 (permalink) |
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Join Date: Apr 2004
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in one direction.
Is it REALLY gonna make much difference? nah, its just a finer point.
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Carey Shurley Proprietor - Gas Powered Helicopters |
09-12-2011, 05:51 AM | #4 (permalink) |
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Join Date: Jun 2011
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Carby spring
Hello there...
If this may help, my first JR Ergo 230 came with the Zenoah engine.The Walbro carburetor did not had the spring mounted originally from the factory. Without the spring in place however, you do get a fraction of side play on the butterfly shaft, but it doesn't affect in any way the functionality of the carburetor. Burt |
03-21-2012, 08:51 AM | #5 (permalink) |
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Join Date: Oct 2011
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Good thread
>>>If you've flown gas helicopters for a while you know that if you've got a lot of vibration in the model, you're going to see a higher failure rate on the throttle servo. <<<
Interesting....I knew this from my own personal experience flying only gassers. I just had not seen anyone put it into words. In the 8 years I've been flying them I've had 3 throttle servos die and several pieces of 3mm aluminum brackets just shear off for apparently no reason at all. Even though my engine's are balanced this still happened. I'd recommend replacing the throttle servo's every year. What are others thoughts on this? good flying. ~L |
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