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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › Spring loaded throttle servo arm on nitro engine
06-26-2014 10:59 AM  6 years ago
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Vaderluck

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Melbourne - Australia

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Spring loaded throttle servo arm on nitro engine
I am thinking of putting a spring on the throttle servo arm of TREX 600N.

The theory is in the event of total power failure, the throttle arm would return to the closed position and shut the engine down. THis is different from a signal loss event, with power still on, throttle returns to fail safe position.

Is this a good ideas ? Has anyone done it ? Please show us a picture.
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06-26-2014 11:31 AM  6 years ago
Josh Kussman

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Superior, NE

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I have not done it and yes it it's a good idea.
I know a couple people that add springs but they don't hook it to the servo it's self they connect it to the throttle on the engine because if u pop a link it will still shut it off.
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06-26-2014 01:59 PM  6 years ago
dumbthumb75

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Oslo, Norway

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Not done it on a nitro, but I kept the original th. spring on the MA Spectra gasser I previously owned (Walbro carb).
Just in case a link popped off.
Worked great, although it never popped a link in the 5 years I owned it (about 80 hours of flying).

That spring was fairly weak, well strong enough to to close the th. with no servo connected, but nowhere near the force needed to push the servo back too.

I'm thinking that a spring strong enough to force the unpowered servo will put an unnecessary high load on the th. servo.
Diabolo, TDR, X50e, X50n, Raptor 50
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06-26-2014 02:20 PM  6 years ago
Stephen Born

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USA

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....
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06-26-2014 08:24 PM  6 years ago
JKos

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Redondo Beach, CA

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The link provided by Stephen will probably talk about this as well, but I'll just put it out there that part the equation is the throttle servo selection. It needs to be a servo that is easier than not to move when not powered. Some are very easy. Some are not.

This is quite a common practice on gassers by simply leaving the stock spring on the carb.

- John
RR rules!
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06-26-2014 10:10 PM  6 years ago
Andy from Sandy

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UK

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Originally when this first started doing the rounds the Futaba 9254 tail servo was an excellent choice as it is very easy to turn when powered off.
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06-26-2014 10:12 PM  6 years ago
JKos

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Redondo Beach, CA

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> Futaba 9254

Yep, and the 9253 before that.

- John
RR rules!
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06-26-2014 10:19 PM  6 years ago
Andy from Sandy

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UK

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Indeed. I think the 9253 was just being phased out in favour of the 9254 when I started in the hobby.

The return spring is a very good idea though but I have not used it myself.
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06-26-2014 10:38 PM  6 years ago
ICUR1-2

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Ottawa, Ontario

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Return Spring :
if you install it you will never need it, if you don't install you might.

spending time, paying attention
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06-27-2014 07:18 AM  6 years ago
Toddc72

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weed,ca-usa

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Seen a guy at a fun fly use rubber bands on his nitro throttles.. Told me it saved him once so he always does it now.
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06-27-2014 11:50 AM  6 years ago
Richardmid1

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Leeds, England

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It's a good just don't make the spring too strong or it'll shorten the life of the throttle servo and also slow it down!60% of the time, it works every time!
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06-27-2014 02:15 PM  6 years ago
Rudy

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Houston TX/Bend OR

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I had my throttle linkage come apart a couple weeks ago. I have a throttle return spring and it worked that day. The engine died and I autoed in.

While it worked for me that flight, I'm sure there are other times with other people where a throttle spring caused problems.
Rudy Ackerman Houston TX/Bend OR
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06-27-2014 10:50 PM  6 years ago
Vaderluck

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Melbourne - Australia

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Looks like people are using return spring for a good reason. Why major engine manufacturer like OS, Thunder Tiger ... don't supply them as part of engine ?
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06-28-2014 03:12 AM  6 years ago
kingmeow

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The Garden State, US

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Because not one spring fits all. You have to find the right one for the particular throttle servo you are using. Too strong and your servo will burn out. Not strong enough, it will not close the throttle.
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08-07-2014 11:08 AM  6 years ago
Vaderluck

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Melbourne - Australia

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I just made a spring from .025" music wire. It works well, the strength is about right for a DS615 throttle servo.
I have tried .020" wire but it's too weak.

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08-08-2014 11:32 AM  6 years ago
ChristianM

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Oslo, Norway

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Nicely done. Here is a picture of one of mine

Christian
Burn fuel, be happy
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