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Old Mar 21, 2009, 04:18 PM
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United Kingdom, England, Hornchurch
Joined Mar 2009
30 Posts
Help!
Chris Foss WOT Trainer Throttle Servo Rod Problem!

Hey guys,

I recently bought the Chris Foss Wot Trainer. Well I stumbled into a problem whilst building it. Ive connected up the servo rod to the servo. And when I powerup on my controller the servo arm goes down and therefore the servo rod bends a lot. Im scared that the rod may snap during flight. Plzz reply quickly!
I'm due to do its first maiden flight tommorow! Any help will be very appreciated!
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Old Mar 21, 2009, 04:40 PM
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Letchworth, Great Britain (UK)
Joined Jul 2004
12,006 Posts
Welcome to the forum

I haven't seen the Chris Foss Wot Trainer, though there's many other Chris Foss models at our flying field.

To answer your question, generally speaking servo pushrods should not touch anything between the servo and the thing they're moving. I doubt that your throttle pushrod is going to break, but it sounds like the hole where it goes through the firewall may not be in the right place for the throttle arm on the engine you're using. If that's the case, you can either enlarge the hole a little bit (but not too much because you don't want oil from the exhaust getting inside your model), or put a bend in the pushrod so it goes through the hole without touching.

The throttle pushrod on my Extra Wot has a Z-bend just after it comes out through the firewall, to make it line up with the throttle arm on the engine. Putting a bend in it is acceptable for the throttle pushrod because it doesn't have any real load on it, but it's not recommended for other pushrods because of the loads the elevator, rudder, etc. put on them
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Old Mar 21, 2009, 04:58 PM
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United Kingdom, England, Hornchurch
Joined Mar 2009
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Thanks for the reply. I'm going to a friends house to fix it. I will be checking the idea out . Oh yeah btw. Ive been on this forum for very long. I just made a new account because I didn't quite like my user name.

Thanks 4 help,

iRiddim
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Old Apr 20, 2014, 10:05 PM
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Joined Mar 2013
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hello I'm trying to take advantage of a lipo 3600 mAh (about 150 more gs), the wing must surely make it bigger someone try this?
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Old Apr 21, 2014, 02:06 PM
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Joined Feb 2013
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Well, I am presuming that the rod is bending because of the direction change and not because of excess throw from the servo arm. If it is excess throw, it will jam the rod against the carb arm with enough force to bend the rod. In that case, move the servo rod connector in toward center to reduce the amount of servo rod travel.

If it is directional, the previous poster mentioned z-bending forward of the firewall, or, sometimes a Sullivan goldenrod will solve the problem with its ability to curve or flex.
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Old Apr 23, 2014, 08:59 AM
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United States, MD, Elkton
Joined Oct 2011
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If the servo is 'stalling' you can run down the battery fairly quickly..

To check the 'throws'- disconnect the servo from the push rod...Push the throttle stick to full throttle, then see if you can reattach the linkage, while holding the pushrod at the wide open throttle position.

Make whatever adjustments are necessary, at full throttle and idle, so they don't bind.
As suggested earlier, maybe your access hole doesn't align correctly.
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