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Servo pushrods for big jets

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Servo pushrods for big jets

Old 10-12-2022, 01:22 PM
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jetsflyin
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Default Servo pushrods for big jets

What is the best (strongest) method you guys are using for your big jets? I had a 440 rod break on my F-16 and lost the

Jet. I need advise since I am curently working on a 1/3 Skymasters Hawk.
Is the method on the pic below sufficient? and where can i purchate the parts to make them?
Thank you in advence

Last edited by jetsflyin; 10-12-2022 at 01:25 PM.
Old 10-12-2022, 02:08 PM
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The pic is blurry and hard to tell if you have carbon fiber tubes over the rod. I always do that to threaded rods. I always have the CF tube completely up against the end fittings. It looks like the CF in the pic is a bit short.

Threaded rods are weaker than solid rods. Also threaded rod is not hardened. There are prefabbed titanium rods available. They do not break.

Also, could it be that you are hitting the physical endpoints of the surface's travel? I use an ammeter in line on the servo if I think I am even getting close to that point.
Old 10-12-2022, 03:38 PM
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I like the prefab titanium or stainless steel rod because of the left and right tread….make install easy with ball link….there’s a variety to seller for these, like Horizon, Secraft and others
Old 10-12-2022, 05:09 PM
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H9 Prolink turnbuckles
Old 10-13-2022, 02:34 AM
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jetsflyin
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The Picture above I found online somewhere and thank you for confirming the corrected method.
Old 10-13-2022, 02:43 AM
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H-9 Turnbuckles and Dubro Monster link ball links
Old 10-13-2022, 02:16 PM
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That looks like it is the flap? For flap extension, I do not like the flap being pulled by the servo. I’ve about lost a jet this way, due to 500oz servo failure. Fortunately, high enough to recover. I modify all flaps to be pushed from the top inside flap joint. It is an extremely easy mod that reduces servo, pushrod, link failure. The servo arm rotates on the inside of the top skin. This way the short servo arm is almost straight inline with the flap pushrod, and creates less fulcrum torque on the servo.
As others have said, using titanium pushrods, 6/32 threaded rod with a carbon fiber tube sleeve.



I simply cut a slot in the flap inside leading edge. I used G-10 with 9462. I beveled the control horn to fit as deep as possible into the flap.

This is the original setup as per SkyMaster.

You only see the control horn when flaps are extended.
Old 10-14-2022, 03:22 AM
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jetsflyin
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Mosttitanium pushrods I see online are 4/40 does anyone have a source for 6/32 threaded rods?

Thanks
Chris
Old 10-14-2022, 03:54 AM
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Originally Posted by jetsflyin View Post
Mosttitanium pushrods I see online are 4/40 does anyone have a source for 6/32 threaded rods?

Thanks
Chris
I used either 3mm or 4-40….at least for jet a little I’ve 10’ without problems….
Old 10-14-2022, 04:02 AM
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Originally Posted by jetsflyin View Post
Mosttitanium pushrods I see online are 4/40 does anyone have a source for 6/32 threaded rods?

Thanks
Chris
Hey Chris,

Amazon has both SAE 6/32” threaded rod and 3mm or 4mm Threaded rod. I usually then search Amazon for CF rods with ID of 6/32 or the 3mm or 4mm rod. Sometimes it is easier to work in mm.
Good luck!
Old 10-14-2022, 04:01 PM
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jetsflyin
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That's great!! Thank you so much
Old 10-14-2022, 05:22 PM
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sc0tt
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I've been using Lunsford Racing titanium turnbuckles for years with zero issues. Made in USA and range from 2.5mm to 5mm and 4-40
For big jets like an EA Havoc, I use their 3.5mm and Dubro Monster ball links.
https://lunsfordracing.com/products/...-turnbuckles-2





The following 3 users liked this post by sc0tt:
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Old 10-15-2022, 05:20 AM
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jetsflyin
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Scott,
I like your set up, I will go that route. I assume the 3.5mm turnbuckles are comparable with the Dubro Monster Ball Links Correct?

Thanks
Old 10-15-2022, 07:29 AM
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I'm using Lunsford 3.5mm turnbuckles with Dubro # 2320 3mm Monster Ball links.
I did need to drill the Dubro ball link up a bit for the 3.5mm to thread in easier but still tight.
I have not tried Dubro #2316 6-32 size, they may work with no drilling?

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