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HelicopterMain Discussion › Tail servo linkage popped off?
09-13-2007 11:14 PM  10 years agoPost 1
AnnihilaT

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The Netherlands

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Hey Guys,

Had something weird today that i cant really come up with an explanation for... 90 size ship, boom mounted servo, tail servo pushrod made of wire thro the plastic guiders on the boom (raptor 90 v-max conversion)... in a hover, the tail linkage popped right off the servo arm. new linkage... rocket links... werent loose, never, ever seen that happen before... Anyone else seen this happen and have a good explanation what would make something like that happen?





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09-13-2007 11:30 PM  10 years agoPost 2
AnnihilaT

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The Netherlands

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I should clarify... its not he servo arm or linkage that came loose it was the ball link itself which popped off the ball which is securely bolted to the servo arm and blue loctited.





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09-14-2007 01:48 AM  10 years agoPost 3
Steff Giguere

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St-Eustache, Quebec,​Canada

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We had a guy at our club to whom it happened, more than once, two weeks ago...and he still does not know why? He stopped flying this heli for the time being.

Team Synergy, Rail blades, Team Scorpion, V-Team

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09-14-2007 02:17 AM  10 years agoPost 4
Furious Predator

rrProfessor

Kitchener, Ontario,​Canada

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i have had the odd link pop off in the past, still dont know why

mine were not worn either.

Shawn
Team Leisure-Tech
Team HelixRC

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09-16-2007 10:15 AM  10 years agoPost 5
AnnihilaT

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The Netherlands

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So it gets even MORE interesting. I secured the ball link to make sure that it would not be able to pop off again with a washer over the ball and took it out again yesterday for another flight. 2nd flight I lost the tail yet again! I hit throttle hold immediately and was able to auto it in with no damage again (yay!) but what i found as the reason for the failure this time blew my mind. Absolutely unbelievable... im willing to bet this is a first. It certainly is the first time anyone at my club has ever seen something like this happen.... what about you guys.

See pic below.

The ball links were still firmly attached at both ends of the pushrod but that doesnt really help much when the pushrod itself BREAKS IN HALF!!!

Now im going to a QUK CF pushrod with ball links secured with washers. I wonder what will fail this time. The epoxy holding the alloy ends to the CF tube would be my guess.

What the hell is going on? HF Vibration amplified by the CF boom, CF TT, and CF boom supports?





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09-16-2007 10:20 AM  10 years agoPost 6
Furious Predator

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Kitchener, Ontario,​Canada

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sounds like a vibration problem for sure...

i would first start looking at the tail. check the tail shaft and hub for straightness. and check the balance.

could even possibly be a bent main shaft...doesn't have to be a LOT, but its possible...i have had my tail explode due to a vibration from a slightly bent main shaft.

Shawn
Team Leisure-Tech
Team HelixRC

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09-16-2007 10:41 AM  10 years agoPost 7
AnnihilaT

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The Netherlands

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Main shaft is new, tail shaft is straight, but one thing i did do different this time was skimped a little on the tail blades... ms composite 110mm this time instead of the vblades 105mm i normally use. Now i have just switched back over the the 105mm v-blades when i added the QUK CF pushrod. I also was thinking that perhaps the cheaper tail blades and the fact that they are larger could have caused an issue especially if they were out of balance.





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09-16-2007 10:52 AM  10 years agoPost 8
Furious Predator

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Kitchener, Ontario,​Canada

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thats a possibility...personally i run 105 Rotor tech's...and i have personally never tried anything over 105mm. your 110's shoudl work as long as they are balanced.

i always check the balance of the entire tail assembly at the same time, its pretty easy that way.

Shawn
Team Leisure-Tech
Team HelixRC

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09-16-2007 11:11 AM  10 years agoPost 9
altima1779

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Toledo, oh u.s

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I had the same problem with my x-spec and i believe it was due to vibration. I also would think that the push rod you were using might be a little thin for use in a 90 size bird. A buddy of mine is using the Quick UK cf push rod and that seams to be working good.

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09-16-2007 12:20 PM  10 years agoPost 10
AnnihilaT

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The Netherlands

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I had the same problem with my x-spec and i believe it was due to vibration
So how did you resolve it?





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09-16-2007 02:21 PM  10 years agoPost 11
altima1779

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Toledo, oh u.s

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In my case i dial indicated my motor and i actually made my own push rod that i believe to be a little stronger than the stock x-spec push rod.

Here are some pics of were my rod broke.

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09-16-2007 03:41 PM  10 years agoPost 12
Stu.

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Abrakebabra Kebab​shop

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Few questions

A) Have you dial ndictaed your engine. If so what was the runout?
B) The wire guides were evenly spaced along the boom?

Its funny how resonance has wonderful effects on materials!

Stu

www.waterfoothelis.com

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09-16-2007 04:11 PM  10 years agoPost 13
AnnihilaT

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The Netherlands

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stu,

a) no, i never do this.
b) yes





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09-16-2007 04:13 PM  10 years agoPost 14
Stu.

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Abrakebabra Kebab​shop

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right, well theres your problem.

A sympathetic resonance built up, which resulted in a standing wave.

If the vibes did that to your pushrod, then can you imagine what its doing to your electronics?

Dial indicating and spacing pushrod guides unevenly will stop all that

Stu

www.waterfoothelis.com

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09-16-2007 04:15 PM  10 years agoPost 15
pphil611

rrApprentice

South Dakota

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push rod

Ever think about using a flex rod? I'v been using Sullivan #517 golden rods for over two years now and will never go back to solid rods. Pic in my gallery if you look real close.

Spectra-G, MAH, CSM

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09-16-2007 07:21 PM  10 years agoPost 16
AnnihilaT

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The Netherlands

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Stu,

I have never dial indicated any engine and never had issues before... I am not saying its unneccessary... i just know alot of guys who dont do this...

Anyway, i thought of something else... This is also the first time i have ever used a CF tail boom, and CF boom supports. Ive heard that vibration issues that would normally go unnoticed and not really be an issue become a much larger issue when you put such a stiff material on for the boom. Can you shed any light on this?

Altima,
Am i correct in assuming from the pictures that you actually had a threaded pushrod fail or is that a bolt?





A day without sunshine is like, well, night.

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09-16-2007 10:52 PM  10 years agoPost 17
RCMed-x

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westpalmbeachflorida​usa

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Vibrations are a crashes best friend balance fan, indicate run out and tuning could cause vibes

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09-16-2007 11:05 PM  10 years agoPost 18
Butch

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New York

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He might have had to convert to a 4-40 swivel ball link.

If the failed black pushrod is made of the material I think it is, then vibrations (normal/everyday) amplified by the weight of the coupler nearby, would indeed make short work out of that pushrod.Just a thought.

The Whirlybug Bit Me!

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09-17-2007 03:14 AM  10 years agoPost 19
altima1779

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Toledo, oh u.s

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yes it was the threaded part of the pushrod that comes standard with the Hirobo x-spec.

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09-17-2007 06:24 PM  10 years agoPost 20
AnnihilaT

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The Netherlands

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I was also thinking... if i had so much vibration wouldnt i have a very frothy fuel tank as well?





A day without sunshine is like, well, night.

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HelicopterMain Discussion › Tail servo linkage popped off?
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