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HelicopterScale Model RC Helicopters › Close freekin call
01-21-2017 03:18 AM  10 months agoPost 1
Mojave

rrElite Veteran

Palos Verdes, Ca.​USA

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So, I had a tail vibe in my big R22 that I was chasing down for a while now (gremlins suck) Replaced the tail rotor shaft, checked the shimming and grease in the tail box, replaced the front drive coupler, checked the balance on the tail blades (they were fine) etc.. Took her up for a check flight (yes in this crap weather and heavy wind) and I'll be damned if that vibe didn't get worse!! But now the tail was hunting all over the place and vibing. Landed, pissed off, packed up and went home. I took the entire boom off the heli and what did I find??? The tail pitch control rod had come un-bonded and the graphite op rod had cracked. So the threaded rod was just doing it's own thing, moving in and out at will. The graphite tube had split 1/2" down from the end and the adhesive had lost it's grip on the inside of the tube, but stayed bonded to the threaded rod. This heli was partially built when I bought it and converted it to e-power, so I had no idea how little of the rod was actually bonded inside the tube (very little). I also didn't know that standard hobbypoxy was used to bond it.

So, I cut .750 off the end of the graphite tube and used a very long 2.5mm control rod to replace what was originally installed. I used a Dremel to rough up the rod for bonding, then used BVM/Hysol adhesive to bond the new rod in place. Lesson for today: Some days we just get lucky...
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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01-21-2017 03:39 AM  10 months agoPost 2
ssmith512

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Indianapolis, IN USA

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Heli gods were watching over you today!!

Glad no helis were harmed!

Steve

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01-21-2017 04:00 AM  10 months agoPost 3
hrc37

rrApprentice

Derry, PA

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What to use?

Hey Barry,
Funny that you bring this up....not funny with what you found but funny that I've always wonder what most guys use to glue threaded rod into a carbon tube. I've always used JB Weld (for well over 20 years) and have never had one fail but sometimes I wonder if there is something better or would just give me a better piece of mind....even though I've never had one fail. And now that Steve just introduced me to Hysol, maybe I'll start using it.
Thanks! Mark

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01-21-2017 12:59 PM  10 months agoPost 4
goodhunting

rrApprentice

Slovenia ...​somewhere in Europe

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A few CF puchrods that I have and have used... I always made myself...
Inserted waaay more of the metal rod in the CF tube than what I can see on your picture...
and used the two part epoxy...

nice find and a great save....
I guess this is one more check to add on the list of things I check annually... maybe I should start a bi annual inspection...

gh

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01-21-2017 01:53 PM  10 months agoPost 5
doorman

rrProfessor

Sherwood, Arkansas

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Great Catch..

Some days you get peanuts and some days you get shells... buy a lottery ticket buddy!!!
It is amazing what we get away with at times!!!
Great catch!!!
Stan

AMA 2918-Team JR, Spin Blades, East Coast Scale Helicopter,Castle Creations

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01-21-2017 03:39 PM  10 months agoPost 6
fastflyer20

rrKey Veteran

N. Tonawanda, NY

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Good find!

As added insurance to prevent CF from splitting, wind thread around the diameter of the ends for approximately 3/8" of the CF and wick in CA. An old technique used by plankers for making push rods.

Tom
CAUTION - my posts are based on my experiences, yours may be different.

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01-21-2017 04:49 PM  10 months agoPost 7
coptercptn

rrElite Veteran

Mesa AZ. USA

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Good catch Barry... and me too.
Last flight at a local fun fly, I heard a strange noise coming from the tail of my 53... also, a tail "twitch".
Landed and brought it home..
Pulled off the tail pylon and low and behold, one of the pitch slider bearings had decided to come apart and seized up on the brass slider..
I found some nice ceramic replacements at Boca..but was lucky that I had a spare brass sleeve!
Anyone know where I can find a replacement sleeve? This is an "OF" tail gearbox/rotor....

Home of the "Sea Cobra".....

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01-21-2017 09:19 PM  10 months agoPost 8
Mojave

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Palos Verdes, Ca.​USA

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Stan: That's it, I'm playing the lottery tonight!!

HRC37: JB weld is great stuff and very strong. The reason I use BVM/HySol is because it retains a little bit of flexibility after cure. I think JB weld would work fine in this application because the bond line(gap between the parts) is very small.

Klem: Those pics are deceiving I actually have over 1.75" of the rod bonded in the graphite tube. It just looks funny, because I had to trim back the damaged end of the tube.

Tom: Great idea. I had forgotten about that old planker trick...

Jim: That was a hell of a save on your end too!! Looks like it's our lucky week. Let me know if your lottery ticket pays off. Then we can start the adoption paperwork... my new dad LOL...

Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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01-21-2017 10:49 PM  10 months agoPost 9
Mojave

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Palos Verdes, Ca.​USA

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So here's the final fix: Thank you Tom for your suggestion. I wrapped the end of the graphite tube with high strength thread, then hardened it with CA, then I gave it a shrink tube sleeve (just for looks).
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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01-22-2017 12:22 AM  10 months agoPost 10
Copter Doctor

rrProfessor

Enterprise/ft.rucker​,al- home of army​aviation

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Good move Barry, I've prevented a few catastrophes with my "hundred hr" inspections

drive a rotary, fly a rotorcraft

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01-22-2017 01:05 AM  10 months agoPost 11
rcheli808

rrApprentice

Mililani,Hi-USA

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Thanks for sharing this Barry.
Made want to re-check my homemade push pull tubes.

Tim

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01-22-2017 10:00 AM  10 months agoPost 12
PETER ROB

rrElite Veteran

Devon UK

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carbon push rod

Barry, a lucky find
Carbon tube comes in different degrees of make up
1, carbon fibre drawn in straight taws and glued together
2, carbon fibres wound (like the thread example) and glued together
3, carbon sheet wrapped (this example found because of the joint line)
My guess is the failed rod was first example
This failure has happened to me on a few occasions, particularly when (in large scale) where the rod is prone to flex more because of limited support, and too much throw on the servo arm, and where the limits on the gyro have not been set correctly
Minitature aircraft used to supply their rods with a captive aluminium end, there was for a while a few other suppliers of these end, not seen so often now
Peter R

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01-22-2017 03:59 PM  10 months agoPost 13
Mojave

rrElite Veteran

Palos Verdes, Ca.​USA

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Emile: Yeah bud, I dodged the bullet on this one...

Tim: You're very welcome. I posted this because I don't want it to happen to anyone else. Passing on info helps us all.

Hi Peter, you're correct it was the first example. It's stranded uni-directional CF laid over a mandrel. Another issue is that it's not easy to abrade and clean the inside of the CF tube prior to bonding (this is critical for good bond adhesion). The mfr uses mold release on the mandrel that they form the tube over and this needs to be removed. I use a small round jewelers file to rough up the inside of the tube, then I clean it with acetone and let it dry before bonding. I agree, the old MA style ends are the best.
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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01-23-2017 09:08 PM  10 months agoPost 14
fastflyer20

rrKey Veteran

N. Tonawanda, NY

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MSH offers an end that slips over the tube for the Protos 700 Max V2 that is threaded. The CF is available in different lengths for the stretch kits. The diameter seems larger than other 700 kits I have built

The p/n's are:
MSH71196, MSH71197, MSH71198

Tom
CAUTION - my posts are based on my experiences, yours may be different.

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01-23-2017 09:48 PM  10 months agoPost 15
old nitroman

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Naples florida

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Wow very very lucky

E5s and E7se,and a 766, Roban bell 222 800 superscale,450 bell 4 bladed head,gobby 380and 420 ,180cfx

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01-23-2017 09:52 PM  10 months agoPost 16
old nitroman

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Naples florida

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people think I'm crazy I use jb weld stuff that takes 24hrs

E5s and E7se,and a 766, Roban bell 222 800 superscale,450 bell 4 bladed head,gobby 380and 420 ,180cfx

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01-24-2017 06:56 AM  10 months agoPost 17
tonysrepair

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portland oregon

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glad you didn't crash your baby barry

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01-30-2017 10:43 PM  9 months agoPost 18
PETER ROB

rrElite Veteran

Devon UK

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Heads up

Barry, since your post, I have taken the booms off 2 R22, the yellow one's push rod, had been split in the past
The original builder noticed a small crack when he cut the rod, he put the original thread on as a precaution
No idea about the second one further down the rod, this heli has had 3 owners before I bought it back in
Peter R

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01-31-2017 11:04 PM  9 months agoPost 19
Mojave

rrElite Veteran

Palos Verdes, Ca.​USA

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Hi peter,
I'm glad that you had a look at the fleet, PM and inspections are always a good thing. I agree. They should last a long time if set up correctly.
Barry

All helis and planes have an expiration date stamped on them...you only find it after you crash!!

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02-01-2017 12:18 AM  9 months agoPost 20
doorman

rrProfessor

Sherwood, Arkansas

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JB Weld

I have used JB since day one when building the cf pudhrods, and it has worked very well for me.., just say'n

AMA 2918-Team JR, Spin Blades, East Coast Scale Helicopter,Castle Creations

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