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HomeAircraftHelicopterHelicopter Main Discussion › Jesus Bolt Snapping Saved My A$$
03-10-2014 08:30 PM  4 years agoPost 1
NitroMedic

rrApprentice

Southwest, Louisiana

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Hey guys,
Well, I was out doing a bit more testing this morning and had a small incident with the Hughes. THANKFULLY, I wasn't off the ground yet. Long story short, After spooling up to 70% throttle it appeared as though a grenade went off at the swashplate. Damage can be seen in pic below.

Good news, there was virtually NO cosmetic damage to the fuselage. I was shocked beyond belief because it was ugly as hell when it happened.

After talking with a fellow pilot, we think maybe the pushrod snapped at the base due to fatigue which kicked off a nasty chain reaction.

Blessing in disguise - Jesus bolt snapping in half saved me from much more damage. The rotor head immediately lost power and slowed to a stop which caused the heli to just settle down and relax.

Will be ordering replacement parts today with expedited shipping. Still planning on being at CHF with Big Betty in full swing.

Hey y'all, watch this!

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03-10-2014 08:41 PM  4 years agoPost 2
JKos

rrProfessor

Redondo Beach, CA

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Perhaps the Jesus bolt snapped first? That would leave the swashplate driven and the head undriven.

- John

RR rules!

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03-10-2014 08:50 PM  4 years agoPost 3
NitroMedic

rrApprentice

Southwest, Louisiana

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Food for thought...
John,

Didn't even think of that. Good possibility. Thanks for the input.

Hey y'all, watch this!

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03-10-2014 08:58 PM  4 years agoPost 4
xcellgasman101

rrElite Veteran

WOODWARD, OKLA....

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Did you go buy a Lotty Ticket yet?? Congrats with the save, With 70% of throttle, it could have been the jesus bolt that let go first,, XGM/VGM

John Crotts
www.soonerhelicamproductions.com

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03-10-2014 09:00 PM  4 years agoPost 5
NitroMedic

rrApprentice

Southwest, Louisiana

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Got My Ticket!
Man, ain't that the truth?! It literally scared the be-jeezus out of me. It happened so fast that by the time I realized something had went wrong the blades were slowing to a stop. I found pushrods 20 ft. away.

Hey y'all, watch this!

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03-10-2014 09:06 PM  4 years agoPost 6
ssmith512

rrKey Veteran

Indianapolis, IN USA

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Definitely the jesus bolt snapped first.

Is your jesus bolt a fully threaded bolt? Looks like it in your pic. I would not recommend that. I would use a shanked bolt and make sure you just barely snug the locknut, you dont really want to "tighten" it as you will stretch the bolt and cause a similar failure.

The heli gods were looking down on you!!

Steve

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03-10-2014 09:52 PM  4 years agoPost 7
NitroMedic

rrApprentice

Southwest, Louisiana

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Steve, you are correct
Yes sir, it was threaded end-to-end. Also, I did tighten it probably more than I should have. Looks like I was asking for this one. Have definitely learned from my mistakes. Just thankful it wasn't any worse than a few replacement parts.

Hey y'all, watch this!

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03-10-2014 09:53 PM  4 years agoPost 8
HeimD

rrVeteran

the great southwest

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I'm not sure about this particular heli, but on a "regular" FBL heli, I'd say something else broke first. The upper rotating star of the swashplate is driven by the follower arms which are directly connected/bolted to the head block. Just the upper Jesus bolt breaking wouldn't tear up head parts like that. If it broke, the still being driven main shaft would spin inside the head block, but the rest of the entire head would slow down as a complete unit with no phasing differences.

Something else "popped" and jammed up the rotating/non-rotating stars of the swashplate while the head was still being driven under power which bent those parts and, ultimately, sheared the upper Jesus bolt.

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03-10-2014 09:58 PM  4 years agoPost 9
NitroMedic

rrApprentice

Southwest, Louisiana

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Positive Pitch
Well, I was at +5 degrees on the pitch when it happened. With the downward forces at play, I would think this would cause the head to rise up the shaft, causing the pushrods to stand up taller, therefore closing off that clearance between pushrods and swash driver. At that point, contact is made between rods and driver causing the grenade effect. I could be way off base.

Hey y'all, watch this!

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03-10-2014 10:03 PM  4 years agoPost 10
JKos

rrProfessor

Redondo Beach, CA

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I'm not sure about this particular heli...
This particular heli has a swash follower as shown in the picture. Thus, if the Jesus bolt breaks, the head stops being driven and will decelerate quickly while the inner swashplate remains driven by the swash follower.

- John

RR rules!

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03-11-2014 12:10 AM  4 years agoPost 11
icanfly

rrElite Veteran

ontario

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Ever wonder what happens at the threads where they become the shoulder, or non-threaded part of a bolt? Figure, long bolt, repeated twisting of nylock and or threadlock'd nut, torquing it on and releasing it off a few times. I'll tell you what happens, the loctite becomes a non slip lube when you put it on, you over tighten which twists the most susceptible part, the area between the threading and the non threaded shoulder of the bolt. A crack may form, high freq heli vibes begin to un-twist the metal, they crack, they snap clean off without further adue. baboom.

A dude at a local hardware store humored me about guys with gorilla hands, who tighten everything to the breaking point.

Bolts that are torqued are twisting and are highly not recommended for re-use, a little v8 engine building can teach you a lot.

I dunno, maybe?

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03-12-2014 08:23 AM  4 years agoPost 12
wc_wickedclown (RIP)

rrProfessor

long beach calif

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might i add try not to over tighten the Jesus bolt it might stretch get weak and snap.

Insha Allah made in america

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03-12-2014 03:59 PM  4 years agoPost 13
Ladymagic

rrKey Veteran

South Korea

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Hard to say what snapped first, but my money's on the jesus bolt snapping first and a loose piece of it jammed up your drive train which caused the rest of the mess.

In any case...it's good to see it wasn't catostrophic and looks to be fairly inexpensive to get you back up.

I love the term "gorilla hands." That made me chuckle a little bit. Like those who've already said, use a shanked bolt next time and only tighten it enough for a snug fit. Happy flying!!!!

Mellisa

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03-12-2014 04:03 PM  4 years agoPost 14
rudyy

rrElite Veteran

E. Amherst, NY

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You should use only the shoulder threaded screw for the jesus bolt.

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03-12-2014 05:38 PM  4 years agoPost 15
ticedoff8

rrKey Veteran

Morgan Hill, CA. USA

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Use a bolt with a shoulder that is long enough to pass through to the other side - the shoulder should be contact all the "sharp edges" that you would imagine are trying to shear the bolt in two.

And, the threads should be long enough to expose at least 4 threads past the nut.

Use these type of bolts on top (head) & the main gear jesus bolt.
Same for the tail & main rotor blade grip bolts.

Using a threaded bolt in these areas is a gamble.

Believe 1/2 of what you see and none of what you hear.
Fake News will be the downfall of our Republic!

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03-13-2014 05:27 AM  4 years agoPost 16
NitroMedic

rrApprentice

Southwest, Louisiana

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Good Advice
Thanks so much for all the feedback, guys. It's truly appreciated. I definitely think I've learned a very valuable lesson with minimal collateral damage. Looking forward to getting her put all back together and showing her off at CHF.

Thanks again!

Hey y'all, watch this!

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03-13-2014 10:00 AM  4 years agoPost 17
McKrackin

rrProfessor

Lucasville,Ohio

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Thus, if the Jesus bolt breaks, the head stops being driven and will decelerate quickly while the inner swashplate remains driven by the swash follower.
The swash follower is driven by the head so when the head is no longer driven...neither is the swash.

Ooooohhhh....I keep forgetting that not all swash drivers are on the head block.

Don't know why I finished this post.lol...

Good call John.

I literally never use the word literally right.

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