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HelicopterCentury Radikal G20-30 N640 Hawk Predator › What's left of my Jesus bolt - NX50
04-26-2011 03:16 AM  6 years agoPost 1
mikefoy6

rrApprentice

Thief River Falls, MN

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~20 flights on my 50NX. Last time out the head wouldn't spool up even though the engine would rev. Tail was going just fine. I thought my engine started backwards but come to find I have no jesus bolt.

Here's what is left of it. I had to hammer it out of the main shaft. The hub sheered the head of the bolt right off.

Any Ideas as to how / why my this happened or how to prevent it? Or is my new YS56 really that powerful?

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04-26-2011 10:13 AM  6 years agoPost 2
HarveyR

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France - North

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That's happened to me a few times on my Hawk (OS50). Luckily, it seems it never falls out during the flight, it's always been on the ground when it's happened, just like in your case (motor revs but rotor is still...).

I guess it just boils down to the crap quality hardware we get in this hobby (Century and Align at least share this).

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04-26-2011 10:43 AM  6 years agoPost 3
Paul Woodcock

rrElite Veteran

Dubai - United Arab Emirates

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Hi

It should be a shanked bolt.

If you cant find one, go down to a hardware shop that has metric bolts and buy a longer bolt that is shanked enough to go all the way through to 'just about sticking out the other side of the head'. You will need to cut it down to the correct length.

What you are trying to achieve is the area where the head and shaft touch is solid 3mm bolt, with no thread.

Regards
Paul

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04-26-2011 02:48 PM  6 years agoPost 4
RCHSF

rrKey Veteran

NC

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Would starting the heli while holding the head caused this? Being it has not failed during flight. Just an idea.

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04-26-2011 02:59 PM  6 years agoPost 5
Frank Bostwick

rrElite Veteran

Cincinnati Ohio

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100% of what Pwood said. It really really needs to be shanked all the way thru the contact area.
The head should ALWAYS be held tightly when starting, no matter what. Holding the head will not cause undue stress (unless its a hot start) Jbolts should be considered a wear part IMO (but not every 25 flights!)

RIP ROMAN

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04-27-2011 06:24 AM  6 years agoPost 6
canbarelyhover

rrVeteran

Sunnyvale, CA

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If there's play between gear center hub opening and bolt it will also lead to accelerated wear and failure. In which case just replace the center hub.

Citizen #830

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04-29-2011 12:13 AM  6 years agoPost 7
rotormonkey

rrKey Veteran

Ottawa, ON - Canada

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I've always used a threaded bolt myself, though I know the shanked one would probably last a lot longer (indefinitely). If it failed on you in 25 flights you probably over tightened it. That bolt is already under a lot of stress as you can imagine. Over torquing it will always cause premature failure.

Just make it snug, and trust that the locknut will do it's job. Also make sure not to use a worn locknut.

If it can't hover, it ain't worth flying.

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04-29-2011 09:12 PM  6 years agoPost 8
MartyH

rrProfessor

USA

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Thats not the correct jesus bolt. It should have been smooth shanked with just enough threads to capture the locknut. The smooth shanked bolt is rated for a higher load than a threaded one. You can also chock up the random failure of a bolt like that to iffy quality control we sometimes experience in almost any brand of these kits.

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