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HomeAircraftHelicopterMain Discussion › What the heck - My Jesus Bolt Sheared!
04-29-2013 02:22 AM  5 years agoPost 1
Rockohaulic

rrElite Veteran

Canyon Country, CA, USA, 3rd Rock from the Sun

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There I was... Flying my Whiplash 700E and having a great day when suddenly...

...I had no power, and I had to do a forced auto.
At first we thought it was an ESC issue and that it shut down. If there is a thermal shutdown, it still provides some power, and that is how it felt.

But once I got it home, I was going to remove the stripped main gear and I found the bolt missing (the lower Jesus bolt) . Or more correctly, just a stub of it was left in the main shaft. I punched it out.

So this leads me to 2 questions:

1. Has anybody had a Jesus bolt issue with this bird??? Are there better, stronger Jesus bolts for this thing???

2. The more pressing issue is: I still can't get the head off!!! I removed the pinch bolts and the 3 ball links to the swash. The main shaft/head came up about 3/4 inch, but now it is stuck. It will not come up any more, and it will not go down. I can turn it in place, but I can't move it! Arghhhhh! How do I remove this thing???

HELP!

Saturday morning I flew my helicopter in my pajamas
How it got in my pajamas I'll never know

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04-29-2013 03:05 AM  5 years agoPost 2
sonnyhad

rrProfessor

Holland,Mi

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Oh man, that doesn't sound good! Try some penetrating oil!

Bald Pilots usually wear hats!

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04-29-2013 03:16 AM  5 years agoPost 3
DougPenhall

rrApprentice

San Jose, CA - USA

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When you shear the jesus bolt, the main shaft got a small bump on it. You'll have to carefully force it off and hope you don't break anything in the process. Once you get it off you'll be able to file off the bumps. If you're able to pull the gears out you might be able to push the shaft back in, then file the bumps off before pulling it out. You may have to tap the top of the main shaft with a hammer while holding the heli in you hand to get it to go back in.

You're lucky it didn't slip right out and drop your heli from 50 feet.

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04-29-2013 03:27 AM  5 years agoPost 4
GetToDaChopper

rrElite Veteran

Las Vegas , NV

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is your "Jesus bolt" threaded all the way like the 1st pix or does it have a shank like the 2nd pix ?


    ▲
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▲ ▲ ▲ One of a Kind !!!

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04-29-2013 03:44 AM  5 years agoPost 5
Rockohaulic

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Canyon Country, CA, USA, 3rd Rock from the Sun

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Shank.

So I now understand that MA has an upgraded Main Gear Hub that helps resolve an apparently known Jesus bolt issue.

I'm going to get this hub and a new main shaft....

Thanks guys............

Saturday morning I flew my helicopter in my pajamas
How it got in my pajamas I'll never know

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04-29-2013 03:48 AM  5 years agoPost 6
Rockohaulic

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Canyon Country, CA, USA, 3rd Rock from the Sun

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You're lucky it didn't slip right out and drop your heli from 50 feet.
Actually, I've seen someone lose a Jesus bolt before and the head pulled up and the swash links kept it from pulling off. Problem was that now he had no control of the heli and it went in.

In my case there are pinch bolts in addition to the Jesus bolt. So they kept the main shaft from slipping up, and therefore I could perform an auto.

I've never thought about it before, but the pinch bolt design is really a great design for this reason, and for the reason that they take some of the load off the Jesus bolt.

Saturday morning I flew my helicopter in my pajamas
How it got in my pajamas I'll never know

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04-29-2013 04:03 AM  5 years agoPost 7
carcrasher

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east coast

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Is the hub for the eWhip only or for any of the whips?

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04-29-2013 04:56 AM  5 years agoPost 8
Rockohaulic

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Canyon Country, CA, USA, 3rd Rock from the Sun

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I think all 3. WHy?

Saturday morning I flew my helicopter in my pajamas
How it got in my pajamas I'll never know

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04-29-2013 05:02 AM  5 years agoPost 9
carcrasher

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east coast

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Just wondering if I should change it out or not on my nitro whip.

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04-29-2013 06:33 AM  5 years agoPost 10
Rockohaulic

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Canyon Country, CA, USA, 3rd Rock from the Sun

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Well, unfortunately they did a rolling update and did not change the part number. So I have no real way of telling you if you have the old design or the new.

And I don't know when they made this change.

Here's what I found out:

They increased the width of the gap on both sides where the pinch bolts are. This was to get more clamping force.

The gap on my old one is paper thin. Really paper thin! You'd need a really thin feeler gauge to check it.

If your gap is thicker than this, then you possibly have the new upgrade.

Unfortunately HeliWholesaler is out of stock at this moment (Sun Apr 28), and I ordered one tonight from HeliProz.

When it arrives I'll check the gap thickness. Also, tomorrow when they are in, I'm calling to ask if they have the new ones or the old ones.

Saturday morning I flew my helicopter in my pajamas
How it got in my pajamas I'll never know

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04-29-2013 01:06 PM  5 years agoPost 11
icanfly

rrElite Veteran

ontario

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heyo rockohaulic, if you set the main shaft in a vise or closely fitting aluminum pipe or sheet with a hole big enough for the shaft to fit through with the head resting on top, it is possible to plunge the mainshaft out from the top. A washer under the head where the pinch bolts are will preserve the condition of the head.

Feathering shaft, and button get removed for you to tap a rod through the top. use some heat and light machine oil before chasing the shaft out.

If you have to enlarge the button bolt hole and tap for larger threads later it will be fine, actually better than original in some respect. You have to drill/tap as straight as possible though, use a drill press for both steps if you have one.

You can increase the gap on the slit by running a fine bade hacksaw or hobby saw ticker than the original gap, taking your time cutting evenly while removing material in an arc to keep it lined up in the original slit. Clamp the head in a vise to perform these steps.

Clean up with fingernail sanding boards, file, or something of your own devising. Clean up any roughness in the gap and along the edges inside and out, or send it to a machinist buddy who will slit it wider with a router saw.

A little machinist tip, drill a hole where the slit ends slightly larger than your finished slit size. This will bottom out your slit without leaving a squared shape while giving you a distinct place to stop.

The pinch design is used everywhere.

good luck on the repair

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04-29-2013 04:23 PM  5 years agoPost 12
ddavison

rrVeteran

Brownsville, Pennsylvania

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Try heating the head with a heat gun or hair dryer. The head block is alum so it should expand and loosen.

DaveDavison,GasGob,WhiplashGas,Spectra,JRXG11MV,12X

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04-29-2013 04:43 PM  5 years agoPost 13
icanfly

rrElite Veteran

ontario

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You might get "galling" on the parts which mess with the original finish inside the hole. You'll have to chase all the damage off and see that the shaft doesn't bind going in again. Galling usually happens when the parts are dry, dis-similar metals are used, and no lube is present. Clean everything before re-assembly. Use a heat gun for high heat, not a torch if it has colored anodizing.

and so on

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04-30-2013 11:28 PM  5 years agoPost 14
RockohaulicrrElite Veteran - Canyon Country, CA, USA, 3rd Rock from the Sun - My Posts: All  Forum  Topic

Turns out MA has an updated hub which helps the issue.

However, apparently the Jesus bolts in the kit are not the strongest out there, and an upgrade to a 12.9 grade bolt will also help the problem.

On another site, they were thinking that a 4mm x 40mm bolt would have the correct shoulder length. But the shoulder length is far too long as you can see in the pic below.

So I am going to attack this issue in two ways.

1. I ordered the upgraded hub.
2. I'll be using a grade 12.9 4mm x 35mm SHCS for a Jesus bolt.

Saturday morning I flew my helicopter in my pajamas
How it got in my pajamas I'll never know

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04-30-2013 11:50 PM  5 years agoPost 15
Dan Minick

rrKey Veteran

Columbus, WI

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be sure only to snug up the lock nut. you can do all the upgrades in the world and still have problems if the bolt is over tightened. im not saying this was the cause but many many people make this mistake

Team Synergy, Team FBL Rotors-------if its not broke...it will be!

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05-01-2013 12:58 AM  5 years agoPost 16
Rockohaulic

rrElite Veteran

Canyon Country, CA, USA, 3rd Rock from the Sun

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be sure only to snug up the lock nut. you can do all the upgrades in the world and still have problems if the bolt is over tightened. im not saying this was the cause but many many people make this mistake
You are absolutely correct!

Saturday morning I flew my helicopter in my pajamas
How it got in my pajamas I'll never know

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05-22-2013 09:43 AM  5 years agoPost 17
snowman999

rrNovice

nottingham

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I have ordered the new hub, seems exactly same with that shown in your picture, is that the new one?

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05-22-2013 10:15 AM  5 years agoPost 18
Climax

rrVeteran

West London, United Kingdom

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I had a lower bolt shear quite a few years ago on a Century Hawk when I was first learning to fly...

Fortunately not all of it fell out and the torque of the hub acting on the main shaft via the remainder of the bold kept the heli flying... I didn't actually notice that there was a problem until after I had landed and tried to spool up again. By this time the remaining part of the bolt had been ejected, probably as I spooled down after the flight.

Since then I've always used the best quality shouldered bolts and try my best not to over tighten them!

Electronics, Physics, Helicopters, Fixing Things...

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