Broken Jesus bolt

[whoodie]

Guys, I just found something unnerving, my jesus bolt (100-325A M3x25 Special Bolt) is broken.  It has broken right at the base of the threads.  It looks like (in the 2nd attached picture) the shank should reach all the way over to the other side of the spur gear hub but does not.  The shank is 15mm and the width of the spur gear hub, flange to flange is 20mm.  I'm certain I didn't overtighten it, as instructed in the manual.  Here is where it gets interesting, my good friend and flying buddy broke his today too.  He's had many other Synergy helis (N5C, E5, etc...) and has never had this problem before.  We both noticed an unordinary amount of slop between this assembly and the main shaft right from the start.  He has replaced his with a bolt that has a longer shank and most of the slop on his has been eliminated.  I'm going to buy a longer shanked bolt tomorrow and see if I can get some of the slop eliminated.  Let us all know what you find, thanks guys.

[Barry Tilson]

I have broken or bent this bolt three times with three crashes. Never noticed it loose. I don't fly hard either.
Dose seem like it may make sense to use a longer grip range bolt and cut off the excess threads.
I think the bolt in the collar above carries all the vertical load. This one is just for power delivery?




Barry

[Matt Botos]

When tightening this bolt, there should be no tightening involved, it should only close the gap and the Nylock nut should rely on the locking mechanism of the nut to stay in place. I've personally never broken this bolt with hundreds of flights on all of my models. This same bolt is used in the E7 which has twice the torque of the N7 with a 105 installed.

I will look into replacing this bolt with a longer shoulder for future kits but I really think the jesus bolts are just being over tightened. Again, this bolt should not be tightened at all, it should only close the gap and you are done. The bolt in the picture was broken right at the first thread which is indicative of tension being placed on the bolt.

Let me know if I can help in anyway! I can even send you a bolt with a longer shoulder if you feel more comfortable with it.

Thanks,

Matt

[whoodie]

When tightening this bolt, there should be no tightening involved, it should only close the gap and the Nylock nut should rely on the locking mechanism of the nut to stay in place. I've personally never broken this bolt with hundreds of flights on all of my models. This same bolt is used in the E7 which has twice the torque of the N7 with a 105 installed.

I will look into replacing this bolt with a longer shoulder for future kits but I really think the jesus bolts are just being over tightened. Again, this bolt should not be tightened at all, it should only close the gap and you are done. The bolt in the picture was broken right at the first thread which is indicative of tension being placed on the bolt.

Let me know if I can help in anyway! I can even send you a bolt with a longer shoulder if you feel more comfortable with it.

Thanks,

Matt

Thanks Matt, I'll take you up on your offer for the bolt, I've had a miserable time locating a suitable replacement at the LHS today, even if I cut the threads on a longer bolt.  I'll send you a PM.