bolt on the main shaft upper collar broke on the 3rd flight from the maiden.

[robertvizzo]

On the 3rd flight no damage just noticed I had lots of head play when I got it down. And the upper main shaft collar was spinning freely. I saw that the bolt head had broken off. Anyone else have this issue? I also notice that there seems to be extra play in the head like the dampeners are already worn is this normal? My friends head has no play and he has 100s of flights.
__________________
BK Servo Team Pilot......Team Pilot Zeal Blades
Goblin 700 comp-----Goblin 570 12s-------Goblin 380
Mikado Logo 480-----Synergy N7 ----Mikado Vcontrol

[Mike Spano]

I know you know how to build, but check go be sure the shims are between the thrust and radial bearings in the grips and not behind the thrust bearing. That can cause play.

Your broken bolt, on the pinch collar on the top?

[Mike Spano]

You have not changed any bolts to stainless by any chance have you? They are weaker. They typically don't break though, they stretch.

[Roger]

That bolt  has a warning to NOT over tighten.  Not sure why but it is clearly labeled.  I don't think it has much load on it while the machine is running. 

ROG

[robertvizzo]

I know you know how to build, but check go be sure the shims are between the thrust and radial bearings in the grips and not behind the thrust bearing. That can cause play.

Your broken bolt, on the pinch collar on the top?

I will pull the head apart and check the shims when the new collar comes in. Yes the pinch collar on the top. I used the factory socket head bolt. I didn't think I over tightened it, if its that critical then I would suggest calling about a inch pound torque in the manual so people don't over tighten it.

[Darren Lee]

Over tightening that bolt shouldn't be an issue.  It has to be tight to do its job, unlike the Jesus bolts which should NOT be over tightened.

[Mike Spano]

I know you know how to build, but check go be sure the shims are between the thrust and radial bearings in the grips and not behind the thrust bearing. That can cause play.

Your broken bolt, on the pinch collar on the top?

I will pull the head apart and check the shims when the new collar comes in. Yes the pinch collar on the top. I used the factory socket head bolt. I didn't think I over tightened it, if its that critical then I would suggest calling about a inch pound torque in the manual so people don't over tighten it.

yes, check the shims in the head concerning the slop. i have not had one of those bolts break. i havent read about many breaking either, so this may just be one of those weird things that happens to our helis. just replace the bolt with a new one, tighten it up good (it is the jesus bolt that cannot be too tight or it will cause problems, this one has to be tight), and give it another go. sorry your having issues, but these are not problems we see every day, trust me.

let us know how things go.

[Kevin Dalrymple]

As Darren said. Don't tighten the Jesus bolt to tight. I have had 2 of them brake on my N7. Use a good lock nit and just snug that bolt. You will be good to go.

[robertvizzo]

Getting ready to pull the head apart I noticed that the blade grips are not equal distance from the head block. I took the head completely apart and everything was installed correctly including the shim locations between the race bearing and thrust bearing. I then cleaned and re-greased and reinstalled as per manual. But still there is unequal distance from the head block the beginning of the blade grip? I have never had this before all the bearing fall in nicely nothing hangs up. It is normal to have to shim one side more than the other? I don't see any burrs on the blade grips holding the bearings from seating since they are pretty easy to move in and out. It looks like one .5mm shim will do it. However I just ordered some extra shims and wont be able to see if that resolves it until Saturday.

[Mike Spano]

did you measure the shims that are in there now to ensure they are both the same size? the kit comes with 2 different sets of shims for the head (the shims between the damper and the radial bearing...

no, this is not normal to have to shim one side and not the other, in fact, that would cause you issues.

if a bearing was sticking and not seating all the way down, it would actually get the heat too tight, not leave play, so something is amiss here. we just need to figure out exactly what it is.

what dampers are you using? synergy, or trueblood?

[robertvizzo]

to much locktite build up on main feathering shaft bolt caused build up on the washer.

[Mike Spano]

Good deal! Just clean the head axle out and bolt off good and use just a drop, no need to glob it on.

[rcnut]

I knew this guy that practically dipped his heli into a 55 gallon drum of loctite! That's how much he used on every single bolt! I had to use a heat gun to take everything apart.

[Rodney Kirstine]

I use the stick kind now but when I use liquid I pour a small amount on a piece of plastic and then just dip the ends of the screws in it. It's a lot easier to control how much I'm applying, that way.

[peteowlsmith]

I moved topic to N5c