N5 - Inflight failure - Preflight check warning!!

[Britflyer]

Would it be beneficial to add a second grub screw opposite to the first one on the collar, and when assembling it all, tighten the grub screws to mark the main shaft, remove the shaft, and grind (Dremel) a flat where those marks are. That way you have double fixings, and something for them to lock on to.

Rob, the N5 uses a split collar rather than grub screws. So doesn't use point location like the grub screw method.

The problem with the grub screw method in this location on an N5 is that you deform the shaft abit with the grub screw making it hard to remove the shaft thru the upper bearing.


Paul

[Rctintin]

Just to add, if anyone wants drilling, tapping etc done, send it to me and I'll do it for you. I have a small milling machine and a lathe. Just send me a PM.

[Rctintin]

Paul, my mate owns a bearing supplers so will ask tomorrow for you.

[SRH990]

Would it be beneficial to add a second grub screw opposite to the first one on the collar, and when assembling it all, tighten the grub screws to mark the main shaft, remove the shaft, and grind (Dremel) a flat where those marks are. That way you have double fixings, and something for them to lock on to.

The Outrage 550's collar is fixed this way and it causes it's own problems. Because the grub screws are exactly opposite each other, it tends to 'rock' causing it to walk up the shaft, the fix in this case seems to be to only use one grub screw.

A better option is either to have two grub screws spaced 90 degrees apart or three at 120 degrees.

[waveydavey]

Paul is there another number on the bearing, there should be a part number like 63800-ZZ or something and are you sure it's 6mm not 7

[neilb]

How much cylic pitch can you use with the balls in the manual placements

[rspblake]

Paul,

Bearing is a bit confusing, as for some manufacture was coded as 6800zz but that is for the 10x19x5mm version, on 95% of the list I looked at.

Although you get to choose the dia.. on some using that code..

It looks like it's a more common size in the states using the 6mm version.

Locking collar..The Kn sport uses a double grub screw at 90 deg offset, the kn3d uses a steel locking collar version that you could really crack up, but I suggested to replace the bolt every other time it was undone if beating the model

I have both if any ones worried..

[Kwickkwack]

A better option is either to have two grub screws spaced 90 degrees apart or three at 120 degrees.

Spot on in my opinion, I was always taught the 90' method as that way they do not work against each other.

[00boto]

A few notes on this topic.

Grub screws used on locking collars does not work. This was tried on the Hirobo Freya, Synergy N9, and many other helicopters in the past. It simply does not have the holding power needed for 50 - 90 sized machines.

The pinch collar. This method has been proven effective over the past ten years. We used it to fix the N9 grub screw collar when it was slipping badly causing crown gear stripping. Also, back when I was flying for Miniature Aircraft we used this method on the Fury Extreme and Stratus. Bergen also uses the same method.

The lock collar must be tight. I have over 900 flights on the prototype with no slipping. We have over 20 Synergy N5's in my area and I have seen some guys only tighten them moderately and they will get 1 or 2mm of slippage. After I showed them how much to tighten them they have not slipped at all.

Hope this helps!

Matt

[Tom Burgess]

A few notes on this topic.

Grub screws used on locking collars does not work. This was tried on the Hirobo Freya, Synergy N9, and many other helicopters in the past. It simply does not have the holding power needed for 50 - 90 sized machines.

While I am in no way qualified to criticise your engineering skills Matt, the locking collar on the Aurora uses 2 grub screws at 90* and it works. Unless we are talking about another application here?

[00boto]

I should probably rephrase my statement.....

In order to get the grub screw lock collar to work, it should be designed as follows.

- 90 degree offset grub screws.
- Flat spots on the main shaft that are only large enough for the tip of the grub screw. Any larger and you might see some slippage.
- Flat spots also serve the purpose of not buggering up the main shaft making it difficult to disassemble.

Most manufacturers won't go through all of this to get the grub screw collar working properly. After its all said and done, the cost of production for the main shaft will go up an possibly the lock collar as well.

Matt

[00boto]

As I was working on one of my N5's today, I remembered something critical I saw during the pre production build. One of my split collars was tapped on both sides, this is not correct! The split collar should be tapped on one side and a through hole on the other side, otherwise the split collar will not clamp the main shaft all of the way. With both sides tapped your screw will basically bottom out without adequate clamping.
The factory was notified but this does not mean that a few collars escaped through Q/A.
Everyone should check their split collars to make sure the bore side is a through hole. If it is not, use a 2.5mm drill bit and carefully drill the side of the split collar which has clearance for the head of the bolt.

My apologies for not remembering this earlier.

Matt

[mark Taylor]

As I was working on one of my N5's today, I remembered something critical I saw during the pre production build. One of my split collars was tapped on both sides, this is not correct! The split collar should be tapped on one side and a through hole on the other side, otherwise the split collar will not clamp the main shaft all of the way. With both sides tapped your screw will basically bottom out without adequate clamping.
The factory was notified but this does not mean that a few collars escaped through Q/A.
Everyone should check their split collars to make sure the bore side is a through hole. If it is not, use a 2.5mm drill bit and carefully drill the side of the split collar which has clearance for the head of the bolt.

My apologies for not remembering this earlier.

Matt

just checked mine matt

it seems i've got one that's slipped thru the net ,treaded all the way
my clamp was coming loose after each gentle flight approx 1-2mm play

i'll get a 2.5mm drill bit tomoz and drill the front side out

cheers

[electricsceadu]

if it helps at all i changed the pinch collar type to the grub screw type collar on my freya as the pinch type kept slipping
after the grub screw type was fitted the problem was cured
and every time you undo the grubscrews replace them, never use a grubscrew twice

[Britflyer]

just checked mine matt

it seems i've got one that's slipped thru the net ,treaded all the way
my clamp was coming loose after each gentle flight approx 1-2mm play

i'll get a 2.5mm drill bit tomoz and drill the front side out

cheers

And mine slipped thru aswell! Mine is tapped both sides.

Guess that explains it! And why I kept developing play so quickly after apparently tightening the collar up each time. And why the bolt felt just as tight after strip after the event. Bare in mind I've only had about 8 flights with the N5 and a new engine so each flight was getting more and more extreme and therefore slowly increasing the load on the collar to the point that .......

So we had build error, broken collar or faulty collar as cause. Guess a faulty collar contributed to my event.

Synergy gonna pick up the bill?

Hopefully at least a warning will be posted on your site Matt and my event will be the last to be seen of it.


Paul