600efl Counter bearing issue - anyone else had this?

[Paulo uk]

Finally got my 600 in the air today after getting an esc sorted - cant keep waiting for cc!

It flew absolutely beautifully straight away and I was just getting into some moves when the counter bearing just disintegrated and started screaming. I got it down no probs and only damage was the bearing itself.

Just to say that the bearing was free when fitted and the rotors and motor were moving freely.

Anyone else had this or might know what happened or what to watch out for when I fit the new one?

Paul

[Si_B]

Is this the support bearing for the pinion ??

[Zeeflyboy]

Yeah it is...

I'd just say there's two things to look out for...

- Don't tighten the screws on the lower support until the motor is installed... just like when installing a main shaft. This ensures everything is properly aligned. Since yours failed on the first flight I'd suggest this might be the issue.

- Make sure the pinion is not pushed down too hard on the bearing (just resting on top) and make sure of course that the pinion is firmly tightened to the shaft.

The problem here is that the helical cut of the gear effectively creates a strong downward force as the motor spins the gear. This means the pinion is pulling down hard putting a load on radial bearings that are not designed for those loads... a thrust bearing/radial bearing combo would be more appropriate.

The counter bearing, even though it's just a radial helps to reduce the load on the motor bearings though and takes some of the stress... of course its better that your counter bearing pops than your motor bearings.

Also keep it well lubed, its working hard.

[Si_B]

There should be a small gap between the pinion and that bearing so that if there is any movement in the motor shaft it doesn't end up putting all that side load on the radial bearing which they are not designed for.

Also check that the bearing is well fitted into the support bracket. Mine was loose, so I refitted it with some bearing retainer and its not going anywhere now !!

[Zeeflyboy]

But it's better that the counter bearing takes that load than the motor bearings...

As such, I wouldn't leave a gap, I'd just leave it lightly resting on the bearing, or at most a tiny tiny gap for thermal expansion of the shaft.

[Paulo uk]

Are the Motor and counter bearing not at fixed heights?

Paul

[Zeeflyboy]

The bearings are, but the pinion isn't

[Si_B]

I'm sure it says to leave a gap, but that might be the 700e manual.

[Zeeflyboy]

I'll have a look - I have the manual on my iPad.

Lol, in fantastic engrish "make sure the motor pinion gear is contacted with the bearing in the motor gear case downwards"....

There is a diagram with it, still not entirely clear but there's a big downwards arrow next to the pinion suggesting the pinion should be in contact with the lower bearing. Page 16 on the manual.

[Si_B]

Well considering the number of machines you see without a 3rd bearing, I guess the motor bearings should be capable of supporting the loads put on it. However, that third bearing is their to take the thrust loads between the pinion and the main gear. Radial bearings do not like thrust loads and from my experience fail quite quickly. I will be leaving a slight gap, but I guess the instructions should be followed. Could have been unlucky with a bad bearing.

[Zeeflyboy]

Yes but most heli's don't have a helical gear and thus don't have the thrust loads....

The motor bearings are also radials and are no better suited to the thrust load from the helical gear than is the counter bearing... The difference is the counter bearing is much less problematic to replace and won't nuke your motor when it goes, so I'd rather put the majority of the stress on there.

For it to go in a single flight though there's clearly something wrong.