New G255 - Catastrophic grip failure resulting in major destruction

[Rob Cherry]

Just fired up my new G255, all balanced and ready to roll. Put it on my test stand and fired up to 60% throttle to setup gyro, tracking, etc. 3 minutes into the test the head exploded and the rest of the unit went south. Who builds and tests these things? What could have went wrong? This thing put a hole in my wall and destroyed the rest of itself. Also I didn't witness any vibrations of any kind before it went postal.

After further inspection, the inner race of the bearing pulled through. Is this just poor design by Gaui to have a 3000+ rpm head without using true thrust bearings in the grips? Even e-flite uses thrust bearings on their grips. Can a standard bearing be expected to handle that much lateral force. I tested the other bearing and it pulled out at 90 lbs. I don't know if that's a lot but I calculated at 3500 rpm each blade has a pulling force of roughly 51 lbs. but at 4500 rpm each blade pulls 85lb. Max rpm is 4700 with no load, could this be right? Are the bearings underrated for this machine? When sizing bearing loads, wouldn't they factor in maximum possible head speed? OR are they leaving it up to the user to not exceed the books recommendation of 4240RPM.

Anything else like this out there with these new units?

Man, I've just lost a level or two of confidence in this hobby as far as my safety and well being are concerned.

[odieser]

Sorry for the failure but would the fact that the heli is tied down to a test stand and there are no other places for the forces that are developed in your heli to escape as in flight ( up , down, sideways ) be the cause of the failure. Or perhaps just a crappy bearing that gave way. have not seen this in all the posts here or elsewhere with any Gaui heli I had or anyone else.
Just throwing that out there.
Mark

[ferrettmerr]

From everything i have heard test stands are a bad idea. They reverberate vibrations that the heli would not have in the air. This can cause many issues and destruction in a lot of cases. Was the heli at 0 pitch during the test?

[Rob Cherry]

Thanks, I hadn't heard about test stands being a bad idea, but now that you mention it, I think I won't be using it any longer. Yes, 0 pitch.

[Stump3r]

I fly my fair share of Gaui birds and I've never had a catastrophic bearing failure like that, and I've put my Gaui birds through a lot!

I'll echo what's been stated above, test benches are not a great idea. I've heard a lot of horror stories of things failing on birds strapped down to a bench.

[SurfCity]

Originally Posted by Stump3r

I'll echo what's been stated above, test benches are not a great idea. I've heard a lot of horror stories of things failing on birds strapped down to a bench.

+1.

[yys5617]

Originally Posted by csdstudio

Just fired up my new G255, all balanced and ready to roll. Put it on my test stand and fired up to 60% throttle to setup gyro, tracking, etc.......

How about contact GAUI via e-mail directly?

Just want know what GAUI will do about this?

I heart that their customer service is pretty good!

[flerpie]

So test stands aren't a good idea. I can believe it after seeing
a couple videos of helis self-destructing due to ground resonance.

It would be interesting to know just how Gaui does their testing.
Either they don't use test stands and don't recommend them
-or-
They have a kind of test stand with builtin rubber or foam or something
to kill the resonances. A picture of their test stand would be interesting
if they use one.

Maybe the Stacy's happen to know since they went to the Gaui factory?
Or Bobby Watts? He went there too. Any way we could find that out?

[nexgen]

I run 4900 rpm on my G200. dont know what the difference in load is, but never had any trouble with the bearings under load. maybe it was all screwed down too tight, there is a such thing as that you know.

[egicar]

Seeing the first pic, the retainer in the grip is seriously deformed. It is normally positioned between the last bearing near the head (n.8 on the manual - pag. 4) and the spacer (n.7) and should have its "retain blades" open, but in the other direction. In the pic, now it is over the first bearing and the "retain blades" are closed, in the wrong direction. Why? I don't understand. Very strange .
I have the G255 and mount the SAB 0370R blades (heavier than the stock ones) and the rotor speed is about 4000 rpm; right now, no problems (double checked) .

[nexgen]

csdstudio, I think your bird, like an unruly foster child, is unhappy with where it is living. better send it to me so I can whip it into shape, hehe

[egicar]

Originally Posted by nexgen

csdstudio, I think your bird, like an unruly foster child, is unhappy with where it is living. better send it to me so I can whip it into shape, hehe

I strongly recommend Nexgen's therapy

[bugdozer]

Ok, I've been going over the manuals for the EP200 and EP255 blade grips and it seems Gaui made a change, for the worse, in the bearing placement. On the EP200, two radial bearings are inserted into the grip from the blade end, sharing the load across both bearings. On the 255, one bearing is inserted into the blade end and one from the head side of the grip. The only bearing carrying the lateral load is the single outer bearing. Not only do they not have a thrust bearing, they have reduced the strength of the blade grip by 50% with this change. This be bad!

Outrage designed the tail on their G5 this way and they have a bad habit of throwing tail blades. Mine has gone down twice. I now use the Align Pro tail grips.

I was about to hit the Add-To-Cart button for a 255 but I holding off a bit.

[g-bru]

Bugga, now I am really worried! Gonna be giving my 255 its maiden hover this weekend with this problem burning a hole in the back of my head.

On my 255, I had a poorly machine arc tail pitch slider, the bracket which attaches to the tail boom has a bearing in the upper and lower branch, there was poor milling on the upper branch which meant the bearing was not making contact to mounting stem causing serious binding. I had to file the upper branch down till the bearing made contact again.

Is it worthwhile stripping the blade grips down checking for anything out of the ordinary and re-assembling it, or is it a case of you will just never know and hope for the best.

G.

[flerpie]

Considering that you found a poorly machined part to begin with
my mind would rest easier if I had a look at it.
That way, if it happens to you too you can be pretty sure
it was all put together correctly, therefore the problem
is something else. Less questions if the worst happens.
I wonder if perhaps the 1st batch of 255s didn't have the kinks worked out.

[g-bru]

Originally Posted by flerpie

Considering that you found a poorly machined part to begin with
my mind would rest easier if I had a look at it.
That way, if it happens to you too you can be pretty sure
it was all put together correctly, therefore the problem
is something else. Less questions if the worst happens.
I wonder if perhaps the 1st batch of 255s didn't have the kinks worked out.

Yup, took it apart, all components there and in the right places. The screws that attach the blade holders to the feathering shaft were super tight!!! I had to grit my teeth to get them loose!

G.

[egicar]

Originally Posted by g-bru

Yup, took it apart, all components there and in the right places. The screws that attach the blade holders to the feathering shaft were super tight!!! I had to grit my teeth to get them loose!

G.

No one can ever make sure that this or that thing will happen, especially if this or that thing has already happened to others.
The possibility that a bearing break in that way is pretty remote, but becomes real if you put the helicopter in the conditions more favourable to make this happen (very high head speed, heaviee blades than the original, hard flight, etc.).
I bought a couple of SAB blades: very nice and performant, but heavier than the stock ones.
After reading about the bearing broblems, I removed the SAB, restarted the stock ones and lowered the head speed at 80%.
If you don't feel confident, be careful not to fly this helicopter and wait for an effective solution: many friends are working on it

[flerpie]

Ya know, that could be. Heavier blades and a higher head speed.
Glad I got helitach and a cross check - the turnigy RPM meter.
I'll check that piece of it out. Maybe the combination is a failure point
and not any one part failing.

[klausk]

Originally Posted by bugdozer

Ok, I've been going over the manuals for the EP200 and EP255 blade grips and it seems Gaui made a change, for the worse, in the bearing placement. On the EP200, two radial bearings are inserted into the grip from the blade end, sharing the load across both bearings. On the 255, one bearing is inserted into the blade end and one from the head side of the grip. The only bearing carrying the lateral load is the single outer bearing. Not only do they not have a thrust bearing, they have reduced the strength of the blade grip by 50% with this change. This be bad!

Outrage designed the tail on their G5 this way and they have a bad habit of throwing tail blades. Mine has gone down twice. I now use the Align Pro tail grips.

I was about to hit the Add-To-Cart button for a 255 but I holding off a bit.

Hi,
same thing happened yesterday to my 200 FES bird (thats why I searched here for broken bearings today ;-) ). It's the same placement of bearings in the blade grips as you described for the 255. I just think about changing to blade grips from my flybar 200 to be on the safe side.


Btw: Gaui 200 FES with black plastic flybarless blades 200mm from gaui. headspeed ~3500 rpm.

[bugdozer]

I sent Gaui a link to this thread and this was their reply. They also included a page from the manual with the mod to the grip.

--------------------------------------------------------------------------------------------------------------------

Dear,

There should be a thrust bearing in the regular merchandise.
Because the EP255 is too small, the proper thrust bearing is too small to find in the present market.
So we have done some improvement on it as the following:

1.We replace the bearing by the high-level bearing of 3x6x2.5, so it's stronger.
2.The screw set is added in order to prevent the bearing from breaking and the main grip from
　flying out.You can see the screw set in the mannual in the attached.

Through these two improvements, the problem must be solved chiefly. It's welcome for further inquiry.
Thanks & regards

Nick
--
TSH GAUI