450 Trex 450L with gPro - Dolphin effect

[Erfan]

I tried it almost as you said, but I only took the main and tail blades off, I left the head is it is.
Gave it full throttle and collective pitch back and forth, no issues at all. I gave it slow pitch back and forth, fast back and forth, cyclic (AIL & ELE). No issues...

But as soon as the blades come on its like it has no power at all.

I even checked the rpm with Aligns Multi-function tester (with blades of course) and it as the rpm I expected, around 3000-3200 depending on my idle-up on midstick. So when throttle is either on 80 or 90%.
The blades are btw 360mm blades so the rpm should be good.

I remember once on my t600 I thought the tail had to much play, so I installed couple of shims and no more play. On the bench everything was perfect but as soon as the blades picked up speed the servo could not move them at all.
So the load of the speed forced the tail to get stuck. I wonder if the same is at play here, when the speed picks up and there is force the bad trust bearings jammed the head somehow and the servos are not able to move them.
As with the 600 tail my head moves without any restriction, nothing binds but then its also without any load. Same with that tail, on the bench it was perfect but with full speed and force it could not move. Removed the shims and everything was OK again.

 

[Tony]

If getting the grit out of the head doesn't work (and like smoggy, I dont' think it will) you may need to invest in an ammeter to test those servos under a load. I'm wondering if they are not pulling more amps than the gyro can handle.

 

[Erfan]

If the blade grips feel notchy when turned that's hardly ever thrust bearings to blame. The problem is virtually always that the inner radial bearing is getting 'squeezed' too much by being compressed against the head damper, which gives a notchy feel. If there are shim washers fitted you can remove them or replace with thinner ones to resolve it.

As for you losing collective. Often that's due to having vertical play on the main shaft so that when you apply pitch the whole shaft and head assembly lifts up and by doing so reduces collective pitch.

I know but there is no notchy feeling on the bench, when I remove all the links the head feels smooth. I know what you mean, had that with another heli, changed 2 bearings and everything was good. This time you really could feel the balls between your fingers, exactly the feel you get with bad bearings, you "hear" and feel the balls for each turn.

And there is zero vertical play on the main shaft, I really tried to pull it up and down with some force and it does not move at all.
And there is no vertical play at all on

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If getting the grit out of the head doesn't work (and like smoggy, I dont' think it will) you may need to invest in an ammeter to test those servos under a load. I'm wondering if they are not pulling more amps than the gyro can handle.

Not sure, could be. But we are talking about stock align parts, all the parts that come with the Trex 450L Combo Kit, GoPro FBL kit, now they use Microbeast instead... So most likely its their gyro as usual
Strange becuase I have had one of the exact kit before and flew many many times with it without any issues. Exact same parts.

The gyro should even handle 8.4v so it should be able to handle 6v Align DS430M servos.

But who knows...

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I have servo tester on the Align multi function tester and also in my iCharger, not sure how to test under load. I tried one of the servos and it moved perfectly. Could test all of them but the one I tested moved as it does on the heli.

 

[Tony]

You need an inline tester. You hook it inline while the helicopter is running and see how many amps it's pulling. It's not just a servo tester or just a volt tester, it will measure the actual current that is going through teh wires.

Another thing to check is the wires from your ESC to the gyro. If they are not big enough, it will bottleneck right there.

You can also try connecting a halfway charged 2s pack directly to the Rx and remove the red wire from teh ESC when it plugs in to the gyro. This will bypass the BEC in teh ESC and give you another testing point.

Might be time to look into an Ikon or BX... Just sayin lol.

 

[Erfan]

You need an inline tester. You hook it inline while the helicopter is running and see how many amps it's pulling. It's not just a servo tester or just a volt tester, it will measure the actual current that is going through teh wires.

Another thing to check is the wires from your ESC to the gyro. If they are not big enough, it will bottleneck right there.

You can also try connecting a halfway charged 2s pack directly to the Rx and remove the red wire from teh ESC when it plugs in to the gyro. This will bypass the BEC in teh ESC and give you another testing point.

Might be time to look into an Ikon or BX... Just sayin lol.

Its just to much hassle
I will try with the new trust bearings, if that does not work I will try with a 3GX I have laying around that I know works. And if that does not work either then I at least know it is the servos and I will get new ones. Been looking at KST DS215MG, cheap enough and they have got some good reviews.

But an Ikon is on my list, I have it on my t700, love it. I have cgy750 on my t600 but that is to much for the 450, there is not much room for a gyro "main" unit and then also a gyro sensor, shame they did not fit everything in 1 unit like most other gyros.
Getting to like the cgy750 more and more, specially after the v2 software, sure not as easy to setup as the Ikon but it has a ton of settings, most likely to many for a me but still

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Was reading around on the web and ran into this:

"
I have two 700L's I fly with a 2s Lipo and have never had any trouble at all. I use ikons (set to 1520/300) instead of Gpro. I had trouble with the Gpro in my 450L, so did two of my friends that I built helis for. They would burn up servos left and right. They too switched to ikons and have had no other issues. IMHO the Gpro is SH!T and should be avoided at all costs.... The servos are awesome, I have never owned any better regardless of the brand.
"

Wtf...

 

[Smoggie]

Sorry, duplicate post (why does that happen?)

 

[Tony]

Without the head spinning, raise and lower the throttle (with TH on) and put some pressure on the servos. Try to stop them from moving, but just add resistance with your fingers. If they stop with little pressure, then you know it's either the gyro or servos. If all 3 of them do this, it's more than likely the gyro. If only one, then it's the servo.

 

[Smoggie]

FWIW.. the gyros dont affect the collective input. Essentially when you move the collective stick the FBL unit passes the command straight to the servos. It's only cyclic where the servos dont necessarily follow stick movement directly.

If we rule out the possibility of incorrect FBL setup then my bet would be vertical float in the main shaft or if that's ruled out a (very) sloppy swash assembly.

If the servos were jamming under load then you would have probably burned them out by now. Plus, the clincher, if the grips were locking due to bad bearings then cyclic wouldn't work either... something just doesnt add up.

 

[Erfan]

Without the head spinning, raise and lower the throttle (with TH on) and put some pressure on the servos. Try to stop them from moving, but just add resistance with your fingers. If they stop with little pressure, then you know it's either the gyro or servos. If all 3 of them do this, it's more than likely the gyro. If only one, then it's the servo.

Well, the head is apart and I don't have any trust bearings, could I do the same with swash only, try to hold each ball back with my fingers?

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FWIW.. the gyros dont affect the collective input. Essentially when you move the collective stick the FBL unit passes the command straight to the servos. It's only cyclic where the servos dont necessarily follow stick movement directly.

If we rule out the possibility of incorrect FBL setup then my bet would be vertical float in the main shaft or a (very) sloppy swash assembly.

The swash seems fine and like I wrote before the vertical float in the main shaft.
Also this happened on my seventh flight, it flew perfect the first 6 times and then this started, And no crash of any sort.
And everything is new on the model, the entire heli has been up 7 times only and on the seventh time this started to happen.

 

[Tony]

Yes you can. I just want to see if the servos don't have enough force to move the blades under a load. But don't hold them wicked tight, you can strip the gears.

 

[Erfan]

Well, I changed trust bearings and now it flies perfectly
Something new learned, if you have bad trust bearings and the head does not move when blade is spinning but works perfect on the bench, just change the trust bearings and be done with it

Thank you all for your time and help!

 

[Smoggie]

Great to know that it fixed it.. i'll store that away for future reference, I didn't think it would have had such a serious effect.