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07-21-2002 05:05 PM  16 years agoPost 1
Parsifal

rrVeteran

Singapore

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Had a massive moment today when my Sceadu started vibrating madly during an inverted hover...rightened it up, landed took it to hover again...and perfect...not a twitch...tentatively flipped it over again and after about 10 seconds...it started vibrating again...

We narrowed it down to weak cyclic servos allowing the blades to flutter at certain head speeds achieved during the inverted hover...at least, thats our best guess right now...

That'd teach me for using 3001s on a 50 sized model...having them changed now...just thought i'd let everyone know in case they were thinking of going cheap on servos....Don't! Scared the bejeezus out of me!!!

Indy

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07-21-2002 08:37 PM  16 years agoPost 2
elad

rrApprentice

beer sheva (in south) israel

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I HAD THE SAME PROBLEM
I installed 5 9202 on my sceadu 50
after i have breaked twice 9202 on my sceadu 50 and discover that a 9206 is a must to install on the pich.

the sceadu have a lot of vibration problems especially the 50 size machine 90% of those related to rotors size (must be 600 mm)
and to the servo used on the pich (don't ever use 9202 for the pich!)
if you will do some 3d thay will snap in on time,
3 bring block is a must ,and I highly recommended to install frame brace .
but still the sceadu is a gentle macine, so have mercy on the succer.

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07-22-2002 04:28 AM  16 years agoPost 3
Parsifal

rrVeteran

Singapore

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The servo i have on Pitch is fine, it was the cyclics which were 3001s and somewhat underpowered, not the fault of the machine though...I have had a number of issues so far but mostly due to my inexperience with hirobo machines.

And as for it being a gentle machine, i am not so sure coz i have seen a friend thrash the living crap out of it every weekend for months on end with no problems...until of course he decided to fly up a tree.

Indy

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07-22-2002 11:41 AM  16 years agoPost 4
Ken B

rrElite Veteran

Phoenix, AZ

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Look at your fuel system. Was your engine getting starved for fuel while inverted? That would cause the engine to run ruff and then get vibration from that.

It doesn't make since that your servos work fine on one side and not the other...

Ken B

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07-22-2002 03:34 PM  16 years agoPost 5
ycwoon

rrNovice

Taiwan for now / Born in Malaysia

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electronics
how about the electronics? maybe when inverted the cable/connection is subjected to some sort of stress?

YC

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07-23-2002 03:03 AM  16 years agoPost 6
Parsifal

rrVeteran

Singapore

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Thought about that too Ken, but the symptoms were very much like the Woofs everyone is chattering about on another thread. I think it has something to do with the blades reaching a certain RPM at a certain pitch angle before all hell breaks loose, The shakes are pretty violent, violent enough to have the fuel tank pop off its little rubber grommets.
i was fully fueled up at the time and my filters and tubing are sparkling clean as i changed them all while replacing the main tank. I run a header too.

I am gonna try switching my cyclic servos and checking my rubber dampers for wear too. There seems to be a heck of a lot of free play in the control system right now and you can literally see the servo horns swivel slightly from side to side. Elevator see saw moves around too.

It happened after a series of flips too 3 flips and vibrate...land...bring it to hover and all is fine...header is always full...and keep in mind this is a very recent thing...hmmm....the more i think about it the more it seems like the dampers may be shot...must check when i get home...

Thanks guys.

Indy

PS: YC...the electronics are fine...i am totally anal retentive when it comes to neatness and securing stuff when it comes to helis...hehehe..

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07-23-2002 03:54 AM  16 years agoPost 7
Chris.C

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Hong Kong

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To eliminate blade flutter, you can either put in a metal push-pull collective or a servo with metal gear. On top of this, a good pair of blades is also very helpful.

Before these upgrade, suggest you to eliminate the free play on the control. I replace the servo frame, main gear, mixing arms after about 50 flights even there is no damage.

Cheers,

Chris

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07-23-2002 04:32 AM  16 years agoPost 8
Parsifal

rrVeteran

Singapore

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Yikes!!! thats a little dire, replacing everything every 50 flights or so. I fly about 10 to 15 times each weekend, i would have to rebuild every month!!!

I have a servo with metal gears on the Pitch, and it is rated more than sufficient for the Sceadu if you go by Hirobo's requirements.

I use FunKey 600mms at the moment. Its not the blades as another pilot at my field uses the same and his has been flutterless.

I guess i'll work on in and keep you guys informed. Maybe some more durable parts may be in order, wonder what cyberheli has in stock...hmmm... one step at a time i guess..

Thanks guys...

Indy

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07-23-2002 05:04 AM  16 years agoPost 9
Chris.C

rrVeteran

Hong Kong

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Whether to replace the parts I mentioned is a personal choice and depends very much on the style of flying. Because I like to do mild 3D (flip, inverted flying, backward loops, etc) with my Sceadu, I think it is necessary. Even you upgraded with push-pull collective and metal gear servo, it all depends on whether the servo frame is rigid enough to hold when the main rotor is loaded and unloaded.

After all, these parts are not expensive(I just replaced with stock plastic parts, no upgrade) and easy to change with a electric screw driver. Compare to the damage that blade flutter may results. this is really not much.

I am using Funkey 600mm blades too. I said a good pair of blades makes difference because I tried a pair of Hi-Product 600mm (PG50M) on it. Very good aerobatics but the price is too high.

Cheers,

Chris

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