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Thunder Tiger Raptors 30-90 - Imperio > Here we go again - Flutter, Woof whatever !!
 
 
heliraptor
Key Veteran
Location: Colchester, Essex, UK

Hi Guys

Im getting tired of this.............al I wanna do is fly the thing.

Right Raptor 50, OS50, MS 600 120g blades, blade griops have the usual up and down flap but its nowhere near as bad as my 30 which Ive had for longer.

The problem as if you hadn't guessed it is fluter. Pullingnout of a turn and either descending or inot level flight on the odd occasion, maybe 3 times a flight I get a massive out of track situation where th eblades go out of thrack approx 3 inches. This all happens around 0 degree pitch.

On the second flight today half way throuhg I came out of a turn and it was the worst yet and to be honest I braced myself ready for a boom strike, I'm sure it wouldnt have but it felt like it........................time to pack up and go home.

I've searched the forums and all the sugestions like wrapping tape round the collars, head flip and swapping blades all seemmto be hit and miss sometinmes it works other times it doesnt.

Ive posted a poll with a few questions, I'd appreciate it if anyone has realy cured it, how did you do it??

Cheers

Lee

PS - If anyone has the instructions for the head flip email them to me please. Thanks
03-03-2002 Over year old.
HOMEPAGE  
 
 
heliraptor
Key Veteran
Location: Colchester, Essex, UK

Flutter

Hi Pauk

Well the heli is 4 months old. Due to the crap weather we've had over here I've had a maximum of 30 flights.

Tach'd the head speed today before and after flight at 1790 !!! Work that one out, dampers are fine and lubed, headspeed is low and it goes out of track in flight, I'm sure most of the other guys round here aren't dreaming it up either.

Guess you guys just got lucky.

Cheers

Lee
03-03-2002 Over year old.
HOMEPAGE  
 
 
steve9534
Key Veteran
Location: yakima, wa.

R30 flutter

If you care to learn more about the problem search for "Sceadu 50 flutter". I listed some of the reasons and problems in that post. The blade flip works as long as your blades aren't too unstable, you don't have too much slop in the system, and your servos are adequate. Steve.
03-12-2002 Over year old.
 
 
Remy
Senior Heliman
Location: Washington, D.C. - MHA Member

Cured the flutter on R30 by replacing woodies blades with MS Composite carbon ones.

Later on the heli started woof & ploof, despite a relatively slow (1850 rpm) head speed. After few scary woof, I flipped the head and never had any problem since. And yes the damper were new and properly lubed.

Remy
03-12-2002 Over year old.
HOMEPAGE  
 
 
Heli-Driver
Elite Veteran
Location: Arlington, TX

Flutter...

Lee,

What kind of servos do you use on your cyclic? Just curious. If they are weak in holding power it could possibly lead to vibration and eventually flutter.

I thought I emailed you the blade grip flip directions recently, did you not get them?

I suspect some of the problems are from the radial runout of the blade grip bearings, My metal grips ended that problem on mine but I flipped the grips anyway so it would match my R60.

Have you tried a new main rotor hub and the round metal insert the spindle goes through? If that insert is loose or worn it can cause the spindle to gall and bind, you can see the wear on the spindle itself if it is wearing out in the center of the spindle shaft.

To be honest, I only had flutter one time on my R30 back when it was stock, just once. After that I tore it down and converted it to a 46 and added metal grips and head. No more flutter and I'm flying 3D with it now and haven't had any tracking problems.

I'm running 1800 RPM in IdleUp1 and 1900 in IdleUp2 with SAB 600mm 3D blades.

Email me if you need me to resend the grip flip.

good luck,

PS I see you're building a Sceadu as well, seems like those have some flutter issues too but not as prolific as the Raptors.



Raymond

Predator Gasser SE/231 X 2
Century Helicopters
03-12-2002 Over year old.
HOMEPAGE  
 
 
Nige
Senior Heliman
Location: Hull, UK

Blade Instability

I found that my machine would sometimes show blade instability...but only with my MS 600 Night blades on . I noticed that I could provoke the situation by applying sharp roll inputs. The occurrence was reduced by going round the machine and reducing the play on the various bellcranks (combination of green loctite on bearings and cyno on the screws). Changing the damper rubbers also appeared to help. I came upon the cure for my machine when I changed the plastic roll servo cage for the metal one. This increases the stiffness from the collective servo to the roll bellcranks. This produced a complete cure and now I can fly the Night blades with no tracking instability.
03-13-2002 Over year old.
HOMEPAGE  
 
 
Waldo
Veteran
Location: Middle of the corn patch (Iowa)

oops

[b]Bill[/b]
03-28-2002 Over year old.
 
 
ed vega
Key Veteran
Location: nyc, queens

let us know why - could it be the wrong motor to rotor head speed .. or your using those square tip blades where it's more prevelant than swept tips .. hope your using super quiet tips .. or are you using woodies where it happens all the time there as oppose to glass blades , is there an out of balance condition ?.. are the bearings within the blades grips not seated correctly or loosen up under load and theres play there too ?..

03-28-2002 Over year old.
 
 
Raj Patel
Senior Heliman
Location: Humble, TX

Flutter

I have been messin with raptors since they came out. I have experienced flutter with every one I have owned. After years of tinkering with different mods, etc. I have finally found the cause.

Remember, flutter may be caused by simple things like bad thrust bearings, aft chord c.g. blades (the model sports I had were very trailing edge heavy, causing them to lead (instability, big time).

But forget the grip flip, tightening the bushings, and all the other recommendations out there, yes they can help or even "delay " the onset of flutter, and there is nothing wrong with tightening up your control system, but none of those fixes will cure flutter for good.

I have found the cause to be inaccurately molded head blocks.
Every head block I have bought has been "crooked" in more than one axis.

An easy way to find out is just check the static tracking. Every crooked head block I have owned, did not track statically. (Just pull your radio antenna up and set it under one of the blade tips, rotate the head and check to see how high / low the opposite blade is.)

I had a machine shop build a jig which would accurately locate the head block so we could line bore and ream the hole. We then steel sleeved it and NO MORE FLUTTER!

Most people wont be able to do the above, as it is time consuming and expensive to do if you don't own a machine shop or have a good friend who owns one :+)

I just bought 2 metal cnc head blocks from Heli-hut for a test, and they were machined very well. The static tracking was dead on and even the flybar axis was accurate. (I found the flybar axis is off on the molded plastic TT headblocks as well, which was discovered at my buddies machine shop)

I would recommend that you try a heli-hut machined head block, I am confident it will fix your flutter problems. I would not recommend a Quick WW metal headblock , simply because everything CNC'd I bought made from them was "crooked"

I also don't recommend using aft chord c.g blades like I mentioned above,as they are very unstable and will have a tendency to flutter, especially when using with plastic (springy) control systems such as the raptors, they are also hard on the servos, but that is just my opinion, but I feel, even those will track properly if using a accurate head block..

Raj
03-30-2002 Over year old.
 
 
Waldo
Veteran
Location: Middle of the corn patch (Iowa)

Good to know Raj, so far I haven't had any flutter problems but if I do I will get the metal head block, thanks again for doing all the hard work for us.

[b]Bill[/b]
03-30-2002 Over year old.
 
 
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Thunder Tiger Raptors 30-90 - Imperio > Here we go again - Flutter, Woof whatever !!
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