Servo Hardware Question
 

What are you all using on the servo-end for arms and linkage? I'm to reduce the last bit of play play on my F-22 stabs. Replaced most of the gears on the 8411 servos with the plastic set and that cut the play in half. Tried the dubro items but they are plastic and flex. Anyone using the Hanger-9 BB conectors?

I've used this set up for awhile
 

no problems

Servo Hardware Question
 

Worth a thousand words...

Thanks Matt :)

Servo Hardware Question
 

That's overkill for an Isobar, but for the speeds that Matt regularly achieves, its required!

that's not all I had to do to avoid flutter.
 

I did this on all the surfaces, probably overkill but I wanted some peace of mind.

Servo Hardware Question
 

The first photo looks like a very stiff system for solid control. As I understand it from an article I read, stiffness the the only method to iliminate flutter. Counter weight, closing of gaps and so on do very little if any. A stiff SYSTEM is the solution to flutter. :)

Hi Ehab
 

If the surface is properly balanced, it won't flutter even if there is NO linkage...of course you would not have very good control that way :-)

I agree that closing the hinge gap the way I did does not help prevent flutter, in fact if done wrong it could even increase the chance of flutter!

Oh and I don't use servo grommets anywhere!

Servo Hardware Question
 

Matt, are those the big size Robart hinges with the rivet drilled out? If so, I assume you are using a piece of wire to pin the hinges. What size? Thanks.

robart pins
 

Hi Mark,

You can order the robart pin hinges without pins, or just snip the end of the rivet off and pull them out.

I think the wire is .055 music wire.

BV's new hinges are an improvement on this same theme. You can now remove all of the hinges surfaces from a Super Bandit and I assume from the F-100 as well.

Re: Servo Hardware Question
 

Hi I-NAV,

Are these the 8411SA gears? I have had these on order for weeks if not months and nothing?

Thanks

Servo Hardware Question
 

Do you order them straight from Robart without the pins, or from your local hobby shop? Thanks Matt!

hinges
 

my LHS orders from Robart.

#322
3/16" Unassembled Steel Super Hinge Point Half
(50 pkg.)
MSRP $8.25


just saw they have a cool fowler flap hinge now too. I have always liked robart stuff.

Servo Hardware Question
 

Hi Mr Matt;

I respectfully disagree that balanced surface w/o a push rod will not oscillate at our jet speeds. It is the turbulance and drag/lift of the surface that will cause what we call flutter of our control surfaces. I BELIEVE that even full size fighter jets do not have their control surfaces STATICALLY balanced like we do our models, they are of course computer and hydrolically controlled. I maintain that at subsonic speeds, stiff hinged and controlled surfaces are the only practical requirements, then again here I am at 3:30 am with my son screaming for milk....so what do I know!!!!!

flutter
 

Hi Ehab,

Do any random search on the words "flutter" and "balance".

I just did and a random hit from

http://www.iasa.com.au/folders/Safet...lent_vibes.htm

<<snip>>

.......if the aerofoil moves slightly upward, the mass of the control surface causes the control to lag behind and rotate with its trailing edge down. Because of structural flexibility this tends to happen even if the control system is held firmly. The deflected configuration momentarily increases lift on the aerofoil and acts to increase its initial displacement. Eventually, structural stiffness overcomes the aerodynamic forces and the aerofoil starts to return to its normal position. As the aerofoil moves down, the control surface again lags behind, but now rotates trailing edge up and so again accentuates the displacement, this time downward.

Above a certain speed, there is sufficient aerodynamic energy for successive vibrations like this to build up progressively. This is flutter.

This simple type of flutter can be suppressed by adding balance weights to the control surface ahead of its hinge line. Doing this eliminates the tendency for the control surface to lag behind the vertical flexure of wing or tail and consequently the two motions no longer interact.........<snip>

There are a ton of references out there.....

Check with Bob Parks, he can explain it as well

ps
 

I agree if the surfaces are stiff enough (both the fixed and movable parts) and the control system it powerful enough then you do not need to balance anything (for a particular speed)

But all things equal a balanced surface will always have a higher flutter speed.

Servo Hardware Question
 

I will confirm w/Bob. But in the excerpt above, It did not seem to say that a statically balanced surface WITHOUT linkage would NOT flutter at speed. Seeing some footage of air tunnel test on wings and control surfaces shows quite a bit of eddie currents? and dirty air at the trailing edges of control surfaces which would easily start the surface into oscillation and with no linkage nto flutter?. But then again I digress or is it dygress:):):)

!!
 

yeah maybe saying no linkage was an exaggeration on my part....it would not be the first time for me!