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HomeAircraftHelicopterHelicopter Main Discussion › Leading edge blade control?
04-06-2010 07:18 PM  8 years agoPost 21
Hamo

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Ireland

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BarracudaHockey, I have a lot of respect for you, but sorry, I'm still not convinced. When the feathering shaft rocks in the dampeners, one side moves up and the other side moves down. If trailing edge control is used, the rising side will increase the blade pitch and the falling side will reduce the blade pitch. With leading edge control, the opposite will happen, ie the rising blade grip will reduce the pitch and the falling side will increase the pitch, so I don't see any difference.
Hamo

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04-06-2010 07:24 PM  8 years agoPost 22
ErichF

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Sutton, NH

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You repeated exactly what BH said.

Bear in mind,also, that Delta works in very small amounts. It's hard to demonstrate it on a real rotor head, esp with stiff dampers.

Erich

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04-07-2010 12:07 AM  8 years agoPost 23
dkshema

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Cedar Rapids, IA

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Raptor 30 V2 has trailing edge control, not leading edge.
Yes, it does have trailing edge control, as did the original Raptor 30. Those who OWNED the original R30s cured their woof/poof by flipping the grips.

TT, in the meantime, essentially re-engineered the R30 to come up with the R30V2. They retained trailing edge control, but corrected the problem through the re-engineering effort.

AS an aside, they didn't quite learn the lesson, as they soon introduced the Raptor 60, only to once again, have to re-engineer THAT kit to fix a host of similar problems. The R60V2 was born.

The introduction of the Raptor 30 also invented a "new" phenomenon on its own. In addition to resurrecting Woof and Poof from the Original Hirobo Shuttle, the R30 introduced us all to the "wah wahs". Does anyone reading this remember the "slipper clutch"? The R30V2 also fixed the wah wah thing, and the slipper clutch became a relic.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

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04-07-2010 12:26 AM  8 years agoPost 24
dkshema

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Cedar Rapids, IA

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When the feathering shaft rocks in the dampeners, one side moves up and the other side moves down. If trailing edge control is used, the rising side will increase the blade pitch and the falling side will reduce the blade pitch. With leading edge control, the opposite will happen, ie the rising blade grip will reduce the pitch and the falling side will increase the pitch, so I don't see any difference.
Did you bother to READ what you WROTE?

In your own words:

Trailing edge control == increased blade pitch.

In a blade that's already rising, that ADDs to the problem (positive feedback).

Conversely, on the other side of the head, the blade's moving down, and by your own admission, it gets additional negative pitch. That's bad, and that's called positive feedback.

Leading edge control == decreased blade pitch.

In a blade that's already rising, that SUBTRACTS from the problem (negative feedback).

On the other side of the head, that blade's going down, but the amount of negative pitch is decreased, again subtracting from the problem, or what's called negative feedback.

Just exactly how is that different from what I said initially?

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When the blade pivots up, the pitch doesn't change, why should it ?
What you are ignoring in all of this, is that the link to the blade grip from the swashplate does NOT stretch. It is fixed length.

As the blade flaps upward, the ball on the end of the grip is restrained by the fixed-length pushrod. The result is that the pitch of the blade increases, as the trailing edge is pulled down as the blade flaps up.

The other blade is most likely flapping downwards due to the movement of the other end of the spindle. BUT again, with the control rod of fixed length, the trailing edge on THAT blade moves UP, increasing the negative pitch of the blade, exaggerating THAT blade's downward movement.

You most likely have never witnessed a heli explode in mid air after a woof-poof episode.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

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04-07-2010 12:37 AM  8 years agoPost 25
dkshema

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Cedar Rapids, IA

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As for Mckrackin's original post,

The head of the Trex 250 and most of the other Trex helis is already pretty well behaved and the collective controls are good and tight, with little slop or sponginess.

You probably wouldn't see much of a noticeable difference in performance. You might THINK you do, but for most of the people who go to the effort to make the flip in a well-behaved head, the increased performance is probably one of those "I made a change, it should be better, so it feels better" proposition. Kind of a self-fulfilling wish. Besides, it's a pain to have to undo it all, and put it back the way it was, so you HAVE to rationalize a reason for keeping the new configuration.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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04-07-2010 09:56 AM  8 years agoPost 26
Hamo

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Ireland

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OK, I get it now and thank you for persevering with explanations and not getting annoyed with me. I apologize if I sounded pig headed, but I had to understand it to accept it. Many thanks again BH and Dkshema.
Hamo

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04-07-2010 02:08 PM  8 years agoPost 27
BarracudaHockey

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Jacksonville FL

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The problem is pretty easily agrivated by blades with an aft chordwise CG, more stable blades like SAB's are less prone, the white and silver mavrikks are known to do it on stable heads.

Andy
AMA 77227
http://www.jaxrc.com

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12-02-2010 07:16 PM  8 years agoPost 28
Jerry K

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Houston Area

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[quote]You most likely have never witnessed a heli explode in mid air after a woof-poof episode.[quote]

I do now understand the flip thanks to you guys now can you explain the Woof-poof in the same eliquent way

Jerry

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12-03-2010 12:32 AM  8 years agoPost 29
JasonJ

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North Idaho

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The "woof" is blade flutter. It has already been explained about trailing edge verse leading edge control. When blade flutter occurs, it makes an ungodly noise and control is dramatically reduced. The cause of flutter, the violent oscillations of the blades, can cause a crash. The crash is the "poof".

I never had a problem with my Raptor, but I flipped the grips anyway after doing the SE conversion, just to be safe.

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12-03-2010 07:14 AM  8 years agoPost 30
shawn037

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mo

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The p/c rod is normally put in front of the m/r blade to offset gyroscopic precession along with an offset swashplate ( on the uh-60 when fwd cyclic is applied the swashplate tilts fwd and to the left) this combined with the p/c rod in front of the m/r blade ( offsets gyroscopic precession to less than 90 degrees). In other words if you were to look at your swashplate from straight above think of it numbered like a clock, when fwd cyclic is applied the the swashplate tilts fwd the blade starts getting the input at the 9 o'clock position and is fully taken out at the 3 o'clock positon or vice versa. pitch is taken out in the fwd half of the disk and increased if the aft portion of the disk.

The placement of the p/c rod determines how soon the the control input is put into the rotor system. And at what clock position.

This woof some of you have mentioned sounds like the blade is stalling out and retreating or pivoting backwards, are your blades tight enough?

on a rigid rotor system, with a rigid shaft, when one side "tilts upwards" the opposite side tilts downwards. unless you have what is called a feathering shaft or maybe even spindle. which allows each blade to "flap" seperatly. this is called aerodynamics which really can't be a valid argument, even if you "can't" see it happening.

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12-04-2010 12:41 PM  8 years agoPost 31
pigs dont fly

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City, State - Country

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I've swapped both my 250 and 500 to leading edge control, both were quite easy to do. The 500 let me flip the washout base too, as I could push the sleeve out, and mount it back in on the other side. I also swapped the ball links on the 500 to shorter ones, 6.2mm over to 4.3mm, on the lower and upper mixers(for clearance at extreme pitch angles).

Both heli's need less stick to hover now, and feel very much like a Mini Titan in flight.

Warning...This hobby is very addictive and may damage your wealth

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12-07-2010 08:42 AM  8 years agoPost 32
GetToDaChopper

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Las Vegas , NV

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pigs dont fly
Ever see one shot out of a canon ! but for some reason they don't fly very long, this must be something to do with aerodynamics i think ?

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12-07-2010 08:36 PM  8 years agoPost 33
BarracudaHockey

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Jacksonville FL

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Actually the "poof" is when the blade hits the boom from the excessive flapping and the helicopter explodes in mid air. Its pretty cool to watch (if its not your helicopter)

Andy
AMA 77227
http://www.jaxrc.com

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12-07-2010 09:02 PM  8 years agoPost 34
GetToDaChopper

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Las Vegas , NV

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ya i've seen that, not pretty !

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12-07-2010 11:36 PM  8 years agoPost 35
ChopperCrazy

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Sykesville, Pa. USA

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Just being curious, which choppers have leading edge and which ones have trailing edge control? Trex 600 trailing edge, Pantera 50 leading edge, Logo 600 leading edge.

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12-08-2010 01:16 AM  8 years agoPost 36
fenderstrat

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Aston,Pa

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FWIW,my Mini Titan, MTSE,Atom,KNIGHT and 6HV all have leading edge control on the main rotor.The Atom and Knight have trailing edge on the tail.

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12-08-2010 02:44 AM  8 years agoPost 37
Jerry K

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Houston Area

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Question: Does this apply to tail blades also and do tail blades "flap" The reason I ask is I have a T500 with a vibration In it I cannot find. In looking at it of the helis I have(8) from 450-700 they all have LE control but the 500, which I must have reversed by accident. Can TE control in the tail cause vibration? the vibration originates in the tail and resonates in the boom as high frequency vibration

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12-08-2010 03:07 AM  8 years agoPost 38
fenderstrat

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Aston,Pa

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A lot of guys have done the "grip flip" on the tail of their Atoms.It is supposed to give a better control response.There were no reports of vibration problems from what I have read,so it was fine running them either way.its really not changing anything mechanics wise other than the arm on the grip being the other way,so it SHOULDN'T cause issues.

A ton of guys have also done the "chinesse weight " mod and this is supposed to(I only say supposed because I have no experience with it) make the tail hold better.it requires adding weights and this doesn't seem to cause vibration issues either.

On another note i had a heli with a vib in the tail that was driving me NUTS.I had tried everything.Turned out to be a bearing not being secure in the housing(tail shaft bearing) allowing slight movement.2 small drops of green loctite cured it

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12-08-2010 03:15 AM  8 years agoPost 39
fenderstrat

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Aston,Pa

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A friend reversed the direction of rotation on his Pantera tail with no ill effects.It just gave control to the leading edge and reversed the gyro and rudder.
just for the record,on most helis you can do this mod without reversing the direction the tail rotates,all you need to do is "flip" the grips. this will depend on the design of the tail blade grips/linkages

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HomeAircraftHelicopterHelicopter Main Discussion › Leading edge blade control?
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