What do the paddles do on a helicopter?

[Artemetra]

Do they provide a local inertial "disk," which anchors the main rotor - or something like that?

[vintage1]

vibartion reduction I think. Ensure the CG is more or less where the shaft is.

[Andy W]

I thought they provided mechanical advantage to help change blade pitch..
..a

[jlk]

The paddles change pitch and their movement causes the rotor head to tilt moving the helicoter,this is called cyclic. The main blades only change pitch on a helicopter with collective. On these helis the speed that the rotors turn is kept constant and the pitch of the blades is changed to increase or decrease the lift. The motor increases and decreases power to compensate for the pitch change so the rotor speed can remain constant. This gives faster reponse and less change in torque in the system.

Jordan

[vintage1]

Shows how little I know about model helicopters :D

[jolllyroger]

the rotor disk only seems to tilt, caused by blade flex. Most Helis blades can only change pitch and rotate along the long length. Take a good look at how a heli blade is mounted.......there are other mounting methods but this is most common.
The paddles are moved by the control linkage and are tilted .....in a counter clockwise rotating head....if the left (reward moving) paddle is tilted downward the right (forward moving paddle) paddle is tilted upward they impart through another linkage 90 degrees from the first changes in pitch as the blades swing through a full rotation. assuming that the blades were at 0 pitch originally then as the blades swing over the tail boom they will be in a negative pitch situation giving negative lift at the rear of the rotor disk as the blade swings through the forward most position it will have a postitive pitch causing the nose to rise and the tail to drop while swinging through the 90 degree position on either side of the copter they will be at zero. the paddles use the upward and down ward lift forces created by their airfoil to impart the pitch control to the main blades independent of the (collective or lifting pitch) Half of the rotor disk has more lift and half has less lift relative to overall lift. this almost completely maintains a balance of lift over the whole disk. the paddles also contribute some gyroscopic forces depending on their weight and size of lifting area creating more stability with more weight and smaller paddles. occasionaly you will find paddles on tail rotors that work as a gyro to fight tail drift..........whew what a mouthful i could spend an hour esplaiiinin this subject. hope this clarifies it some

[jolllyroger]

sorry you were all partially right. i spoke to quickly

[jolllyroger]

in the above scenario you will go backward
even in a fixed pitch heli the blades change pitch by paddle control. you just use rotor speed to go up an down by incresing overall lift created

[Bill Mixon]

assuming that the blades were at 0 pitch originally then as the blades swing over the tail boom they will be in a negative pitch situation giving negative lift at the rear of the rotor disk as the blade swings through the forward most position it will have a postitive pitch causing the nose to rise and the tail to drop while swinging through the 90 degree position on either side of the copter they will be at zero.

Say what..!
Now I have to admit I'm no expert on helicopter mechanics, but the above just doesn't make sense.
In the above condition of cyclic with neg pitch over the boom this should make the helicopter move or roll right not pitch up..
In other words if you wanted to move forward with the heli. Forward cyclic input would cause high pitch to be at 9:00 if we were to call the nose the 12:00 postion.

Isn't that right..?

[jolllyroger]

actually no that isn't correct the pitch at the left and right sides would be 0' causing no roll of the hei no lift left or right no roll the senario with neg pitch at the boom neg pith = neg lift pushing down at the rear causing backwards movement. However the paddles would be at 90 defrees to the blades and not producing 0' pitch one woul be positive one negative.
check it out on your heli if you have one you'll see what i mean. blades and paddles operate 90' out of phase with each other.

[jolllyroger]

oops my bad the paddles would be at 0' pitch at the 9 oclock and 3 oclock positions beginning to change pitch reaching max pitch at the fore and aft positions.

You are looking at the blades tilt or pitch change over the boom as creating lift to the side. in an airplane that is nosed over the lift component is still upward
Think of it in terms of a hand pushing down in neg pitch and up in positive pitch.
an airplane at a high angle of attack (increased pitch) traveling at 100 mph in a 100 mph wind does not move backwards unless its speed is changed, which brings up the subject of the blades advancing and retarding which causes the whopping noise of a heli, I'm not going to get into that.
Back to the hand pushing up or down,the hand at the 0' pitch 3 oclock and 0' 9 oclock position dosent push up or down.

[Bill Mixon]

I'm getting confused..
I know that the paddles work opposite (90 degrees) to the blades and that's my point.
If the rotor blades are directly over the nose and boom of the helicopter, and the flybar is 90 degrees to that. Now when you input forward or aft cyclic the flybar and the paddles rotate in the same direction as the swashplate which also tilts for and aft. But that's the only thing that moves. The blade pitch stays where it's at. Now if you advance the whole rotor head 90 degrees while holding for or aft cyclic the blades do change pitch. One will be pitched up and one down. So to move forward and backwards the blades are at their max deflection(s) when at 3:00 and 9:00.

This is all from memory, but I'm pretty sure that's the way it worked on the helicopters I used to have. I remember looking at this for quite a while trying to understand what was going on.

[Earthchain]

"In other words if you wanted to move forward with the heli. Forward cyclic input would cause high pitch to be at 9:00 if we were to call the nose the 12:00 postion."

This is correct. To get the rotor disk to tilt forward, you must input that change 90 degrees before the actual change will take place. Its due to gyrosopic precession.

The paddles (some helicopters use weights) help stabilize the retreating blade.

Maurice

[Purdue Aero Man]

In other words, you're a witch and you make it fly with your evil magic.

[Artemetra]

Well. Interesting stuff. Thanks for the replies.

Ben74 (thanks!) posted a great link on a different thread about the same question:

http://www.w3mh.co.uk/articles/html/csm9-11.htm

For more of the same type of thing, and also about how gyros work:

http://www.w3mh.co.uk/articles/html/csm7_8.htm

Other articles in the series: (includes setup of a heli, etc. - great stuff)
http://www.w3mh.co.uk/articles/html/csm5_6.htm
http://www.w3mh.co.uk/articles/html/csm3_4.htm
http://www.w3mh.co.uk/articles/html/csm1_2.htm

[jolllyroger]

Great heli Setup sites. Thanks for posting them

[Li-Pu Batteries]

I'm no heli expert, but I know that the paddle system was created by Mr. Hiller, of the Hiller Helicopter company that was in Palo Alto, CA in the 1940's. If you google search for Hiller, you'll find photos of full-size Hiller helis - with BIG paddles installed. From what I have read, there'd be no RC helicopters today without the Hiller system.

Hiller's full-size birds were and are, capable of hovering hands-off. Mr. Hiller, who I think is still alive, has a nice air museum in Redwood City, CA that has an annual all-helicopter air show. Visit at www.hiller.org.

If you go out that way, stop at the Burger King down the street, they have a Hiller chopper parked outside, and you can eat lunch in it. :-)