[question] Two bladed rotor system
Thread Starter
Join Date: Aug 2004
Location: NE
Posts: 68
Likes: 0
Received 0 Likes
on
0 Posts
[question] Two bladed rotor system
Hello
in a hangar talk discussion, this come an argument:
"...in a two bladed rotor system, the blades can change from the 180º position (lead lag)... to equalize the forces in each blade during forward flight ... this is accomplished by the hub itself ... "
using, as example, the rotor head of the R22, and what is written in the POH - "main rotor articulation : free to teeter and cone, rigid inplane",
i always have the idea, that 180º is always maintained and the forces are resisted by the hub itself, that "fights" to maintain it (resistance of the materials)
comments?
thanks
regards
in a hangar talk discussion, this come an argument:
"...in a two bladed rotor system, the blades can change from the 180º position (lead lag)... to equalize the forces in each blade during forward flight ... this is accomplished by the hub itself ... "
using, as example, the rotor head of the R22, and what is written in the POH - "main rotor articulation : free to teeter and cone, rigid inplane",
i always have the idea, that 180º is always maintained and the forces are resisted by the hub itself, that "fights" to maintain it (resistance of the materials)
comments?
thanks
regards
Join Date: Nov 2004
Location: Cambridgeshire, UK
Posts: 1,334
Likes: 0
Received 0 Likes
on
0 Posts
CS-Hover,
I would have a look at the various types of rotorhead that exist:
Aircraft in Detail - Helicopter Rotorhead Gallery Index
You could also lookup "effective hinge offset" in Prouty.
2 bladed rotors "teeter" about a bush on the hub to keep the machine weight (and cost) down. The blades actually cone slightly above the plane so that centrifugal forces carry the weight of the heli.
I would have a look at the various types of rotorhead that exist:
Aircraft in Detail - Helicopter Rotorhead Gallery Index
You could also lookup "effective hinge offset" in Prouty.
2 bladed rotors "teeter" about a bush on the hub to keep the machine weight (and cost) down. The blades actually cone slightly above the plane so that centrifugal forces carry the weight of the heli.
Join Date: Dec 2001
Location: Philadelphia PA
Age: 73
Posts: 1,835
Likes: 0
Received 2 Likes
on
2 Posts
The lead and lag forces are absorbed by the hub, but as these forces change due to rotation, they are taken up by the mast.
The mast actually has a slight twisting and untwisting as the blades go around.
If that helps confuse the situation.
The mast actually has a slight twisting and untwisting as the blades go around.
If that helps confuse the situation.
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
Shawn has given the answer that you are looking for. Undersling reduces these unbalanced in-plane forces.
The following sketch is of a Kaman intermeshing twin-rotor. It requires another means of handling the lead-lag, because the two rotors are mechanically interlocked. You can see that Kaman uses lag hinges and a friction damper.
Dave
The following sketch is of a Kaman intermeshing twin-rotor. It requires another means of handling the lead-lag, because the two rotors are mechanically interlocked. You can see that Kaman uses lag hinges and a friction damper.
Dave
Join Date: May 2001
Location: queensland australia
Age: 77
Posts: 563
Likes: 0
Received 1 Like
on
1 Post
the underslinging of the yoke, holding the blades on to the gymbal with pillow blocks, allows the yoke to rock under the head and this small action absorbs all the hunting stresses bought about by acceleration and deceleration of the blades. very simple and very effective.
