3 - Bladed Rotor systems for gyros, Video and Diagram from Chuck Beaty

[barnstorm2]

http://gyrowiki.com/GyroWiki/3%20Bladed%20Rotorheads.aspx

http://gyrowiki.com/Video%20Library/Forms/Video%20View.aspx?RootFolder=%2fVideo%20Library%2f Chuck%20Beaty%20Videos&FolderCTID=&View=%7b4EBC17B6%2dD653%2d4DB3%2d965C%2dC31262C018 72%7d


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[joe nelson]

I've read here on the forum that this rotor system had a lot of vibration. It would be interesting if Chuck could post some of his observations and experiences with the three bladed head.

[barnstorm2]

I've read here on the forum that this rotor system had a lot of vibration. It would be interesting if Chuck could post some of his observations and experiences with the three bladed head.

Really? I would have expected it to have less vibration then a 2 bladed system.

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[C. Beaty]

I've read here on the forum that this rotor system had a lot of vibration. It would be interesting if Chuck could post some of his observations and experiences with the three bladed head.Where did you read that, Joe? I wasn’t aware of any vibration.

[joe nelson]

My appologies Chuck,

I have re-read the 5-21-07 post and I'm wrong. I guess my CRS is worse than I thought. You were comparing a three bladed system to a teetering blade system with wide cord blades with Jim Mayfield.

With humble pie on my face, Chuck, I would still like to hear about your rotor system. How well did it fly, how did it maneover and how did you convey the control inputs to the head, ect? Once again, sorry and thanks.

[C. Beaty]

My appologies Chuck,

I have re-read the 5-21-07 post and I'm wrong. I guess my CRS is worse than I thought. You were comparing a three bladed system to a teetering blade system with wide cord blades with Jim Mayfield.

With humble pie on my face, Chuck, I would still like to hear about your rotor system. How well did it fly, how did it maneover and how did you convey the control inputs to the head, ect? Once again, sorry and thanks.Joe, it flew about like any other rotorcraft. Being swashplate controlled, there was no force feed back into the control system; not necessarily a plus.

With the rotor tied to the airframe via the rubber bushings, there was higher control power, i.e., a greater control moment per degree of cyclic tilt which reduces lag and overshoot.

The thing on top of the rotorhead, sometimes called a spider, is in no respect different, functionally, from a conventional swashplate; it’s tilted for cyclic and raised or lowered for collective.

[joe nelson]

Again thanks Chuck,

I'm very interested in any new idea in rotorheads and blades. Unfortunately, it takes a little time for me to digest all the technical aspects of each component of the system.

My swash plate prototype is a two pin type gimbal mounted on a follower which rides along the rotor shaft via a DU or linear bearing for collective control. It's simple but so far it works!

[C. Beaty]

Joe, the attached sketch illustrates, diagrammatically, the cyclic control scheme Dick DeGraw used on his wife’s partially powered rotor gyro. It is the same principle used on a Bell-47 but without swashplate or collective.

The reason he chose not to use a tilt head was to eliminate coupling of rotor drive torque into the cyclic system.

[Passin' Thru]

Chuck, am I correct in assuming the teeter bolt (or pin) teeters thru the control rod also?

[C. Beaty]

Pete, that sketch was meant only to be a schematic. The scale isn’t accurate; the width of the “U” joint block should have been shown as being greater than its length.

The control rod, naturally, has to hinge freely on the teeter axis.

I think Dick used a bushing with a 3/8 inch bore to keep the stuff pinned together for rotor removal.

The control rod would be terminated with a square or rectangular head where the teeter bushing passes through.

[joe nelson]

Thanks Pete,

I was having some trouble visualizing the schematic until your input.

Chuck, can you explain about the coupling between the drive shaft torque and the cyclic system, please. Was your reference to a tilt head the "Benson Type Head"?

On my design, I have the intention of using a Bell 680 type head with two pillar block bearings connecting the hub bar to the teetering hinge.

[C. Beaty]

Joe, picture a drive shaft with a “U” joint in the center, bolted to a sheet of plywood using pillow block bearings like the attached sketch.

Torque applied to the input shaft tries to lift the output shaft off the plywood as well as to rotate it.

A gimbel head is a “U” joint and torque applied to the rotor must be reacted against the airframe by passing through a “U” joint.

The component of torque fed back into the control system is equal to: rotor torque x tangent of ½ the tilt angle.

Pilots of gyros with strong prerotators feel this effect every time they prerotate.

That’s the reason no single rotor torque driven helicopter uses a tilt head. Tilt heads are possible with coaxial helicopters where there is no torque reaction against the airframe.

[joe nelson]

Thanks Chuck,

That's very clear and I'll put that in my notebook for future reference.

I hope to begin the construction of my test stand within the month. I'm looking forward to putting my creations to work or making a million toothpicks:-) which ever comes first.