Rotary Wing Forum rotor pitch
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#1
07-05-2012, 03:42 PM
 lame duck Member Join Date: Nov 2009 Location: butler, missouri Posts: 30
rotor pitch

#2
07-05-2012, 05:13 PM
 Gyro28866 Gold Member Join Date: May 2009 Location: Dickson, Tn. USA Posts: 994

I can not give you the answer you look for; but with my 23' Bensens on my machine, I have found less pitch gives higher rotor rpm, and more pitch gives less rotor rpm.
My bensens are happiest at about 375. 1 degree gives 400 average, 1 1/2 degress gives 375 and 2 degrees give about 350.
This all makes sence, because if you increase the angle of attack you increase lift at the same given airspeed; to a point. Increase the AoA to a certain point and you stall the airfoil. So to say this in another way - for an example - if you are All Up Weight of 750 pounds, the wings will have to produce 750 pounds of lift to maintain straght and level flight. so lets say this is at 45 MPH and 5 degress and you increase airspeed to 50 MPH the lift will increase also, for illistration - 800 pounds of lift. So to maintain the original straight and level at 50 MPH, you would have to lessen the AoA to say 4 degrees; thereby 750 pounds of lift is being produced at 50 MPH at 4 degrees.
I think 10 degrees may be too much, and might cause a stalled condition and flap the rotor. but I am not familiar with Rotordynes.

So back to the original question you asked:
The type of engine has no bearing on the rotor rpm, only the all up weight, the lenght of the blades, the airspeed flown, density altitude, etc..
Here is a spreadsheet by Ernie, which may help you calculate the wing loading and rpm you desire.
Attached Files
 HP3.xls (19.0 KB, 77 views)
__________________
David McCutchen
615-390-2228
PRA Chapter #16
#3
07-05-2012, 09:42 PM
 lame duck Member Join Date: Nov 2009 Location: butler, missouri Posts: 30
Rotor pitch

#4
07-06-2012, 04:59 AM
 CLS447 Platinum Member Join Date: Oct 2003 Location: Reading, PA Posts: 5,303

Did you try the Skywheels yet ? How did they work ?
__________________
Happy Flying, Chris S.
#5
07-06-2012, 07:45 AM
 Gyro28866 Gold Member Join Date: May 2009 Location: Dickson, Tn. USA Posts: 994

It is not a link, it is a spreadsheet.
Download it and open it with excel or Open Office, etc.
If yo double-click on the attached file HP3.xls, it will bring up a window, asking: open, save, or cancel.
If you click open - it will open the spreadsheet
If you click Save - it will save to your default location on your harddrive
If you click Cancel - it goes away.
You will have to have a program which recognizes a .xls format file.
If you do not have a program, you can download Open Office for FREE.
I use it daily for spreadsheets, data basing, and word processing.
If you need the format changed to meet a need of a program you use, let me know what format to resave it into, and I will see if I can resave to that format for you.
__________________
David McCutchen
615-390-2228
PRA Chapter #16

Last edited by Gyro28866; 07-06-2012 at 07:52 AM.
#6
07-06-2012, 07:53 AM
 NoWingsAttached Unobtainium Member Join Date: May 2006 Location: Villa Rica, GA Posts: 3,709

If you are using a Rotordyne hub bar and Rotordyne blades, the blades are pre-pitched for proper angle of attack, 3 degrees. Rotordynes are not supposed to have any twist to them. They are "straight" blades. The only twisted-blade rotor set I am aware of is the Dragon Wing. Those start out at 1 degree and end up at 6 degrees at the tip, but that varies with each set of blades depending on the weather and the angle of the setting sun.

The Rotordyne block has four bolts. If you draw a line length-wise down the middle of the block, you have two bolts on the left, two bolts on the right, and increasing the angle of attack of one blade decreases the AOA of other one. There is no independant adjustment available for the AOA of each individual blade.

There should not be a need to remove the rotor from the gyro head to track and/or adjust. You get an adjustable plastic protractor at any school-supplies isle at the drug store for a buck or two and do your rough-in adjustments easily enough.

You say you FLEW these blades with only 1-1/2 degree AOA? Either you were measuring wrong or you never left the ground. They simply won't fly that flat.

You are right about one thing: You dont' measure the AOA of the blade at the root.

Next, 10 degrees is WAY too much, I can't imagine you could get the blades to spin up fast enough to fly. If you did leave the ground without flapping the blades you were were probably very lucky. Don't try that again, or you'll be picking up the pieces.
Attached Thumbnails

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Last edited by NoWingsAttached; 07-06-2012 at 04:56 PM.
#7
07-06-2012, 08:48 AM
 NoWingsAttached Unobtainium Member Join Date: May 2006 Location: Villa Rica, GA Posts: 3,709

Assuming you have the Rotordyne blades, and hub bar, and assuming you have NOT changed the settings on the bolts shown in the "top view" drawing above, you would spin up your blades, track them using one of a few methods available (to be discussed seperately) and use the four bolts to adjust the blade tracking. In order to properly adjust blade tracking, you would (for example) loosen bolts 1 & 2, 1/2 turn each, together, and tighten bolts 3 & 4, 1/2 turn each, together. Then recheck tracking, and continue to adjust and refine until both blades pass through the same plane at the tips.

You can't really measure these small adjustments to track your blades, they are far too fine, and there are many other elements that play into proper tracking when the blades are spinning and loaded that aren't worth getting into here.

If you have played with the 4 tracking adjustment bolts and have changed the settings that came with your equipment, then here's what I would suggest: Loosen up all four bolts. Measure the gap between the top half of the blocks and the bottom half, and snug up the four bolts in synchronous fashion. Your new target is to get all four corners to have the same gap when the bolts are finger tight. You can use feeler guages to get to this point. THen tighten each bolt 1/8 turn until you get to the desired torque for safe operation. I dont' have my torque specs in front of me, I can get back to you with them later.

But it really sounds like you have something like a Sportcopter adjustable hub bar. In that case, you should be setting up your blades to both be at 3 degrees, leading edge higher than trailing edge.

Rotordynes loaded with one pilot, no passenger, 27 ft disk, on a light tandem like you are talking about might turn 310 -320 in cruise, and upwards of 340 with two passengers. Anything below 280 is not recommended to fly at all, as you are in serious danger of flapping the blades and damaging things at take off if your blades turn less than 280 in straight and level flight. Ideal should be over 300 RRPM minimum. Don't worry about maximum RRPMs, not reaching minimum RRPM is far more dangerous. You should be able to break ground around 260-280.

Do/did you take lessons? Your CFI can most likely help you out. Post some pics of your blades and hub bar, and the rest of your gyro please.
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"Scuze me while I kiss the sky!"

http://MohawkAeroCraft.com

http://Gyrocopter.co

Last edited by NoWingsAttached; 07-06-2012 at 04:58 PM.
#8
07-07-2012, 09:16 AM
 lame duck Member Join Date: Nov 2009 Location: butler, missouri Posts: 30
Rotor pitch

I have a good picture of the rotor hub bar in my Android smart phone if you can tell me how to get it on here without using a computer. Then you can tell me if they are rotordynes. Or maybe they are a different brand.
#9
07-08-2012, 10:54 AM
 lame duck Member Join Date: Nov 2009 Location: butler, missouri Posts: 30
rotor pitch

#10
07-08-2012, 11:20 AM
 lame duck Member Join Date: Nov 2009 Location: butler, missouri Posts: 30
rotor pitch

to NoWingsAttached, I have read every word you wrote several times, my blades did fly me at all the different settings i have used so far i didn't feel like i was ever on the edge of being dangerous, just didn't have much lift. I understand your adjusting the rotor block even to the point of putting a slice of a beer can under one side to change the pitch on that style. but i have adjusting blocks at the ends of the rotor hub bar itself. does this mean i don't really have rotordynes or are there different style rotor hub bars for rotordynes. i only use my android smart phone for this i don't have a computer as i'm so far out in the country i'm still on dial up. i do have pictures in my phone if i could figure out how to put them in here without a computer. Jerry from missouri
#11
07-08-2012, 03:01 PM
 NoWingsAttached Unobtainium Member Join Date: May 2006 Location: Villa Rica, GA Posts: 3,709

send the photos to me at: gregorymills@bellsouth.net

Either way, I would start out with the blades at 3 degrees. If you are hitting 300RRPM that is just fine for a single pilot, flying alone in a tandem Parsons.

You talk about a feeling of a lack of lift. WHat are you comparing your feeling to, that is, what other gyros have you flown before? How fast are you going when you experience this lack of lift?
__________________
"Scuze me while I kiss the sky!"

http://MohawkAeroCraft.com

http://Gyrocopter.co
#12
07-08-2012, 03:28 PM
 CLS447 Platinum Member Join Date: Oct 2003 Location: Reading, PA Posts: 5,303

What is stopping you from trying the Skywheels on the Mac powered machine ?

Both machines are 2 place machines...right ?

I wished you could give some thrust test results.......It might not be a lift problem.
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Happy Flying, Chris S.
#13
07-08-2012, 05:19 PM
 lame duck Member Join Date: Nov 2009 Location: butler, missouri Posts: 30

while i'm learning how to post... i have my bill parsons 2 rotor head apart for 125 hour inspection all looks good the jesus bolt could have been just a little tighter but my question is? what is the proper way to lube the bearings with grease or heavy oil or not at all or i bought some liquid grafite from napa the other day i really like its feel but i havent tried it on anything yet. any help guys i'm learning all i can. o.k. so i tried to send you pictures NoWingsAttached i hope you got them. thank you for helping me and everyone else also. Jerry from missouri
#14
07-09-2012, 06:40 PM
 lame duck Member Join Date: Nov 2009 Location: butler, missouri Posts: 30
rotor pitch

to cls447 great point, i will try the sky wheels. my teter towers are over an inch taller on my bill parsons rotor head. than my air command head. question how much angle if i tilt my blades to the stops out to the side do i need to fly safe. it seems like i have read at least 9 degree to 12 degrees is this right? or is it much more than that. Jerry from missouri
#15
07-10-2012, 04:24 AM
 CLS447 Platinum Member Join Date: Oct 2003 Location: Reading, PA Posts: 5,303

I believe 9 degrees in all directions is what you need for the rotorhead travel.

18 degrees from front to back stop & 18 degrees from side to side stop.

This has nothing to do with the blade movement......just rotorhead movement.
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Happy Flying, Chris S.

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