RunRyder RC
WATCH
 2 pages [ <<    <    ( 1 )     2     NEXT    >> ] 4890 views Post Reply
HomeScale✈️AircraftScale HeliScale Helicopter Main Discussion › Phasing 4 Blade Head
07-31-2007 02:06 PM  13 years ago
Topic Vote0Post 1
heli_madken

rrApprentice

Liverpool, England

MyPosts All Forum Topic
Phasing 4 Blade Head
I know this will have been asked before but I cant seem to find a definitive answer at the moment - can anyone explain to me how you manually set up phasing on a 4 bladed head?

Thanks, Ken
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
07-31-2007 02:46 PM  13 years ago
DenisS

rrKey Veteran

england

MyPosts All Forum Topic
Put one of the blades over the tail boom (in line with it), then you move the swash driver around so that the blade over the boom does not change pitch when you move the elevator stick. The actual phase angle for straight forward flight is slightly off of this point according to rotor direction due to progression, but that is a good place to start.
Cheers
Denis
SHARE  PM  EMAIL  Attn:RR  Quote
07-31-2007 03:17 PM  13 years ago
heli_madken

rrApprentice

Liverpool, England

MyPosts All Forum Topic
Thanks Denis,

In effect then with one set of blades pointing fore/aft the swashplate balls to which their links are attached would be at 90' to fore/aft so any movement of the swashplate with elevator input would not move the blades, am I right as I had been given information that the swashplate balls should also be fore/aft at the same time as the set of blades which of course is giving full movement on elevator input.
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
07-31-2007 04:02 PM  13 years ago
Dr.Tim

rrElite Veteran

Mojave Desert

MyPosts All Forum Topic
Here is a good multi blade setup page on our website written by Mr. Peter Wales.
http://www.starwoodmodels.com/products/of/multihelp.php

Hope this helps!

Dr.Tim
From Simple minds come simple ideas! Approach Engineering
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
07-31-2007 04:10 PM  13 years ago
heli_madken

rrApprentice

Liverpool, England

MyPosts All Forum Topic
Thats great DR Tim thanks, it also gives me comfort that the angle at which my links end up is acceptable, they are much like the ones in Peters picture
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
07-31-2007 07:57 PM  13 years ago
heli_madken

rrApprentice

Liverpool, England

MyPosts All Forum Topic
Sorted my problem out got it cracked now, I made a swash driver -

Rather than my original idea of a coupler which basically sucked -

The problem with the coupler was the angle of the links which was causing a problem on increasing pitch and changing phasing, the driver is a better idea, the coupler works fine with a three blade head

Thanks everyone
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
07-31-2007 11:46 PM  13 years ago
The_Dave

rrVeteran

Las Vegas / Pahrump, Nevada

MyPosts All Forum Topic
~
I believe that phasing is not in play on a 4 blade head. As the head is on the 90's no phasing is required. NOwthen, you COULD phase it +/- 90 degrees, but why would you?
Mark McAlpine - 2005 - We will never forget.
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
08-01-2007 12:14 AM  13 years ago
Dr.Tim

rrElite Veteran

Mojave Desert

MyPosts All Forum Topic
Dave, Phasing is 45 degrees into the rotation on a 4 bladed head. Were you thinking of the flybarless 2 blade head?
Hope all is well!
Dr.Tim
From Simple minds come simple ideas! Approach Engineering
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
08-01-2007 12:33 AM  13 years ago
The_Dave

rrVeteran

Las Vegas / Pahrump, Nevada

MyPosts All Forum Topic
~
No, I was not thinking of two blade flybarless...

As gyroscopic precession dictates, input results in result 90 degrees after the input in the plane of rotation. As each blade is 90 degrees apart and assuming that when you want to move forward you push forward then the blades would be set up with 0 phase, or another words, they would not have any phasing at all. Forgive me, but 45 degrees does not seem correct at all.

I suspect we are both saying the same thing in different ways. My position is, if you are on the 90 you have zero phase ( on a two or four blade head, odd numbers are another horse altogether).

Now with all of that being said, I fly my 4 blade on the 90 and it flew perfect. I was able to loop, roll, auto, whatever and had zero problems.

One thing that was told to me was "phasing" would change with rotor speed, I have found that not to be true on either my 4 blade head or my three blade head. I will say that the 3 blade did take some getting use to as the rotor head tends to "park" itself in a turn and requires you to "push" the machine through the turn, the 4 blade does not seem to have this problem....
Mark McAlpine - 2005 - We will never forget.
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
08-01-2007 12:44 AM  13 years ago
Dr.Tim

rrElite Veteran

Mojave Desert

MyPosts All Forum Topic
Not going to get in to physics here Dave but, Pull your books out and look at Dissymmetry of lift. What your speaking of is true for a 2 blade system but Rotational "Control" inputs change for multiblade although gyroscopic precession still has an effect. You Have to ask yourself .. why do the Multiblade mixers on the market do the 45 degree phasing for you? Have a look at the Helitronix Mixer.
Regards.
Dr.Tim
From Simple minds come simple ideas! Approach Engineering
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
08-01-2007 01:58 AM  13 years ago
The_Dave

rrVeteran

Las Vegas / Pahrump, Nevada

MyPosts All Forum Topic
~
No book required, I have practical experience.

My head is on the 90's, no mixers, nothing. I push forward, it goes forward, not forward and to the right, or forward and to the left...forward.

I guess you could throw down on retreating blade stall, but do our machines move that fast for it to be a factor? I doubt it. I know I had a 4 blade on a fury and it really moved, nothing funny happened when it did.

I can tell you that I would set a two blade head up on the 90 as well, and I suspect it would be just fine, touchy...but fine. Although I have no practical experience on two blade flybarless unless you count the time I flew with my flybar lock still installed (long story...don't ask <G>.

PS...

If I don't get back to your next reply, nothing personal it is just that I am off to a turbine rally and will be away from the boards for a while.
Mark McAlpine - 2005 - We will never forget.
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
08-01-2007 02:10 AM  13 years ago
Dr.Tim

rrElite Veteran

Mojave Desert

MyPosts All Forum Topic
No Prob. Dave ... Have a good Trip!

Dr.Tim
From Simple minds come simple ideas! Approach Engineering
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
08-01-2007 08:51 AM  13 years ago
heli_madken

rrApprentice

Liverpool, England

MyPosts All Forum Topic
Interesting debate, I havent got the practical experience but experimenting with the head I can see that moving the position of the swashplate relative to the head gives completely different results in relation to stick input so its obviously very important to get the position correct.

In my case its even more important as I am dealing with two heads on my project -

Thanks for your help everyone
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
08-01-2007 09:49 AM  13 years ago
DenisS

rrKey Veteran

england

MyPosts All Forum Topic
Hi helimadken
Just to clear up something that may have got lost through this highly technical post- phasing DOES apply, the 90 degree position will be slightly off depending on rotor direction. The 45 degrees that is referred to when using the Helitronics mixer (or others) is basically so that a better angle of the pushrod from swash to blade arm can be achieved. If you look at my gallery I think there is a pic of my 4-blade BK117 that has flown for 12 or more years, no specil mixing, just a slight advance to the phase using the swash driver to get it to go forwards instead of off to the right by a couple of degrees. Follow what I said initailly and you are very close to being perfect.
If you rotors tilt too it will be difficult to see if this is happening. Very interesting projct by the way.
You can always PM me with specific questions regarding mixers, head gyros etc and I will try to help.
Denis
SHARE  PM  EMAIL  Attn:RR  Quote
08-07-2007 10:00 PM  13 years ago
trunkmunki

rrApprentice

Bangor

MyPosts All Forum Topic
Bottom line is this: Gyroscopic precession will apply the force 90 degrees ahead of where it is introduced. The 45/90 (or any other) degree phasing has to do with where the ball link is in relation to the blade grip and the axis of the main shaft. If it is a two-blade setup, it is probably 90 degrees. If it is a 4 blade, it is probably 45 degrees or something close. What you need to have happen when you move the sticks is more important than actually measuring the phase.

If you set a blade over the tailboom as previously mentioned, you need to either electronically or mechanically set the swash/pitch links so that when you move the cyclic fore/aft the blade will not move, and when you move the cyclic left/right it will have full cyclic deflection. So if you have a CCW rotor system, one blade is over the boom, and you input left cyclic, the blade will pitch up and 90 degrees later you will have the lifting force which will roll the aircraft to the left.

If you look at a paddle-type head(hiller control system, forget the bell-hiller for now, it just complicates the discussion, but this all still applies with that system), when you make a cyclic input, say right (CW rotation), when the paddle is over the nose it will pitch down, 90 degrees ahead of that point of rotation (because of precession) the flybar "banks" to the right, which pitches the main blade over the nose down, and over the tail up. The force from the main blades is now applied 90 degrees from here (again, precession) and now the whole head is tilted to the right. You can run the head at low (just fast enough to be stable) speed and watch the flybar as you move the cyclic, and static watch where all the forces are applied (max pitch). This pricipal works on any rotor system, it is only 90 degrees on the hiller-head because the flybar linkages are 90 degrees to the mains.
SHARE  PM  EMAIL  Attn:RR  Quote
08-08-2007 11:51 PM  13 years ago
hooked124

rrNovice

BC LA

MyPosts All Forum Topic
"heli_madken"

In my case its even more important as I am dealing with two heads on my project -

WOW

that's all I can say, great looking job so far. And an even better use of that table, mirror images! What is that?
And are those two "tail" sections of the "twin-Rexx?"
SHARE  PM  EMAIL  Attn:RR  Quote
08-09-2007 08:26 AM  13 years ago
heli_madken

rrApprentice

Liverpool, England

MyPosts All Forum Topic
Mirror image - maybe its four heads I am dealing with!!

It uses the same micro controller as the Twin Rexx but frames are my own design, the heads are a mix of Eco 8 shaft and Swashplate, Trex maingears and hubs, home made 4 blade heads and swashplate drivers plus Trex 335mm wooden blades.

Hope to have first trials at the weekend, you can see info on the build in this thread -
http://www.rcgroups.com/forums/showthread.php?t=679820
Havent posted her as I dont quite know which forum to put it in it really isnt a tandem, it is very close to scale but I am not sure its the sort of thing people would want to see in this forum as its almost a plane
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
08-14-2007 07:03 PM  13 years ago
heli_madken

rrApprentice

Liverpool, England

MyPosts All Forum Topic
I wasnt happy with my first attempt at a swash driver as it wasnt operating smoothly so I have cannibalised some ECO 8 parts which introduces some bearings into the linkage, its really smooth now and works well -

I have another question about phasing this time electronic timing. The TH2 controller I have does not have a timing function however I have a JR PCM10X that has a swash timing facility, it has 4 inputs marked AILE>ELEV (L + R) and ELEV>AILE (D + U), has anyone any experience of using this TX with this function, how does it work and can I use it to fine tune the phasing?

The last of the ESC's should be here tomorrow so I plan to have my first test flights at the weekend
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
09-24-2007 12:44 PM  13 years ago
heli_madken

rrApprentice

Liverpool, England

MyPosts All Forum Topic
Hi Tis me again harping on about blade phasing.

I have had my first flights (hops really) with this heli and although cyclic inputs give the desired effect I cant help but feel somthing isnt right, I have taken a picture to illustrate what I mean -

The head is setup correctly with no blade movement of the blades aligned longitudinally with the fuselage when applying fore/aft cylic. In the picture the blades numbered 1 and 3 are fuselage aligned, I have exagerated the amount of forward elevator applied to show the result.

In the picture the blades have the following pitch -

Blade 1 - 4'
Blade 2 - 16'
Blade 3 - 8'
Blade 4 - 0'

If I am right about my understanding of 90' precession this appears correct as blade 2 is at its maximum pitch at 90' before the required forward movement.

However in practice when the rotors have reached RPM forward application of cyclic appears to tilt the rotor disc forward and to the left (because I guess the greatest lift is in the right / rear quadrant of the disc). Is this correct as its quite disconcerting to look at, I am sure that as this is a twin rotor heli and the other rotor tips forward and to the right then I get the desired result but if I fitted this head to my ECO 8 it would immediately tip over to the left in a shower of shattered carbon blade fragments.

looking at Peter Wales example of a 4 blade head setup mine looks almost identical in terms of link positioning.

Is this just a visual thing?
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
09-24-2007 04:53 PM  13 years ago
DenisS

rrKey Veteran

england

MyPosts All Forum Topic
If it does that forward/left thing while still on the ground it is normal. You would be best to fit some training gear on and give it a couple of small 'hops', then see the reaction. It seems to fight itself when still on the ground, but behave alright in the air.
Your set-up looks right.
Denis
SHARE  PM  EMAIL  Attn:RR  Quote
WATCH
 2 pages [ <<    <    ( 1 )     2     NEXT    >> ] 4890 views Post Reply
HomeScale✈️AircraftScale HeliScale Helicopter Main Discussion › Phasing 4 Blade Head
Print TOPIC

 4  Topic Subscribe

Saturday, September 26 - 10:16 am - Copyright © 2000-2020 RunRyder   EMAILEnable Cookies

Login Here
 New Subscriptions 
 Buddies Online