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Scale Model RC Helicopters > How much cyclic pitch? 2 blade flybarless...
 
 
Rodan
Senior Heliman
Location: Prescott Valley, AZ

I'm working on a 60 size Jet Ranger, using OF airfoil 670 blades on a flybarless, and was wondering if anyone had any input on how much cyclic pitch to dial in.
07-04-2008 09:40 PM
 
 
WIRLYBIRD
Senior Heliman
Location: CAPE TOWN / SOUTH AFRICA.

I use 3 degrees left , and right , and forward and back , would be a good start.
Dave.

WHAT GOES UP MUST SURELY COME DOWN.
07-05-2008 08:11 AM
 
 
BarracudaHockey
rrMaster
Location: Orange Park FL

That little? Wow, I would have said 5 to 6 but that would have been a guess.

What kit are you building Rodan? Are you using a helicommand or Vbar?


AMA 77227
http://www.jaxrc.com
07-05-2008 11:55 AM
 
 
Rodan
Senior Heliman
Location: Prescott Valley, AZ

I was thinking around 6... 3 seems pretty low, how does it respond?

I'm building a FunKey 60 size JetRanger with stretched TRex 600E mechs. I'm using an SK360 for stabilization, and am probably about two weeks out on a test flight (still scraping up the $$ for lipos...)
07-05-2008 01:44 PM
 
 
Super-Hornet
Veteran
Location: Singapore

Hi there. I have no experience in "helicommand or Vbar" and "60 size" flybarless so what I about to say may not be applicable at all. So, think about it, if it does not sound logic, then forget what I'm about to say.

OK. Here we go:
Now, we know that blades will go into stalling when the blades reaches 20Degree of angle (or pitch).
The collective pitch you normally set is around 10 to 12 Degree. That left around 10 to 8 Degree of allowable pitch (cyclic) to work on.
In order to stabilize the heli in flybarless, the helicommand/VBar will auto adjust the cyclics in order to create stability on the heli. So, even if u set your cyclic to max of 6 degree, your helicommand/VBar may further increase/reduce the cyclic in order to create stability. Thus, the overall pitch/angle the blades (for cyclics) may exceed 6Degree. If all angle add up together and it somehow more than 20Degree, one of the blades might goes into stalling state.

With that in mind, do careful not to overshoot the maximum pitch/angle the cyclic can go.

SH
07-05-2008 01:55 PM
 
 
Rodan
Senior Heliman
Location: Prescott Valley, AZ

S-H, every time I turn around, you are there with some great information and ideas! Thanks!

Here's a teaser shot (with my shop assistant):

07-05-2008 06:43 PM
 
 
WIRLYBIRD
Senior Heliman
Location: CAPE TOWN / SOUTH AFRICA.

Guy's I meant 3 degrees on either side of neutral . that's total of 6 degrees.
Dave.

WHAT GOES UP MUST SURELY COME DOWN.
07-05-2008 07:02 PM
 
 
Rodan
Senior Heliman
Location: Prescott Valley, AZ

OK, FYI guys I've got some information on other forums that when using the SK360 for stabiliztion, 10 deg of cyclic is desirable. Apparently there have been some problems on larger birds with the gyro running out of room to 'fix' things with low cyclic pitch. I think this probably applies more to 3D birds, but I'll post back here when I have more info.
07-05-2008 10:02 PM
 
 
HS10
Senior Heliman
Location: Elk River, MN

Hi Rodan

Quote 
Apparently there have been some problems on larger birds with the gyro running out of room to 'fix' things with low cyclic pitch.

Could you give more detail about the gyro situation... My Jet Ranger (OH-58A) has developed some "tail hunting"... I am running 700mm blades @ 1350 in a flybarless configuration (HC)...

I just put a set of larger tail rotor blades on this weekend.. Since the mechanics were designed for 600mm at a higher rotor speed, maybe there is not enough tail authority???




Logo 14/24 (Agusta 109A-MKII) (MH-6 Little Bird) (OH-58A) Navy - Retired
07-06-2008 01:39 AM
 
 
Rodan
Senior Heliman
Location: Prescott Valley, AZ

After reading some other threads, I couldn't find a lot more detail, and I'm not sure it would apply to your situation (you're using Helicommand, right?)...

The logic seems to be that having a good amount of cyclic pitch available will help the gyro to recover in extreme maneuvers. Apparently large collective and or cyclic inputs in FFF were causing some issues, but I don't think that applies to us scalers...

Not sure about your tail issues, but I have wondered about that issue with my project... I'm looking at a 25% decrease in main and tail rotor rpm (from the design point), but with more weight in the disc (670 v. 600 blades), but no flybar. I put 90 size blades on the tail (can't remember the measurement at the moment), but won't know where I'm at until it's flight time...

BTW, the Kiowa is looking good!
07-06-2008 02:50 AM
 
 
HS10
Senior Heliman
Location: Elk River, MN

It seems that if the mechanics tail rotor (size & rpm) were designed for 550 - 600 blades at a high speed, running 600 - 700 blades at a much lower speed would provide much less thrust...

To complicate things for scale work, I remember reading that flipping the tail to to opposite side has consequences also...

Here is my helicopter dog...



Logo 14/24 (Agusta 109A-MKII) (MH-6 Little Bird) (OH-58A) Navy - Retired
07-06-2008 03:33 AM
 
 
BarracudaHockey
rrMaster
Location: Orange Park FL

You flipped the tail rotor, I love it!!!


Whirlybird, I was talking 12 degrees, 6 plus and 6 minus, measured with the blades at 0 degrees and giving full cyclic you should read 6 degrees with a pitch gauge.

3 seems very inadaquate.

HS10, I agree, sounds like low tail authority.


AMA 77227
http://www.jaxrc.com
07-06-2008 12:39 PM
 
 
HS10
Senior Heliman
Location: Elk River, MN

I don't know precisely what my pitch is set at... The pitch gauge I have is used with the flybar...

How are you folks measuring pitch?

I would like to know as a baseline...

Logo 14/24 (Agusta 109A-MKII) (MH-6 Little Bird) (OH-58A) Navy - Retired
07-06-2008 12:59 PM
 
 
Rodan
Senior Heliman
Location: Prescott Valley, AZ

You can use the same pitch guage, you just need some sort of reference to replace the flybar. Since scale ships often have the main mast at an angle, finding the right 'spot' for the flybar can be an issue anyway.

I use a couple of methods: one is to use a piece of masking tape laid out on a wall behind the heli that is perpendicular to the main mast. Another is to use a small level across the top of the main grips. Set up the heli so that this reference is level (shim under the skids), and then use the same level on the top reference of the pitch gauge when you take your measurement.

Measure the cyclic pitch for elevator and aileron in the same fashion with the cyclic stick at full deflection (you will have to turn the heli 90 deg between these measurements).

HS10 - I took another look at your pic, (Kiowa) and it appears that the T/R is rotating down with the main wash at the front (clockwise viewed from the heli's port side). Is this correct? If so, can you reverse the rotation?

You will increase tail authority by having the front side of the T/R rotating up into the downwash so each individual tail blade sees more relative airflow. If it's a belt drive, you should be able to flip the belt to reverse rotation. You'll then have to fiddle with the tail grips/ gyro/ rudder servo to make sure you have proper t/r control when you flip the blades to the proper direction.

Whirlybird - 3 deg in each direction seems very low....
07-06-2008 04:59 PM
 
 
HS10
Senior Heliman
Location: Elk River, MN

Hi Rodan

Quote 
HS10 - I took another look at your pic, (Kiowa) and it appears that the T/R is rotating down with the main wash at the front (clockwise viewed from the heli's port side). Is this correct? If so, can you reverse the rotation?

You will increase tail authority by having the front side of the T/R rotating up into the downwash so each individual tail blade sees more relative airflow. If it's a belt drive, you should be able to flip the belt to reverse rotation. You'll then have to fiddle with the tail grips/ gyro/ rudder servo to make sure you have proper t/r control when you flip the blades to the proper direction.

THANKS FOR CATCHING THE TAIL ROTOR DIRECTION ERROR...

When I installed the larger blades I REVERSED them (dumb move)... Maybe age, maybe MAD-COW!!!


I planned to test fly the new tail blades today... I don't know what would have happened if it tried a test flight... You most likely saved me from a CRASH!!!

Logo 14/24 (Agusta 109A-MKII) (MH-6 Little Bird) (OH-58A) Navy - Retired
07-06-2008 06:26 PM
 
 
Rodan
Senior Heliman
Location: Prescott Valley, AZ

Glad to be of help!

I'm sure you would have noticed in your pre-flight!
07-07-2008 04:32 AM
 
 
WIRLYBIRD
Senior Heliman
Location: CAPE TOWN / SOUTH AFRICA.

What I can't understand is , I've always flown my multi blade hellis , being 2,3,4,and 5 bladed on a total of 6 degrees , they all flew perfectly , even looped and rolled the 3 blader. There was more than enough control power in the system , no mixers were used , now I don't see the difference in stick control or a gyro control , moving the swash plate. In other words why should the gyro have to move more degrees than the stick to have the desired control.

I have fitted my helicommand into an old Robbe Futura gas p/boom and am busy getting used to it's operation , will shortly be changing the head to flybarless , and will use maximum of 6 degrees , and will report the out come. After I'm used to the system , it will be installed into my NH90 , with a 4 bladed head by Peka , and OF blades , and a 4 bladed tail.

WHAT GOES UP MUST SURELY COME DOWN.
07-07-2008 06:47 AM
 
 
AirWolfRC
Elite Veteran
Location: 42½ N, 83½ W

Flybar or no, the pitch and pitch range of the blades will still be the same. The flybar helps with the blade settings or the servos do it all, the resulting blade angles will be the same.

Either way, 4º to 5º hover pitch is a good starting point with maybe 5º cyclic for a scaler.

If your head speed is down aroung 1200 or so, you may need to increase the hover pitch a degree or two.
07-08-2008 01:54 AM
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Scale Model RC Helicopters > How much cyclic pitch? 2 blade flybarless...
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