HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Feb 20, 2013, 04:56 AM
Registered User
Joined Apr 2009
5 Posts
Discussion
V22 Osprey and CG

I dont think i understand this correctly, so please enlightened me.

I would expect the V22 to tilt either up or down, if the rotors were not placed exactly at the CG, but in practice, I find it hard to believe that this is always correct.

So is the CG a variable size - relative to the weight of the V22?
Meaning that the CG could be moved +- 1 meter in a real V22 and the aircraft would not experience any problems flying or hover?

Lotus21 is offline Find More Posts by Lotus21
Reply With Quote
Sign up now
to remove ads between posts
Old Feb 20, 2013, 07:08 AM
Registered User
Joined Oct 2004
2,770 Posts
Probably even more. The rotors on a V22 are like those on an helicopter, each blade can change pitch cyclically through the rotation. This means that the center of thrust on the rotors can be moved forward and backward while maintaining their tilt fixed, and this is what the V22 uses to control the pitch while in an hover. The nacelle tilt is only used for transition, it would not be fast enough to be used to control pitch, and as you mention, controlling pitch using the nacelle tilt forces an exact CG position that might well be impossible to achieve, especially on a transport aircraft.
Brandano is online now Find More Posts by Brandano
Reply With Quote
Old Feb 20, 2013, 07:40 AM
Registered User
v22chap's Avatar
United States, IN, Granger
Joined Jan 2003
3,105 Posts
As Brandano said ... with large rotors and cyclic control the CG can be a long way off from the airplane CG . On my rotormast V I can move the battery any where on the front ... it just flies with the tail level or hanging down , but the large rotors and cylic control will just force it through .
Using small airplane props to control pitch axis through engine vectoring is a different story .... and the CG better be right on or you will have your hands full trying to control it .
There are many threads on here dealing with bicopter attempts and some of them have pretty good results but they are light ,,well balanced birds with Multi wii type controllers working the controls hard all the time .
v22chap is online now Find More Posts by v22chap
Reply With Quote
Old Feb 20, 2013, 10:45 AM
Will fly for food
ilektron's Avatar
United States, CA, Carlsbad
Joined May 2011
532 Posts
Fixed pitch bicopters are an entirely different game, and the CG will end up directly below the pivot point in a hover. Don't confuse this with the craft hanging by the props, this just happens to be to only orientation where the static forces all cancel themselves out to achieve a motionless hover.
ilektron is offline Find More Posts by ilektron
Reply With Quote
Old Feb 20, 2013, 11:33 AM
Winging it >
leadfeather's Avatar
Joined May 2006
9,573 Posts
Quote:
Originally Posted by ilektron View Post
Fixed pitch bicopters are an entirely different game, and the CG will end up directly below the pivot point in a hover. Don't confuse this with the craft hanging by the props, this just happens to be to only orientation where the static forces all cancel themselves out to achieve a motionless hover.
I gotta disagree, for a fixed pitch bicopter the cg needs to be directly below the prop centers.
leadfeather is online now Find More Posts by leadfeather
Reply With Quote
Old Feb 20, 2013, 11:47 AM
Will fly for food
ilektron's Avatar
United States, CA, Carlsbad
Joined May 2011
532 Posts
Quote:
Originally Posted by leadfeather View Post
I gotta disagree, for a fixed pitch bicopter the cg needs to be directly below the prop centers.
You are right
ilektron is offline Find More Posts by ilektron
Reply With Quote
Old Feb 20, 2013, 03:20 PM
Registered User
Joined Oct 2004
2,770 Posts
Actually, you could build a fixed pitch bicopter where the pitch is controlled by swinging the props forward and back. Essentially it would be the same as weight shifting. I can't think of a solid and precise enough way to achieve this, though. Perhaps with separate tilt and swing axes?
Brandano is online now Find More Posts by Brandano
Reply With Quote
Old Feb 20, 2013, 08:32 PM
Registered User
RCvertt's Avatar
Joined Aug 2007
4,107 Posts
Didn't notice much difference when I moved the CG back an inch and a half on my little V22-Osprino.

This is what it looked like when the CG was right under the motors...
Asprino- (Arduino) RC Osprey (1 min 18 sec)


This is after the CG was moved back an inch and a half...
Almost hit by V22 Osprey! (RC Foamy) (6 min 13 sec)

I think it hovers a little more nose up now but it doesn't seam to be very noticeable like I thought it would have been.

A one meter difference on the real thing I doubt would be noticeable. I'm sure a person can walk around in it while it hovers with no adverse problems as long as a bunch of people don't all rush towards one side.
RCvertt is offline Find More Posts by RCvertt
RCG Plus Member
Last edited by RCvertt; Feb 20, 2013 at 10:28 PM.
Reply With Quote
Old Feb 20, 2013, 08:53 PM
Will fly for food
ilektron's Avatar
United States, CA, Carlsbad
Joined May 2011
532 Posts
Quote:
Originally Posted by RCvertt View Post
as long as a bunch of people don't all rush towards one side.
Maybe that's what caused some of the initial crashes
ilektron is offline Find More Posts by ilektron
Last edited by ilektron; Feb 21, 2013 at 01:09 AM. Reason: Removes offensive smiley
Reply With Quote
Old Feb 20, 2013, 09:07 PM
Registered User
United States, OH, Youngstown
Joined Nov 2004
593 Posts
thank you.
RedLine19k is offline Find More Posts by RedLine19k
Last edited by RedLine19k; Feb 21, 2013 at 10:05 AM.
Reply With Quote
Old Feb 20, 2013, 09:25 PM
Registered User
rimshotcopter's Avatar
United States, CA, Los Angeles
Joined Aug 2009
11,692 Posts
Nice
rimshotcopter is online now Find More Posts by rimshotcopter
Reply With Quote
Old Feb 20, 2013, 10:40 PM
Winging it >
leadfeather's Avatar
Joined May 2006
9,573 Posts
RCvert, Excellent work on the Osprino, really good!!

What size battery are you using and how far did you have to move it to get a cg change of 1 1/2"? ...that's a big change.

Hovering nose up allows the aft cg to swing under the props to some degree. I'll bet you won't be able to hover with the fuselage level, craft motionless, in no wind with the 1 1/2" aft cg.
leadfeather is online now Find More Posts by leadfeather
Reply With Quote
Old Feb 21, 2013, 01:50 AM
Will fly for food
ilektron's Avatar
United States, CA, Carlsbad
Joined May 2011
532 Posts
Quote:
Originally Posted by RedLine19k View Post
Why does your mention of crashes involving the deaths of 30 people have a smiley face after it? azzhole.
I'm sorry I have offended you. Those were not my intentions.
ilektron is offline Find More Posts by ilektron
Reply With Quote
Old Feb 21, 2013, 01:01 PM
Registered User
RCvertt's Avatar
Joined Aug 2007
4,107 Posts
I can see how an unexpected load shift could cause a problem for the pilot but there doesn't seam to be a lot of room inside so most stuff like heavy vehicles are connected to the underside of the aircraft near its CG.

Quote:
Originally Posted by leadfeather View Post
RCvert, Excellent work on the Osprino, really good!!

What size battery are you using and how far did you have to move it to get a cg change of 1 1/2"? ...that's a big change.

Hovering nose up allows the aft cg to swing under the props to some degree. I'll bet you won't be able to hover with the fuselage level, craft motionless, in no wind with the 1 1/2" aft cg.
Thanks. I fly with a 15c 2100mah thunder power 3 cell pack that weighs 149 grams and a 40c-50c 1800mah Turnigy 3 cell pack that weighs 168 grams. I moved the battery about 4 inches back. It hovers a little nose up but acceptable for me. I'll have to fly it in forward flight next time before adding the motor pivot point so I can get the two flight mode CGs to line up better.
RCvertt is offline Find More Posts by RCvertt
RCG Plus Member
Last edited by RCvertt; Feb 21, 2013 at 01:11 PM.
Reply With Quote
Old Feb 21, 2013, 01:35 PM
Registered User
v22chap's Avatar
United States, IN, Granger
Joined Jan 2003
3,105 Posts
Good job on the Osprino RCvertt I like that name too,, cross between osprey and the Audrino board that controls it all ,,, wish I would have had these boards back when I was playing around with the idea ,,, now I just don't have time to do anything with it

Do the nacelles have to be tilted in that much or that is just the way it happened ???

Reason I ask is the real one and all that I built seem to fly better with the nacelles out about 3 to 4 degrees

How much wind will she handle ... and when are you going to put out kits ????
v22chap is online now Find More Posts by v22chap
Last edited by v22chap; Feb 21, 2013 at 02:19 PM.
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Video V22- Osprey (Foamy) crash! RCvertt Electric Plane Talk 14 Feb 26, 2013 11:55 PM
Question Looking for mini 2ch V22 Osprey j_doug Micro Helis 0 Feb 05, 2013 09:28 PM
V22 Osprey Warbird@home Scale Fuel Planes 24 Aug 19, 2006 02:45 AM