RunRyder RC
WATCH
 4 pages [ <<    <     1     ( 2 )     3      4     NEXT    >> ] 3311 views TOPIC CLOSED
05-30-2011 06:31 AM  9 years ago
James

rrVeteran

Del Mar California

MyPosts All Forum Topic
quote: from Darrens

don't believe it is important to add weight at the CG point. I believe it is about "effective" weight balance e.g. you could add say 1 gramme of weight to the tip of one blade and 10 gramme to the route of the other yet they could be balanced rotationally. This would give the blades different weights from each other when statically weighed and different CG points, but they could be in centrifugal balance when rotating

the words centrifugal balance when rotating really makes since to me.
this has talked about my question i was asking earlier about if i have multiple blades, that the C.G. of a single blade is not as important, as having the blades together and finding the CG in this manner, as a unit of two blades i like that method.
Any other ideas please post away im looking for the easiest way to get five blades balanced correctly but not perfect because a very small amount of a blade being off is not going to make that much difference in vibration that i do know.
Jim
flying is the easy part paying for it whole different story
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR
05-30-2011 06:47 AM  9 years ago
James

rrVeteran

Del Mar California

MyPosts All Forum Topic
these blades were very afforable and made my Airstar international and were balanced before they were sold to me, but after painting them i really do not know were they are with C. G. and weight

Jim
flying is the easy part paying for it whole different story
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR
05-30-2011 09:24 AM  9 years ago
PETER ROB

rrElite Veteran

Devon UK

MyPosts All Forum Topic
WHY
James,
quote "the C.G. of a single blade is not as important"
It is that one blade that is out, which causes the inballance when rotating
I fly off a active heli Pad,
I watched two engineers with pilot, spend 5 hours setting up the blades on an old five bladed scout,( have a video )
I also watched an engineer with pilot spend hours setting up the blades on a full size Hughs 500 (after they were painted)

It is so easy to read a book, watch a video, get some one to tell you, to learn how to do some thing, what so many of you, hobbiest fail to under stand is WHY

It is the why, and the experience gained, from learning why, that is the important part

Me, I have gained a lot of experiencs from years of breaking and repairing things, of course, the downside of experience is you get older,and me, I am very old
Peter R
SHARE  PM  EMAIL  GALLERY  Attn:RR
05-30-2011 11:01 AM  9 years ago
darrens

rrKey Veteran

United Kingdom

MyPosts All Forum Topic
I'm confused Peter, are you now saying that having equal CG on all blades is important?

Are people confusing CG with Balance possibly?

My understanding (and im not suggesting I have the answers) is that CG is the balance point if a blade on it's own axis, where balance is each blade having the same weight when considered from a centrifugal point (not static weight) and compared with all other blades.

I am interested in all points of view as if the CG is important, I would really like someone to explain why?? Like I said earlier, I am no dynamisist so would like to learn from this discussion if someone has some definitive answers.
He who dies with the most toys is the winner!
SHARE  PM  EMAIL  GALLERY  Attn:RR
05-30-2011 11:33 AM  9 years ago
PETER ROB

rrElite Veteran

Devon UK

MyPosts All Forum Topic
CofG
Darren
Quote," are you now saying that having equal CG on all blades is important?"
I have been saying from the beginning, that equal CofG is important
What it appears to me is that you are now playing the Matt Jenner game

You for one with all your knowledge of full size helicopters should know exactly what I have said

The CofG of a blade,is not determined on one axis alone, but on two axis
1, On its length
2, on its width
When you understand this, then you will maybe understand that the CofG of a blade is closer to the leading edge than the trailing edge, I will not explain why, go look it up
If one blades CofG is different, then it will react faster or slower to the others on the head, when receiving inputs from the swashplate

It also appears to me reading these post's that not one of you knows how to determine the true CofG of a blade, and all that you are doing is ballancing the blades
Peter R
SHARE  PM  EMAIL  GALLERY  Attn:RR
05-30-2011 12:48 PM  9 years ago
darrens

rrKey Veteran

United Kingdom

MyPosts All Forum Topic
Peter, no games here, I am genuinely interested in opinions.

You are right that with my understanding and involvement in full size I do understand that CG is a cross point found on 2 axis of a blade. I also understand that adding weight off the line chordwise can cause issues on the full size, but length wise I am not so sure......I will ask somebody with more knowledge than me and report back here.

As for our models, I'm doubtful it is as crutial. I seriously doubt lengthwise whether it makes any difference, especially as we do not have fully articulated heads. To my knowledge all models I have seen have a rigid head.

Also, how are you finding the CG chordwise, that would be very difficult on blades our size. I would be interested to understand the process and give it a try to see if it improves the flight charectoristics of my EC. Please can you tell me how you guys are doing that?

Cheers
Darren
He who dies with the most toys is the winner!
SHARE  PM  EMAIL  GALLERY  Attn:RR
05-30-2011 01:41 PM  9 years ago
PETER ROB

rrElite Veteran

Devon UK

MyPosts All Forum Topic
To my knowledge all models I have seen have a rigid head.
Darren, thats the problem with limited knowledge
there are teetering heads, I think thats how it;s spelt
There are the Hirobo multi blade heads, with rubber mounts
There is the latest three blade head from Starwood (Chinees cross between a hirobo and an 'OF' head)

This is the genuine Hirobo head, the blades for this head cost with all the discounts I could arrange, £920.00, special order from Hirobo Japan, and made to order, these blades are absolutly spot on

Quote that would be very difficult on blades our size.
Not at all it is as simple as finding the ballance of the blade

Peter R


ps, From the Vario page
The GRP blade holders are extremely rigid due to their high glass fibre content, yet they retain a degree of flexibility.
SHARE  PM  EMAIL  GALLERY  Attn:RR
05-30-2011 02:40 PM  9 years ago
darrens

rrKey Veteran

United Kingdom

MyPosts All Forum Topic
Yes, but a "retained degree of flexibility" is by no means an articulated head. Also, a teetering head could be a head with dampers for example, as they allow the blade to teeter, yet the head is still rigid (or at least semi-rigid) by definition/classification. I will of course ignore your comment about my limited knowledge, but instead offer a definition of an articulated system so you know what I am refering too. As yet, I have not seen a model version of this type of head.

A fully articulated rotor system usually consists of three or more rotor blades. The blades are allowed to flap, feather, and lead or lag independently of each other. Each rotor blade is attached to the rotor hub by a horizontal hinge, called the flapping hinge, which permits the blades to flap up and down. Each blade can move up and down independently of the others. The flapping hinge may be located at varying distances from the rotor hub, and there may be more than one. The position is chosen by each manufacturer, primarily with regard to stability and control.
Each rotor blade is also attached to the hub by a vertical hinge, called a drag or lag hinge, that permits each blade, independently of the others, to move back and forth in the plane of the rotor disc. Dampers are normally incorporated in the design of this type of rotor system to prevent excessive motion about the drag hinge. The purpose of the drag hinge and dampers is to absorb the acceleration and deceleration of the rotor blades.
The blades of a fully articulated rotor can also be feathered, or rotated about their spanwise axis. To put it more simply, feathering means the changing of the pitch angle of the rotor blades.

So I still want to know how you are measuring the CG chordwise as that could be of interest to me to check my EC head?

Thanks
Darren
He who dies with the most toys is the winner!
SHARE  PM  EMAIL  GALLERY  Attn:RR
05-30-2011 03:20 PM  9 years ago
PETER ROB

rrElite Veteran

Devon UK

MyPosts All Forum Topic
Darren, The photo of the Hirobo head, This is an exact copy of the real thing it has all the functions of the cut and paste description,
Now with this ability to find things in other peoples articals, you should be able to find this very simple way of finding the exact CofG of our model blades

We have now gone a long way from James's original post
My advice to james is carry on with what you are doing if the head fly's well after it is tracked in then no problems, if you find vibration you can not explane or fine tune out, then ask the question again
I am done, There is not much more I could add
Peter R
SHARE  PM  EMAIL  GALLERY  Attn:RR
05-30-2011 04:32 PM  9 years ago
darrens

rrKey Veteran

United Kingdom

MyPosts All Forum Topic
Peter

It's a shame you get on the high horse yet refuse to answer my question and attempt to skilfully avoid it. If there is anyone else out there who knows how to find the chordwise CG of such small blades please can you share it.....Peter and I would appreciate knowing how it's done!!!!
He who dies with the most toys is the winner!
SHARE  PM  EMAIL  GALLERY  Attn:RR
05-30-2011 05:08 PM  9 years ago
payne1967

rrElite Veteran

uk

MyPosts All Forum Topic
Darren
my method to check cord wise c of g
get a workmate (make sure its level)
clamp a meter steel rule into the jaws (thin edge up)
use the upper edge to place the blade onto the ruler
when you have found the c of g mark the blade
do the same with all the remaining blades
compare the markings on each blade
if out (i've never had the cord wise c of g out on a set blades)
add weight to the trailing/leading edge
re-balance the blades and then re-check the c of g
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR
05-30-2011 05:14 PM  9 years ago
Phoenix NOTAR

rrApprentice

Tallahassee, Florida USA

MyPosts All Forum Topic
Darrens,

I use a Koll rotor blade balancer for all of my blades (except the very large Vario models like my R22)

Here is a link to the to the original instructions (poor image quality)that discuss both spanwise and cordwise balancing:

http://www.rchelibase.com/tools/koll.pdf

Here is a link to a shop selling the Koll balancer:

http://www.heliproz.com/prodinfo.asp?number=114145

A quick "google" of the Koll balancer should answer most of your questions.

I believe that this is one of the best tools availible to get model rotor blades to fly as best that they can.

Sandy
SHARE  PM  EMAIL  GALLERY  Attn:RR
05-30-2011 05:21 PM  9 years ago
MattJen

rrElite Veteran

UK

MyPosts All Forum Topic
James,

1 Paint your blades tip to root as evenly as possible all lying next to each other on a bench one side only first.

2 once dry turn em over

3 lying all next to each other paint the other side tip to root as evenly as possibble, let dry

then
4 find c of g on each blade tip to root,
(do this see saw balancing each blade on a thin piece of metal or main shaft)
having found c of g mark with pencil on each blade

5 put all blades together and look at where c of g is on each blade relative to each other.

6 Pick a blade as your master c of g blade
this should be the blade that has closest c of g to the others.

your goal is to match c of g all other blades to that master blade.

then 7

take each blade 1 at a time then apply paint or aluminium adhesive tape to underside of tip or root till c of g is matched to your master blade.
8 repeat with all other blades till your c of g are identicle.

1 - 8 painting cg balancing

9 congratulations all your blades are now painted and have identicle
c of g

10 Dont fly yet though you still have to balance your blades overall weight to each other.

so
11 weigh all blades, take out heaviest blade.
12 now add WEIGHT ON THE C OF G ONLY until they all weigh the same

13 Congratulations you now have all your blades painted,weighing the same and with the same end to end c of g,

14
Technically you havent balanced the blades chord wise ie trailing edge to leading edge, but if you have a set of blades that are actually out of balance relative to each other, accross this dimension, then they are only useful for stiring paint ,in my opinion because unless you are making blades yourself or the manufacturer has put the lead in wrong place when making them, it is impossible to get the c of g out in this dimension just by simply painting them. Believe me I have only ever had 1 set of blades where the chord has been out, I would have add to add weight which would have then altered the moment of inertia and you have to get into some real calculations,so the ismplest thing was to send them back.. funny they were vario blades, never had any trouble with others.

If you now want dynamically balance the head, put it in a blade balancer and balace the head on its own.

happy flying mate
SHARE  PM  EMAIL  GALLERY  Attn:RR
05-30-2011 05:26 PM  9 years ago
modtron

rrKey Veteran

Oxford. UK

MyPosts All Forum Topic
Darren,

As no one appears to want to tell you how to check chord cg - this is how I have done it for the last 30 years or so.....

1, Using a level edge (steel ruler is good) in a vice.
2, Place one blade at 45 degrees to the ruler edge and move up and down it's length until balanced level.
3, Then gently press down and make a mark on the underside of the blade.
4, Now rotate the blade by 90 degrees and repeat the process again.

You should now see a cross marked on the underside of the blade - this will indicate it's balance point over it's length and it's cg/balance position in reference to it's chord.

It is not uncommon for the chord cg to be out and in need of adjusting - especially with multiple blades.

If the chord cg is to far foreward, then the blade will "lag" in the holder and give a softer response.
Likewise, if the chord cg is to aft ,then the blade will "lead" in the holder, and will result in a quicker response.

This is all about fine tuning, which also includes setting up for particular rotor speeds to be used.

This used to be common place adjustment years ago when we were into FAI flying and blade changes made big differences in flying styles.

modtron
Oxford UK
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR
05-30-2011 05:32 PM  9 years ago
modtron

rrKey Veteran

Oxford. UK

MyPosts All Forum Topic
Just one more quick thing.

I have always been led to believe that dynamic balance is more important than static balance, as our machine do not fly when not rotating !

The mass should always be balanced as a complete unit and preferably at the required rotor speed to be used if at all possible.

I have experienced rotor heads in the past, that when checked statically are wrong, but run as smooth as silk when flying.

modtron
Oxford UK
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR
05-30-2011 05:40 PM  9 years ago
Bell Bloke

rrKey Veteran

UK

MyPosts All Forum Topic
Ha ha ha, dynamic balance a head and mechanics on a model, now that sounds like fun!!

Don't loose you heads on this one chaps!

Sorry Modtron you are right, but could not resist.
SHARE  PM  EMAIL  GALLERY  Attn:RR
05-30-2011 05:59 PM  9 years ago
Bell Bloke

rrKey Veteran

UK

MyPosts All Forum Topic
Backing up Modtrons point here:

I once dynamically balanced a V12 Muira engine, many moons ago.
This is basically the practice that even if all your 12 pistons weigh the same and that all your con rods weigh the same.
And... you fanatacle blade c of g finders will love this next one..
Yes the c of g on all of your con rods are the same end to end and weigh the same and your crank is balanced and your clutch and flywheel assembly is balanced.
Even with all of your large mass moving items statically balanced, it is still possible that once all of these items are assembled, the sum of all of these parts can add upto an overall error in balance.
It's for this reason we balance the assembly as a whole at the very end.
However it would be a very bad practice indeed to try and cheat by not balancing the individual components and just skip strait to the end and do the dynamic engine balance only.
Only a 'Cowboy' would do this, sorry to our American cousins but it is a term commonly used over here.

To dynamically balance a helicopters entire mechanics would need a costly rig I suspect...OR you could run it up to working rpm and add lead.
SHARE  PM  EMAIL  GALLERY  Attn:RR
05-30-2011 06:16 PM  9 years ago
modtron

rrKey Veteran

Oxford. UK

MyPosts All Forum Topic
Bell,

Never had the money then for costly rigs - only by trial and error, but you do get there in the end !
I watched two engineers with pilot, spend 5 hours setting up the blades on an old five bladed scout,( have a video )
Peter, I'd like to see the video at some time as I've never seen a Scout with 5 blades - all the one I know of only have 4.
Must have been a special one ?

modtron
Oxford UK
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR
05-30-2011 06:22 PM  9 years ago
Tiltrotor

rrNovice

Poitiers,Vienne - France

MyPosts All Forum Topic
Hello Peter Rob !

As you said in your first reply, how you do to balance a 5 blade rotorhead ? Thanks a lot. Have a nice day.
SHARE  PM  EMAIL  Attn:RR
05-30-2011 07:48 PM  9 years ago
Camflyer68

rrNovice

Northern Ireland

MyPosts All Forum Topic
Peter Rob quote 1
James, why waste your money, you already have all you need on the helicopter
You then back peddle
I have been saying from the beginning, that equal CofG is important
You can only measure C of G statically, you have to take the blades off.
CONTRADICTION.

PeterROB
what so many of you, hobbiest fail to under stand is WHY

You then insult the rest of the bobbiest people making us all out to be mindless idots,and only you have the knowledge.

Me, I have gained a lot of experiencs from years of breaking and repairing things,

Maybe if you had listened and applied what you were told and seeing you would have saved yourself a lot of trouble.

Ian
SHARE  PM  EMAIL  GALLERY  Attn:RR
WATCH
 4 pages [ <<    <     1     ( 2 )     3      4     NEXT    >> ] 3311 views TOPIC CLOSED
 Print TOPIC  Make Suggestion 

 8  Topic Subscribe

Tuesday, June 2 - 1:28 pm - Copyright © 2000-2020 RunRyder   EMAILEnable Cookies

Login Here
 New Subscriptions 
 Buddies Online