Blade Balance Tolerance??

[Wazzer]

Hi Guys

when balanceing blades on a gram scale what do you consider close enough?

i have two sets of wooden blades that are only 0.2 grams diference

I am haveing a hard ime getting them to match perfectly.

Is 0.2 grams close enough?

Cheers

[Mikej]

Ben,

I try and balance them to the smallest level of resolution that I have - i.e. X.Y grams where X and Y are the same for both blades. I know it's stating the obvious, but the closer they balance the smoother the heli will fly.

Cheers,
Mike.

[worldofmaya]

Just balancing by getting the weight isn't a good way. Just screw them together and and have look which one is lighter. If it's just a little bit, than just ad a little bit at the tip. Otherwise you would have to check cg of both blades and dynamically balance your blades. Bob has a nice video in his 101 thread.
-klaus

[Wazzer]

ok thanks guys will see how good i can get them

cheers

[Pinecone]

You can only balance them by screwing them together if you first match the CG of the blades.

This is because hooking them together is doing a moment balance, and that only works if the moments remain the same. When you mount the blades on the head, the hbolt holes are further apart and this changes the moment only balance.

There is a thread on it this with the math that shows how ti works.

So proper way to balance is:

1) Measure blade CGs.
2) Adjust the CGs to match
3) Bolt together and balance, using tape ONLY at the CG to cahnge weight.

All that said, with my Gaui Hurricane 200 and Blde CP I have had OK luck with just matching CG and weight to 0.1 grams.

[mjdee14]

I use the Helimax seesaw blade balancer and as PC stated....you check the cg, ajdust cg...then seesaw the blades till the balance perfectly and make any adjustments on the cg.

Never really care or know what the actual weights are. depending on where the weight is off changes the affect on the blade....that's why you get the cg's the same first.

http://manuals.hobbico.com/hmx/hmxr4855-manual.pdf

check the above website...it's the manual from the helimax balancer

[mysticmead]

that's the same balancer I use.. very easy to get the CG and then balance the blades..... a GOOD set of CF blades will have the CG pretty close as well as the blades pretty close to being balanced.. I've even found some woodies (for my 450) that were close enough to dead on that I just bolted and flew..

[mjdee14]

that's the same balancer I use.. very easy to get the CG and then balance the blades..... a GOOD set of CF blades will have the CG pretty close as well as the blades pretty close to being balanced.. I've even found some woodies (for my 450) that were close enough to dead on that I just bolted and flew..

I agree, most of my cf blades are dead on the cg...and only take a few wraps of scotch tape on the cg to balance. That balancer works really nice.

[Graeme67]

I don't know if I have just been lucky, but I have never bothered with the CG stuff. I saw the finless videos on balancing & I have only ever used the bolt together on knife edges way. On the numerous 500mm woodies I have been through, the worst case was only 2 x 40mm strips of tracking tape to get them level. My hurri always runs very smooth.

If you want to run insane headspeeds it would become more important to have the whole CG balance done correctly but for my 1900 - 2100 HS range the simple way has worked fine.

Cheers
Graeme

[mjdee14]

If you want to run insane headspeeds it would become more important to have the whole CG balance done correctly but for my 1900 - 2100 HS range the simple way has worked fine.

Cheers
Graeme

It does get more critical as HS increases..

lets say you moved your flybar 1 inch...to one side and added weight to the short side so it would still be perfectly balanced on a seesaw....then flung them out at 2000 rpm...although the weight would be the same the longer moment arm would make a difference.

At slower speeds it's not as important.....they make a ceiling fan with only one blade and a counter weight on the other side...and it runs smooth.

[skigolfmike]

Some of the old control line speed models used single bladed props withe a counter weight. Worked pretty well at 25-35Krpm.

[mjdee14]

Some of the old control line speed models used single bladed props withe a counter weight. Worked pretty well at 25-35Krpm.

Small blades....small mass.....I'm just not sure heli's would spin a 52 inch blade with a counter weight.....

Actually a one bladed prop is pretty efficient because it's always spinning in "clean air"

[skigolfmike]

Yep - it's in clean air, not sure I'd do it with a heli either. Probably showing my age that I remember that.

[mjdee14]

. Probably showing my age that I remember that.

Just turned 61.....next year I get to retire a "Second" time....as my retirement job turned into 10 hrs a day...and my flying field is only open M - F 8am - 3pm....to allow the "soccer suckers" to use thier playing fields....

[woz]

So proper way to balance is:

1) Measure blade CGs.
2) Adjust the CGs to match
3) Bolt together and balance, using tape ONLY at the CG to cahnge weight.
.

Hi , This is the way I have always done it and works well ( From Ray's Helicopter guide ....the old Book still)
one other thing that I have read recently that I feel can contribute is to weigh the blades first then do as before but get the CofG so that if counter weight is necessary, you apply this to the LIGHTER of the blades.

so theoretically this should give the lightest blade combination.
BUT hey .......I still just do it the basic way........don't even own a scale !

cheers

[Wazzer]

OK so

I just watched the Finless video and balanced all the blades I have available to practice on

balanced 2 pairs of woodies

1 pair Gaui 500 carbons

1 pair assymetrical FG / CF dihedral! 500s (more on those in another post

Very easy method and makes alot of sense.

However

When I weigh the blades with my gram scales they end up about 0.2-0.5 grams out BUT balance perfectly on the "Teter Totter" as finless likes to call it.

CoG matched perfectly

when i get the weight perfect on the scales and then balance them using bolt "Teter Totter" they dont always balance?

Anyway i will see how smooth they are in the morning when i get to fly next

Cheers all for the advice.

Ben

[kahn10]

just a thought but you have to have things in exactly same pos on scales very small changes lead to diff readings.i've found if they balance with the roots bolted together sitting on a bearing at each end of the bolt their perfect. i'll find those paddle numbers tomorrow

[mysticmead]

I don't even bother weighing blades.. I get the CG's to match and then balance them.. once that's done they track perfect

[kgfly]

BTW I have seen photos of a one-blade-plus-counter-weight full-size heli so it can work. In fact it was on the strength of that demonstration and an explanation from Spork that I gave up matching CoG and simply balance the blades in teeter-totter mode (bolt together for the 325mm, HeliMax for the 500mm). So far no problems with tracking or vibration and I run the T450 at ~3000rpm and the H550 up as high as about ~2400rpm.

[Wazzer]

Well they are way better balanced than ever before so i am sure they will be great in flight tomorrow morning.

Will report back when I have flight tested.