Sabot

someone showed me one how to balance them but ive long forgotten

Im just interested to know how many people actually do know

Sabot

Come on guys... 42 hits and 12 votes.... no need to be embarrased [joke]

Want2BRealPilot

My Feedback: (3)

Sabot, I simply bolt the blades together, with a long bolt. Tighten them together, and balance the ends of the bolts on two drinking glasses. Add tape to the "high" blade, until they balance.
Mike

Sabot

oh, thanks ill try that

i was more thinking about CP blades but never mind

wisdom-seeker

What he meant to say is add tape at the CG of the high blade. If you don't do this, you will introduce dynamic instability.

chipracer

What do you mean add tape to the cg of the high blade? I thought you could just add it anywhere on the blade.

sceadu37

can someone post a guide to doing it?

i balanced my blades by putting a long bolt through, and hanging the ends on some cotton from the ceiling...

they were pretty balanced, and i didnt want to go fiddling...

ive got some carbon blades on their way now though. do these need balancing?

wisdom-seeker

If you add tape anywhere along the blade, you would move the CG for that blade. The only place this does not happen is if you add tape at the CG and nowhere else. The blades are only in balance if the CG's match AND the blades weigh the same. If the blades have different CG's then when the blades are spun up, there will be a dynamic instability. In plain language, even though the blades weigh the same, there will be vibrations. Is that more understandable?

sceadu37

where is the cog of the blade, or how do you find it?

wisdom-seeker

I use a round pencil. For each blade, place the pencil on the table and place the blade on the pencil, and move it until the single blade balances on the pencil. Mark this point. When you have both blades marked, then compare the marks. Both marks should be exactly the same distance from the bolt hole on the blades. If not, add tape to the tip of the blade with the CG closest in until the CG moves out to the same place as the other blade. The simplest way to do this is to mark the target CG onto the blade, and set it onto the pencil. In this way you can determine how much tape is needed. After the CG's match, then you can balance the blades against each other by adding tape at the CG of the lighter blade.

Usually, carbon blades are balanced from the factory. For woodies, where you have to epoxy the blade roots on, the CG can be affected by using more or less epoxy. You usually don't have exact control of the epoxy amount, so you have to balance it with tape to put the CG where it must be. Wood can also have variable density which can affect the CG.

chipracer

Hey thanks for the help on understanding how to correctly ballance blades. I was always adding tape to the end of the high blade, wich made me wonder why I went through the troble of finding the cg. Now that you spelled it out it makes perfect sense, Thanks again!

Sabot

woah i forgot i made this thread

my heli isnt working now anyway because i keep having trouble my lithium batteries dieing [sm=disappointed.gif]
cheers for the replies anyway guys

Nitrofever3D

i use a clamp and a razor blade and balance each blade seperate to finf the CG and i use the razor to mark the spot then once i find the cg of both i put the blade grip bolt thru both blades and check to see if both blade will balance with the razor touching the side of the bolt on the hex side not the nut i estimate to get them as close to blance as posible since the bolt wont let me get them right in the middle but every time they balance perfect.About the tape u could add it to the middle of the blade were u made the mark for the CG of the blade for small weight gain for more added weight u can add tape to the tip of the light blade.I use clear X-mass wrapping tape works great for me

heli-john

I must be the odd one out but I do a lot more than this. For instance I weigh the blades to find which is heavier before I do any work involving balancing or CoG. Also, if I am adding weight to get CoG equal I'll add it to the root - this is why you need to know which blade is lighter. When CoG is equal you can add weight at the CoG to make the blades weigh the same. Then there's the adding of tracking tape which has to be factored in and so on - it's a forever task. No matter how good the blades are supposed to be they nearly always need work. Question is, how far are you prepared to go?
And finally, I will always check the balance on a Dubro Hi Point balancer having already checked and balanced the paddles before the blades are added to the head.
Then we have the tail blades etc.

Gorgok

My process is much the same:

Weight/balance both blades at the same time, remember or mark the lighter one.
Find CG of heavy blade.
Copy CG mark of heavy blade to light blade.
Check the lighter blades CG using the mark, note the lighter end.
Add tape to the lighter blade at the tip or root to get the CG where the mark is.
Test and repeat taping until you get the light blade at the CG mark.
Weight/balance both blades at the same time again, remember or mark the ligher one.
Add tape to the lighter blade CG to make it as heavy as the other blade.
Test and repeat taping until you get the blades to weight the same/be balanced.

Sure, its a involved process, but when i put my last blades on the heli they made what looked like a perfect disk.

johndale

Guys I have been Track and Balancing real helis for 30 + years and what you are saying is not right . Balancing the blades gives you a starting point but far from the finish part. You have got too include the rotor head too. Back years ago we use to take a roll of masking tape 2 inch wide at 6 inches from the tip of the blade and make a complete wrap around it and go fly. if it got better you were on the right blade and if it got worse try the other one. But now we use what they call a Micro vib. And it is kick butt. If you are having that much problem with blade flight then you may want to change brands. Oh yea Bell Helicopter even tells you if you run out of weight room you will have to repaint the tip of the blade. The area you are talking is called product balance and on the smaller blades you are wasting your time on this. so balance the whole assembely and it will be smooth. To get the best flight on the little ones none of us has the money to buy the blades[X(].

heli-john

johndale - Er, we've said we use a hi point which includes the head. You need to get the blades on the way first but as I said, even when it's all seemingly perfect the hi point almost always still shows more needs doing. It also facilitates chordwise balance!!!
I also mentioned the paddles as well etc.
So which part is not right?

johndale

With the system you have and the type of rotor heads you can not do cord or lead lag balance. in order to do lead lag the blade cannot pivot. it has to be put in the infight condition and with a single bolt system you cannot do it. If you can then there is a lot of real heli places will give you a job. To do what you say you are doing the blades has got to be 0 degree of pitch you have got to have 5 degree precone and the tips of each blades at a certin point in the blade has got to cross the center of the hub and you use a machine called marvel balancer. What you are saying is to hard to do and not worth the time and effort. on these machines.

RCer22

I used to run into balance problems with the wood blades all the time Ever since I started using the carbon blades I haven't had to balance blades at all. If you install them and have a problem then you have to do them. Otherwise no shake no problem.

If it ain't broke don't fix it.

chipracer

Wow, finally a post I can understand. Those other ones were starting to hurt my brain. I think I'll try a set of the carbonfiber blades.

heli-john

We do the chordwise balance without the blades on the head. You want to simulate perfect lead/lag in each blade. Rather than put on the blades and take a chance on a slight lead/lag error in one blade, simply eliminate the blades altogether.
I take it you use a Hi Point!
I don't want to lock horns but my point was that you missed the point that some of us do balance the blades thoroughly and to that end the Hi Point is the way to go after buying scales, pivotal balancers etc. etc.
As was said by someone else, often carbons are good enough to throw on and use but, at the end of the day, rarely are blades perfect (and woodies just aren't) and maybe some of us want to go that extra yard.