Balancing Blades - Page 2 - RCCanada - Canada Radio Controlled Hobby Forum
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Old 07-29-2010, 02:32 PM   #11
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Re: Balancing Blades

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Originally Posted by Riddick View Post
Originally Posted by nickzz1 View Post
My way , check both blade on a scale I use .01 scale , mark them , take the heavy blade find the C.G. mark it, put both blade together with a rod or bolt & mark the light blade, so you going to kill 2 bird with 1 stone, now put both blades on main heli shaft line them up 90 deg ( both C.G. marking ) roll them if the light blade fall first put tape on the light oppsite side( bolt-end ) , if the heavy blade fall first put the tape on the light blade ( tip ) THEY MUST FALL & weight THE SAME
I have found this method to be the best.
I respectfully disagree. There are 2 different methods for balancing blades, both work very well, the method you choose to follow will be based on personal preference. In the case of the OP, he is already using what I call a "dynamic" balancing method, which is a lot less tedious is as much as all you do is add weight to the low blade while it is on the balancer until the blades hang level and that is it, no CG marking or weighing is necessary. I explained it a lot more on a previous thread regarding balancing here:

Originally Posted by Max View Post
I dont mean to take this thread off topic, but to answer the question of the two terms I used to describe blade balancing, there are 2 ways to balance a set of blades, one that is CG and mass dependent and one that is not.

When I learned the 2 methods, the term we used to describe the difference between the 2 is static balancing is a "one-off" balancing process and the dynamic balancing is when you put the 2 blades opposite each other on a balancer, hence the movement on the balancer being "dynamic".

Dynamic balancing DOES NOT require the mass or CG of the blades to be matched. Static balancing MUST have both blades identical in mass and CG.

Does this make sense so far?

Explanation of what I call "Dynamic" Balancing
To understand the difference between the two, one has to understand that you CAN use a single bladed propeller on an airplane engine. You only need to look at the C/L speed models to see that they use a single bladed propeller on their planes. (I made several of these types of props back in the '70's) What makes the single bladed propeller work is that the propeller is balanced by a counterweight. The heavier the counterweight, the closer it needs to be to the hub. The lighter the counterweight, the further it needs to be from the hub. In either case, the MASS and CG difference between the blade and the counterweight do not matter. To balance out a pair of blades in this fashion, you need a balancer. After you install a pair of blades, you find the high blade and add mass to the tip until the blades balance and you are done.

Explanation of what I call "Static" Balancing
As I mentioned earlier, Static balancing is a one-off process where you do not use a balancer device. All you need to do is match the blades in mass and CG. Without going into a lot of detail, the only tools you need is a straight edge(a razor works best) and a scale. The straight edge is used to find and mark the CG of each blade, and the scale is used to measure its mass. This is done one blade at a time. Once you have the Mass and CG of each blade ,you compare them to each other.
If the CG is off, you need to add mass to the light blade to move the CG in line with the heavier blade. Once the CG is correct, you re-weigh the mass of both blades and then ADD just the right amount of mass to the lighter of the 2 to get it to match the mass of the heavier blade. You add this mass right on the CG thus preserving the CG relationship between the 2 blades

Phew.... Sorry for the long-winded explanation but it was necessary to allow you to understand the differences between the 2 processes
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