For Bashers, By Bashers!

Raging Rotors: Blade Runner, Part 2: It’s All About Balance

In this week’s conclusion to ‘Blade Runner’ we discuss an important aspect of multirotor and airplane flight, propeller balancing. Granted an unbalanced propeller doesn’t keep something from flying, but it can cause propeller based failures as well as increased noise due to the blade imperfections. There are two parts to propeller balancing: Horizontal and Vertical Balancing.

To start, one needs a propeller balancing apparatus. This can be as simple as a pen placed across two boxes, or a commercial balancer from companies like this one from Dubro or this option from Great Planes. Next, you need either sandpaper to shave down the prop, or some clear tape or stickers to add to the prop. I’m a big fan of tape/stickers, but there are many schools of thought when it comes to prop balancing, so work with what makes you comfortable.

Prop Diagram

For reference, above you will see a diagram of a prop courtesy of Horizon Hobby. When I talk about the leading edge of a propeller, I’m making note of the thicker part of the propeller, shown as the light gray area of the propeller. The trailing edge of the prop is the thinner edge of the prop and is marked on the diagram as the black area.

Before any balancing can occur, don’t forget to ream the mount hole to fit your propeller shaft (similar to making body post holes, for you surface RC people). If you do not ream the hole until after balancing, you will have to do it again, and no one wants that.

Horizontal Balancing

Propeller Balancing Horizontal

Once you have the propeller on your balancing post, place it into the horizontal position. Here is where the sandpaper or tape/stickers come in: See what direction the propeller spins after in the horizontal position, and either add tape to (or near) the leading edge of the lighter half of the blade or sand down the trailing edge of the heavier half of the blade. Continue this process until the prop only deviates from the horizontal position 5-10 degrees.

Vertical Balancing

Propeller Balancing Vertical

The same applies to vertical balancing. Place the blade on the balancing post into the vertical position and, like horizontal balancing, either add tape to (or near) the leading edge of the lighter half of the blade or sand down the trailing edge of the heavier half of the blade. Continue this process until the prop only deviates from the vertical position 5-10 degrees.

…And that is all there is to it! With your propellers balanced you will see an instantaneous change in the noise coming from your motors as well as small changes to performance.

If you have any propeller or other RC Aircraft questions, feel free to contact me (kevin (at) bigsquidrc.com). If you have not yet, check out the big Multirotor Build Project I’m working on right here. Until next time, Stay Shiny and Keep Flyin’!

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Posted by in Columns, rc helicopter on Wednesday, April 16th, 2014 at 3:33 pm

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