How-to Balance a Propeller

An unbalanced propeller produces excessive vibration.  This vibration travels through the entire airframe affecting the handling of the aircraft,  produces inaccurate readings by the sensors, and creates premature failure of motor bearings and parts.  A balanced propeller is paramount to a stable aircraft.  A balanced propeller produces less vibration and draws less current, which results in greater stability and extended flight times.  You should balance any propeller before installing it on your aircraft.  Balancing a propeller requires the use of a special tool, you guessed it a propeller balancer.  The propeller balancer that I use is the Top Flite Propeller balance.  It is essentially a shaft held by two magnets.  The magnets create a frictionless surface for the shaft to spin freely. 

To check and see if a propeller is balanced or not.  Give the propeller a gently spin on the balancer.  If the propeller is balanced, it will come to rest at any position on the balancer.  If one of the blade on the propeller stinks down, this indicates that one of the blades is heavier than the other and that the propeller is unbalanced.  If the propeller comes to rest in the horizontal position, this indicated that the hub is heavier on one side.

To balance the propeller, gently spin the prop and wait for the propeller to come to a rest.  The heavier blade will stink down.

In order to balance a propeller,  material needs to be removed from the heavier blade.  One method is to take fine grit sand paper and sand the back side of the heavier blade until the propeller is balanced.  I choose to use a razor blade or X-ACTO knife and shave off the back edge of the heavier blade.  Either method you choose, repeat the process until the blades no longer stink down.

Here is a video explaining how-to balance a propeller.  He is using the Du-Bro Propeller Balancer.  This is a fine propeller balancer, but I recommend the Top Flite Propeller balancer.  It is cheaper and works great.

6 Responses to “How-to Balance a Propeller”

  1. Soo-Hyun Yoo says:

    An unbalanced prop can cause vibrations, but so can an unbalanced motor, at least in theory. I’ve seen one youtube video that showed how to balance a motor using tape, but I’ve never been able to tell if my motors are actually unbalanced or if they’re just loud by nature. Have you had such problems?

    • Russell says:

      A balanced motor should have a high pitch whine. I have experienced an unbalanced motor but it wasn’t from the motors housing. One of my motors shafts gotten lose after a crash. I notice that the shaft move ever so slightly out of it’s pin. This created play in the motor bell housing. The bell housing move only about .5mm but this was enough to create huge vibration issue. I fixed it by reseating the pin back into the shaft.
      Push and pull the bottom part of the motor and the top of the motor. If the two part move that mean the shaft pin came lose. The shaft pin is located at the bottom of the motor, where the cross plate mounts.
      Another cause for loud motors is the ESC switch rate. Generally, ESC’s have a switch rate of 8kHz. This frequency is very unpleasing to the human ear and can resonant the motors bell housing. If your ESC is adjustable try a higher frequency setting. Do you have a similar motor to compare the noise too?

      • Soo-Hyun Yoo says:

        I use the Turnigy SK3542-1000 on my tricopter. The reason I’m worried is that earlier in my build, (long story short) my tricopter broke apart in my garage and the motor/prop assemblies flew into the concrete floor. The bell housing is very, very slightly asymmetrical on one or two of the motors, but I don’t know if that’s a manufacturing flaw or damage caused by the earlier crash. There is no play in the bell housing, though, so I don’t think anything’s loose.

        I didn’t think about the ESC frequency affecting the high-pitched whine. My Mystery ESCs have a 16kHz option — I’ll have to try that sometime. Thanks!

  2. Mark says:

    Hi, I’m building an x-copter of my own and I have a few problems:
    When I fly my x-copter, it starts to spin in circles and then eventually crashes.
    When I push the elevator up on the remote, the x-copter gets faster and faster, even if i’m not pushing the elevator higher
    Please help!
    Thanks

  3. Rakesh says:

    @Mark do find that your velocity cutter is not working.
    and you need something to resist your copter to spin in opposite directions

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