So you’ve finally got that flashy new quadcopter, or you have owned one for a while. You head out for FPV flying sessions to capture photographs and video. However, your experience is diminished by a ‘wobble’ effect. What a bummer! You wonder why this is happening. It is safe to say that most propellers are not manufactured to be a 100% balanced, particularly the cheaper ones. Balancing propellers is hence, very important.
Unbalanced propellers on your quadcopters are not only a mere annoyance, but can also damage your internal electronics and engine bearings over time. An unbalanced propeller also turns relatively lower RPM. So why let this problem linger?
This post will guide you through the very simple process of balancing your propeller to immediately reduce the vibration and increase the performance (including longer flight times) of your craft.
Tools you’ll need
• An unbalanced propeller
• Cyanoacrylate (super glue)
• Prop Balancer. The Du-Bro Tru-Spin is an excellent choice. I believe it is also the most widely endorsed prop balancer out there and it works great even on bigger propellers.
Step 1: Balancing the Prop Balancer
Ironically, the first thing you have to make sure is that your prop balancer itself is balanced. For this, you have to make sure that the rod that holds the propeller on the balancer sits horizontally as shown in the figure below:
To do this, make sure that both the sides of the balancer are at the EXACT same level. You can use a wooden block or some other symmetrical object below each of the platforms one after the other to check and get it to the same exact level
Do not overlook this balancing step!
Step 2: Balancing the blades
Check if the blades are unbalanced
You need to check if your blades are unbalanced in the first place. To do this, mount the propeller on the prop balancer.
Rotate the propeller around and if the propeller is unbalanced, you can easily see that the blade doesn’t rest when you leave it alone. Instead, it will have a tendency to tilt.
When you try to keep it at a perfect horizontal line and the propeller tilts to one side, it suggests that the blade that goes down is probably heavier than the other blade. If it stays relatively stable, it is time to move onto the next step. If it is unbalanced, make sure to mark the side of the hub which was facing up when you tested for the imbalance. You will need this further in this step and for the next step.
Balancing the blades
Apply some tape on the lighter blade so that the weight of the lighter blade matches the heavier blade. If the relative weights are near even, then when you place the propeller back on the balancer, the propeller should align horizontally without tilting.
Make sure that the same side of the hub is facing up when you checked for the imbalance in the beginning of this step. If you don’t, then the propeller will probably tilt even if the blades weigh even due to imbalance of the hub.
Step 3: Balancing the hub
Check if the hub is unbalanced
Like the previous step with the blades, you need to check if the hub is unbalanced. Balancing propellers will remain incomplete without this step. To do this, mount the propeller onto the balancer horizontally with the other side of the hub (the one that wasn’t marked in the previous step) facing up. If the blades tilt, then it is a sign that the hub itself is unbalanced.
Another great way to check if the hub is unbalanced is to mount the propeller vertically. If the propeller doesn’t stay that way and tilts, this is also a sign of an unbalanced hub.
In both tests, the heavier side of the hub tends to pull on the lighter side, causing the tilt.
Balance the hub
To balance the hub, add weight to the side of the hub that is lighter. To do this, add some super glue onto the lighter side (be frugal) and wait for it to dry up. The added material should balance the lighter side with the heavier one.
You can also use tape for this, but due to the nature of the surface of the hub, tapes tend to fall off quickly.
End result: Balanced propeller
Once you have balanced your propeller, no matter what way you mount it, it should stay balanced without tilting.
Remember that it doesn’t have to be a 100% aligned at all times. A little bit of tilt is still okay. Just try and get it near perfect even if it isn’t perfect.
As long as the propeller isn’t moving as crazy as before, you should be good to go.
Don’t rush. Take your time through the process. Balancing propellers might take a while, but I assure you that the end result will be worth it.
Common Issues and solutions for it
Balancing propellers for large propeller
A common problem you might face with large propellers is that the rods of the balancer may not be long enough. Because of this, the propeller may hit the desk, limiting your testing for imbalance.
To work around this, first get one of the platforms to the middle. That is, remove the rods which you would have placed at the ends of the balancer to the middle and mount the platform on top of the rods there.
Slide down the other platform to the bottom. Place the platform on the middle rods such that the hole of the platform aligns with the head of the other platform.
The rod that holds the propeller should now be perfectly horizontal.Mount the propeller and place the balancer it at the edge of the desk to do your tests.
Balancing propellers with 3 or more blades
Some of you may own propellers that have 3 or more blades. The basic principle behind balancing 3 or more blade propellers is the same as balancing the regular 2 blade propellers.
With 3 or more blades (Lets name the blades X, Y, Z), usually the weights of the blade tend be X > Y > Z (X being the heaviest blade) when they are unbalanced.
Following similar principles laid out in the steps above, all you have to do is match the weights of the lighter blades to the heaviest blade by adding tape to it.
Since there are three blades, you might also have to use the balancer at the edge of the desk like the larger blades
When balanced, the propeller will stop tilting and moving, just like before.
That’s all folks! I hope this helps with balancing propellers. Do let me know in the comments below if you have any further questions or if something is unclear. Happy flying!