You’ve got your sights set on a spectacular setting for your upcoming session. But when you finally pull your drone out of its case and power it up, your excitement immediately dies down.
One or more of your drone’s propellers just won’t spin. It’s needless to say that you’ll have to put your plans on hold.
But don’t worry, I’ve been there too. It most definitely doesn’t mark the end of your drone’s lifespan.
Here’s the thing: these issues are bound to pop up on your drone flying journey, especially if you dilly-dally on the maintenance side of things.
The good news is that all your propeller problems have answers.
In this post, we’ll be pinning down exactly what the fix may be for you. Most of the adjustments I mention will also apply to propellers that spin improperly or have an anomalous speed.
Before we dive in deep, it’s important to touch on a bit of context. There are a couple of things that can possibly be at play for our issue. Take a look.
Your drone propeller is most likely not spinning due to its corresponding motor having issues or an electronic speed controller (ESC) problem. Other common causes include obstructions, improper calibration, damaged wires, weak (or lack of) connectivity, and a bad battery.
If you’ve built a quadcopter yourself, you may have screwed a component on too tight or left a mount too loose. These little things definitely have an effect on the smooth turning of propellers.
Now, it may sound like this wide range of causes takes forever to eliminate. However, most of them only require a visual inspection.
The real question — in the case of novice pilots — is how to differentiate between a motor problem and an ESC problem.
They’re very closely linked. At the same time, those are also the two areas where the blame typically lies.
The test, though, is pretty simple.
Once you know the issue isn’t plainly obvious, start off by noting which propeller isn’t spinning. Then, switch its motor with one that is spinning.
If the motor that wasn’t initially spinning still isn’t, it’s safe to assume you have a bad motor. But if it does start spinning after the switch, you have a bad ESC and may have to replace the whole board.
We go deeper on exactly how to tackle each of the causes I mentioned in the following sections.
So, you now know about the usual culprits. Here’s how you can start narrowing your list of causes step by step and eventually fix your propeller.
You can fix a propeller that won’t spin by making sure it’s charged, clearing up obstructions, reconnecting the drone controller, reinitializing calibration, reinstalling the propeller, replacing damaged wires, and inspecting the motor. However, sometimes the issue may require expert evaluation.
Let’s take a look at these fixes in a bit more detail.
This one’s a safety measure but still a super important step.
There’s nothing more frustrating than delving into the technical fixes only to later realize the drone wasn’t charged. This is why I suggest checking the battery as the very first thing.
Make sure you charge the drone’s battery to its full capacity before your session. And when you’re finally ready to fly, remember to do the final check.
Drone batteries can be plugged in for hours but that doesn’t always result in a full charge. Similarly, they may drain far too quickly. If your drone is always indicating a low battery level, you may have to look into fixing the drone battery.
This would ultimately supply the propellers with enough power to start spinning — assuming the battery was the only issue.
This step applies to you if none of your drone propellers are spinning.
To tick this one off, there are two things you need to take into account:
The process of establishing the connection may vary from model to model, but it’s generally meant to be super quick and seamless. I recommend checking out the instruction manual to avoid missing any steps.
In some cases, there may not be a response from either side. This would mean there’s an error stopping the two devices from syncing.
A drone not connecting to its controller can be software-related. Or maybe you just have to switch out the controller’s batteries. It’s something you’ll have to separately troubleshoot.
Once the devices successfully sync and the signal doesn’t drop, you can move on.
One of your drone propellers may not be functioning properly because the gyroscopes haven’t been properly calibrated.
Why is this the case?
Well, the gyroscopes are used to make measurements to keep drones stable. The measured data is used to vary propeller speeds.
You can probably see where I’m going with this. If you haven’t followed the right calibration process, the gyros may not be working as they’re programmed to.
Make sure you reinitialize them before drone flight by following instructions exclusive to your model. As a general rule, the process is started from the drone’s app and a flat surface is meant to be used.
If you’ve gotten to this step with the main issue persisting, it’s pretty likely the issue is internal. You’ll have to pop the hood and get a bit more technical with your troubleshooting.
This step in particular, however, is pretty straightforward.
Check for any small obstacles that may be blocking the propeller shafts and brush off the dust caught inside your drone.
If you use paper towels and alcohol to perform a thorough clean, make sure you leave the propellers absolutely dry.
This one’s a common cause for pilots who’re yet to gain a lot of experience in building drones. In other cases, it may just be a silly, overlooked mistake.
Your drone propellers need to be installed in a balanced way.
People often fit their propellers as tightly as possible. While it’s important to secure them, overdoing it only causes damage.
I recommend loosening the screws of the propeller that won’t spin. This will allow its corresponding motor to spin freely.
The goal is to have them just tight enough to ensure the propellers don’t come flying off.
The internal wiring is pretty fragile, but the drone frame acts as a guard against light damage. So, the wires typically aren’t an issue unless the drone is put through a hard landing or collision.
If you do come across severed wires, the fix would be pretty complex. You’ll have to replace the damaged wires while making sure you route the cables correctly. They’ll then have to be tied securely.
I strongly recommend getting this done by an expert whether or not your drone is under warranty. Playing around with the internal wiring can open up a plethora of issues that weren’t there before.
Finally, you may have to point the finger at the component that directly turns the propeller. There are a few ways you can identify a bad motor.
Start off by turning the motor yourself to see if it spins smoothly. If it jams midway, try using a separate motor for the same propeller.
Another thing you can do is look for damaged parts by taking apart the motor in question. A bad motor could possibly have a bent shaft, broken bearings, burnt windings, or loose magnet chips.
Similarly, damaged motors are very likely to cause excessive vibration. This, in turn, heavily slows down the speed of propellers to the point where the system’s balance is disrupted.
The easy fix to a bad motor is replacing it entirely. However, you may try adjusting it yourself if it’s not too damaged.
So, you’ve decided to take on the repair project yourself. How can you go about it? Here’s the answer.
You can fix a drone rotor by removing accumulated debris, tightening the screws to get rid of unnecessary vibration, straightening the motor shaft, and replacing damaged motor components. Sometimes, however, a full replacement is required as not all rotors can be fixed.
You probably don't have spare motor components available if you don’t regularly work with drones.
In that case, there’s no point looking for specific parts when you can simply replace the whole thing. Most small components can be hard to find and drone motors, in general, are fairly cheap.
Motor shafts, on the other hand, are typically available in relevant stores. So, if you have a bent motor shaft and can’t straighten it yourself, consider buying a new one.
The other important thing I’d like to emphasize (again) is the importance of minimizing vibration. By tightening the screws that hold the motor to the frame, the propeller is more likely to have a standard rotation rate.
These screws, of course, aren’t related to the propeller screws. The mounts need to allow the motor to work without jamming. You can always try lubricating the motor so it spins more freely.
The YouTube video below is a detailed tutorial on replacing a motor. It may also help you reinstall your motor once it’s fixed.
In the previous section, I mentioned getting rid of excess debris in the drone motor. Here’s the proper way of doing that.
A drone motor can be easily cleaned without disassembling it by washing it with water. It can be dried by controlling the motor to spin it momentarily and then letting it sit. On the other hand, you may take the motor apart and use compressed air, isopropyl alcohol, and a brush to clean it.
In reality, there are several methods you can use to get the job done. It ultimately depends on how dirty the motor is and the cleaning equipment you have.
Disassembling the motor is more time-consuming but allows for a complete clean. Compressed air is ideal for getting rid of dirt deposits and isopropyl alcohol is used as a cleaning agent.
You may use oil as a lubricant before gently reassembling it.
If you decide to use water, make sure to keep the electronic parts away from stray drops. And once you’re done, dry the motor (especially the bearings) using a cloth before reattaching the propeller.
One thing to note is that you don’t have to do this on a regular basis. It’s perfectly fine to just dust off the motors unless there’s clearly a problem.
If you aren’t sure whether a propeller is spinning slower than others, you can test them one by one. Here’s how.
You can test a drone propeller by using an electronic scale, frame arms, a motor, an ESC, and a PDB, amongst other small tools and equipment. The motor is installed onto the frame arms which are fixed onto the scale. The propeller is then mounted and the devices are wired together to get a reading.
You’ll be using a radio transmitter to make the propeller turn.
Once you have a value, note it down before switching the propeller (or the motor) out for a different one.
The same test is also used for optimizing areas of flight performance, like flight times, range, and payload capacity.
Connecting the wires of the ESC (electronic speed controller) and the PDB (power distribution board) to the motor can get a little confusing.
The YouTube tutorial below shows exactly where the wires go and the little accessories you’ll need to secure things together.
To bring things to a close, the drone motor is a vital component responsible for the working of propellers. The motors have small parts of their own that can prevent them from spinning.
Your drone motor may not be spinning due to visible obstructions, a bent motor shaft, worn out mounts, or other broken components inside the motor housing. Similarly, the bearings may have been affected by erosion from water damage. These causes refer to potential problems with the motor itself.
The truth is that drone motors rarely get damaged to the point where they don’t spin at all. So, make sure the motor in question is being supplied with enough voltage in the first place.
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