Motor Vibration Problems!!

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pranav_rane

Member
Hello. I am trying to get my copter flying but I am running into issues with my motors. Every time I push the throttle to 50-60% the motor starts to shake violently. I have tested the motors without props on without any vibrations. As soon as I put a prop on the motor starts to shake as shown in the video below. This is my first build and I have not been able to get it up in the air for over six months now. The props have not been balanced but I do not think it should create such a problem. Please look at the video below and help me out. Thanks!!
Specs:
-hexTronik DT750 motors
-20A Hobbyking ESC's
-KK2.1.5 Flight Controller
-11x4.7 propellers
 
Props out of balance and spinning at a few thousand RPM are a BIG problem. Balance your props and you should be fine. Some of the cheaper props won't balance because they are drilled off center. If you find you can't balance yours then buy a grade or two up set of props.
Also, it looks like your motor mount is a bit loose as well. It would be wise to go over everything and tighten it back down. All that vibration likely loosened a few fasteners. Vibration control is important on any copter but is even more important on those with aluminum arms. Aluminum has a tendency to develop sympathetic vibrations from the motor/prop and transfer them unchanged to the chassis. If they are severe enough they may cause trouble with your FCB and the electronics.
Welcome to the forum, by the way. Next time please don't wait 6 months before seeking help. There is a great group of people here who will be more than happy to help! :)
 
pranav_rane said:
Hello. I am trying to get my copter flying but I am running into issues with my motors. Every time I push the throttle to 50-60% the motor starts to shake violently. I have tested the motors without props on without any vibrations. As soon as I put a prop on the motor starts to shake as shown in the video below. This is my first build and I have not been able to get it up in the air for over six months now. The props have not been balanced but I do not think it should create such a problem. Please look at the video below and help me out. Thanks!!
Specs:
-hexTronik DT750 motors
-20A Hobbyking ESC's
-KK2.1.5 Flight Controller
-11x4.7 propellers
Click to expand...
I don't believe that I have ever seen a prop that bad out of balance. Is the prop upside down? I put a plastic prop on upside down and it did this also sounded REALLY loud.
 
First of all thank you for your quick reply and welcome to the forums. I am currently shopping for a prop balancer on amazon. I have heard good things about the Du-Bro prop balancer. Hopefully this will fix the problem. I will also loctite the motor from twisting. The prop also is not upside down.
 
I really like my Du-Bro. Especially for larger props. I have a magnetic one for small props. Be sure not to breathe on the prop while balancing or you'll be right back where you started! Haha! I did exactly that when I first started and blamed the supplier for sending me a whole batch of bad props!
 
Ok I will definitely buy the Du-Bro balancer off amazon. Around $22 is a pretty good deal. Hopefully this will solve the problem, but if anyone else has encountered this problem and has found a solution please notify me. Thanks!!
 
pranav_rane said:
Ok I will definitely buy the Du-Bro balancer off amazon. Around $22 is a pretty good deal. Hopefully this will solve the problem, but if anyone else has encountered this problem and has found a solution please notify me. Thanks!!
Click to expand...
If you are out of balance enough that your mount screws loosen then that is likely to be your problem. I had my quad up around 400 feet, and I was decending. I brought it to a hover at about 10 feet off the ground and the motor mount had vibraded enough that two of the screws came out completely and the others were pretty loose, after it started vibrating the aluminium motor mont actually twisted and sheared a screw and broke the mount's ear on one side. I was lucky it got that close to the ground before it happened hahaha. If vibrated exactly like that before breaking.
 
Wow, 400 feet that's impressive! Hopefully the prop balancer will come within a week or so. I will update you on how it goes and hopefully I can get it to fly. Thanks!
 
pranav_rane said:
Hopefully the prop balancer will come within a week or so
Click to expand...

You can start now.

IMG_7166.JPG
 
Hi thank you for your response. Will anything that fits through the hole in the propeller work or do I need something that fits exactly through the hole?
 
pranav_rane said:
Hi thank you for your response. Will anything that fits through the hole in the propeller work or do I need something that fits exactly through the hole?
Click to expand...
exactly is preferred, but with a prop adapter to make the two steps of the hole the same diameter you could use something smaller just to get a rough idea how out of balance you are. There is a a pretty good method which involves a rod and a couple cups. You set the rod across the two cup to keep one side from getting higher than the other so you don't create extra friction.

These methods won't do as good as the actual balancer, but if imbalance is causing your problem, then it is more than a little off hahaha.
 
pranav_rane said:
Hi thank you for your response. Will anything that fits through the hole in the propeller work or do I need something that fits exactly through the hole?
Click to expand...
Anything will work. I have a long, thin finishing nail (leveled) pounded into the side of my desk. Perfect? Not exactly. Good enough? Sure is. I've also used it to balance my power lawn mower blade after sharpening. :)
 
My prop balancer came yesterday and after balancing the props the vibration was slightly reduced but still happens. Not sure what to do next :(
 
Thanks for your replies but I have seemed to fix the problem and I got the tricopter flying. The problem ended up being the glass fibre motor mounts that came with the tricopter. I cut out some new ones from a piece of wood and attached the motor from there. This fixed the problems and I got it out flying. There was a little oscillation but I should be able to fix that.
 
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