Beginner need help with propeller / motor vibrations!

[raf]

Hi.
This is my first post so I would like to say hello to everybody.
As per title I'm having a trouble with my first multirotor (quadcopter) build. I can't get rid of vibrations on my propeller / motor?
Please have a look at the video below.
I have ordered all parts from HK due to price and availability.

Parts used:
- NTM 2830 800kv motors (inc. accessory pack for NTM 28 motors)
- 12x4.5 SF Carbon Fiber Propellers (I have also tried 10x5E Carbon Fiber Propellers - even worst vibrations)
- X580 quad frame
- Multiwii Pro (2.3 firmware)
- 30A Afro ESC (SimonK firmware)
- turnigy 5000mAh 4S Lipo
- turnigy 9x transmiter +receiver


I have used "HobbyKing Universal Magnetic Propeller Balancer, For T Style And Standard Hub Propellers" to balance propellers blades and hubs.


As you can see on the video even after balancing propellers I'm having extremely strong vibrations. I have no idea how to eliminate them... Any thoughts please help!


P.S. Sorry for my language but my native language is Polish

Ohh.. And one more question, when having let say over half a throttle for some time it seems like the motor slows down and as per video above when the motor got those serious vibrations it seems like it is shut down? The red light on ESC comes on and the motor stops.. Is it normal FC and ESC behaviour?

Regards,
Raf

 

[Motopreserve]

Welcome to the forum!

It looks like the whole arm/boom is moving. Have you checked to see that they are mounted securely at the center, and that the motor mounts are solid?

also, do the motor mounts have holes to mount the motors directly? Perhaps adding the aluminum mount adapter under the arm is not allowing the motor to be secured tightly?

 

[raf]

Thanks for quick reply.
Answering your questions:
- the vibrations are so strong that whole arm is vibrating
- arms are mounted securely and tight and you can lift whole quadcopter with battery by one arm only
- motor mounts are quite solid as well, all connections are tight, however: centre plates are carbon fibre, arms are aluminium, motor mounts are carbon fibre - therefore are very flexible (that's why those bottom X shape adapters got bent)
- motor mounts (those carbon fibre ones) have some kind of long holes so I can fit the motor with adapter only - please have a look at the pictures below.
- as above I can't mount the motors directly to mounting plates however when using those aluminium adapters motors are secured tightly

Any other ideas?


View attachment 19026View attachment 19025View attachment 19027View attachment 19028

 

[Motopreserve]

Just to be clear, it looks like those mounts are glass - not CF. May have some impact on rigidity, but shouldn't been the cause of your problems if that is the case.

Have you tried balancing the motors? There are a couple techniques using a laser or an iPhone vibration app.

Also, can you tell if it's happening with individual motors or all of them? If it's one motor, perhaps bad bearings? You could try narrowing it down by unplugging all the motors and testing one at a time.

 

[raf]

You are right.. It's glass fibre - my bad
I have tried balancing them with android vibrometer app or simillar but I couldn't get any better than it was without balancing. I have no laser to try that method.

Out of four motors two have very strong vibrations, one have slightly less vibrations and one seems to be quite allright.

I have ordered some plasfic SF 10" props to see if I can get any better. I'm also thinking about ordering some proper balancer - DU-Bro?

What do you think?

 

[Motopreserve]

I suppose it's possible that prop balancer didn't work correctly - but I would think even a bad balancer would get them close enough to eliminate horrible vibes like that. I have had great luck with the DuBro.

Your app should work well enough for balancing the motors. All you need to do is make some marks for 1/3 around and place a small amount of tape on each mark - watching for the least amount of vibrations. Make sure you only have 1 motor running at a time. If all of your motors were best without tape, I would find that strange - or the motors are not Hobby King

I'm not sure what SF props are??? I've had great luck with HQPROPS and APC. But I really don't think it should be that - since you said they held position with how you balanced them previously.

Did you do the ESC throttle calibration before you hooked up the motors?

 

[raf]

That's what I thought that even a bad balancer should balance props enough to eliminate strongest vibrations. But... after balancing prop I take it off the balancer shaft and then put it back on it, the prop is slightly off balance (not much).
From what I have been reading DU-Bro seems to be a good quality balancer, I just have to find a right place to buy it. It's strange that the same balancer cost $27 in US and £30+ in UK...
I'll try with balancing motors once again, and of course I do only one motor at a time.

SF (slow fly) props I meant just some cheap HK plastic green coloured props - from what I have found online they comes quite good balanced except hub. I just want to see if more flexible blade wouldn't help me?

Yeah I have had a read about APC props today so if the HK ones will turn out to be s**t I'll order some of them.

Yes I have calibrated ESC's one at a time connecting them to ch3 on my rx and with standard procedure for simonk firmware. Or should I calibrate them by Multiwii? I can see there is such a option in config.h file.

Thanks again for your reply

 

[Motopreserve]

If you've already calibrated the ESC I would leave it. The multiwii works well if you're all rigged up already - but you have to reload the sketch a couple times.

Sorry, thought the SF was some new brand

honestly, dont bother with the HK. ALMOST impossible to balance and they can break mid-air. Just get some of the cheaper, but decent props to save yourself the headache (or worse).

Id id have a go at the motor balancing - and if that doesn't help, maybe see if you can recognize any strange feeling caused by bad bearings?

thats all I can think of.

 

[raf]

Which ones you prefer then? APC or HQPROPS?
All of the motors seems to work the same... I'll try some more balancing tomorrow

 

[Motopreserve]

Which ones you prefer then? APC or HQPROPS?
All of the motors seems to work the same... I'll try some more balancing tomorrow

I personally like the HQPROPS best. But I have so e APC flying now - and they are fine. Just depends what's available in the hqprop when I'm ordering.

if your CF props are balanced - they should be great for stiffness (except when they're more expensive to replace!). I'm leaning away from the props - but it's always nice to be able to try different types to find what's best suited to your specific MR.

Good luck with the balancing - let us know how it goes.