Prop balancing.

I noticed today that the black/gray dots wobble when the blades are spinning. Now I am just learning to fly so I have crashed several times. So how sturdy are the motor shots themselves? And how do you “true up” an unbalanced propeller?
 
The only reason the central 'dots' would 'wobble' could be because shafts are bent or the props hub dots are poorly centred.
I would also question if any damage after 'crashed several times' .....

Next time I power up my P3P ... I will have a look to see my 'dots' ....

Edit : I just powered up and I have no 'wobble' ... if first looking - the 'dots' initially appear blurred - but careful viewing shows that is just the 'dots' spinning and the eye catching any slight mark / cosmetics of the 'dots'.

If anyone actually has 'dots' wobbling - then a serious look at props and shafts is called.

A simple test is to mount a pointer hanging down fixed above the shaft or 'dot' centre. Power up and see any variation of reference pointer to centres. Do this with and without props to find out if its shafts or prop hubs.
 
No, there should be no "wobble" of the dots on the prop hubs. I would suggest you've bent the motor shafts!

You don't stay which drone you're flying or where you're flying that you keep crashing? The P3's are the easiest drone I've ever flown, very stable.
 
Well that isn’t very encouraging. It ha a P2. A soccer field with some trees around it. I have hit a few trees, tipped over on the ground.
 
Have a look at the edges of the prop when spinning. If you see two of each of the edges, the shaft is bent, the prop is not sitting true.
IMG_5668.jpg
 
This reminds me of all the time spent on knees watching heli rotors !!
 
Ah yes, nearly lost my thumb to a hell! Took off from an oil drum into the breeze when a gust hit it just as it lifted off and it came back at me. Put my hands up to protect myself and the blades took my high thumb off, just hanging by a bit of skin! Brilliant surgeon and it's fully functional again :D
 
Yep ... we all have our moments.

I was having no end of trouble with one of my 450's one day. For some reason the IDLE UP switch wasn't working properly ... so without thinking I placed on the floor in the large 'party room' we have in the house ... flicked switch ... nothing happened ...
My Radio was a non model match jobbie - so any RX bound to that radio would work whatever model was selected ... I think you know whats coming ...

In a fit of brain fade ... I switched model memory and the 450 took off ... crossed the room - hit the TV ... bounced of and hurtled past my left ear straight into the Xmas tree my 'dearest' had just finished decorating. Where it proceeded to tangle itself up in the lights and baubles !
Then I noticed the dogs noses just peeking round the door wondering what all the fuss was !!

Needless to say - you only forget to remove rotor blades ONCE !!
 
Thanks for the laugh!! :p

Talk about 'brown trouser' moment !! I sat there after asking myself how could I be so stupid !

Believe me - when it went past my left ear - it was so close I could 'feel' it !!
 
So I just bought a brand new set of OEM props for my P3P. Did the quick screwdriver tip balance check and they all seemed fairly well balanced however after installing them and doin a motor start 3 of them looked awfully unbalanced. Particularly the front arm ones. The left rear arm was perfect. I also noticed the silver and black "caps" seemed to also be wobbling abit on the noted props. Wondering if i had motor shaft issues i swapped the left rear and front right props and oddly they both settled right down to a nice smooth balance. Did the same with the "black" props and that also fixed it. Is it possible that it was just the brand new threads in the props that weren't quite seating properly? After loosening them and firmly tightening them onto the shafts again all imbalance disappeared. Makes me wonder how many times my props weren't tightened snugly enough to properly seat balanced. I try not to overtighten them but maybe I've been too cautious??? Opinions?
 
Not sure what you mean by "they looked awfully out of balance". You cannot see out of balance but you could see if the props were not seated properly, they would appear to wobble as they rotated. You do need to snug them up on the motor shafts however they will self tighten as you increase the load on them.
 
Not sure what you mean by "they looked awfully out of balance". You cannot see out of balance but you could see if the props were not seated properly, they would appear to wobble as they rotated. You do need to snug them up on the motor shafts however they will self tighten as you increase the load on them.
3 of them looked awful, like a ceiling fan thats way out of balance, they were clearly wobbling. But like i said, after i swapped each set with it's mate (maybe loosening up the new threads?) And retightening them they seated nicely and looked clear and level, nice balance.
 
Straight, seating properly, not bent, yes, but not "nice balance" 3rdof5. It's just a case of terminology! Balance is the even distribution of weight, which you cannot see, around the central axis and in the case of our single plane propellers we only need use static balancing.

From the manual:
"Ensure propellers are attached to its corresponding motors, otherwise the aircraft cannot take off.
Wear gloves when handling propellers.
Hand tighten each of the propellers on the corresponding motors to ensure it is attached firmly"
 
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In addition to unbalance, there is an even more serious condition that could lead to large vibration. The up-down (flapping) motion of a propeller blade has a resonance exactly at the rpm of the blade. That is why helicopters blades always operate near resonance, and the designs are tuned to minimize such vibration as much as possible.
 
"The up-down (flapping) motion of a propeller blade has a resonance exactly at the rpm of the blade." so has static imbalance.
They certainly do not operate helicopter rotors, or any other rotating mass for that matter, anywhere near its resonant (critical) frequency (speed), it would shake itself to pieces! Rotors operate either well below their critical speed, a rigid rotor, or above their first critical speed, flexible rotor. If the rotor is flexible, as was the case of a large steam turbine I used to operate, one has to accelerate it rapidly through its first critical or it would jump off its mountings!
 
I did not imply they operate helicopters at resonance. Yes, I agree about not operating near a critical speed. My point is that, the physics of the problem make it such that the resonance frequency of the blade up-down depends on the RPM i.e., the resonance is NOT fixed. For typical turbine rotors and the like, the critical frequencies are FIXED, as they correspond typically to bending/torsional natural frequencies where the rotor has 'zero' dynamic-stiffness. For a propeller blade, the faster you spin the blade the stiffer the blade gets (owing to centrifugal stiffening). It's as if the resonance (or critical speed) is increasing proportionally with the RPM. As such, you can't go through a critical speed that quickly, because it's there tail-gating you all the time.
 

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