Getting rid of some vibes!

[Gregor77]

Here is a topic that I found very interesting.

As I started to get into bigger planes and wood planes, i noticed that some of my motors had a bad vibrations.  After lots of investigating and playing.  I discovered a few reasons.   And not pointing figures at our Cheap sources of motors in the past year or two.  But I see people complaining about motors not being balanced.

Reasons for vibrations:

1) Motor not balanced, 9 times out of 10, if you remove the HK label, 90% of the vibration is gone.  I also went to the extreme to add tape to one side and it removes the vibration.  But this is time consuming.  The easy match series from the King is bad for this.. but the motors are great!.

2) Props not balanced.  This is a bit of an art, but a nice smooth pen or screw driver, insert in the hole of the prop and see what side drops.  Sand the furthest point of the prop and keep checking.  Once the prop doesn't drop.. you are balanced.  Love it!  But make sure the prop looks normal and don't over sand.

3) Ok I tried everything and there is a still a vibration in the airframe at 50% throttle.  This is where the big 1/4 scale was effected the most.  I did two things.. filled the firewall with foam.  Reduced the sound vibration.  The next was to add rubber gromets to the motor mount,  Where it attaches to the firewall and to the motor mount to motor.  This helped alot!  This reduced all the vibration that the prop and motor generated.

The reason that I brought this up, I did three planes this week and they all suffered from vibrations.  They are about 99% solved now and are very smooth.

Happy building.

[Papa]

Once the prop doesn't drop.. you are balanced.

Not quite. If the prop returns to the same point then it is still not balanced but the boss is probably out of true. A properly balanced prop should stop in different parts of the circle each time it is spun.

Jack.

[Gregor77]

Good pointer!   I will check this... Most have been OK after the fact it doesn't move. Mind you I am not paying for a prop balancer.. lol!