On machine prop balancing

Wibble · Oct 1, 2015

Just as with cars and many machine the most accurate way to balance something is when it is actually attached.
Has anyone tried to balance their props actually attached to the phantom? Maybe with a strobe or something?
You would not only be balancing the prop but the whole rotating mass. The only drawback would be that the props would need to be fitted to the same motor each time.

bobmyers · Oct 1, 2015

Wibble said:
Just as with cars and many machine the most accurate way to balance something is when it is actually attached.
Has anyone tried to balance their props actually attached to the phantom? Maybe with a strobe or something?
You would not only be balancing the prop but the whole rotating mass. The only drawback would be that the props would need to be fitted to the same motor each time.

Interesting concept would like to see some constructive input-- motor hubs need balance and I believe that DJI goes thru that process. The is actually a Youtube video that shows balancing a motor hub off the mounting-- not DJI== but generic.

Wibble · Oct 2, 2015

I was thinking maybe doing one prop at a time spinning it up - mark on prop - then using a strobe. You can also see vibration in the airframe.

Chris P Duck · Oct 2, 2015

There's plenty of iPhone apps that measure vibration.
You'd need to be able to spin up one prop at a time and it takes some time as its a bit of trial and error but should work well.

Wibble · Oct 2, 2015

I thought of it because even after balancing the props I noticed the machine wobbling slightly on a hard surface with the rotors spinning. Can't be doing the frame much good. Like driving a car with the wheels out of balance!!!

bobmyers · Oct 2, 2015

Wibble said:
I thought of it because even after balancing the props I noticed the machine wobbling slightly on a hard surface with the rotors spinning. Can't be doing the frame much good. Like driving a car with the wheels out of balance!!!

Yes, that has to be a motor hub out of balance

ksphantom · Oct 2, 2015

One way to balance the props/hubs while on the machine (taken from a flight test video a while back).

Detach all but one prop.
put the machine on a sturdy table and place something heavy across the skids to prevent liftoff/tipover (a bag of rice or sand)
temporarily attach a small mirror to the outer tip of the arm with the prop to be balanced with servo tape or similar.
put a laser pointer on another sturdy surface, temporarily tape the power button on the laser on and put something on it to keep it from moving.
aim the laser at the mirror and find the place in the room where it is reflecting.
idle up the Phantom and watch the reflection of the laser beam.
Use trial and error (adding small bits of tape to the prop underside) to get the reflected point of light as steady as possible.
Rinse and repeat for the remaining 3 props
It might even work to temporarily attach the laser pointer to the arm itself but depending on how/where its attached it could dampen the vibration a bit, a reflection across the room from a tiny mirror is going to really show vibrations

bobmyers · Oct 2, 2015

ksphantom said:
One way to balance the props/hubs while on the machine (taken from a flight test video a while back).

Detach all but one prop.

put the machine on a sturdy table and place something heavy across the skids to prevent liftoff/tipover (a bag of rice or sand)

temporarily attach a small mirror to the outer tip of the arm with the prop to be balanced with servo tape or similar.

put a laser pointer on another sturdy surface, temporarily tape the power button on the laser on and put something on it to keep it from moving.

aim the laser at the mirror and find the place in the room where it is reflecting.

idle up the Phantom and watch the reflection of the laser beam.

Use trial and error (adding small bits of tape to the prop underside) to get the reflected point of light as steady as possible.

Rinse and repeat for the remaining 3 props

It might even work to temporarily attach the laser pointer to the arm itself but depending on how/where its attached it could dampen the vibration a bit, a reflection across the room from a tiny mirror is going to really show vibrations

Boy, I would like to see a video of that-- just to make sure I did it right.