Really bad vibrations after balancing?

[Longbaorder23]

Hey all,
Maiden flight of my skywalker 1900 today, and the flight was great. Landed after a few minutes to check for heat or parts coming loose, and my motor was really hot and had come very loose because of really bad vibrations. I've spun the motor up by itself, zero vibrations. The prop is very balanced, more so than I usually would. I used a balancer. 1400 prop drive motor with a 9x6 g/f master airscrew. Spun at low rpms, there is little to no vibrations at all when I touch the plane. Spin it up to even half throttle (on 4s) it starts vibrating and making an awful noise, and I can even see the hub shaking. How do I fix this? Ideas? Never seen this before... Thank you!

 

[CrashRecovery]

Take the prop off and see if it's still wonky on you. If so you will need to balance the motor. Other wise your prop is still out of balance

 

[Longbaorder23]

Tested motor, no vibrations still. Could the fact that my prop is rather heavy be an issue? Thanks!

 

[Snarls]

Is your prop mounted completely centered on the shaft? Also, are the blades completely perpendicular to the shaft? Like if you spin the prop mounted on the motor is each blade slicing through the exact same air as the other?

 

[Longbaorder23]

yes and yes, the prop fits snugly on the adapter as well. im betting the adapter is the thing at fault here, because master airscrew propellers have never caused me any trouble before, and ive had plenty of problems with bad adapters before... whats a good adapter to use? ive tried 2 random ones i have at home from HK, both came with 35mm motors. i am using the prop drive motor that works with this special adapter:
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=24241

not sure if that would be better or not, comments welcome. but im currently using a shaft-gripping style prop adapter on a 4mm shaft. why is this happening? Thank you!

EDIT: so uhh, i went to master airscrew's website, and on there they have a doc describing the ideal conditions in which a prop should be working at, and in there they describe a tip speed thats ideal of about 600 feet per second. i got to thinking, and i calculated mine out, and in THEORY, my prop is spinning just shy of 900 feet per second on the tip at full throttle...? thats almost the speed of sound, dang! no wonder it freaks out... again, theres no vibration when spun at anything really less than half throttle, but half throttle is a LOT. 1400kv, 9x6, 4s lipo... ridiculous? for a skywalker 1900? Thanks!

 

[jhitesma]

9x6 on a 1400kv at 4s sounds like it's way over propped to me.

Which motor exactly are you using?

 

[makattack]

I concur with jhitesma. I run a 9x4 on a 1100kv 55g motor (emax 2210/11) on 3S and that's pushing it. At max/peak I get right up to the 17A max limit, but when I fly outside, it just gets warm. If I do a static run indoors with the prop on, it gets hot.

 

[Longbaorder23]

I see my error in choosing a motor for this application. The prop drive 35mm motor is the one I bought. I'm thinking in gonna keep this 9x6, and drop to a 900kv motor of the same diameter. Another question, what specs do you look for to find an efficient motor? I've heard large props with low kv is general more efficient, so would dropping 1400 to 900 aid in this? (aside from motor differences and actual efficiency ratings) also, does a power rating contribute to deficiency? My friend said an 800W motor of the same kv as a 500W motor would be the same amount efficient, more or less. Though, the 800W would weigh more... Is that the only trade off? I want max efficiency with my 9x6. 60A esc, a bit overkill, but wouldn't hurt. Motor options? Thanks!