Nylon Props Snapped

[NorcoT]

Hello all, I've been having some bad experiences with nylon props recently. In the past two months I've had two props snap mid flight. Both times the props have been relatively new and had no crashes before hand with them, they were both balanced.

My set up was a quad 1.6kg in weight running 10x4.5 props from hobbyking. On both occasions it was windy so I'm starting to think it was overloading the props when the gusts were hitting the quad.

Looking at the snapped props it looks like a fatigue fracture followed by failure due to critical crack length or sudden high loading. The crack surface is clean break from the trailing edge and transitions into a rough surface which shows signs of plastic deformation at the leading edge.

Anyhow I was wondering what experiences other people out there have had with cheap plastic props? I have since ordered some carbon props so hopefully I won't encounter this again!

[waltr]

I have read that this is not un-common with many of the cheap plastic props. This comes up from time to time on the RCgroups multi-rotor forum.
http://www.rcgroups.com/aircraft-electr ... otors-790/
Trya search of that forum for more discussion on this issue.

How tight are tighten the prop nut?
One theory is that over tighten the nut is deforming the hub of the prop causing cracking.

There seem to be higher quality plastic props available that do not have this issue.
Also, there is maximum RPM that a prop can withstand without throwing a blade. APC is the only company I know of that publishes this spec.
http://www.apcprop.com/v/html/rpm_limits.html
However, this is only valid for their props.

[NorcoT]

Thanks waltr, will have a read on rcgroups. I just received my shiny carbon props today so hopefully no more prop releases! Perhaps I have been over tightening my props though.. I do nip them up but not extremely tight. How tight should the be? No instructions with my ntm hobbyking motors..

[waltr]

Tight enough so that the nut doesn't loosen when the motor changes speed.

I'm currently reading through thread in rcgroups and came across some prop that broke in flight. Here are links to these htreads:
http://www.rcgroups.com/forums/showthread.php?t=2127263
http://www.rcgroups.com/forums/showthread.php?t=1835070

Just put "quad props breaking in flight" in google and there are many cases of this happening.

[sismeiro]

Just put "quad props breaking in flight" in google and there are many cases of this happening.

The same thing happened to me at least three times with cheap propellers. One of the times the flying debris was recorded on my 808 camera:



Since I change to carbon fiber propellers I never had another one broken while flying, only while crashing into trees and the ground.

[waltr]

Wow, and the quad was basically just hovering when the prop blew.

[sismeiro]

Wow, and the quad was basically just hovering when the prop blew.

At that time I was hovering but the propellers had some hours flying with some aggressive moves and in the wind. Forces from different angles stress the blades where they connect to the central hub.

[regzgz]

Getting chills down my spine, I have a set of props that I have crash, hit and abused beyond the capabilities of the props, and they are cheap plastic!
I'm getting a new set, the picture on my mind of my Quad coming down from 500 ft at high speed into the ground is not a pretty one...

[scrat]

Buy carbon props for your 1.6kg quad. Plastic are not good.