To anyone flying Hobbywing X8 combo please GROUND your ship and take a close look at the screws that keep the blades attached to the hub. We had a catastrophic shear of that screw today.
Blade didn’t have any previous crash and had around 50 hours fly time.
Ouch. Chinesium screw?
Original screw in the hobbywing x8 system.
We think it is a fatigue shear due to the fact that the screw thread is not rolled and is exposed in the part where the blade pulls. It broke exactly along the first exposed thread.
They should pull it from market and fix the problem. This kind of propulsion system are meant for big copter and can cause very high damage.
Quad or Hexa?
Many companies think short on the folding propeller hub design. Including big names.
Quad.
Yes, hub design is poor.
I am sorry for your accident. We have 33 hexa drones using the X8 motor for the past year and a half and have not seen this. Maybe the screws were overtightened?
Is there a torque spec? That’s what they call the X9 Series?
Not overtightened, we check them before every day of flight, just tight enough to have the blades move freely but not fall on their weight.
There is no torque spec specified anywhere in the manual. Combo is X8.
OK, was just looking at the website, hub adapter looks different than your photos. Design Rev I suppose.
Interesting to me as I did quite a bit of FEA work on an aircraft application on a failed fastener.
I see on the torque spec. It’s essentially a bearing pre-load torque, the bearing being the washers.
Just saw the new hubs, it doesn’t look like they solve the prob, will take a look at the new ones once new blades arrive.
I agree with your assessment. The bolt shank should be at the shear plane(s) not the threaded section. Significant difference between the stressed area of the threaded section compared to the area of the shank.
Out of curiosity what’s the blade mass, fastener size and material (Aluminum, steel) , max RPM and radius of the bolt CL from the motor shaft?
I wrote, ground your ship and take a look at the screws. If you don’t want to do it, no problem, maybe others do. Remember that these are heavy machines potentially they can kill a person if something goes wrong.
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I’m glad to see someone take this seriously.