G+_610GARAGE Posted July 8, 2015 Share Posted July 8, 2015 A little over a month ago, my props kept falling off in mid air. This happened with self tightening nuts. This boggled not only me but a couple members of the know how community. So I decided to figure out what was going on. My conclusion, bad propellers. I did some benchtop tests that showed massive deceleration to be a culprit which isn't a big surprise. But the major problem is that the keyed propellers were too tight. I bought some new ones to do field testing and found that they were all loose while the batch that I had originally were rather tight on the motor shank. I believe this to have left the propeller with no slack to tighten the prop nut. I emptied a battery with these new props and none of the prop nuts loosened. During my testing, however, I came up with a solution (before I realized that I got a bad batch of props). Using a rubber seal or washer between the prop and the prop nut. Bench Test proved promising, but the lack of defective props leaves me unable to test in the field. However, I believe that a rubber seal has a couple of benefits. One, it allows the nut to apply a more constant pressure on the prop if the prop is given the chance to wiggle up and down on the motor shank (if even possible). Two, it increase friction between the prop and the nut, increasing the self tighten effect. I have not tested this idea with non locking props yet, but it may be worth considering. Especially if you are getting a lot of prop slippage. P.S. Sorry for the length of my post. Link to comment Share on other sites More sharing options...
G+_Seth Leedy Posted July 8, 2015 Share Posted July 8, 2015 No need to apologize, this is not Twitter. Link to comment Share on other sites More sharing options...
G+_Jason Marsh Posted July 8, 2015 Share Posted July 8, 2015 Sounds like you have it licked, but I wonder why the motors and props aren't keyed. Considering the available torque, the fairly small interface area between the prop and shaft, and the likelihood of slip, I'd have thought it a no-brainer to have keyed/registered motor shafts and propellers. Sure, it would cost a tiny bit more in manufacturing to make it so, but that can't be the whole reason it isn't done. What am I missing? Link to comment Share on other sites More sharing options...
G+_Jerry Ham Posted July 8, 2015 Share Posted July 8, 2015 Jason Marsh I would guess that they want to encourage some slipping to reduce the chance of removing fingers? Link to comment Share on other sites More sharing options...
G+_610GARAGE Posted July 8, 2015 Author Share Posted July 8, 2015 Jason Marsh I think Jerry Ham is correct. I tried to find 9" props that are keyed, and I don't think they exist. At least not in carbonfiber. Link to comment Share on other sites More sharing options...
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