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Bearingless Rotor for Variable Pitch Quadrotor

Posted by Randy Sonnicksen on March 28, 2017 at 8:12am

3689713369?profile=originalThis video shows the fabrication of a prototype bearingless rotor hub/blade design.

The rotor diameter is 93 cm (36.6 in) and will operate at 1,410 rpm generating 2,000 g's of acceleration at the rotor tip, and developing 1,600 Lbs of tension in the flexelem rod due to centrifugal force.  The blade (pair) is designed to generate 104 Lbs of lift with a power consumption of approx 6.5 HP.

This is part of an "ultralight" quad-rotor design that I've been tinkering with over the past 18 months.  After running this rotor through some basic structural tests (40% overspeed) the true testing of pitch angle stability, pitch control forces, and flapping stability in forward flight will be tested on a test stand

Bearingless Rotor Assembly

Tags: bearingless, fiberglass, pitch, quadrotor, rotor, ultralight, variable
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Comments

  • Gary McCray March 31, 2017 at 10:42am

    Hi Randy,

    I couldn't find Brad's page searching in DIY drones, but here it is from an external Google search.

    http://diydrones.com/profile/BradHughey345

    I don't think the DIYdrones search is working very well any more.

    Definitely looking forward to seeing how your rotor works out.

    Best Regards,

    Gary

  • Randy Sonnicksen March 29, 2017 at 4:23am

    Gary, Thanks for commenting.  I did not find the Brad Hughey you referred to.  Do you have a link to his page?

    Don't know if you saw my other posts about how rotor diam. affects response time, but it's pretty dramatic.The approach with large electrics is to use lots of small rotors.  This approach has the added benefit of built-in redundancy.  Hopefully I'll have some meaningful rotor data within a few weeks.  I'm on a push to get these blades built and spinning.  With all the effort I've put into developing this rotor design, I sometimes wonder if it wouldn't have been simpler to just use a fully articulated rotor hub with pitch, flapping and lead-lag hinges, but alas, here I am.  Now that I have the rotor molds, it should be a fairly straightforward process to build the 8 blades I need for the vehicle.  And I keep learning tricks to speed up, and clean up the process.Composite fabrication is messy, and time consuming.  Any efficiency is welcome.

  • Gary McCray March 28, 2017 at 2:06pm

    Very interesting design Randy.

    Most people don't know how unmanageable fixed pitch multirotor propellors become as the diameter increases.

    Your self compensating variable pitch system is an interesting approach to overcoming this problem.

    I think Brad Hughey (a frequent contributor on DIYD) may have come up with a similar solution but I haven't heard from him for a while.

    I will be very interested to see how this works and specifically if it can solve the response time problems associated with large diameter fixed pitch multicopters.

    Best Regards,

    Gary

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