From: pcdhSpamMeSenseless@electrooptical.net   
      
   On 05/06/18 20:36, etpm@whidbey.com wrote:   
   >     I want to use a hobby BLDC motor to power a compact high speed   
   > spindle to be used for engraving and the like. Mainly because they are   
   > so compact for the power and speed. I cannot find, for a price I can   
   > justify, a 24,000 to 40,000 RPM spindle that will fit in the space I   
   > want to put it.   
   >     Looking at some hobby BLDC motors and then buying some to   
   > experiment with leads me to think that one of these motors may work.   
   >     I have looked online for answers about these motors and maybe I'm   
   > just dense (good possibility) but I haven't been able to find exact   
   > answers. Maybe someone here can help.   
   >     Motors are rated RPM/volt. This means maximum RPM per volt of   
   > course. If the motor is supplied with a higher voltage from a supply   
   > that limits the current to stay below the specs of the motor will   
   > higher RPM be possible?   
   >     The ESCs (Electronic Speed Controller) are voltage and current   
   > rated. Could the output an ESC rated for a lower voltage and current   
   > be used to drive control power transistors in order to get around the   
   > lower voltage and/or current rating if a sensored motor is being used?   
   >     I don't need to use a hobby ESC but they are plentiful and cheap.   
   > And all assembled. Which is most important.  But I would be fine using   
   > some other BLDC motor driver in order to get the desired RPM that I   
   > want.   
   >     I can do all the precision machining necessary to make the spindle   
   > that will hold the carbide cutting tools and to interface the motor   
   > with the spindle. I do not yet know enough about balancing in order to   
   > dynamically balance a motor which causes too much vibration from an   
   > out of balance condition but I think I can learn enough to do it. I am   
   > good with mechanical systems and have a pretty good intuitive feel for   
   > them. It's the electronics I'm no so good at.   
   > Thanks,   
   > Eric   
   >   
      
   You have to watch out for shaft whirl, which happens when the rotation   
   rate is close to the first bending resonance of the armature.  It'll   
   destroy itself if run near that speed for anything but the briefest of   
   moments.   
      
   Cheers   
      
   Phil Hobbs   
      
      
      
   --   
   Dr Philip C D Hobbs   
   Principal Consultant   
   ElectroOptical Innovations LLC / Hobbs ElectroOptics   
   Optics, Electro-optics, Photonics, Analog Electronics   
   Briarcliff Manor NY 10510   
      
   http://electrooptical.net   
   http://hobbs-eo.com   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)