From: muratlanne@gmail.com   
      
   "Richard Smith"  wrote in message news:m1wmbd29er.fsf@void.com...   
      
   Hi everyone   
   I have been shown how to do this with power-electronics and   
   "off-the-shelf" gearbox, etc.  With all speed-control needed.   
   A friend had made a small welding positioner.  Hence adapted it:   
   * VFD - 1ph-to-3ph   
      v   
   * 3ph induction motor   
      v   
   * worm-drive gearbox   
   You turn a knob setting the output Hz.  Adequate speed range.   
      
   Having seen this - that it works and does everything wanted - will   
   simply do it this way.   
   Have friend's equipment on "unspecified loan' in my car to take home and   
   play with more.   
      
   -----------------------------------------   
      
   That is an excellent way to learn what works. The potential problems are   
   cost and custom machining. In that instance I'd look up and save the   
   components' data sheets and see how their max power ratings compare to what   
   was needed and what you intend to do. I've been burned by guessing that   
   something was good enough, my sawmill left a trail of broken ball bearing   
   innards until I switched to a more reputable and expensive brand for the   
   blade guides.   
      
   I hardly ever find the same device twice as second hand and must decide on   
   the spot if what I found is suitable, which may depend on its power rating.   
   People dispose of what they can't use, typically because they are either   
   inadequate or broken.   
   I tested that contactor for pull-in voltage and contact resistance.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)