[NSRCA-discussion] Electric vs. Glow

[Bob Richards]

Ed,
   
  Ok, I'll buy that. Taken to the extreme, a non-spinning prop will have less drag than one that is windmilling.  I would think that there is a point where the braking is at a maximum (rpm/mph) and perhaps this would be free spinning, but my gut tells me there is some amount of resistance that could be added to the prop before this maximum is reached.  And this point would be different depending on the prop used. This reminds me of the old 4C vs 2C engines, the 4C is supposed to (does?) have more "braking" in down lines.
   
  Also, the props we use are not designed for reverse lift -- like a flat bottom airfoil flying upside down. They may be -- and probably are -- stalled when trying to add resistance over freewheeling.
   
  Bob R.
  

Ed Alt <ed_alt at hotmail.com> wrote:
          Bob:
  The faster the prop turns in a freewheeling mode, the more braking effect, so the less load on it from expending energy into a load, the faster it will turn.  When you have an electrical generator being propelled by some force and the voltage generated from the windings is not connected to an external load, then no current other than eddy currents is going to flow in the motor, which ought to be fairly insignificant.  So there is an EMF, but no significant power generated by the motor windings when being driven by an external mechanical force when there is an incomplete circuit from the windings into any external electrical load.  
   
  Ed
   
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