F3A--Electric.

[Wayne Powell]

Just thinking out loud here.  Isn't there more to the electric drivetrain
than just the motor and prop?  I'd suggest the gearbox as a significant
source of sound beyond the prop.  If the tip speed between the two is
virtually identical, assuming similar design, there should be negligible
difference in prop noise (within reason).  Taking it further, that would
mean the exhaust and carb noise are equivalent to the noise created by the
gearbox?  It would be neat to compare a direct drive set-up running a prop
at the 395 mph tip speed vs. the geared system on a dB meter...

Wayne Powell
Bolly Props North America
http://www.BollyProps.com
  -----Original Message-----
  From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]On
Behalf Of Troy Newman
  Sent: August 8, 2003 7:09 PM
  To: discussion at nsrca.org
  Subject: Re:F3A--Electric.


  Also some have claimed its silent flight....Tony said the sound meter was
tipping 93db(A)...That means prop noise is our greatest noise issue....Who
cares about in flight noise...the Sound meter is 3M away from the model....

  Just some FYI.....YS 140DZ turning a 17-12 at 7800rpm is 92-93db(A)...OS
140RX same 17-12 at 7800rpm is the same 92-93db(A) this is roughly 394mph
tip speed....

  Jason is using a 22" prop at around 6000rpm its hit 93db(A) and if you
calculate the tip speed its 392mph.

  So guess what prop noise is the kicker....its not silent flight when you
are tested at 3meters.
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