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<DIV><SPAN class=400170301-18092004>Dean & Matt,</SPAN></DIV>
<DIV><SPAN class=400170301-18092004> Yes. I forgot to mention the the
"programmability" factor of an electric motor. Whereas a glow motor's
characteristics come from mechanical things (bore, stroke, port timing, etc.),
an electric motor and speed controller can work together to alter the torque
curve. Some speed controls take advantage of this now, but most people
don't realize it. The better speed controls use a non linear type of output (I'm
oversimplifying here) to make the electric motor "feel" more like a glow motor.
I haven't worked much with the brushless motors but I have a bit of experience
with the can motors (from R/C car racing). It seems like what we need is a speed
controller with a P.I.D. control loop. The currently available ones are one
dimensional / open loop. The throttle stick simply increases or decreases the
output of the motor. The speed controller just changes the PWM duty cycle in
direct response to the stick position. We need some feedback and Fuzzy Logic to
do this right. Dean: If you design the hardware, I'll work on the
code...</SPAN></DIV>
<DIV><SPAN class=400170301-18092004>
<P><FONT size=2>John Pavlick<BR><A href="http://www.idseng.com/"
target=_blank>http://www.idseng.com</A><BR> </FONT> </P></SPAN></DIV>
<BLOCKQUOTE dir=ltr
style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">
<DIV align=left class=OutlookMessageHeader dir=ltr><FONT
face=Tahoma>-----Original Message-----<BR><B>From:</B>
discussion-request@nsrca.org [mailto:discussion-request@nsrca.org]<B>On Behalf
Of </B>Dean Pappas<BR><B>Sent:</B> Friday, September 17, 2004 12:55
PM<BR><B>To:</B> discussion@nsrca.org<BR><B>Subject:</B> RE: Motor Costs
Comparison (more pro-electric)<BR><BR></DIV></FONT>
<DIV><SPAN class=326065015-17092004>Hi Matt,</SPAN></DIV>
<DIV><SPAN class=326065015-17092004>I suspect that you're right, even if the
timeframe is a little longer. Some pieces of hardware are still lacking. The
first among these is a speed controller that offers braking. Probably the
easiest way to do this is to make the controller so that stick
position actually controls the motor RPM, and then mess with the timing
to get braking when the RPM is above the target. The potential for slow
downlines is staggering. For the geared motors, an RPM limit would also allow
the selection of a lower resistance , higher Kv, winding and corresponding
change in prop or gear ratio that would overspeed the motor under a
W.O.T. dive, but will improve efficiency everywhere else. </SPAN></DIV>
<DIV><SPAN class=326065015-17092004></SPAN> </DIV>
<DIV><SPAN class=326065015-17092004>just some ramblings,</SPAN></DIV>
<DIV><SPAN class=326065015-17092004> Dean</SPAN></DIV>
<P><FONT face="Times New Roman">Dean Pappas</FONT> <BR><FONT
face="Times New Roman">Sr. Design Engineer</FONT> <BR><FONT
face="Times New Roman">Kodeos Communications</FONT> <BR><FONT
face="Times New Roman">111 Corporate Blvd.</FONT> <BR><FONT
face="Times New Roman">South Plainfield, N.J. 07080</FONT> <BR><FONT
face="Times New Roman">(908) 222-7817 phone</FONT> <BR><FONT
face="Times New Roman">(908) 222-2392 fax</FONT> <BR><FONT
face="Times New Roman">d.pappas@kodeos.com</FONT> </P>
<BLOCKQUOTE dir=ltr style="MARGIN-RIGHT: 0px">
<DIV align=left class=OutlookMessageHeader dir=ltr><FONT
face=Tahoma>-----Original Message-----<BR><B>From:</B>
discussion-request@nsrca.org [mailto:discussion-request@nsrca.org]<B>On
Behalf Of </B>Rcmaster199@aol.com<BR><B>Sent:</B> Friday, September 17, 2004
1:13 AM<BR><B>To:</B> discussion@nsrca.org<BR><B>Subject:</B> Re: Motor
Costs Comparison (more pro-electric)<BR><BR></FONT></DIV>
<DIV>
<DIV>John there are at least a couple more good points:</DIV>
<DIV> </DIV>
<DIV>Throttle response of an electric can be made more
effective compared to most engines, even many four strokes. You
don't get the wind up on downlines like you do on 2 strokes, and you don't
need to wait until the 2 stroker settles down on landing</DIV>
<DIV> </DIV>
<DIV>I doubt we will ever have to worry about the motor "flaming out"
on take-off, 10 feet off the deck in no man's land, even if one cell drops.
Or the motor going fat or lean and flaming out somewhere in the
flight.</DIV>
<DIV> </DIV>
<DIV>There are many more good points to be made. It makes sense for
pattern even if initial cost or the cost per flight is prohibitive
for many right now. Consider the afforementioned flame-out on take off, or
flame out on landing approach that got a little too far away. A cracked
pattern plane is often the result of either condition. </DIV>
<DIV> </DIV>
<DIV>I still hold to a statement I made more than a year ago: in five years
more than half of us will be flying electric</DIV>
<DIV> </DIV>
<DIV>MattK</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<BLOCKQUOTE
style="BORDER-LEFT: blue 2px solid; MARGIN-LEFT: 5px; PADDING-LEFT: 5px"><FONT
face=Arial>Here are my thoughts on electrics:<BR><BR>Good
points:<BR><BR>1. They are VERY quiet. This is a good thing. I've never
heard of someone<BR>losing a flying site because the planes were too
quiet.<BR><BR>2. They are clean. The airframe will last longer because
there's no danger<BR>of being fuel soaked. Electrics are more "politically
correct" in that they<BR>don't pollute the air (although the energy
required to charge the batteries<BR>my come from something that does), and
most of the new batteries are safe<BR>when disposed of properly (to the
best of my knowledge).<BR><BR>3. They produce less vibration, even when
the motor is mounted directly to<BR>the airframe.<BR><BR>4. Modern
brushless motors have as much usable power as glow motors.
When<BR>properly matched to the airframe, an electric motor feels almost
like a glow<BR>motor.<BR><BR>5. They are easier to fit with a gear drive.
This allows a wider range of<BR>props that may be used.<BR><BR>6.
Brushless motors require very little maintenance.<BR><BR>7. The C.G.
doesn't change as the battery discharges.<BR><BR>8. They are easy to
start.<BR><BR><BR>Bad points:<BR><BR>1. An electric power system for large
airplanes is VERY expensive. You can<BR>buy a lot of glow fuel for the
cost of a few battery packs. Batteries are<BR>reusable, but they don't
last indefinitely.<BR><BR>2. Power system design is much more critical.
Props, gear ratios and current<BR>draw must be considered very
carefully.<BR><BR>3. Batteries must be charged. This takes a long time
compared to how fast<BR>they discharge. Owning a lot of battery packs
merely delays the inevitable<BR>truth: If it takes 10 times longer to
charge than discharge, eventually you<BR>will end up waiting for something
to charge.<BR><BR>4. With LiPO's the energy density is fairly high
(capacity wise) but it<BR>normally takes quite a few packs in parallel in
order to handle the required<BR>current loads.<BR><BR>5. LiPO's must be
handled with care. I don't need to elaborate on this one<BR>although I
personally don't think they're DANGEROUS. People are
more<BR>dangerous.<BR><BR>6. High output electric power systems are
relatively heavy, although this is<BR>improving at a rapid
rate.<BR><BR><BR>To sum things up - I fly glow and electric. I like them
both. I have a few<BR>S400 planes that fly very fast and track very well.
I also have a few slow /<BR>park flyers that are great when the air is
calm. Small electrics are great.<BR>Most of the time, however, I prefer
glow motors. Mostly because of cost and<BR>ease of use. A .40 glow motor
costs $50.00 (used) to $100.00. A brushless<BR>motor and battery that
provides equivalent power could easily cost 3 times<BR>as much. I don't
like to wait for batteries to charge. I hated it when I<BR>raced R/C cars
and I hate it even more now. I don't mind wiping the slime<BR>off of my
plane at the end of the day. I do believe electrics may be the way<BR>of
the future. The key word is future. At the present time, I think the
best<BR>bang-for-your-buck comes from the glow stuff. There's a lot of
energy stored<BR>in dead Dinosaurs, and we pretty much perfected how to
extract it in the<BR>'70s. If money is not an object and you want to be a
pioneer then fly 2<BR>meter electrics. I think I'll wait until technology
catches up with our<BR>expectations.<BR><BR>John
Pavlick</FONT></BLOCKQUOTE></DIV>
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