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<DIV><FONT face=Arial size=2>I have used 9411's on ailerons and 3421's on
elevators (metal gears) for quite some time. I find these servos to be
excellent. The 9411's on the ailerons do get lose fairly quickly, and
metal gear replacements are pricey. I investigated converting both servos
(9411 and 3421) to SA type, but I had second thoughts when I looked at the size
of the plastic gears, particularly on the 3421. I suggest caution
here.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Regards,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Andre'</FONT></DIV>
<DIV> </DIV>
<DIV>----- Original Message ----- </DIV>
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<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=tkeithb@comcast.net href="mailto:tkeithb@comcast.net">Keith Black</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, July 02, 2004 8:19 PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Digital Servos vs analog
servos on Ailerons</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial size=2>Don,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Interesting report. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>If you get a chance I suggest you try out the JR
9411SA's (nylon gears), they are incredibly tight with absolutely no slop. I
flew the 9411 for about 200 flights and they developed quite a bit of slop. I
then switched to 9411SA and was amazed how tight they were, much tighter than
the 9411 brand new. It made a noticeable difference in how steady the plane
flies. Also did the same on my elevator servos in the stab, changed the
3421's to the 3421SA's. The 3421's had also developed a lot of slop after 200
flights. For the rudder I run the 8411SA. Unless I run into problems with
the nylon gears stripping I'm really sold on the SA's. Of course, flying FAI
you put a lot more stress on your servos. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>On my second plane I run pull-pull on the
elevator and use the JR 8417 which seems to be the defacto digital elevator
servo in the JR line. It's a great servo but even brand new it's not nearly as
tight and slop free as the SA's. I'm considering changing the elevator to the
8411SA, though it's not as fast as the 8417.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Keith Black</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=dszczur@maranatha.net href="mailto:dszczur@maranatha.net">Don
Szczur</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, July 01, 2004 10:51
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Digital Servos vs analog
servos on Ailerons</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial size=2>At the urging of Dave, I have finally switched
to digital servos on the ailerons. After flying analog servos for 25
years, it was explained to me that digital servos on the ailerons help
looping and radius of maneuvers. Here is my assessment.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>The baseline servos were JR
7005. The digital servos changed to are JR 9411 servos.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Loops and lines. The first thing I
noticed was that, just as Dave mentioned, loops and loop segments are more
locked-in. The 9411 servos made the wings more stable, requiring less
effort on the maneuvers involving loop segments (most all of the
maneuvers). Analysis- why this occurs- the theory is that during
loops, wing panels generate quite a bit more lift. since the digital
servos lock, and hold center much more agressively than analog servos
(holding torque) this provides very little give in the ailerons during the
loop. Regardless, its a noted difference and clear advantage of these
servos.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Rolls and rolling segments. This part of
the analysis was quite a bit more complex. Clearly the digital servos
have more speed and resolution than the analog servos. The holding
torque and contol surface power requires that control throw be reduced to
attain the same roll rate. However, the analog servos would "blow
back" at high speed, but stay deflected at lower speeds. Incredibly,
the advantage to this is a more constant roll rate- independent of
speed. The ailerons (roll rate) would feel more the same
at low speed (like the top of an immelman, loop or vertical
line).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Snap rolls. This is what I call the
"rubber band" effect. The analog servos would deflect quite a bit
during snap rolls, requiring one to "unload" the snap (start coming out of
the ailerons before the snap is complete). Otherwise, the snap would
be over-rotated. Actually, this was not too hard to get used to, since
its a very consistent effect. With digital servos, however, there is
much less deflection and thus a more "honest" snap roll. It does snap
differently, but the exit is much cleaner (or easier to have a clean
exit).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Exponential. Here is another item of
interest. My initial perception was that I would have to add
additional expo to get the same feel for the digital servos. Since
control thow was reduced (moved in one notch on the servo arm) there was
still more roll rate at full stick deflection (since the ailerons are no
longer blowing back like the analog servos), but not as much roll around
neutral. I actually had to cut my expo in half. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>So, the overall analysis is that the
digital servos provide greater stability of flight, more consistent snap
exits and loop segments that are more locked in. Analog provide
more control roll authority at slower speed and more forgiveness with shaky
hands (the rubber band effect does dampen shaky thumbs). Conclusion-
overall benefits outweigh analog servos- favor the use of digitals.
Will stay with the 9411's.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial
size=2>Don</FONT> </DIV></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>