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<DIV><SPAN class=474344820-04012008>Hello Ron and Glenn,</SPAN></DIV>
<DIV><SPAN class=474344820-04012008></SPAN> </DIV>
<DIV><SPAN class=474344820-04012008>You hit the nail on the
proverbial head... I don't know if you know but I have done
some experimenting on making a APU for my sojourner robot project. It is
basically a gas driven electrical power system for long range high power
generation. </SPAN></DIV>
<DIV><SPAN class=474344820-04012008></SPAN> </DIV>
<DIV><SPAN class=474344820-04012008>One of the items that a coworker of mine
introduced me to is that of tuned exhaust systems. It is much easier
for a constant RPM system than for a dynamic RPM system like the one on that
robot, however the idea is to remove all of the back pressure from the motor,
and then in the exhaust system to generate a small amount of back pressure by
carefully reflecting a certain amount of the exhaust pressure wave back to the
engine. The careful part is that the wave front being reflected back is
adjusted such that it creates a nodal point or standing wave in the appropriate
part of the muffler / exhaust system. If it is done correctly the nodal /
standing wave can be adjusted to disrupt a significant amount of sound
energy.</SPAN></DIV>
<DIV><SPAN class=474344820-04012008></SPAN> </DIV>
<DIV><SPAN class=474344820-04012008>The guys who build those large scale replica
airplanes have been doing this for years, but rather they tune them to create
more sound to get that deep throaty replica sound.</SPAN></DIV>
<DIV><SPAN class=474344820-04012008></SPAN> </DIV>
<DIV><SPAN class=474344820-04012008>Anyway, when the volume of exhaust is kept
constant due to constant RPM this can be done fairly effectively. In
the case of the Parallax robot the easy way to do that would be to run the
engine consistently in its power band and use a needle spool valve to regulate
the delivery of power. Ultimately this would lead to higher gas
consumption which is probably why they did not do it, however it would allow
them to tune the exhaust system to something extremely quite.</SPAN></DIV>
<DIV><SPAN class=474344820-04012008></SPAN> </DIV>
<DIV><SPAN class=474344820-04012008>From my tracking the project, the production
version is no where near Gen-I of the project but I am sure there are
versions I've not been privy to as I don't work there and am not affiliated with
the group in any way. I'll bet however that the significant feedback
they receive after field launching a few thousand Gen-XI robot leads them
quickly to considering this for implementation in the next Gen
product.</SPAN></DIV>
<DIV><SPAN class=474344820-04012008></SPAN> </DIV>
<DIV><SPAN class=474344820-04012008>If you care to see, my prototyping
was done on a configuration that looks like this. (Link below)
That is a weed whacker motor, read = loud. I am most definitely
*NOT* a small engine guy. One of my coworkers is a mechanical
engineer who works on forward field emergency power generation systems and way
(way way) back in the day they used to use small gas engines. He
turned me on to the technology. I haven't modified mine yet but he had me
over to his shop and showed me what he has done on several of the gas powered
scale race boats that he runs. It is quite amazing. There are
just tooo many fun (read = lots of research) avenues of technology to track down
related to robotics and this is just one of them that I have not had the time to
finish up on yet. I wish I lived closer to a big group like the DPRG where
one can find like minded people to work with and share out little bits of the
research work. Man you guys are lucky, that is one of the things I
miss about moving away from Pugetropolis.</SPAN></DIV>
<DIV><SPAN class=474344820-04012008></SPAN> </DIV>
<DIV><SPAN class=474344820-04012008><A
href="http://nikita.argia.net/kmaxon/soj_pwrplnt_007.jpg">http://nikita.argia.net/kmaxon/soj_pwrplnt_007.jpg</A></SPAN></DIV>
<DIV><SPAN class=474344820-04012008></SPAN> </DIV>
<DIV><SPAN class=474344820-04012008>One company out there that makes this sort
of mufflers that can be modified to tune for standing wave noise cancellation
can be found at the following link.</SPAN></DIV>
<DIV><SPAN class=474344820-04012008></SPAN> </DIV>
<DIV><SPAN class=474344820-04012008><A
href="http://davisdieseldevelopment.com/muffler/giant.htm">http://davisdieseldevelopment.com/muffler/giant.htm</A></SPAN></DIV>
<DIV><SPAN class=474344820-04012008></SPAN> </DIV>
<DIV><SPAN class=474344820-04012008>BTW, I don't mind if this is reposted to the
list, some others out there may get some info out of it or it may spur follow on
conversation, I'll leave that up to you...</SPAN></DIV>
<DIV><SPAN class=474344820-04012008></SPAN> </DIV>
<DIV><SPAN class=474344820-04012008>-Kenneth</SPAN></DIV>
<DIV><SPAN class=474344820-04012008></SPAN> </DIV>
<DIV><SPAN class=474344820-04012008></SPAN> </DIV></DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma
size=2>-----Original Message-----<BR><B>From:</B> DeltaGraph@aol.com
[mailto:DeltaGraph@aol.com]<BR><B>Sent:</B> Friday, January 04, 2008 7:33
PM<BR><B>To:</B> kmaxon@qwest.net<BR><B>Subject:</B> Re: .Parallax
Robot<BR><BR></FONT></DIV><FONT id=role_document face=Arial color=#000000
size=2>
<DIV>Hey Kenneth,</DIV>
<DIV> </DIV>
<DIV>Very interesting.</DIV>
<DIV>Very nice on your generator setup.</DIV>
<DIV>Interesting on RC mufflers too -- my other thought -- how could you make it
sound cool.</DIV>
<DIV>Like professor Fate's car in the Great Race -- if per chance you ever saw
that movie -- from 60's</DIV>
<DIV>Dim memory was that car sounded cool -- twin V-8s as I recall...</DIV>
<DIV> </DIV>
<DIV>sure post what you like -- maybe this what I wrote: ;)</DIV>
<DIV> </DIV>
<DIV>Ron</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV>Hey Kenneth,</DIV>
<DIV> </DIV>
<DIV>Neat platform, but seems a bit noisy.</DIV>
<DIV>
<DIV> </DIV>
<DIV>If I had to use a gas engine I would waste some payload on a really good
muffler.</DIV>
<DIV>Maybe go with some kind of active sound
suppressor?</DIV></DIV></FONT><BR><BR><BR>
<DIV><FONT style="FONT: 10pt ARIAL, SAN-SERIF; COLOR: black">
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