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<p class=MsoNormal><font size=2 color=blue face="Comic Sans MS"><span
style='font-size:10.0pt;font-family:"Comic Sans MS";color:blue'>Stuart…..here
is an old email from </span></font><font size=2 color=blue face="Comic Sans MS"><span
style='font-size:10.0pt;font-family:"Comic Sans MS";color:blue'>Mike</span></font><font
size=2 color=blue face="Comic Sans MS"><span style='font-size:10.0pt;
font-family:"Comic Sans MS";color:blue'> McCormick that is interesting.</span></font></p>
<p class=MsoNormal><font size=2 color=blue face="Comic Sans MS"><span
style='font-size:10.0pt;font-family:"Comic Sans MS";color:blue'> </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=blue
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:blue'>>>>></span></font><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>Because the YS piston compresses in both the up and down
stroke, the ring is </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>serving double duty. It must not only seal the mixture being
compressed, but </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>it must also separate the two compressed mixtures. Once the
piston begins to </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>rock and the ring loses its seal, then surge begins. If you
think about it, </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>the YS engines with the highest compression are the most
problematic (SC and </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>the L; the L is really just an SC version of the FZ). Why do
the pistons </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>rock? No side wall. Plus (as Dick stated) the pistons are
made of soft 2017 </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>aluminum and will wear quickly (especially if the engine is
run lean or fuel </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>with low oil content is used). This piston design has been
in use since the </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>AC and always been a pain. But in the 1.2's we could alway <b><span
style='font-weight:bold'>install an FS </span></b></span></font></p>
<p class=MsoNormal style='text-autospace:none'><b><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext;font-weight:bold'>Piston and cure the ill's.</span></font></b><font
size=2 color=black face="Comic Sans MS"><span style='font-size:10.0pt;
font-family:"Comic Sans MS";color:windowtext'> FYI, I once did a test on an AC
just to see how </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>much more boost the AC piston created vs the FS piston; it
was less than 1/4 </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>psi! I also noticed that any engine in which I installed a
FS piston ran </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>better than it did with the compound type piston. I figured
this occured </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>because the FS piston ran "truer" in the bore; it
created less drag because </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>it was less prone to rock or cock in the bore (more side
wall). But along </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>comes the 1.4 and we no longer have the FS piston to fall
back on, Plus the </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>1.4 piston was shorter and bigger in diameter,i.e, more
rocking force </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>(around) the wrist pin is created and there is less length to
stabilize the </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>force. Things didn't get too bad until YS increased the
compression of the </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>engine (L version) and then the piston really started to get
beat up. </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>Because of the higher compression, the ring seal is even more
important and </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>the piston/ring fit has to be right for the engine to perform
optimally. And </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>the optimal fit is within a narrow range. I set the
piston/sleeve clearance </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>at .003 to .0035". Max clearance is .005"
.0035" is tight, and engines I </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>set up must be run rich for a long time to properly break
in. I also set the </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>ring end gap as tight as I can get it, usually at
.0055", though I like it </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>best if I can get it at .003". But when set up at these
clearances and run </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>rich, they will last 500 plus flights.</span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>So what is boils down to is the old piston is soft and has
very little side </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>wall. The forces on the piston are high and attack it from
both ends. This </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>creates high side forces on the piston. The minimum side
wall works hard to </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>keep the piston straight, but even in the best of conditions
(running the </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>engine rich and using lots of oil) it is a losing proposition
for the piston. </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'> The new piston has 4 times as much side wall area under the
ring groove </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>(where the old style piston experienced the greatest forces
and therefore the </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>most wear). It runs very smoothly and I believe this is
because it too tends </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>to run very true in the bore. I am sure it will last longer
because of the </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>increased side wall area. </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>Sorry for the length of this reply, and I hope it answers
your question. But </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>heck while I am at it I might quickly address one other issue
I see a lot of </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>problems with. Many flyers tend to set the mixtures too lean
on 1.4's. </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>Because of the different plumbing in these engines, the
regulators do not </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>respond as quickly as did those on 1.2's. To set these, you
must do it </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>slowly and wait a few seconds for the regulator to equalize
with the change. </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>If you move the needle quickly, and not wait it is very
possible to get a </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>false reading on the mixture and usually it ends up too
lean. Kills the </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>engine quickly. </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'> </span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>Mike</span></font><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'> McCormick<<<<<</span></font></p>
<p class=MsoNormal><font size=2 color=blue face="Comic Sans MS"><span
style='font-size:10.0pt;font-family:"Comic Sans MS";color:blue'> </span></font></p>
<p class=MsoNormal><font size=2 color=blue face="Comic Sans MS"><span
style='font-size:10.0pt;font-family:"Comic Sans MS";color:blue'> </span></font></p>
<div>
<p><font size=2 color=blue face="Times New Roman"><span style='font-size:10.0pt;
color:blue'>Regards<br>
<br>
Dave Harmon<br>
NSRCA 586<br>
K6XYZ[at]sbcglobal[dot]net<br>
Sperry, Ok.</span></font><font color=blue><span style='color:blue'> </span></font></p>
</div>
<p class=MsoNormal style='margin-left:.5in'><font size=2 color=black
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;color:windowtext'>-----Original
Message-----<br>
<b><span style='font-weight:bold'>From:</span></b>
nsrca-discussion-bounces@lists.nsrca.org
[mailto:nsrca-discussion-bounces@lists.nsrca.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>Stuart Chale<br>
<b><span style='font-weight:bold'>Sent:</span></b> </span></font><font size=2 color=black face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;
color:windowtext'>Monday, July 14, 2008</span></font><font size=2 color=black
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;color:windowtext'>
</span></font><font size=2 color=black face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;color:windowtext'>10:07 PM</span></font><font size=2
color=black face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;
color:windowtext'><br>
<b><span style='font-weight:bold'>To:</span></b> adriancwong@earthlink.net; </span></font><font
size=2 color=black face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;
color:windowtext'>General pattern discussion</span></font><font size=2
color=black face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;
color:windowtext'><br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [NSRCA-discussion]
120 AC issues UPDATE</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt'> </span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt'>I have been mostly using
Cool Power 15%, but tried 30% heli today with the same results. No
special YS blends available locally.<br>
This plane is for my son to fly. Sure makes my electric Beryll seem real
easy :)<br>
Stuart<br>
<br>
</span></font></p>
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