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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…..to
measure the ring end gap you need to remove the piston from the sleeve and then
remove the ring from the piston, then put the ring in the sleeve from the
bottom and then use the top of the piston to push up the ring about ¾ of the
liner. This will also square the piston in the liner.</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'>Then remove the
piston and using a flat feeler gauge from the top of the liner, measure the
ring gap.</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=black face="Times New Roman"><span style='font-size:10.0pt'>Regards<br>
<br>
Dave Harmon<br>
NSRCA 586<br>
K6XYZ[at]sbcglobal[dot]net<br>
Sperry, Ok.</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> Tuesday, July 15, 2008 7:03
AM<br>
<b><span style='font-weight:bold'>To:</span></b> </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'>Interesting email.<br>
I guess in the betterment of science I should do one more test with a different
piston/ring in the offending engine before swapping it out totally for another
motor.<br>
I am getting tired of pulling apart motors though.<br>
What I really want to know is how to measure those gaps :)<br>
I tried but the best I good get was somewhere between 0 and 1 mm with my rulers
:)<br>
<br>
Stuart<br>
<br>
Dave Harmon wrote: </span></font></p>
<p class=MsoNormal style='margin-left:.5in'><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 Mike McCormick that is
interesting.</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><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='margin-left:.5in'><font size=2 color=black
face="Comic Sans MS"><span style='font-size:10.0pt;font-family:"Comic Sans MS";
color:windowtext'>Mike McCormick<<<<<</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><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='margin-left:.5in'><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 style='margin-left:.5in'><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:1.0in'><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> <a
href="mailto:nsrca-discussion-bounces@lists.nsrca.org">nsrca-discussion-bounces@lists.nsrca.org</a>
[<a href="mailto:nsrca-discussion-bounces@lists.nsrca.org">mailto:nsrca-discussion-bounces@lists.nsrca.org</a>]
<b><span style='font-weight:bold'>On Behalf Of </span></b>Stuart Chale<br>
<b><span style='font-weight:bold'>Sent:</span></b> Monday, July 14, 2008 10:07
PM<br>
<b><span style='font-weight:bold'>To:</span></b> <a
href="mailto:adriancwong@earthlink.net">adriancwong@earthlink.net</a>; General
pattern discussion<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:1.0in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt'> </span></font></p>
<p class=MsoNormal style='margin-left:1.0in'><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>
<pre style='margin-left:.5in' wrap=""><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt'> </span></font></pre><pre
style='margin-left:.5in;text-align:center'><font size=2 color=black
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<hr size=4 width="90%" align=center>
</span></font></pre><pre style='margin-left:.5in'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt'> </span></font></pre><pre
style='margin-left:.5in'><font size=2 color=black face="Courier New"><span
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